2. how to use this guide

Output No: 285-124 PAGE i Document JC30631-N-CG-GL-0004

Contents 1. BACKGROUND 2

2. HOW TO USE THIS GUIDE 3

3. INTRODUCTION 5

4. PLANNING THE ENERGY AUDIT 10

5. DATA COLLECTION 14

6. MEASURING ENERGY USE 16

7. IDENTIFYING OPPORTUNITIES 20

8. COST BENEFIT ANALYSIS 21

9. REPORTING 23

10. POST-AUDIT ACTIVITIES 25

11. MONITORING & MEASUREMENT EQUIPMENT 26

12. WATER AND WASTEWATER 27

Appendix A INDUSTRIAL LIGHTING 28

Appendix B COMPRESSED AIR 36

Appendix C BOILERS AND FIRED HEATERS 46

Appendix D REFRIGERATION & COOLING 57

Appendix E ELECTRIC MOTORS & DRIVES 66

Disclaimer

LIMITATION: This guide has been prepared on behalf of and for the exclusive use of Sinclair Knight Merz (Europe) Ltd’s Client, and is subject to and issued in connection with the provisions of the agreement between Sinclair Knight Merz (Europe) Ltd and its Client. Sinclair Knight Merz (Europe) Ltd accepts no liability or responsibility whatsoever for or in respect of any use of or reliance upon this guide by any third party.

Output No: 285-124 PAGE 2 Document JC30631-N-CG-GL-0004

1 BACKGROUND

1. BACKGROUND This guidebook has been developed by SKM Enviros and BRE on behalf of the Ministry of Industry, Commerce, and Consumer Protection, in conjunction with UNDP, the Ministry of Energy & Public Utilities, and the Energy Efficiency Management Office of the Republic of Mauritius. Funding for the implementation of this project has been provided by GEF and AOSIS/SIDSDOCK, through UNDP.

This guidebook is provided as part of a wider programme to facilitate industry in Mauritius to implement Energy Management and conservation in Mauritius. The programme provides the following elements:

n Guide book on energy auditing in industrial applications

n Guide book on energy management in industrial applications

n Software calculator tool to estimate and record identified energy saving opportunities

n Theoretical training in energy management

n Theoretical training in energy auditing in industrial applications

n Practical training in conducting energy audits in industrial applications

This guide book is intended as a self-help guide for use by personnel working in industrial facilities in Mauritius in the assessment of energy saving opportunities.

This guide book is intended to be used in conjunct ion with the software based calculator tool to estimate and record energy saving opportunities.


2 HOW TO USE THIS GUIDE

2. HOW TO USE THIS GUIDE This guidebook provides a basic introduction to the practical aspects of energy audits and surveys in industry. It is not an exhaustive manual but identifies the key steps required to plan the audit process, gather relevant performance data, identify opportunities and report the findings.

Energy auditing is a core component of any energy management system; unless energy use can be measured it is difficult to control and, without baseline performance metrics, a site’s performance improvement cannot be measured over time. Whilst auditing a site that has a limited number of energy meters is a difficult proposition, there are ways of gathering sufficient information to allow a practical engineer to make an educated assessment of the breakdown of energy usage across a complex manufacturing plant and identify suitable energy saving opportunities.

This guide is organised in the following way:

n Section 3 is an introduction to the objectives, information requirements and preparative steps required to begin the audit.

n Section 4 outlines the step-by-step process that makes up an energy audit and how to plan the approach depending on whether the audit is aimed at a site-wide or a single process department.

n Section 5 covers the essential data requirements and how to organise the data for effective performance analysis.

n Section 6 covers energy measurement, analysis and the importance of baseline reporting.

n Section 7 includes some suggestions for identifying opportunities to reduce energy use and managing the development of opportunities from initial concept to implementation. This section also links into the Technical Appendices, which outline opportunities across common technologies including simple checklists to guide the auditor through the processes.

n Section 8 is a summary of cost-benefit analysis, helping to develop the justification for investment in energy efficiency.

n Section 9 covers the contents of an audit report

n Section 10 highlights the follow-up activities that, when carried out on a regular basis, form the core of any energy management system that is consistent with the ISO 50 001 standard for energy management.

n Section 11 introduces some of the useful hand-held monitoring tools that can be used to verify process conditions and check parameters such as power consumption and combustion efficiency.

n Section 12 is a reminder that water is also an important utility and opportunities to reduce water use can also deliver energy savings through reduced pumping and treatment needs and eliminating energy loss from hot effluents.


2 HOW TO USE THIS GUIDE

The five Appendices cover specific issues around key universal energy technologies:

n Lighting

n Compressed air

n Steam systems and fired heaters

n Refrigeration and air conditioning

n Electric motor driven systems.

Included in the appendices are checklists that may be referenced during the course of an energy audit that cover key energy using aspects of equipment.

To complement this guide is a software tool comprising two parts: a database for recording energy saving opportunities and a series of simple calculators for estimating possible savings potential. Both parts require the user to enter data. The assessment tool home screen provides guidance on how to use the database and calculators. It informs where data input is required and where calculation outputs can be found.

References to the software tool are made in this document by the calculator icon (left). The icon indicates that the information presented is supported by a calculator in the tool. References to the information in this guide and use of the software tool will assist the reader in identifying and evaluating potential energy saving opportunities.


3 INTRODUCTION

3. INTRODUCTION Carrying out an energy review is the first step for energy management. The energy audit is the starting point from which an energy review can be carried out and thus a rational energy management programme may be developed. It helps to quantify the energy usage at a site and highlights areas for potential savings and gives the data from which performance indicators can be derived.

An energy audit is essentially a study to determine the amount and cost of energy consumed and to identify opportunities for potential savings. This is achieved by carrying out a technical investigation of the control and flow of energy in the plant or a process, or even a specific piece of equipment.

3.1. Objectives An energy audit helps to identify where and how energy savings can be achieved. Energy audits can be undertaken for the whole site, for a particular process or item of equipment. Whatever the subject of the audit, the objectives of the survey remain the same.

The objectives of the energy audit are to:

1) Quantify energy consumption for audit scope (site, area or item of equipment) 2) Identify practical energy saving projects. 3) Quantify savings in energy and monetary terms.

3.1.1. Determine current position The first objective for a site energy audit is to quantify the amount of energy consumed on site. This will determine the current baseline position and will allow for the current situation to be assessed. When starting an Energy Management initiative it is important to determine the current position. This is necessary as it will facilitate the setting of goals and priorities for future development.

There are various elements of the current situation that need to be defined. These can be divided into two main categories:

n Quantity elements: How much energy is being used? n Quality elements: Where and how is energy being used?

3.1.1.1. Quantity elements The quantification of current energy consumption and cost is a good starting point. In addition to indicating the magnitude of energy consumption it also helps to inform where to concentrate efforts to achieve the best results.


3 INTRODUCTION

Monthly consumption figures over a 12 month period provide a useful method of producing a picture of energy usage. It is also important to record the type and energy intensity (calorific values) of any non-standard fuels although it can sometimes be difficult to obtain this information. Fuel costs are obviously important and any month by month variations should be noted. Cost information should include the unit cost of fuel and supply tariff (if applicable). The source of fuels and any variations in calorific value or quality should also be recorded.

The following issues need to be investigated in order to establish the current position:

Energy sources: Identify all the fuel types and energy sources used on site. These can include Electricity, Liquid Petroleum Gas (LPG), Heavy fuel oil, etc. A list of common fuels is included in the Audit Tool, including typical energy content and carbon equivalents.

Amount of energy: Quantify the amount of energy used of each fuel type. All fuel types will need to be quantified in the same units (i.e. kWh, MJ, etc.) so that their energy consumption can be compared. Consolidating all the information will give the total energy consumption of the site. However, it is useful to be in a position to determine the energy usage for each area of the plant. In cases where the plant is zoned or different areas and/or particular equipment can be measured, the energy consumption for each area should be determined. This will help to target particular areas or processes or big energy users. For example, quantifying the electricity consumption for compressed air or for a specific production line will give an idea of where energy is actually being used.

Cost of energy: The annual energy consumption cost of the site is needed so that the size of the problem is clearer. Energy cost can be compared against other baseline costs of the site. Moreover, the cost for each fuel will be different. Therefore, it is important to establish energy unit costs for each fuel. Again, it helps if all fuels have the same units so that they can be compared with each other. The Audit Tool incorporates typical calorific values of the fuels and normalises energy costs per unit of energy.

Energy breakdown: Having established the energy used from each fuel type, and their respective costs, it will be possible to create a fuel breakdown. This can be done both in energy and monetary terms. CO2 breakdown is also helpful when looking at the environmental impact of the plant. Furthermore, an energy breakdown by area or even equipment is a powerful tool which helps to identify big energy users and allow the audit to focus on areas where the greatest saving opportunities can be found.

3.1.1.2. Quality elements Having established the cost and quantity of each energy source being consumed, the next step is to identify where and how energy is actually being consumed. This in effect is the assessment of the flow of energy through the site.

The objectives at this stage are to identify for each fuel the most important users in cost and consumption terms and to break down the usage as much as possible. Once this has been carried out, it will be possible to identify areas and specific items of plant to target for efficiency


3 INTRODUCTION

improvement measures. Once areas that require improvement or areas where energy is wasted have been spotted, the next step is to find out how and why.

In order to assess the way energy is being used a plant walkabout will be necessary. Plant walkabouts are discussed in more detail in the following chapters. However, at this point it needs to be mentioned that during the walkabout it is important that anything that could be done differently is questioned. This will help to identify process inefficiencies and areas of energy wastages.

The objective here is to reduce energy consumption and improve energy efficiency. These are two different issues and should not be confused. There are two main questions that always need to be answered in terms of energy reduction and energy efficiency:

Energy reduction - Is energy actually needed? This relates to the areas where energy is being wasted. Old practices are not always the best practices. An investigation into such areas can help to identify significant energy saving opportunities with no or very low cost.

Energy efficiency - Can it be done more efficiently? This relates to how energy is controlled and/or is converted from one form to another. For instance the efficiency of air compressors can be improved simply by drawing in air with lower temperature, so that the conversion efficiency of power to compressed air is improved.

3.2. Required information As discussed above the types of fuel used need to be known. Electricity, Liquid Petroleum Gas (LPG), Heavy fuel etc. should be identified and quantified. It might be more appropriate to treat compressed air and steam as separate utilities starting from the output of compressor / boiler. This will allow for a more focused analysis on particular equipment and processes. What needs to be identified is:

The quantity of each fuel: The energy consumption data can be retrieved from the utility suppliers or metering on the site.

The unit cost for each fuel: The utility suppliers will also be able to provide the unit costs. Furthermore, cost breakdown for each fuel type should also be known. For example, the day and night, or peak tariff cost rates for electricity is important for comparison with operation and energy use patterns.

Energy Reduction

•Areas of inappropriate use or waste•Are we heating and cooling at the same time?•Are lights sleft on in an empty room?•Are ovens left on while there is no production?

Energy Efficiency

•Poor control or conversion efficiency•Are we using the appropriate efficient equipment?•Are we controlling machines properly?•Is there a better way


3 INTRODUCTION

Where and how each fuel type is used: Where sub-metering is in place data can be available for specific areas, or equipment. For example useful information can be found in the boiler house or the compressor house log book.

Gathering information about energy consumption is an important process and it is important that all data is recorded properly. The following table is an example of how to record the required information.

Year 2012

Site / area

Energy source Units Quantity purchased in original units

Quantity converted in kWh Cost Unit Cost

$/kWh CO2

(tonne)

Electricity kWh 2,750,000 2,750,000 $330,000 0.120 1,460

Natural Gas m3 840,000 9,240,000 $323,400 0.035 1,760

Oil litres 42,000 445,200 $25,200 0.057 110

Other fuel - - - - - -

Total - - 12,435,200 678,600 0.055 6,616

The data from the above table can be used to create a breakdown of all the energy sources on site. A pie chart is very useful to visualise the various breakdowns. An example is shown below:

CO2 Breakdown

Electricity44%

Natural Gas53%

Oil3%

Cost Breakdown

Electricity48%

Natural Gas48%

Oil4%

Energy Breakdown

Electricity22%

Natural Gas74%

Oil4%


3 INTRODUCTION

From the above figures it can be seen that whilst electricity supplies only 22% of the energy requirement, it accounts for 48% of the cost. Therefore, small energy savings in electricity can bring more significant cost savings.

After the baseline is determined it is useful to look at the most significant energy users on site. Creating a list with all the major users will help in identifying areas where greatest focus should be given for identifying savings opportunities. The list below contains examples of typical users on industrial sites.

When sub-metering is available it helps to measure the actual consumption by each user and they may be sorted accordingly. Where sub metering is not available and a user is known to be significant portable sub metering equipment may be used to take temporary measurements to inform an understanding of the actual energy use.

This type of information is needed to establish the current baseline and to identify and estimate energy saving opportunities. However, additional information will be needed to assess the practical and economic feasibility of any energy saving projects identified. The required information for assessing the feasibility of the projects can include:

The cost of energy saving projects: Having accurate cost estimates for any required improvements / modifications needed to deliver savings will help to estimate the payback period of the project. This will allow the proposer to provide a business case and helps to make an informed decision on whether to invest or not.

Operation pattern of the plant: This is needed when considering changes that will have an effect on or depend on operation patterns. For example, a process heat recovery project will depend on the time when heat is needed.

It is also important to establish the priority areas. The auditor needs to know whether to focus more on no/low cost projects or on bigger energy saving projects:

n No/low cost measures can bring fast results and boost confidence but savings may be limited whereas,

n Bigger projects on major energy users can give significant savings but may need more time and capital investment.

Electricity users Liquid Fuel users

Ovens Steam boilers

Furnaces Thermal fluid heaters

Presses Hot water boilers

Air compressors Ovens

Chillers Furnaces

Hydraulic pumps Space heating

Dust extraction system Presses

Lighting Vehicles

Air conditioning

Motors on conveyor belts

Fork lift trucks

Hot water boilers

Induction furnaces

Space heating


4 PLANNING THE ENERGY AUDIT

4. PLANNING THE ENERGY AUDIT 4.1. Setting the scope The audit may cover an entire site, the services operations or a single production unit. To ensure that the appropriate information is collected during the audit the scope of the study should be clearly defined. However, the energy auditor should also be aware of and note other energy issues that might be observed during the course of an audit (for example, noting a compressed air leak on an adjacent piece of equipment or questioning significant water usage).

For a basic consumption or carbon footprint audit it will be sufficient to collect records of energy invoices for at least the past 12 months or past calendar year. This type of audit will be appropriate for high level reporting of energy consumption, cost and carbon emissions, typically used for annual reporting to shareholders or government or as a pre-audit for a more comprehensive audit of the site or process. In this case, no on-site visit is required; the audit can be completed in an office environment with access to top level energy reports and utility invoices.

The next level of audit is likely to be an assessment of the breakdown of energy use across the various processes on site. This requires a more careful approach as it will involve access to boilers, compressor houses and sub-stations to view any sub-metering and switchgear. It will also require access to utility distribution drawings and a visual inspection of large motors and heaters (or access to a motor inventory) to draw up a list of the main energy consumers. For this type of audit an escorted tour of the factory is required, so an appropriate safety briefing is required from site, including relevant Personal Protection Equipment (PPE) where necessary.

A detailed site audit with the primary objective of identifying opportunities is likely to take one or more days depending on the size of the factory. In this case the auditor may need to access the site independently, to view all major process plant and site services equipment.

For an energy management assessment the auditor will need to meet senior managers, production supervisors and plant operators to enable him to make an assessment of the organisation’s capability to implement energy management change. So, check before arrival that such people will be available either collectively on a one-to-one basis to help you form an opinion of the company’s energy management maturity.

Finally, always prepare in advance of a visit – check the company’s website for any technical background, understand the production processes and inform your host contact of your visit plan so he can ensure you have the appropriate access to people, reporting systems and technical information.

Detailed audits need to be undertaken by the appropriate persons or team. They need to be experienced and familiar with the site’s operations. The skills required cover technical, safety, accountancy and management aspects. The main skills needed are summarised below:



n Data handling skills: Data is necessary to analyse performance and assess efficiency. In view of the large quantities of data analysis involved, familiarity with and access to computers is useful.

n Communication skills: Auditors should have good people and communication skills, sufficient strength of character to question the obvious and initiative to find solutions to problems.

n Technical understanding: An in depth knowledge of specific equipment in use at the site is desirable but not essential, as design information can be obtained at a later date; a feel for product flows and site services is more important.

n Open minded: An open mind is essential. Usually people continue doing things even when they know that there is a ‘better’ way. The fact that things have “always been done like that” doesn't mean it is the right way.

A tour around the plant should follow the process from the raw materials to final product. Each stage of the process needs to be understood. Particular attention needs to be given to:

1) Energy flows into and out of processes. 2) Raw material and product flows. 3) Wastage and effluent flows.

The pattern of operation is also important. It needs to be defined whether the process is in operation for 8 hours per day or 24 hours per day. Also the type of the process (batch or continuous) needs to be identified. For instance, in the case of a batch process the start and finish times as well as the factors that dictate them need to be identified. All the important process parameters need to be highlighted and investigated. The answers to these issues and others will only be gained from talking to the key people at the site who are:

1) Process operators. 2) Process supervisors. 3) Production managers.

It is very important that these people are involved in the audit. It is helpful to identify how they see their job and what affect this can have on energy consumption. The auditor needs to be open-minded and to ask questions and even challenge them. Operators will continue to stick to poor, old practices if unchallenged, as it is easier than changing.

A forward thinking factory will have an energy team, or even energy teams for each production area. Team members are useful; sources of information and process knowledge and will also be custodians of any opportunities, so be sure to make time to meet the energy team, either as a group or individually.

STORES

Offi

ces

Prod

uctio

n 1

Prod

uctio

n 2

Boilerhouse

Production 3



It is recommended that the plant is divided into appropriate zones. This will help when planning the walkabout and it also helps to focus on appropriate areas. As best practice the site layout with the associated zones should be in hand when doing the plant walkabout. An example of a zoned plant is shown on the previous page.

Then, a list with the services and technology used on site can be created on which the auditor can use to track the audit process for every zone. An example of such a matrix is shown below:

Technology topic

Zones Offices Stores

Boiler house

Production 1

Production 2

Production 3

Lighting Ventilation Space heating Air conditioning Hot water Steam Hot oil Compressed air Chillers Dust extraction Building fabric Motors and drives Fans and pumps Conveyor belts Process heat Distribution



4.2. Health and safety considerations The health and safety of the auditor, host company employees and other contractors must always be at the forefront of planning an energy audit. The auditor may wish to use intrusive portable monitoring equipment such as gas analysers or electrical clamp on meters to gather data in which case the relevant permits to work need to be obtained; these are usually accompanied by descriptions of how the work will be carried out and the site will assess these to ensure the proposed activities are safe. Always check with your site host and health & safety manager to ensure that the equipment is fit for purpose and its use is acceptable on site. Always ensure that you have appropriate Personal Protection Equipment (PPE), either your own personal equipment or request this from site. Most companies will have a recognised safety induction for visitors and contractors; always ask to see either an induction video, slide deck or safety procedures sheet. Always be aware of site safety issues, do not be afraid to point out an unsafe act or near miss and stop work and be prepared leave site if you are uncomfortable with the working environment.

4.3. Timescales The time required to deliver an energy audit will depend heavily on the scope requested by the client. A short audit of annual energy use for carbon or sustainability reporting may only require a day onsite and two days to write up, while a detailed survey of a large production facility aimed at identifying opportunities could take weeks or even months. Some rules of thumb to assist in planning are audit are as follows:

n Allow 3-4 weeks for the site to assemble the requested energy and process information

n Allow 1 week before the kick-off meeting to carry out preliminary analysis of plant data (KPIs, high level regressions etc.)

n Time on site will depend on the scale of the project. Allow 4-5 man days for every £2 million (R50 million) of energy spend (your knowledge of the site and process will help to guide you to set site days).

n Allow 2 analysis and reporting days for every site day. This can be reduced if there is a relatively small number of process operations but at least as many man-days as you spend on site.

n Allow 2 weeks for the site to review and comment on the draft report before a close-out meeting.

n Follow up the close-out meeting within one week with the final report.


5 DATA COLLECTION

5. DATA COLLECTION 5.1. Assess the current situation Audit information should be prepared in such a form as to allow comparison with historical data or available industry figures. Comparison between sites may also reveal opportunities for saving.

It has already been mentioned that determining the current position is the starting point of the energy audit. The use of the most recent 12 months’ historical data will help to calculate the annual energy consumption. This will represent the baseline. Establishing a baseline is important as future savings and energy performance will be measured against it.

It is useful to gather weekly or monthly base data on consumption and expenditure over the last year(s). The information that needs to be gathered will include not only energy consumption but also data for the factors affecting energy usage. Even though the source of this various information will be different (energy invoices, log books, accounts, etc.), it is recommended that all the information is kept in a central place where access will be easy for someone wishing to review them. A simple table with the data required is shown below:

Month Electricity (kWh) Natural Gas (kWh) Degree Days* (°C) Production (kg) January

February

Etc...

Total

• Degree days for heating or cooling may be an important driver for fuel consumption or chiller demand

The above table can also include for example different product groups, utility costs, energy consumption by area, and information on throughput including overall production and production by area or process.

Data collected in such a form allows performance indicators to be established in terms of specific energy ratios relating energy usage to production, usually expressed as the energy requirement per unit of production or Specific Energy Consumption (SEC). The units used will vary dependent on the fuels used and the type of product. However, a consistent unit is recommended. The pattern of energy consumption is analysed and correlated with raw materials input, product output or hours run for production related energy usage; and factors such as average ambient temperature for space heating.


5 DATA COLLECTION 5 DATA COLLECTION

Data collected in such a format is also easy to analyse using regression analysis to establish any relationships between energy consumption and production activity or climate factors (e.g. degree days). Such analysis can form the basis for setting energy targets for those processes where we can see a strong relationship between energy and production activity.To develop a good idea of where the energy is being consumed a good understanding of the production processes involved is essential. When an auditor or the Energy Team from another site undertakes the on-site audit, then a plant walkabout is necessary to develop a feel for the site and familiarise with the processes.

Typically, gaining an understanding of the production processes involves discussions with production management, a tour of the plant and the drawing up of a process flow sheet (block diagram). For each element of the flow sheet energy and raw material inputs, products, effluents and waste flows should be identified. Based on information available and visual checks, the relative size of energy flows and wastage should be estimated and the major energy users (both services and processes) should be listed. Sub-metering, where available, is useful in calculating the consumption of end users. A small saving on a large consumer will often be more significant as well as more achievable than a large saving on a small user. This does not mean that small users should be ignored but initial efforts should concentrate on those areas most likely to produce substantial savings.

5.2. Review historical energy consumption information Historical data, perhaps extending back over two or three years, can be used to understand a site’s progress in developing an energy efficiency culture. Although SEC values may often be influenced by production volumes and new production processes it is useful to see how performance has changed. If detailed data are readily available they can be used to establish historical baselines and regression models. Then, the impact of any changes to the site operation can be assessed and quantified through CUSUM analysis.

Comparing performance indicators such as those mentioned above with internal and /or manufacturer standards will then enable a prioritisation of the results into categories according to the outcome:

n Good results à Action is not urgent. When the results show that the energy performance is good then it can be said that no action is urgently needed. However, the energy audit will need to be carried again in the future to ensure that good performance is maintained.

n Average à Action required. Average results will mean that there are deficiencies and issues that need to be resolved. n Poor à Urgent action is need. When the results indicate poor energy performance, urgent action will be needed.

However, it should be noted that even when the results for the site in general are good, specific areas or processes might not be in the same position. For example, the overall energy performance of a site could be good, but the compressed air system is inefficient with many compressed air leaks, poor control of the compressors, etc. Therefore, the analysis should look not only on the overall plant performance but focus on the various processes and systems within the plant.


6 MEASURING ENERGY USE

6. MEASURING ENERGY USE 6.1. What to look for The initial design of a system may not have been optimised. Often, an easy option or one with a low capital requirement will have been chosen, not the cheapest running cost option. The status quo should not be accepted without question. Whether the energy flows are reasonable or not needs to be established. An understanding of the processes involved and knowledge of appropriate available technologies will be needed to identify better options.

When undertaking an energy survey on specific equipment (i.e. air compressors, boilers, steam systems, etc.) the relevant appendices at the end of this guide can be used. These provide useful information on where focus should be drawn.

However, there are things that can be easily identified during the audit and the auditor should constantly be looking out for areas of energy waste. A list of things that can be easily picked up during a walkabout is given below:

Look Listen Feel

Conveyor belts running unnecessarily Machine noise when no production Compressed air leaks

Lights left on when not needed Dust extraction system on when not needed Room temperature too low / high

Oven doors left open wasting heat Compressed air and hot water leaks Air draughts through open doors

Doors left open when heating is on Motors left running when not needed Hot un-insulated pipe work

6.2. Areas to focus When looking at energy usage, the ‘energy onion’ provides a useful analogy to an energy system. The process or end user is at the centre of the onion, which determines the production-driven energy requirements of the site. Once this has been confirmed, the next layer of the onion is the energy distribution system - network of wires, pipes and ducts delivering power, steam compressed air and other utilities to the process.

Once the distribution system has been reviewed, the methods of controlling the supply of energy through the networks to the process can be addressed. This could include pressure or flow controls in steam systems, voltage control in power systems or temperature control of chilled water supplies.



Having assessed the control of the energy supplies, the next layer of the onion represents the energy conversion plants. This is where primary energy supplied to site in the form of fuel and power is converted into useful utilities – steam, compressed air, cooling etc. – that are used by the production process. Finally, once you are happy that the energy conversion processes are appropriate it is time to address the outermost layer of the onion and review the energy supply contracts.

n End User: how energy is used within a specific process / piece of equipment n Distribution system: how energy is distributed (compressed air, steam, water, hot oil distribution systems) n Controls: how energy is controlled (energy management systems) n Generation (conversion): how energy is converted (air compressors, boilers, boilers, chillers) n Energy Supply: How primary energy is supplied to the process.

6.2.1. Energy end use Starting at the centre of the onion, it is important to understand how much energy the production process should require from a theoretical and practical standpoint. This should define the base energy demands for the process and act as a guide for the sizing of distribution networks. Where the end usage is inappropriate such as the use of compressed air for cleaning it may be possible to remove the load altogether. Where this is not possible, it may be possible to reduce energy consumption by reducing leakage or improving insulation.

Reduced end usage demand will also reduce distribution losses as less energy will need to be distributed to meet the reduced demand. It may also be possible to rationalise the distribution system in the light of reduced end use. Investigations into reduced leakage, improved insulation, reduced supply pressure etc. may also increase distribution efficiency.

Before looking at the conversion efficiency, good reduction opportunities should already have been identified. In reality it is often more difficult as end usage is the most difficult aspect to change.

In looking at a process or large consumer the aim is to answer a number of questions. An example of a pump is discussed below:

Question Rationale Why is energy required, and what is the process/plant item doing? Familiarisation with the process. Is the use necessary, and do we need to pump the fluid? Load reduction opportunities. Can the heat demand of the process be reduced? Investigate heat recovery opportunities Do we need to pump all the fluid all the time? Can we better control the pump to meet our needs and reduce energy consumption?

Improve control and match generation to demand.



Question Rationale Is the pump motor larger than it needs to be? Is the pump correctly sized for the task?

Oversized equipment run inefficiently and waste energy.

Alternative ways to meet the need? Old practices are not always the best ways to do a job. Do we need to pump the fluid at all? Could we use a gravity tank, is there some other method of accomplishing the task?

The situation may have changed considerably since the original design and the pump may not be required at all or a much downsized version may be sufficient.

In any situation the focus should be first drawn on the most significant energy users. With the energy breakdown undertaken combined with the list of users mentioned in the third chapter, the major users for each energy source should be easy to classify. This will help in identifying significant saving opportunities and maximizing energy as well as cost savings.

6.2.2. Energy distribution Some rationalisation of distribution systems may be possible. There are several issues that need to be investigated when assessing distribution systems. First of all an assessment needs to be made to determine whether it is economic to decentralise certain loads. Identify any redundant pipe work and make sure it can be removed. Long pipe runs should also be an area to focus and make sure that pipe work is appropriately sized.

For the purposes of this module a steam distribution system is used as an example. Below are a number of the issues to be addressed.

Comparison of useful / parasitic loads: The actual product energy demand needs to be determined. Then the proportion of the total demand that is made up of parasitic loads such as pipeline pressure drops or pumping demands should be estimated.

Pipe work: The correct sizing of pipe work is important. Retrofitting over time can exceed the capacity of base systems and increase pressure drop losses. Conversely, an older site where production plants have been decommissioned leaving an over-sized steam main may suffer from higher than expected standing losses. Insulation is also important, as proper lagging can help to reduce distribution losses significantly. There are several international standards for insulation; one useful reference guide is BS5422 (2009).

Pumps and fans: For centrifugal pumps and fans the electrical power requirement varies as a cube law proportional to pump speed. The application of variable speed control can produce substantial savings in suitable applications.

Steam Pressure: The higher the steam pressure the greater the losses in heat and leakage terms from the system. Flash losses in condensate and pressure losses in pipe work will also be greater.



Condensate Return: All recoverable condensate should be returned to the boiler feed water tank. Check to see how whether condensate is recoverable and if it is metered. If condensate return is metered, make sure that the rate is as expected.

Similar issues should be investigated for other distribution systems, such as compressed air circuit, hot water, hot oil, etc.

6.2.3. Energy controls Once the process energy demand has been established and distribution systems assessed, attention can turn to the control of systems to deliver the required energy. No / low cost savings can frequently be realised by just improving the way the process is controlled. Controlling is very significant for compressed air, steam and hot oil systems.

For example, sequence controls for two or more compressors needs to be optimised to ensure that the compressed air system delivers only when there is demand for compressed air. More sophisticated control systems are now available that makes multi compressor installations more efficient.

When a system has an off-load control, there is a pre-set pressure range such that the compressor off loads at the higher value and loads at the lower. However, the main drawback is that an unloaded compressor will still consume between 20-40% of its full load power for on/off control and 70% for Modulation Control.

For cases where several compressors of varying sizes are installed the selection of the most suitable compressor available for the prevailing duty is critical in terms of energy efficiency. The relative efficiencies of the machines should also be taken into account before setting up the control system.

6.2.4. Energy conversion To achieve savings in this area demands knowledge of the relevant technologies and what is current best practice. Design data on the plant concerned should be obtainable from documents on site or from the equipment manufacturers. Measured performance can then be compared to best practice, design or previous performance data.

System Things to check

Boiler

Fuel / air ratio

Exhaust gas temperature

Feed water temperature

Boiler blow down rate and total dissolved solids (TDS) levels

Air Compressors

Air intake temperature

Moisture content of air intake

Variance in the demand for compressed air



However, there are simple actions that can be taken to improve the conversion efficiency of a system. The list below summarises the items that need to be checked in an energy audit survey regarding conversion efficiency of boilers and air compressors:

Further information regarding these can be found in the appendices at the end of this guide.

6.2.5. Energy supplies Energy supply and conversion often go hand-in-hand, as the availability of primary fuel will often determine the selection of boiler or power generation technologies. If there is a sufficient base load requirement for heat as steam or hot water and an acceptable supply of clean fossil fuel is available, a combined heat and power plant may make economic sense; in an appropriate location with access to a sustainable, managed forestry industry, there may be biomass available as an alternative fuel. Combined Heat and Power (CHP) or on-site generation may also be appropriate if there are grid capacity or reliability issues, and the energy audit should consider alternative fuel sources if appropriate.

6.3. Benchmarking and baseline definition A performance baseline is essential if changes are going to be made to process or service operations, so understanding the starting point is a critical stage in energy auditing. Often this will be a simple performance indicator expressed as kWh of energy consumption per unit of output (SEC). This is a useful measure when comparing performance with sister plants or competitors (if that information is published). Knowing where the plant stands in relation to an industry benchmark is helpful in deciding where investment or operational change is required.

The disadvantage of using SEC as a benchmark is that the production volume inevitably dominates the calculation and it is all too easy to explain poor performance by saying that production was lower than usual. A better tool is to find a relationship between energy and production activity, so that variance needs to be explained in terms of poor or good operation or equipment malfunction. Managers can use such a variance analysis to catch and rectify poor performance at an early stage.


7 IDENTIFYING OPPORTUNITIES

7. IDENTIFYING OPPORTUNITIES Once the data collection phase of the audit is completed, the identification and costing of potential improvement measures and projects begins. This gives an opportunity to collate any ideas and to generate a prioritised list of potential measures.

It is important at all stages to discuss ideas with the appropriate people to see whether similar measures have either been tried before and failed or considered before and rejected because of process or other limitations.

Results should be communicated with the relevant stakeholders in order to evaluate the various measures. The objectives at this stage are to:

1) check what measures will work 2) check what measures are appropriate 3) study interaction with the measure and other projects 4) establish the cost of the measure

5) calculate benefits arising from the measure 6) compare rival measures and prioritise 7) reach conclusions 8) create action plan

For each of the measures identified there are issues that need to be taken into consideration. There should be a check to ensure the measures are acceptable for:

n Environmental and Health and Safety reasons: Make sure the measure does not have a knock on effect and it does not breach existing or proposed regulations.

n Best solutions: Gains should be examined over the long term, not just the short term.

n Acceptable Solution: Take into account any other reasons that may prohibit the implementation of the measure.

n Approximate Costing: Budget figures for suppliers to give approximate area for costs

It is also important to inform staff about measures that are being discussed and what the end goals are. This is vital, especially where measures include projects involving the installation of new equipment or controls. These measures will not deliver the expected savings without people being trained to use the new equipment.

Last but not least feedback should be requested from the staff / operators. Ideally, the appropriate staff should be included in the survey. They are familiar with the various processes on site and they should be able to highlight energy wastages, process inefficiencies and to identify opportunities.


7 IDENTIFYING OPPORTUNITIES 7 IDENTIFYING OPPORTUNITIES

As best practice all identified opportunities should be recorded in a database. This will allow for future review of the status of each opportunity making sure that nothing is missed. A database of opportunities helps to inform an estimate of the expected savings. An example of the database as found in the software tool that accompanies this guide is shown below:

The database should be reviewed frequently and be kept up to date.


8 COST BENEFIT ANALYSIS

8. COST BENEFIT ANALYSIS Opportunities generally fall into three categories:

n No-cost behaviour change, such as switching off lights, reducing thermostat set points or fixing leaks. These should need no financial justification and be implemented as a high priority. The decision to implement such projects should be within the remit of the plant manager, maintenance manager or energy manager. A certain level of awareness and procedures may need to be put in place to facilitate these.

n Low Cost projects that need little additional investigation and are likely to have a rapid return on investment but do require some expenditure. Ideally these should be funded from the revenue budget as they are likely to recoup the expenditure within the same financial year. The decision to implement such projects should rest with site management and should be integrated with maintenance schedules if possible.

n Capital investment projects that either require significant funding despite a short payback, or have a payback period in excess of one year. These usually require a financial justification and an investment requisition to be submitted for board approval.

When considering capital investment projects, some far-sighted companies will ring-fence a proportion of capital for energy, environment or health and safety compliance projects. However, most companies will rank all investment opportunities in the same league table and implement those with the best rate of return.

Energy projects will usually fall into a low risk category of investment – they rarely involve adopting leading edge or untried technologies and the longer term value of savings is likely to rise in step with increased energy prices.

In order to present an effective case to management to gain any form of commitment and investment, a transparent financial and technical appraisal must be put forward. Management will look more favourably on proposals that represent the best investment, that optimise benefits, that sufficiently address risk management issues and which include satisfactory performance analysis.


8 COST BENEFIT ANALYSIS 8 COST BENEFIT ANALYSIS

In putting a case together the steps below should be followed:

n Identify potential savings. n Identify measures. n Establish the costs and savings. n Calculate the key financial indicators:

o Simple payback; o Gross/net returns and their rates; o Discounting and net present value (NPV); o Index of profitability (IOP).

n Optimise the return. n Establish the size of the overall budget. n Optimise capital expenditure. n Prioritise the projects.

The main issues that result in a failed case are poor base data, poor justification and the lack of a ‘do-nothing’ scenario. Ensure the figures add up and can withstand scrutiny.

Other factors that may make the case more favourable are including information on maintenance savings and estimating increased productivity.

Whilst information describing simple payback, is easily presented it can lead to misleading results. In some organisations this may not be in their best interest as they will not lead to the best investment choice. This is because simple payback does not take into account savings over the lifetime of the project or the time value of money. Therefore, better simple metrics are net return (which is a measure of the benefit) and average net rate of return, which annualise this benefit over the lifetime of the project.

Some organisations use discounting and net present value (NPV) for project evaluation. However, even sophisticated metrics have their limitations. For example the disadvantage of NPV is that it does not take into account the initial capital (CapEx) outlay.

The most transparent metric is probably the index of profitability (IOP) which does take into account the CapEx outlay and should be at least 1 for a project to be considered.

Larger projects can be financed in a number of ways such as energy services contracts and shared savings.


9 REPORTING

9. REPORTING The report from an energy audit and opportunities survey may need to address a number of different audiences; the way in which the report is presented will depend on the individual circumstances; a single report may be produced that contains all the information collected during the audit and presented in different ways, or it may be preferable to produce different reports that are tailored to suit each intended audience.

Senior management will want to see headline figures for current total energy consumption and cost, specific energy consumption per unit of output and, where relevant the site’s carbon footprint. The management team will also need to see summaries of the key cost saving opportunities, ideally in a simple table showing a brief description, estimated energy and cost savings, implementation costs and simple payback calculations, prioritised by return on investment.

Energy managers will want to see a more detailed analysis of energy performance, including where possible a breakdown of energy consumption by department, energy targets and recommendations for additional metering and energy reporting processes. This will enable them to provide timely performance reporting for site management and flag any incidences of poor performance. They will also need a summary of opportunities, but with more detail of how to implement projects or what additional investigations are required to reach a go/no go decision for investment purposes.

Production managers will want to see energy allocations for their specific area of responsibility and any operational improvements that may be possible with limited investment or behaviour change. They need to see that they can track the impact of changes and may well be the driving force behind additional metering requirements.

The engineering manager will want to see details of any opportunities that may involve equipment modification or new process plant. He will be concerned with the availability of resources to design, plan, procure and install any new technology. He will also be concerned that he has the resources available for any maintenance programmes such as regular air leak or steam trap surveys.

9.1. Template With these wide-ranging expectations, typical report templates may include the following sections:

1) Management Summary.

2) Action Plan / Recommendations.

3) Review of site energy consumption and cost, including a breakdown of energy use by department where possible.

4) Discussion of existing energy reporting procedures.


9 REPORTING 9 REPORTING

5) Process energy performance, broken down by department. Use this section to discuss regression analysis, target setting and performance reporting.

6) Site services energy performance – boilers, compressed air, process refrigeration, other cooling systems, water and effluent, building services (HVAC, lighting, domestic hot water).

7) Summary of opportunities. Different summary tables according to the sites requirements may be presented; these may include summary tables of opportunities by fuel type, or by no cost/low/capital cost type. Summaries of each opportunity should also be presented, an example format is presented in the figure, right.

8) Metering and measurement of energy use. Indicate any gaps in measurement and recommendations for additional metering.

9) Appendices. Include any detailed calculations, assumptions, spreadsheet models and equipment data sheets here.

The software tool includes a number of tables and graphs that may be suitable for use in reporting of items 3 and 7 above.

Opp ID Opportunity Title

Energy (kWh)

Cost (MUR)

CO2 (tonnes)

Capital Cost (MUR)

Payback (month)

Priority

OPP-00020

Recover heat from air compressors

250000 7500 67 10500 16.8 High

Process / Technology Description Recover heat from the exhaust air from the air compressors

Rationale Recovering heat from the compressors will save fuel oil during the winter months

Opportunity Description Duct the exhaust air from the compressor coolers into the factory next to the locker room.

Risks Overheating the lobby area during a mild winter

Next Steps Obtain firm cost for ducting


10 POST-AUDIT ACTIVITIES

10. POST-AUDIT ACTIVITIES 10.1. Action plan The prime objective of an energy audit is to leave the site with an action plan that will, if implemented, result in cost savings, increased profitability and sustainability for the business. Therefore it is important to follow up any recommendations with offers to support the site in implementing projects. This support could be as simple as identifying equipment suppliers, or could require detailed design, procurement and project management support. Many companies are not focused on energy management and do not have the in-house skills to progress many opportunities; they need advice and support to realise the potential energy savings.

10.2. Continuous improvement cycle Energy auditing should form part of a wider energy management programme such as that described by ISO 50001, “Energy Management System”, and the accompanying Code of Good Practice for Industry. It is not a one-off process; energy audits or plant energy walkabouts should be repeated frequently to ensure the efficient operation of the plant. The position will need to be determined again and re-assessed against the baseline and benchmarks to review progress.

Creating opportunities for regular energy walkabouts by those responsible for energy use, and involvement of operators within this process is a key part of increasing awareness and engagement with the workforce.


11 MONITORING & MEASURING EQUIPMENT

11. MONITORING & MEASUREMENT EQUIPMENT There are various useful tools that can be used during the energy audit. A list of useful tools is shown below:

Permanent or portable electrical meters: When the appropriate sub-metering is not installed, portable meters can be used to measure energy consumption on specific equipment or lines. This will not provide the annual energy consumption of the equipment but it will give valuable information about their energy consumption.

Light meters: Lighting levels can be measured with light meters. When the lighting levels in a room is known, it can be determined whether or not there is excessive lighting. This will help to identify energy saving opportunities by removing excess light fittings.

Temperature probe: The temperature on distribution pipe work, water tanks, etc., can be measured with temperature probes. This will give an indication of the amount of heat losses that can be used to justify insulation improvements.

Thermal imaging: Thermographic imaging is a diagnostic survey technique using an infrared camera for locating areas of temperature differential. Thermal images can help to identify heat losses and reduce energy wastage.

Combustion analysers: Portable combustion analysers are a useful means of checking boiler efficiency or burner performance. Using electrochemical sensors the hand-held device takes a sample of flue gases and tests excess oxygen, carbon monoxide and dioxide. Coupled with the stack temperature these measurements are converted into the fuel conversion efficiency.

Ultrasonic leak detectors: These are especially useful for detecting compressed air leaks in a noisy factory environment and can also be used to detect faulty steam traps. Equipped with a pair of headphones and a directional acoustic sensor, the leak detector can be used to scan the factory and any leaks will be detected as a specific frequency above the general background noise. The user then homes in on the source of the leak, confirms and tags its location and notes the strength of the leak to help prioritise the repair programme.

In a large factory a leak detector such as this can pay for itself in a matter of weeks with regular and frequent surveys.

Monitoring and targeting equipment such as moisture content measurement, run-hour counters on air compressors and ammeters on motors can also help in capturing energy data and identifying energy saving opportunities. Be alert for control panels on inverter motors where kWh readings are often displayed but rarely recorded.


12 WATER AND WASTEWATER

12. WATER AND WASTEWATER Although water is not addressed specifically in this guide, the user is encouraged to consider water as an important factor in energy management. Water is both an energy consumer (through pumping and treatment costs) and a carrier (as a heating or cooling medium), and can also be a source of energy (for example in a heat pump). Therefore the same principles apply to managing and minimising water use:

n measure usage as a function of production;

n define a baseline reflecting current plant performance;

n set targets based on known process performance characteristics;

n monitor consumption against targets and compare against the baseline;

n make a change (process, operational or management);

n measure the impact of that change;

n review targets, reset baselines and continue the management cycle.

Examples of poor water management might include:

n fixed flow circulation of cooling water through coolers that are not operational;

n once-through flow of water on liquid ring vacuum pumps;

n discharge of hot cooling water direct to drain;

n use of high quality process water for cleaning or cooling.

Industrial wastewater is also a potential source of energy, either because it is discharged hot directly to drain or it is cooled before discharge. It can be a potential source of process heat such as pre-heating dyehouse make-up water, or at higher temperatures can be used as a heat source for heat pumps.

As with all forms of energy, avoid unnecessary use, fix leaks as soon as practicable and consider recycling water several times depending on the quality requirements of the process.


Appendix A – INDUSTRIAL LIGHTING

Appendix A INDUSTRIAL LIGHTING Lighting is essential for making the work environment safe and for allowing staff to perform their tasks comfortably. It can be a significant energy user accounting for up to 40% of an organisation’s electricity bill. Even making small adjustments to lighting can significantly improve the working environment, help reduce electricity consumption and, at the same time, minimise CO2 emissions and save money.

A.1 Identifying energy saving opportunities Energy savings in lighting systems can be realised in a number of areas. When starting out looking for opportunities the following suggests a simple approach that could be used:

n Assess the lighting levels. Are the lighting levels suited to the application and can excess lighting be avoided?

n Assess the lighting technology type. Is it the most appropriate and efficient for the given application? Is the rendering and colour suited to the application?

n Assess light distribution. Is the majority of the light delivered to the intended work area and is it correctly dispersed over the work area? Are the most efficient luminaries used and properly cleaned and maintained?

n Assess the lighting controls. Ensure the lighting is controlled in such a manner as to only deliver the right amount of light to the right areas at the right times only.

Definitions:

Lamp: the source of the light (i.e. the bulb)

Luminaire: a light fitting that incorporates the lamp

Watt (W): Measure of electrical power used by the lamp.

Lumen (lumen): Measure of light energy emitted from a source.

Efficacy (lumens/W): the amount of light provided relative to the amount of energy used, once the lamp has reached full brightness. The higher the value the more light is gained for the same energy.

Colour rendering (Ra): the ability of a lamp to show surface colours accurately. The lower a lamps Ra value relative to an ‘excellent’ value of 100, the poorer the lamp’s colour rendering ability.

Colour temperature (K): Measure of the colour appearance of a light source ranging from ‘warm’ light (i.e. the light a candle produces) through to ‘cool’ light (i.e. a bright white fluorescent light). Lamps below 3,300 K are classed as ‘warm’ whilst those above 5,300 K are ‘cold’.

Re-strike: the time taken for a warm discharge lamp to reach 80% of maximum light output when power is interrupted.



The following sections provide background information to assist in the assessment of lighting systems.

A.2 Recommended standard maintained illuminance Providing lighting to higher levels than is necessary wastes energy and is expensive. Ideal lighting levels in industrial applications are presented in the table:

Illuminance (lux) Task / Activity / Interior

2 Healthcare ward night lighting

20 Unstaffed gangways

50 Remote operated processing, person-sized under-floor tunnels, cellars, underpasses, healthcare corridors (night), cable tunnels, indoor storage tanks

100 Circulation areas, entrance halls, corridors, rest rooms, store and stock rooms, healthcare wards (general), changing rooms, auditoria

150 Stairs, escalators, travelators, loading ramps/bays, staffed gangways

200 Toilets, foyers, lounges, plant rooms, switch gear rooms, turbine halls, archives, library bookshelves, monitoring automatic processes, dining rooms

300 General machine work, manufacture and assembly (rough), retail sales area, packing and handling areas, welding, office (lowest), reception desk, filing, exhibition general lighting, sports halls, teaching areas

500 First aid rooms, laboratories, kitchens, writing, typing, reading, data processing, CAD workstations, conference/meeting rooms, offices (highest), switchboard, post room, medium machine work and assembly, general inspection areas, control rooms, retail till area, hairdressing

750 Grinding and engraving, fine machine work and assembly, critical inspection and repairs, paint spraying and polishing, technical drawing, ceramic decoration, meat inspection, chain stores

1000 Healthcare examination and treatment, colour inspection, precision decorative grinding and hand painting, precision assembly, quality control, typesetting, gauge and tool rooms, retouching paintwork, cabinet making

1500 Electronic workshops, testing, precision assembly, fine work and inspection

2000 Steel and copper engraving, assembly of minute mechanisms, finished fabric inspection

100/500 Entrance halls/enquiry desks

100 (at floor level) Corridors, passages and stairs

300-500 General offices and computer work stations

300/500/750 Rough/medium/fine bench and machine work

300/500/1000/1500 Rough/medium/fine/precision electrical equipment manufacture

100/300/300 Bulk storage/small item racking/packing and dispatch



A.3 Lighting power consumption For lighting power consumption, general benchmarks have been set by surveying existing installations. The power consumption depends on the lighting level required, as shown below.

General Factory Lighting Benchmark Consumption (W/m²)

300 Lux 500 Lux

General lighting for open areas 5 – 6 8 - 10

For warehouse areas the power consumption benchmark is dependent on the aisle width and height.

Warehouse Lighting

Aisle width (m)

Mounting height (m)

Benchmark Consumption (W/m²)

300 Lux 500 Lux

1.2 4.5 8 14

2.4 6.5 8 16

3.0 8.0 9 17

A.4 Colour rendering and appearance Colour rendering should be considered when selecting lighting. Each type of lamp provides a different colour of light. In general the more detailed work being performed the closer to white light will be required. Colour rendering is measured according to the Colour Rendering Index. Each lamp type is placed in a colour rendering group depending on its colour rendering index.

The colour appearance of a light source can range from ‘warm’ light (i.e. the light a candle produces) through to ‘cool’ light (i.e. a bright white fluorescent light). Choosing a lamp with the wrong appearance can have disastrous results in businesses where identification or matching is important, for example, food processing, textiles and retail.



Colour Rendering Colour rendering performance

Colour rendering ID

group

Colour rendering index (Ra)

Typical application

Excellent 1A =>90 Wherever accurate colour matching is required, e.g. colour inspection

Good 1B 80-89 Wherever accurate colour judgements are necessary , e.g. shops and offices

Moderate 2 60-79 Wherever moderate colour rendering is sufficient

Poor 3 40-59 Wherever colour rendering is of little significance

None 4 20-39 Wherever colour rendering is of no importance

Colour appearance Colour appearance class

Correlate colour temperature Typical application

Warm Below 3,300 K Domestic-type situations Intermediate 3,300 – 5,300 K Combined daylight and electric light

Cold Above 5,300 Situations where a cool appearance is required



A.5 Characteristics of different lamp types The table below shows the characteristics of different lamp types commonly used in offices or production areas and workshops. For lighting in external areas, such as car parks and storage areas, low pressure or high pressure sodium lighting with photosensors is considered best practice.

Lamp Type General Colour Rendering Index (Ra) Task illuminance (Lux) Average installed power density (W/m²)

Offices

Fluorescent – triphosphor 80-90 300 7



Compact fluorescent 80-90 300 8



Metal halide 60-90 300 11



Production areas, workshops


Fluorescent– triphosphor 80-90 500 10







High pressure sodium 40-80 300 6






A.6 Lighting controls The use of lighting controls will depend on the area use. The decision tree below (section A.6.1) can be used to determine the best practice controls.

A.6.1 Movement sensors and heat sensors These are used to detect whether people or vehicles are present. They work on movement or heat detection. Best practice is to have sensors for individual banks of lights or even on individual fittings. Individual banks of lights will be fitted with controls from a single sensor if the bank of lights covers an area of similar usage, e.g. single sensor for lighting in warehouse racking. Where a switched bank of lights covers more than one area of use it is more cost effective to control individual fittings.

Consideration should be given to installing sensors in corridors, warehouses and storage areas. In these areas there is normally only temporary occupation and often for only a few minutes at a time. Occupancy sensors are suitable for controlling fluorescent, compact fluorescent and induction lighting. Occupancy sensors are not suitable for controlling high pressure sodium or metal halide lighting.

A.6.2 Photosensors Photosensors are used to switch off lights where natural daylight is available. Best practice is to install these on light banks or fittings beneath skylights or next to windows. Individual banks of lights would be fitted with controls from a single sensor if the bank of lights covers an area of similar usage. Ideally the rows of lights should be placed in parallel to the windows and when there is adequate natural daylight available the row closer to the window will switch off or dim down.

For external lighting best practice is to switch external lighting off during daylight hours.

Photosensors can be used for all types of light fittings. It is important with photosensors to regularly clean the sensors to remove any layers of dirt.

A.6.3 Automatic control units Where areas are not used 24 hours per day it is best practice to automatically switch off lighting when the area is unoccupied. This can be done by using sensors as mentioned above or with simple timer controls.



If time switches are fitted, make sure they have a programmable calendar and that working hours are correctly programmed in, including weekends, holidays etc.

A.7 Reviewing the properties of lighting systems The following table presents a number of technical properties of lights and lighting systems. Consult this list when considering efficient lighting, particularly when thinking about a new design.

Consider How? Why

Illuminance Check the lux levels (lumens/m2) needed for different areas. Table in section 8 is a guide. Actual measurements can be made with a lux level meter.

The amount of light needed will depend on what activity is taking place in the area and regulation.

Consider how lamps age and work can out how long they are expected to be in place.

Old lamps emit less light for the same amount of energy. If lamps will be in place for a long time, illuminance may be affected.

Efficacy The higher the number, the more efficient the lamp The more light a lamp can produce, the fewer lights will be needed to meet needs.

Colour rendering and temperature

Check the Kelvin and Ra of the lamp. Choosing a lamp with poor colour qualities can have disastrous results in businesses where identification or matching is important, for example, food processing, textiles and retail.

Lamp life Check the estimated hours of light. By measuring lamp life, you may find that a higher capital expenditure is justified. Choosing long-life lamps for areas which are difficult to reach, could save on the maintenance costs in replacing them less frequently.

Ask suppliers about different control gear that might lengthen the life.

High frequency control may extend the life of the lamp.

Warm-up and re-strike times

Ask your supplier for details If an application needs a quick warm-up or re-strike, such as security lighting, certain lamps will not be appropriate.

Luminaries Identify which luminaires are available / required for types of lamp, and check the light output ratio (LOR) of each.

Luminaires affect the direction and output of light from the lamp. Choosing efficient luminaires can reduce the number of lamps needed.



A.8 Lighting checklist Lighting Systems Walkabout Checklist Compile an inventory of lighting systems on site and prioritise according to annual energy use (size x running hours). Conduct the following checks on each system: NOTE: Many lighting systems require specialist knowledge about their operation; always seek specialist help where you are uncertain about energy saving measures to implement as this will help prevent unintended outcomes.

Check Complete Y/N Lamps 1. Identify opportunities to upgrade to higher efficiency lamps. Look to migrating to LED and T5 florescent

technologies. Especially look to migrating away from mercury vapour lamps. 2. Where fluorescent lamps are installed check they are T8 or T5 types and are fitted with electronic

ballasts. 3. Check that the lamp colour rendering and light appearance is appropriate for the work being carried out. 4. Can florescent lamps with quick on-off control be used in low use areas in place of high pressure

sodium or metal halide lamps? Luminaires, diffusers and shades - Maintenance 1. Check shades, diffusers and luminaries are clean and are cleaned on a scheduled basis. 2. Check all luminaires are suited to the application. 3. Look for opportunities to optimise use of natural daylight and eliminate any glare issues. 4. Check skylights are clean and are maintained on a regular basis. Natural daylight is free; maximising its

use has very low cost and can realise significant savings. Lighting systems Consider the following control measures to switch lights off and / or reduce the numbers of lights in use: a. automatic sensors / controls. b. manual switch off. c. use zone controls. Look to apply the above control measures in the following contexts: 1. Review lighting levels, identify areas where levels are excessive. 2. Identify unoccupied areas / areas where occupancy is low (e.g. warehouses & storerooms). 3. Identify opportunities to use task lighting. 4. Identify opportunities to increase natural lighting including background lighting. 5. Identify opportunities to increase reflection of background light. 6. Check exterior lighting is off during daylight hours and that unoccupied areas are not lit.


Appendix B – COMPRESSED AIR

Appendix B COMPRESSED AIR Compressed air is sometimes regarded as the fourth utility after electricity, water and gas, however it is usually an expensive resource for a business. Producing compressed air takes more than 10 units of electrical power to provide 1 equivalent unit of compressed air. This means a small decrease in compressed air usage can result in significant electricity savings. Compressors that are usually left on when there is no demand can waste energy as power is used to supply air through the leaks in the distribution system, and even when off-load compressors can use up to 20-70% of the full load power. In addition fewer run-hours will reduce maintenance costs. Typical compressed air systems are capable of up to 30% energy savings by better control, maintenance schedules, a comprehensive leak detection and repair scheme, machine selection and heat recovery. Further savings can be achieved by reviewing the current end users of compressed air and identifying suitable alternatives which may be more energy efficient.

B.1 Identifying energy saving opportunities Energy savings in compressed air systems can be realised in a number of areas. When starting out looking for opportunities the following suggests a simple approach that could be used:

n Review compressed air users. Determine whether compressed air is being used appropriately and not wastefully. Are there alternative technologies that could perform the same function more efficiently?

Technology Overview Compressor: takes in air and compresses it to the required pressure. Air receiver: ensures that the system can cope with variation in demand by acting as a reservoir to store compressed air. Filters: removes impurities such as dirt that is found in the ambient air. Dryer: removes water and moisture from the air drawn in the compressor. Cooler: cools the hot air as it leaves the compressor to remove moisture.

Drain trap or separator: removes the condensate as the air cools.

Definitions Absolute pressure (bara): The pressure measured from a baseline of a perfect vacuum. Denoted by (a) after the unit of pressure. Absolute pressure = Gauge pressure + Atmospheric pressure. Gauge pressure (barg): Pressure measured relative to ambient atmospheric pressure at sea level, it is 1 atm less than the pressure in the atmosphere. Off-load: The compressor is running and consuming power but is not delivering air. On-load: The compressor is producing air, either at part load or full load. Pressure drop: The drop in pressure between any two specified points in a system.

Dew-point: The temperature at which the water vapour will start to condense out of the air.



n Determine base load consumption. Measure compressed air energy use when normal site operations have stopped. Identify what is essential and what is not. At the same time look for leaks in the compressed air system.

n Review operational requirements. Look for potential to minimise pressure set points. Review air distribution system (branch lines etc.) and ensure the delivery system has been optimised; look for bottlenecks causing excessive pressure drops. Look for opportunities to zone pipe work systems and isolate sections not in use or even cap off redundant sections. Check air treatment systems are suited to the quality of air required and are not excessive.

n Review sources of compressed air loss. Identify leaks through a leak detection survey. Review operation of drain traps.

n Review air compressor controls. Develop a profile of the site compressed air demand. Check whether compressors are being switched off when there is no air demand. Understand how compressor output tracks demand and use this to review on load and off load operation, check for VSD controls and sequencers and ensure they are configured correctly.

n Examine heat management. Look at intake air temperatures and check if they can be reduced; look for heat recovery opportunities.

n Review maintenance regimes: Check filters, dryers and drain valves are properly maintained and not causing excess energy use.

The following sections provide background information to assist in the assessment of compressed air systems.

B.2 Detecting leaks 1) Listen – Make sure the compressor runs without using any air tools or equipment and when there is as little background noise as possible walk

around the system listening for hissing or rasping sounds. Check all joints, flanges and valves carefully.

2) Look – Run the system without using air tools or equipment and apply a soapy water solution to all pipe work (especially joints) and then look to see where it bubbles up, indicating air leakage.

3) Ultrasonic leak detection equipment – Ultrasonic equipment can detect compressed air leak in a noisy environment effectively.

4) After identifying the location of the compressed air leaks you can tag the place where the leak is and report it to the maintenance team. As a minimum, checks for leaks should be carried out every three months.



B.3 Drying and filtration of compressed air

B.3.1 Contaminants Different applications in the factory may require different quality compressed air, in terms of moisture, oil content and dust content. Air compressors draw in various different contaminants from three sources as follows:

B.3.2 Energy for filtration There are a number of methods for drying and cleaning compressed air prior to use. Usually dust filtration will be required where desiccants are used. The running costs of different methods can vary considerably.

The energy consumption against the achieved air quality (in terms of dew point), of several treatment types is shown on the table below. It also shows the additional spend on energy expressed as a percentage of the basic cost of compressed air.

Dew point achieved Dryer Type Typical levels of filtration installed Additional Energy Costs,

% of Compressor Costs

+10ºC Deliquescent Nil 1% +3ºC Refrigerant General purpose 5% -20ºC Membrane High efficiency 28% -20ºC Waste heat regenerative desiccant Depends on compressor configuration 3-5% -40ºC Desiccant heatless High efficiency before, and dust removal after 10-15% -40ºC Desiccant heated or external blower High efficiency before, and dust removal after 8-12% -70ºC Desiccant heatless High efficiency before, and dust removal after 21%

Atmosphere: Water vapour, Dirt, Atmospheric pollution Compressor components: Oil, Oil vapour, Wear particles, Carbonaceous products from compressor oil Piping system: Pipe-scale, Rust: sludge



More energy is required when:

B.3.3 Classification of contamination In specifying compressed air treatment it must be clear what quality of air is required for each part of the plant. ISO 8573.1 defines the standard air quality parameters. As can be seen on the table above, over specifying compressed air quality is expensive.

The table below shows the contamination classes for major contaminants.

Quality class Dirt particle size (microns)

Dirt concentration (mg/m³)

Dew point (ºC) (ppm vol) at 7 barg

Oil including vapour mg/m³

1 0.1 0.1 -70 (0.3) 0.01 2 1 1 -40 (16) 0.1 3 5 5 -20 (128) 1 4 15 8 +3 (940) 5 5 40 10 +7 (1240) 25 6 N/A N/A +10 (1500) N/A 7 N/A N/A N/A N/A

The actual needs should be assessed before investing in a new treatment system, or when reviewing energy saving opportunities with the existing system. This will help to make the correct selection. Unnecessary air treatment will lead to increased energy use. Where high quality air is required for only a few applications it is best practice to install local filters and dryers to the specific application and not to treat the whole compressed air supply to the highest standards required.

B.3.4 Filtration Filters are used to remove contaminants from the compressed air. They can be fitted before and after the dryer and also at the point of use. If there are undersized, incorrect, poorly maintained or too many filters used, the compressor will generate compressed air at a pressure higher than required to

The generation pressure needs to be increased to overcome the pressure drop across the dryer and the accompanying filters. The additional equipment needs additional energy to run (usually electricity). There are air losses when purging.



overcome these obstacles. On average increasing the generated pressure by 1 barg incurs a 7% additional energy cost. Pressure drops (such as those caused by poor filter maintenance etc.) and energy consumption have a positive linear relationship, with greater costs occurring at higher pressure drops.

The minimum possible number of filters required for the duty should be used and all filters should be equipped with a pressure differential gauge showing when the filter needs cleaning or replacing.

B.3.5 Drying The water must be removed from the compressed air as it cools. Dryer performance is quoted in terms of pressure dew point.

Some common problems associated with dryers include:

Simple measures for achieving more efficient drying include:

B.3.6 After-cooler The after-cooler is the first step to remove water and some oil vapour from the compressed air. The water is condensed as the temperature decreases and about 68% of the water can be removed in the after-cooler when temperature is deceased by 35oC. Usually the power requirement of the after-cooler is included in the total package electrical consumption. The after-cooler needs around 2% of the package power.

B.3.7 Air receivers The air leaving the after-cooler is fed into the air receiver. Normally the volume of this receiver is about 10% of the compressor rated capacity. Best practise is to place the receiver outside, in a cool location. This will further reduce the temperature of the compressed air and any remaining water or oil will condense. Therefore, if some moisture passes through the after-cooler and the separator, the receiver can help to trap it.

Fit dew-point sensing control to desiccant dryers to minimise the energy used to regenerate desiccant Undertake performance measurements of dryers to check whether required air quality is being met Consider dryer energy saving controls when purchasing a new dryer.

Poor dew-point caused by higher than the design inlet temperatures Poor ventilation Bad installation



B.4 Drain traps

Drain traps are attached to components such as after-coolers, air receivers, dryers and filters to collect condensate. There are various types of drain traps. A brief description is given below.

One of the biggest reasons for compressed air leaks is inefficient or faulty condensate traps. Even though the more efficient manual and timed traps are not expensive, their running costs are high. Therefore a life cycle cost analysis may be necessary.

The table below shows that the most efficient drain traps are the electronic level sensing traps (or electronic condensate drain traps). The figures are based on 7 barg operating pressure.

Drain trap type Air loss

(litres/sec) Energy waste

(kWh/day)

Electronic level sensing drain 0 <0.1

Timed drain (typical) 1 0.41

Disc and steam trap drain 1.8 0.76

Mechanical float drain (stuck fully open) 4.7 1.89

Manual drain (half open) 43.3 17.3

1. Level sensing drain traps. Condensate is detected and discharged only when present without losing compressed air by using an intelligent control system. They are very reliable needing little maintenance.

2. Timed drains. Time settings need frequent adjustment corresponding to changes in ambient conditions and system loads. If set incorrectly compressed air will be discharged or condensate will not be removed causing contamination.

3. Manual drains. They require checking and emptying regularly, but they are usually left partially open to remove condensate but also discharge compressed air. Also, the pressure of the compressed air system can be reduced which can have negative impact on the operation of downstream equipment.

4. Mechanical float drains. These drains are sensitive to dirt. They may stick open, and let compressed air through, or they can be stick closed and cause contamination from condensate.

5. Disc and steam trap drains. Usually, these drains let compressed air through even when there is no condensate. They also emulsify condensate, preventing easy on-site separation.



B.5 Disposal of condensate Oil is classified as hazardous waste and should not be disposed of in sewers. An oil/water separator can be installed as part of a compressed air system and is an efficient way to remove oil from the condensate before it is discharged to the sewer. Separators are particularly recommended for oil-injected compressors. Removing oil from the condensate will not reduce energy consumption, but may help to minimise disposal costs.

B.6 Controls There are a number of different control options available for compressed air, including modulating inlet throttles, on-load/off-load controls, variable speed drives and sequencing controllers:

n When demand is 70-100% of compressor capacity compressors using a modulating inlet throttle are more efficient.

n When demand is less than 70% of capacity it will be more efficient to use an on-load/off-load control.

n When demand is less than 75% of capacity variable speed control is also viable.

Sequence controllers can be used to control multiple fixed speed compressors

B.6.1 Variable speed control Variable Speed Drives (VSDs) can be used to control the operation of positive displacement air compressors, such as rotary screw and reciprocating machines. These present a constant torque load and VSDs become viable when the average loading is around 75% of capacity or less. The actual level of savings is dependent on the control regime of the compressor plant, for example for a compressor operating at 50% capacity the energy saving would be 38% compared against modulating control and 20% compared against ON-OFF only control.

Some existing compressors are not compatible with VSD controls and could be damaged if retrofitted with VSD control; the compressor manufacturer should always be consulted when considering retrofitting VSDs.

Dynamic (centrifugal) compressors use a rotating disk or impeller in a shaped housing to force the gas to the rim of the impeller, increasing the velocity of the gas. The most common way to control the capacity of centrifugal compressors is to modulate inlet guide vanes however this is less efficient at part load; VSDs can be used to successfully control their output with greater efficiency.

B.6.2 Pressure controls The operating pressure of the compressed air system should be minimised, whilst remaining high enough to supply equipment demand and overcome system pressure drop and air losses. For example most plants will operate with a compressed air pressure of 6.3 barg; allowing for a system pressure



drop of 0.7 barg, a maximum compressed air system pressure of 7 barg should be possible. Typically energy savings amount to 4% electrical consumption saving for every 1 bar pressure reduction.

It is not uncommon to find the rated supply pressure for a piece of plant may be specified at one level however there is usually pressure reduction and regulation within the unit, e.g. suppliers specification of minimum 8 barg compressed air, but regulators within the equipment reduce the pressure to 6 barg.

If a small amount of plant requires a higher pressure compressed air supply it is best practice to install a local pressure intensifier (pressure booster) or small independent high pressure compressor just for this application.

B.7 Heat recovery About 90% of the energy consumed by a compressor is emitted as waste heat of which 90% is recoverable. The waste heat from the cooling of compressors is usually relatively low grade however it is commonly suitable for building services and other applications. Generally, air cooled compressors can provide hot air up to 80oC while water cooled compressors can provide hot water up to 95oC.

A feasibility study should be carried out to ensure not only the economic viability but the practicality of installing a heat recovery system. The study should look to quantify the available heat, identify an appropriate sink and its temporal heat requirements and assess capital and life cycle costs and payback period.

Whilst the capital cost for retrofitting a heat recovery unit will vary with every application, in general, the cost of the additional equipment is relatively low, providing a quick return of investment. If the heat can be fully utilised, simple payback periods can be under 2 years.

If the recovered heat displaces electricity then the actual cost for generating compressed air can fall by up to 90%. Even when the displaced fuel source is a cheaper fossil fuel like gas and oil, the savings on the actual cost of generating compressed air are still considerable and can be up to 50% depending on the fuel unit cost.



B.7.1 Heat recovery methods Typical heat recovery methods depending on the compressor type are summarised in the table below:

Compressor Type Heat Recovery

Lubricated vane and screw compressors Heat from cooling water using plate heat exchange

Heat on air cooled machines from oil cooler heat exchange

Use air from air cooled machine for space heating

Oil injected screw compressor Heat from oil cooler

Oil free screw compressor Can provide hot water/hot oil at up to 90ºC. This heat recovery method gives the highest grade recovered heat.

Centrifugal compressors Heat recovered from cooling water

Reciprocating compressors Recover heat for space heating

In water cooled machines can recover heat from cooling water

Lubricated vane and screw compressors Heat from cooling water using plate heat exchange

Heat on air cooled machines from oil cooler heat exchange

Use air from air cooled machine for space heating



B.8 Compressed air systems checklist COMPRESSED AIR SYSTEMS WALKABOUT CHECKLIST Compile an inventory of compressed air systems on site and prioritise according to annual energy use (size x running hours). Conduct the following checks on each system: NOTE: Many compressed air systems require specialist knowledge about their operation; always seek specialist help where you are uncertain about energy saving measures to implement as this will help prevent unintended outcomes.

Check Complete Y/N

End users

1. Review end use / users of compressed air. Identify suitable alternatives which may be more energy efficient.

Compressor 1. Look for opportunities to reduce inlet air temperatures

2. Look for opportunities to implement heat recovery on the air compressors

3. Check condition of air inlet and oil filters & ensure they are clean.

4. Check air and oil coolers are clean and ensure face screens are free of dirt and debris.

5. Check operating temperatures and pressures.

6. Match compressor control methods to the site demand profile:

7. Review the lubrication regime; ensure it is in accordance with the manufacturers specifications.

Treatment system 1. Check filter pressure loss is kept to a minimum and filters are changed at recommended intervals.

2. Check pressure dew point.

3. Ensure the gas pressure is correct on refrigerated dryers.

4. Check the desiccant is changed at recommended intervals on desiccant dryers.

5. Check all drain traps are working correctly using test buttons on electronic systems and manual by-pass valves.

6. Check room ventilation to ensure all equipment is as cool as possible.

Compressed air distribution system 1. Check for leaks or damage, ensure checks are carried out on a minimum three monthly basis.

2. Look for opportunities to reduce pressure set points.

3. Establish the base-load demand and identify opportunities to reduce this.

4. Identify bottlenecks and causes of excess pressure loss; check whether these can be reduced.

5. Review compressor load – unload cycles, ensure compressors are operating for at least 70% of their time in the loaded condition. Increased air receiver capacity can help to improve performance.

6. Check oil levels are correct on airline lubricators.

7. Check point of use filters; ensure they are in good condition.

8. Check the operation of production machine isolation valves.

9. Check distribution system condensate traps; ensure manually operated ones have not been left open.


Appendix C – BOILERS AND FIRED HEATERS

Appendix C BOILERS AND FIRED HEATERS Boilers and fired heaters are the most common methods for converting energy stored in fuel into useful energy to drive thermal processes. All combustion processes depend on effective mixing of the fuel with the correct amount of air to ensure complete combustion and an adequate heat transfer area to get the heat from the hot products of combustion to the process fluids. Common losses include too much combustion air, poor control of fuel air mixing, poor insulation around the combustion chamber and heat transfer vessel, high blow down rates in steam boilers and operating at part loads.

Most industrial processes rely on steam as the heating medium; in some high temperature applications thermal fluids will be used as an alternative. Other processes, such as baking, curing or drying, will use direct heat exchange between the product and hot air. Whatever the combustion process, the opportunities for energy efficiency generally relate to burner operation, insulation or additional heat recovery.

Definitions Absolute pressure (bara): The pressure measured from a baseline of a perfect vacuum. Denoted by (a) after the unit of pressure. Absolute pressure = Gauge pressure + Atmospheric pressure. Gauge pressure (barg): Pressure measured relative to ambient atmospheric pressure at sea level, it is 1 atm less than the pressure in the atmosphere. Condensate: Liquid that is formed because of changes in steam temperature and/or pressure. Flash steam: Steam produced when water or condensate at high pressure/temperature is allowed to drop to a lower pressure. Enthalpy (h): A measure of total energy of a unit of mass. Latent heat (or enthalpy of evaporation) (hfg): The amount of heat required to change the state of water at its boiling temperature, into steam.

Technology overview Boiler: A closed vessel in which water or other thermal fluid is heated. Steam generator: A closed vessel or arrangement of tubes used to generate steam. The steam generator has a series of tubes and steam is kept under higher pressure to prevent steam formation in the tubes. Steam trap: A device used to release condensate from the pipe work and prevent non condensable gases and live steam from escaping from the system. Deaerator: A device used to remove dissolved oxygen and carbon dioxide from boiler feed water in order to reduce corrosion in the boiler system. Steam separator:- A device used to removes droplets of water from pipe walls and suspended mist entrained in the steam itself. Sight glass (or sight flow indicator):- It allows observing the fluid flow in the pipeline to detect blocked valves, strainers or faulty steam traps.



C.1 Identifying energy saving opportunities Energy savings in thermal systems can be realised in a number of areas. When starting out looking for opportunities the following suggests a simple approach that could be used:

n Review the heat demand across the site. Determine the opportunity to reduce heat demand; are there wasteful users, can the overall demand be reduced, can temperature set points be reduced?

n Identify areas of radiated heat loss. Assess the levels of insulation on hot pipe work, equipment and boilers. n Identify steam / thermal fluid leaks. Carry out a leak survey. Examine steam condensate traps and ensure correct operation. n Review and identify potential for heat recovery. Determine whether there is adequate heat recovery on boilers such as economisers on flue

gases and heat exchangers on the blow down systems. and condensate return systems n Optimise condensate return systems. Review condensate return systems and ensure steam recovery is maximised and hot condensate is

returned where possible, or there is adequate heat recovery on waste condensate. n Review boiler combustion efficiency. Check fuel types are suited to the boiler. Analyse exhaust gases and ensure excess air is minimised and

full combustion is achieved. Determine whether oxygen trim controls might be suited to the boiler. n Review boiler performance and heat transfer. Determine overall boiler efficiency and ensure the boiler controls are suited to the heat demand

profile, e.g. modulating / turn down control. Examine heat transfer surfaces and ensure these are operating efficiently, for example the combustion side is free of iron oxide and soot build up and the water side is free of scale build up. Look for opportunities to minimise heat loss when the boiler is not firing, e.g. flue shut off dampers and isolating flows through the boiler.

n Review water treatment systems. Determine whether the water treatment systems are sufficient to minimise build-up of deposits and corrosion in the pipe work.

n Review control systems. Look for opportunities to improve the boiler controls such that the boiler output tracks the heat demand profile and unnecessary firing is limited. Look at circulation systems and ensure pumps and other equipment are shut down within a reasonable time when there is no demand.

The following sections provide background information to assist in the assessment of steam and hot oil systems.

C.2 Improving boiler efficiency

C.2.1 Management and control of boiler load The simplest type of boiler load control is when the boilers operate independently on and off load according to a fixed set-point, such as water temperature or steam pressure. This is inefficient because:

n There is no overall assessment of the site heat demand so more boilers may be fired than is actually necessary.



n With only one high firing rate the boiler may be on load for short periods meaning that standing heat losses when the boiler is off will be a high proportion of the total energy input. Air can be drawn through the boiler when it is off, resulting in increased heat losses through the flue.

n The short firing times will also result in high heat losses from the air purge of the combustion space that must take place before each firing.

n Boiler load controls can be improved by at least using high and low level firing rates. The boilers will only go to high fire if the heat demand from the site is sufficient. Otherwise the boilers remain at low fire, reducing fuel demand. After a pre-determined time, if the process load does not call for additional heat the burner will switch off until the demand returns.

n When operating existing boilers their number and size must be carefully reviewed so that all those in actual use operate as closely as possible to their designed ratings. Decisions are easier if the existing or likely future load pattern is known on an annual, monthly and daily basis. On existing plant a load survey will also reveal opportunities to reduce peaks in demand.

n Boilers in-use should be operated as continuously as possible, the maximum firing rate being adjusted to match the maximum demand for heat. This is preferable to frequent on-off operation of a boiler fired at too high a rate. On-off operation aggravates heat losses to cold purging air.

n The wasteful practices of over firing and blowing safety valves can be reduced if increases and decreases in steam demand can be anticipated by using steam flow to initiate changes in firing rates rather than (or in addition to) steam pressure. When heavy and sudden demands for steam are unavoidable large-capacity ‘thermal storage’ boilers or some other thermal accumulator should be considered as an aid to steadier firing conditions.

n Sequence controllers can be a useful method of managing automatic boiler plant. The controller fires the best combination of boilers to meet the particular demand, avoiding the use of excess capacity.

n Sparging a standby boiler with steam generated by more efficiently operating boilers is one option of keeping an otherwise idling boiler up to temperature and pressure. Electrical savings can be made as there will be no need to operate the boiler fans.

n The temptation to make economies by reducing the operating pressure of steam boilers should be resisted. The dryness of steam at the point of use may well suffer and distribution mains may be inadequate. It is better practice to reduce pressure near the point of use to match the optimum steam pressure required for the equipment being supplied.

The following actions should be considered to ensure efficient boiler operation:

n Before increasing boiler capacity seek every opportunity to reduce demand, smooth the load and increase thermal efficiency.

n Try to improve load factor and efficiency by operating boilers as closely as possible to their design ratings. Select plant which will enable you to do this throughout the year.

n Evaluate the need for standby plant or spare capacity.

n Avoid unnecessary on-off operation of boilers by reducing maximum firing rates so that they just meet the maximum demands made on them.

n Check that purging is not excessive, but do not risk plant safety by purging insufficiently.



n Try to anticipate sudden changes in demand by the use of appropriate controls. When heavy demands cannot be avoided use some form of thermal accumulator to smooth firing rates.

n Isolate off-load boilers with flue dampers.

n Operate all boilers at their designed pressures.

C.2.2 Isolating flue dampers When a boiler goes into stand-by mode there is a continuous flow of air through the boiler to the flue due to natural convection resulting in heat transfer from the water and equipment to the cold incoming air. This heat is lost from the boiler to the chimney and can be significant where boilers are put on stand-by regularly due to process load changes. The function of a shut-off damper is to restrict airflow through the flue and prevent heat loss from the boiler when on stand-by. Dampers are particularly suited to situations where intermittent capacity is needed, and where it is necessary to operate a boiler in stand-by mode and cycle it to keep the required pressure/temperature conditions.

C.2.3 Optimising conventional combustion control The ratio of air to fuel supplied to the burner is not necessarily constant but may need to be varied according to the firing level in the boiler. The oil or gas fuel supply to the boiler is controlled by a valve and the air supply controlled by a damper (or 2 dampers if there are separate primary and secondary supplies). The valve and damper are usually linked mechanically to enable the damper setting to be matched the valve setting using a characteristic cam. This essentially works as an articulated lever with a travelling fixed point. The locus of the fixed points can be varied to give the correct damper setting for a given valve setting.

The cam is a pre-set ratio control. The usual procedure is to set up the cam coarsely on the basis of previous experience and then, by carrying out a series of flue gas analyses over the full firing range, to finely tune the settings to optimum efficiency. The efficiency of the boiler can be optimised extremely precisely in this way but the cam suffers the same disadvantages as any other pre-set control; i.e. without frequent checking it will continue to control the same way whilst the optimum operating point of the burner drifts. This could be for a variety of reasons, including:

n The characteristics of the fuel, including viscosity, temperature and calorific value, could change.

n The burners wear, become damaged or dirty.

n The cam and its linkage could wear or stick.

The pre-set control will ignore these factors and the combustion efficiency of the boiler will be compromised. How serious the consequences of this drift will be depends on individual circumstances, with an older plant the drift maybe more rapid than with newer equipment. Burners are precision engineered and need to be regularly serviced and maintained.



In order to ensure efficient combustion it is important regularly monitor the flue gas conditions over the firing range of the boiler and reset the burner gas air-fuel ratio as necessary.

C.2.4 Oxygen trim Oxygen trim control allows boiler plant combustion to be more tightly controlled, producing significant fuel savings. The principal difference between oxygen trim and conventional control is that there is a live measurement of the oxygen content of the flue-gas stream giving a good indication of the real time combustion efficiency. After measurement of the oxygen content, a signal from the control unit alters the amount of combustion air (via damper or fan-speed control) to maintain optimum combustion conditions throughout the range of firing rates at which the burner can operate. Oxygen-trim controls can be added to a conventional combustion control system or can form an integral part of a digital control system. They can take account of changes in air density such as when ambient conditions (for example, air temperature) alter or when airflow is restricted through filters. In addition changes to the fuel conditions, such as calorific value, can be accounted for.

It is most important that the boiler plant flue system is air tight. Air leakage into the flue could produce a false signal at the oxygen sensor, compromising the control logic.

The equipment requires regular inspection, cleaning and calibration, particularly of the probe as it operates in arduous conditions in the stack.

C.2.5 Optimising heat transfer For efficient boiler operation heat must be transferred from the hot products of combustion produced by the fuel to the boiler fluid, usually water, effectively. The boiler plate or tube may well have a layer of iron oxide and soot covering the fire side and a layer of scale covering the water side. Both layers will be poor conductors of heat.

In practice the temperature differences across the soot and scale layers and the stagnant surface films cannot be known with any accuracy but the bulk gas and water temperatures will be known. As the heat transfer surfaces become dirty, the heat transfer to the working fluid is reduced and this results in a rise in the flue gas temperature. A 15oC rise in flue gas temperature indicates an increase in fuel consumption of around 1%.

Monitoring the flue gas temperature at a given boiler load regularly (say once a week) gives a measure of the gradual fouling of heat transfer surfaces and provides a guide as to how frequently the tubes should be cleaned.

A regular cleaning regime on both the fire and water sides of the boiler heat transfer surfaces is important to maintain boiler efficiency.



C.2.6 Blow down control The concentration of dissolved impurities in boiler water is expressed as the ‘Total Dissolved Solids’ or TDS. As water is evaporated in a boiler the concentration of impurities in the boiler will rise. To control this problem it is important to blow down the boiler and introduce fresh boiler feed water to reduce the overall TDS level in the boiler. It is important to set the maximum allowable TDS as high as possible to minimise blow down rates while protecting the steam system. If the desired TDS is set too low blow down rates will be excessive wasting boiler fuel. Maximum TDS values for shell boilers are typically in the range of 2,000 to 3,500 ppm.

C.3 Steam systems

C.3.1 Insulate hot pipe lines Heat loss from steam pipe work and vessels is a significant cause of additional cost. To counter this, pipe work, boilers and vessels containing hot fluids are insulated using a range of materials such as mineral fibre, thermal textiles or polyurethane foam. Older installations may have been insulated using asbestos which is now considered a highly hazardous material, so it is important to be aware of the possibility of asbestos being present under older pipe work cladding.

Insulation should be applied according to a relevant national or international standard. In this guide we refer to BS5422:2009: “Method for specifying thermal insulating materials for pipes, tanks, vessels, ductwork and equipment operating within the temperature range –40 °C to +700 °C”. This provides a means of calculating the minimum economic thickness of insulation based on the thermal conductivity of the insulation material, the diameter of the pipe and the temperature of the fluid the pipe is carrying. These are represented in the standard by the use of generic tables.

Insulation is equally important for refrigeration systems; the heat gain in a poorly insulated chilled water system can cost more in energy terms than heat loss from a steam line.

Observing the condition of insulation should be part of the audit process.

Cost of lost heat

Total cost

Cost of insulation + installation

Minimum cost

Economic thicknessCo

st (M

UR)

Insulation thickness



Exposed material can become wet, which reduces the effectiveness of the insulation. Worse still, wet insulation can accelerate corrosion of steam pipe work, and because the corrosion is hidden under the insulation it can go undetected until a leak occurs.

C.3.2 Maintain steam traps Leaking steam traps can be serious sources of energy waste, they act as a short circuit from the high-pressure portion of the system to the condensate system, and the loss continues as long as the steam system is operating. Where the trap drains to a condensate line the steam loss is invisible and may persist for years. The worst energy loss occurs when the steam trap fails in a fully open position; here the rate of steam loss is proportional to the size of the orifice in the trap and to the pressure difference across the trap. These same characteristics determine the rated load of the trap, so steam loss from a stuck-open trap is proportional to its rated capacity. This is an important reason to avoid over-sizing traps.

The range of steam loss in typical applications varies enormously. A leaky steam trap on a radiator in a low-pressure steam system may lose 2.5 kg of steam (about 1.5 kWh) per hour. At the other extreme, a large steam trap with a valve seat diameter of ½ inch, serving a process application at 20 bars, may waste over 1 tonne of steam per hour (over 500 kWh) if the trap sticks fully open.

Failure of a trap in the closed position may have serious consequences, for example a closed trap will prevent steam using equipment from working, or allow condensate to accumulate in the pipe forming slugs that are propelled at high speed and which can destroy pipe, valves, and equipment.

There are different methods of testing steam traps, none are completely reliable, and most require special skill. The list below briefly describes the most common methods.



C.3.3 Optimise condensate return systems It is important to keep condensate as warm as possible until it is returned back to the feed water tank. However, if condensate returns in a condensate system that works at atmospheric pressure, some of the heat will be lost in the form of flash steam. Only liquid water returns to the boiler; any flash steam that remains by the time the condensate gets back to the receiver is lost through the vent on the receiver. The amount of flash steam depends on the pressure, and hence the temperature, at the discharge of the steam using equipment.

If steam equipment operates at high temperature, much of the energy of the condensate may be wasted. For example if steam is used to heat a vat to 160oC, the condensate temperature is also 160oC inside the heating equipment. When the condensate drains to a condensate system operating at atmospheric pressure, approximately half of the condensate will flash into steam. Part of this flash steam condenses in the return pipe, and keeps the condensate warm. The rest is lost through the vent at the condensate receiver. A variety of techniques to recover the heat of high-temperature condensate can be used. The list below describes some approaches:

1) Checking condensate system vents: In condensate systems operating at atmospheric pressure, leakage of steam traps can be detected from steam blowing at the condensate system vents.

2) Test valves: With test valve the output of the trap from the condensate system can be temporarily diverted to the atmosphere, so the trap output can be seen. The test valve setup helps to briefly shut off the trap discharge and vent the condensate system, so it can be seen if any blowing steam is coming from the condensate system rather than from the trap itself.

3) Audible sounds of trap operation: Most traps snap audibly as they close. Rapid rattling of an inverted bucket trap indicates that it is stuck open. Cycling of a disc trap at too high a rate indicates that it is leaking excessively.

4) Ultrasonic devices: Steam leaking through a narrow restriction emits a large amount of sound in the ultrasonic range, but little in the audible range. Therefore, listening for ultrasound is a valuable method of diagnosing leakage.

5) Sight glasses: Steam traps may be fitted with sight glasses or devices to verify operation. These allow you to directly observe the water level inside the traps. 6) Infrared imaging scanners: Infrared cameras are a versatile tool that allows a user to actually see patterns of temperature variation. With the right equipment and enough

experience, heat patterns can be observed on the surface of the trap and adjacent pipe that indicate whether the trap is operating properly.



C.3.4 Heat recovery from unrecoverable condensate The condensate from some equipment may be contaminated, making it undesirable to return it to the boiler and is sent to drain. Even so, the heat from this condensate can still be recovered with a heat exchanger. A flash tank can be also used, if the condensate is delivered at high pressure. Ensure the heat exchanger is especially easy to clean.

C.4 Heat recovery The following sections provide a short description of a few heat recovery options that help minimise fuel consumption.

C.4.1 Heat recovery from blow down Heat recovery from unrecoverable condensate can be combined with blow down heat recovery. A blow down heat recovery system is a method of extracting heat from blow down water that is dumped to the sewer. If the condensate is being dumped near the boiler, it might be able to use a common heat exchanger to recover heat from condensate and blow down.

C.4.2 Heat recovery from flue gases For fuel-fired industrial heating processes, one of the best ways to improve efficiency is to preheat the combustion air going to the burners. The source of this heat energy can be the exhaust gas stream, which leaves the process at elevated temperatures. A heat exchanger, placed in the exhaust tack or ductwork, can extract a large portion of the thermal energy in the flue gases and transfer it to the incoming combustion air.

Local heat recovery: If there is a low-temperature heating application near the point where the condensate is discharged, the condensate can be discharged through a heat exchanger that serves the lower-temperature process. This cools the condensate, so it will return through the atmospheric condensate system without flashing. If the recovered heat is needed in the form of low pressure steam, a flash tank can be used. The main feasibility question is whether the low temperature application can be synchronized in time with the operation of the equipment that discharges the high-temperature condensate. Low pressure steam line: If a low-pressure application exists elsewhere, a low-pressure steam line can be used to allow the condensate to flash into it. If no low-temperature heat recovery application is available, the flash steam can be returned in a separate line. The high pressure condensate can be drained to a flash tank, which produces low-pressure steam. The steam is returned to the boiler plant or elsewhere for use in low-pressure applications, such as feed-water heating. This method is feasible only with large volumes of high-pressure condensate. A small quantity of low-pressure steam would condense before it is able to travel any great distance. Closed, high-pressure condensate system: There is no inherent reason why a condensate system must operate at atmospheric pressure. The condensate system could operate at the discharge pressure of the steam-using equipment, returning the condensate as high-temperature liquid. A closed system eliminates water loss from vents, and has reduced water treatment requirements. A high-pressure condensate is restricted to applications that discharge at the same high pressure. It cannot accept condensate from any lower-temperature applications. Also, the higher pressure requirements on pipe, receivers, and other hardware may add significant cost.



C.4.3 Heat (and water) recovery from steam vents A blowing steam vent is clear evidence that energy is being wasted and should be seen as an opportunity to recover heat and save energy. Another reason to recover vented steam is to recover the pure water that comes from condensing the steam. Recovering the water saves the cost of replacing it, and also reduces water treatment costs.

Recovering the heat and the water is usually a simple matter of heat exchange. Any liquid, gas, or solid medium can be used to condense the steam if its temperature is below the boiling point of water. Most of the energy of steam is latent heat, so the temperature of the condensing medium does not matter, as long as it is cooler than the boiling temperature.

For example, warm condensate can be used to condense venting steam. This warms the condensate, reducing fuel cost, and allows the condensed steam to be used as makeup water. If a large amount of steam is being vented, it can be used for heating domestic water, heating fuel tanks, process heating, etc.

There is no need for a heat exchanger if the vented steam can be mixed with the condensing medium. One method is to pipe the steam into a tank of liquid; or, spray the liquid into a pipe that contains the vent steam. A vent condenser is a specialized heat exchanger designed specifically to recover heat and water at steam vents. A vent condenser is cooled by a liquid, and the condensed steam falls back into the vessel. Vent condensers are common on deaerator feed-water heating tanks. If there is no application for heat recovery, steam can be passed through an air coil to condense it.

C.4.4 How to find leaking steam vents There are many industrial processes that involve steam vessels with vents. Plumes of steam are generally visible, and a major plume of steam may persist for a long time because everyone assumes that it is intentional or necessary. Within the boiler plant itself, the deaerator feed-water tank is the equipment most likely to be venting steam. Deaerators use steam to separate air from the feed-water. At the vent where the air is ejected from the tank, a considerable amount of steam may be lost along with the air. The tank may already have a vent condenser installed. If so, the vent condenser should operate properly.


Appendix C – BOILERS AND HEATERS

C.5 Boilers and heaters checklist Steam and Heater Walkabout Checklist Compile an inventory of heating systems on site and prioritise according to annual energy use (size x running hours). Conduct the following checks on each system: NOTE: Many heating systems require specialist knowledge about their operation; always seek specialist help where you are uncertain about energy saving measures to implement as this will help prevent unintended outcomes.

Check Complete Y/N Process heating optimisation 1. Check heat users across the site; identify opportunities to reduce heat demand. 2. Check for the opportunity to install automatic demand controls on steam / hot oil system.

3. Check steam / hot oil is only circulated when there is demand (plant is in operation). Check automatic control settings &

ensure they are suited to the application. 4. Look for and repair steam / thermal fluid leaks.

Insulation 1. Carry out an inspection across the steam / hot oil system. Look for opportunities to improve insulation levels on pipe work,

flanges, valves and other inline devices.

Maintenance 1. Carry out appropriate methods to check for faulty steam traps.

2. Carry out inspections to identify steam leaks. 3. Inspect air removal equipment for effective functioning. 4. Check that the correct steam traps are chosen for each application and that pipes are sized correctly.

Condensate 1. Check condensate systems. Assess the most appropriate method for recovering condensate. Is the condensate return

system pressurised or open to atmosphere?

2. Measure quality of un-recoverable condensate and assess the options for alternative uses of its heat. Can heat be recovered with a heat exchanger; can it be combined with blow down heat recovery?

3. Estimate running and warm-up load and evaluate how much condensate can be returned to the feed water tank. Boilers and burners 1. Check combustion is efficient. Is complete combustion taking place? Look for opportunities to tune / trim controls & to

reduce excess combustion air.

2. Look for opportunities to recover heat from flue gasses to preheat boiler combustion air or the boiler feed water. 3. Check the boiler control; establish how well the boiler output is matched to the steam load. Check the boiler is not cycling

excessively. Look for the potential to implement modulating controls or multiple smaller boilers.

4. Check for opportunities to reduce blow down rates. 5. Check for opportunities to recover heat from boiler blow down flash steam. 6. Check stack temperatures are not excessive in relation to steam / oil temperatures. Has the boiler been tuned? Check the

boiler is clean, soot is removed from the fireside, and scale build-up has been removed from the water side.

7. Check heat energy is not being lost when the boiler is off. Is free air flow through the boiler prevented, e.g. stack / flue isolation dampers; is the water flow through the boiler isolated?

8. Check there is adequate insulation on the boiler and there are no air leaks in the flue. 9. Look for opportunities to fit variable speed control to forced draught and induced draft fans. 10. Check heat transfer surfaces, ensure they are clean and free of deposits.


Appendix D – REFRIGERATION & COOLING

Appendix D REFRIGERATION & COOLING In warm and humid climates, cooling and dehumidifying can account for more 50% of a facility’s energy cost. There are many techniques for improving the efficiency of existing cooling equipment. Energy savings of up to 20% can be realised in many refrigeration plant through actions that require little or no investment. In addition, improving the efficiency and reducing the load on a refrigeration plant can improve reliability and reduce the likelihood of a breakdown.

Technology Overview Condenser: A heat exchanger in which a gas, such as a refrigerant vapour cools and then condenses to liquid form. Compressor: A machine which raises the pressure of a gas, such as a refrigerant vapour. This will usually raise the temperature and energy level of the gas. Refrigerant: The working fluid of the refrigeration system which absorbs heat in the evaporator and rejects it in the condenser. Evaporator: A heat exchanger in which a liquid refrigerant absorbs energy from its surroundings and vaporises, producing a cooling effect. Expansion valve: A valve through which liquid refrigerant passes and reduces in pressure and temperature. Receiver: A high-pressure vessel located after the condenser used to store refrigerant. Thermostatic Expansion Valve: A valve which regulates the flow of refrigerant into the evaporator depending on the variations of superheat of the refrigerant leaving the evaporator against a pre-set value. Electronic Expansion Valve: An expansion valve controlled by microprocessor able to operate under low and varying conditions of pressure difference.

Definitions Evaporating Temperature/Pressure: The temperature and pressure at which the refrigerant evaporates. Discharge Pressure (or Head Pressure): The high pressure at the exit of a compressor. Free Cooling: A method of cooling that does not require refrigeration. Evaporative Cooling: Cooling effect achieved by the evaporation of water

D.1 Identifying energy saving opportunities in refrigeration and cooling systems Energy savings in refrigeration and cooling systems can be realised in a number of areas. When starting out looking for opportunities the following suggests a simple approach that could be used:



n Review cooling loads on each refrigeration system. Identify the cooling loads on each of the refrigeration systems, the temperature to which each needs to be cooled and the period for which cooling is required. Consider whether the relevant refrigeration system is the most efficient way to provide the required cooling, if any of the users are being over-cooled and if they could be switched off when cooling is not required.

n Assess whether the temperature of a refrigeration system is well matched to the cooling loads it supplies. The evaporating temperature (or secondary refrigerant temperature) should ideally be no lower than required to meet the cooling demand of each user. It may be possible to raise the evaporating temperature (and secondary refrigerant temperature, if relevant) thereby increasing the efficiency of the refrigeration system. If some users require a significantly lower temperature than the others on the same system, assess whether these could be served by another refrigeration system.

n Review condition of evaporators. Check evaporators to ensure they are in good condition, clean and adequately defrosted e.g. there is no permanent build-up of ice. For air coolers, also check that all fans are in working order and the air flow is unobstructed.

n Review condition of condensers. Check condensers to ensure they are in good condition and the heat exchange surfaces are clean. For air-cooled/evaporative condensers, ensure that they are located away from sources of heat and the air flow to the condenser is unobstructed. Consider whether employing variable speed fans would be worthwhile. For water-cooled condensers, consider whether the water temperature could be reduced.

n Review expansion valves. Check whether the expansion valves have been set up well and whether it would be worthwhile replacing any thermostatic expansion valves with electronic ones.

n Review condenser and compressor controls. Identify the current method of control and set point for the condenser and the compressors on each refrigeration system. Assess whether the efficiency of the refrigeration system could be improved by changing the set points or installing better control systems.

n Assess opportunities to improve compressor efficiency. Determine whether there is scope to improve efficiency by changing the way the compressors are sequenced. Consider how the part-load efficiency of the compressors could be improved e.g. by installing a smaller compressor or a variable speed drive for an existing compressor.

n Review opportunities to reduce the cooling loads. Consider ways that the cooling load on the refrigeration system might be reduced e.g. by pre-cooling with a more energy-efficient alternative, by using free cooling. Determine whether heat gains could be reduced e.g. by reducing warm air ingress to a cooled space, improving insulation, switching off lights/fans/equipment.

n Review operation of auxiliaries. Assess the energy usage of the refrigeration auxiliaries e.g. fans, pumps etc. and consider ways that this could be reduced e.g. by switching off when not required, improving control or installing variable speed drives.

n Review opportunities to reduce the heat gains to chill/cold stores. Assess how warm air ingress to the store could be reduced e.g. by improved door management, use of automatic doors, blinds, air curtains, repairing door seals etc. Consider installing more efficient lighting and automatic lighting controls. Review insulation levels & ensure they are sufficient. For larger, forklift-accessible cold stores, consider incorporating an



airlock or ante-chamber with dehumidification. Also check the condition of insulation of chilled water distribution mains and process coolers to avoid unnecessary heat gain from ambient temperatures or direct sunlight.

n Review maintenance procedures. Ensure that there are routine checks to detect refrigerant leakage and oil leakage.

The following sections provide background information to assist in the assessment of refrigeration and air conditioning systems.

D.2 Cold Rooms Proper maintenance and control of cold room doors can result in significant energy savings. A first step is to keep cold room doors closed whenever possible. The installation of rapid closing or automatic doors can help achieve this. In addition, fitting strip curtains (chill store e.g. +2 °C) or insulated curtains (cold store i.e. -20 °C) can result in further energy savings. It is important to regularly inspect cold room insulation with particular attention given to door seals (is there ice around the door?).

Other energy saving options for cold rooms include:

n Installation of LED lighting (or other suitable lighting) with automatic controls or motion sensors.

n Ensure the product loaded into your cold room has not unnecessarily warmed up by being left in an ambient temperature area.

n Minimise sources of potential heat gain, e.g. direct sunlight.

n Operate the chill/cold store at the highest possible temperature for the product.

D.3 Compressors The energy efficiency of a refrigeration system is expressed as a Coefficient of System Performance (COSP) which is calculated:

In addition to installing more efficient compressors, minimising the part load operation of compressors, especially screw and centrifugal, the COSP can be improved and significant energy savings achieved. If a compressor often operates at low load or the cooling load varies across a wide range, then installing a smaller compressor or variable speed control on one or more compressors may lead to significant energy savings.

On multi-compressor systems, it is important to consider whether compressor sequencing could be improved, for example, by reducing part-load operation of screws/centrifugal compressors, or utilising smaller compressors. In some cases a change in the compressor control logic can improve efficiency. For example, two screw compressors at 60% load use less power than one at 100% and one at 20% load. In addition, compressor suction

COSP = Cooling achieved (kW) / Power consumed by compressor and Auxiliaries (kW)



pressure controls can be improved e.g. by replacing pressure switches with an electronic control system to allow better control and a higher average suction pressure to be achieved.

About 90% of the energy consumed by a compressor is emitted as waste heat of which 90% is recoverable. Assess if it is feasible to install a heat recovery system. In some cases (typically ammonia systems) it may be viable to install a desuperheater to recover heat from the refrigeration system.

D.4 Condensers

D.4.1 Cleaning and maintenance Condensers should be cleaned as part of regular maintenance, typically at least once a year. More frequent cleaning of shell and tube condensers to remove fouling may be required. If your condenser is likely to accumulate dirt, consider fitting a removable condenser screen which can be hosed down or replaced.

D.4.2 Reducing head pressure The pressure in the high side of a refrigeration system including the condenser is commonly known as the head pressure (also referred to as the discharge or condensing pressure).

When head pressure is higher than necessary, the compressor has to do more work resulting in increased power consumption and reduced efficiency. Minimising head pressure saves energy, and also maximises the cooling capacity of the refrigeration system, often resulting in better temperature control. Factors that affect head pressure include the following:

Factor Effect

Condenser size (surface area) The larger the condenser, the lower the head pressure.

Condenser condition A blocked or corroded condenser transfers heat less efficiently, increasing the head pressure.

Air flow Air-cooled and evaporative condensers use air to remove the heat. If the air flow is reduced or impeded the condenser transfers heat less efficiently, raising head pressure.

Ambient temperature The higher the air temperature to which heat is being transferred, the higher the head pressure. It is normal for head pressure to vary with ambient temperature.

Non-condensable gases mixed with the refrigerant

Air and nitrogen can accumulate in the condenser, reducing the available heat transfer surface and increasing head pressure.



It may be possible to improve current condenser head pressure controls e.g. by replacing pressure switches with an electronic control system. This might allow better control and a lower average head pressure to be achieved.

If the refrigeration system has floating head pressure controls, it may also be possible to lower the head pressure by reducing the set point, especially in cooler weather. Floating head pressure controls are often standard features on new systems; however, they can be retrofitted as well. Estimated savings range from three to ten percent.

D.5 Evaporators It is best practice to ensure evaporators are adequately sized for their application and to regularly inspect them to ensure they are in good condition. Dirty evaporator coils and other heat transfer surfaces are inefficient. A thorough deep-clean of the evaporator should be carried out when necessary.

Other evaporator energy saving opportunities include optimisation of defrost controls and installation of electronic expansion valves. These are discussed below.

D.5.1 Defrost controls Improving the operation of the defrost cycle leads to energy savings in the form of reduced cooling demand on the compressors and reduced defrost heating demand. The most effective controls are demand controls; these achieve defrosting in a variety of ways such as measuring the temperature or pressure drop across the evaporator, measuring frost accumulation and sensing humidity. If implemented correctly these methods are more effective than using simple timers to initiate defrosting. Energy savings range from around one percent to six percent of refrigeration system energy use.

D.5.2 Expansion valves The expansion valve is located after the condenser where it reduces the pressure of the refrigerant before it enters the evaporator. The most common type, the thermostatic expansion valve does not control well over widely varying pressure differences. Electronic expansion valves are less dependent on the pressure difference across them and therefore can operate with a lower discharge pressure i.e. lower condensing temperature. Furthermore, they can easily be integrated into a central control system.

D.6 Free cooling When the outside air temperature is lower than the inside, the outside temperature can be used to cool the water in a chilled water system. The evaporative cooling effect of the system cooling towers enhances the cooling. Free cooling techniques are used to reduce the load on the chiller, or even to allow the chiller to be turned off. Free cooling can provide only a fraction of the full-load capacity of the chiller. However, in air-conditioning



applications, the cooling load is usually low when the weather allows free cooling to be used. Free cooling systems can be expensive, so they need to operate for many hours per year to pay back. The potential running time depends on the factors described below:

D.6.1 Favourable cooling load characteristics Free cooling systems are useful only if a significant amount of cooling is required when the weather conditions are able to provide it and especially in applications that have high heat gains during cool weather. Examples include buildings with large areas of glazing having high solar heat gain, and buildings with high internal heat gains from processes.

D.6.2 Suitability for free cooling The feasibility of free cooling systems depends on the cooling application’s temperature requirement. Typically the set point temperature in air-conditioning applications is around 24oC. In a mechanical air-conditioning system, the cooled air supplied to the conditioned space is at about 13°C; where the air has been cooled in a coil by chilled water the water temperature is about 6°C at full load. Given the temperature of the outside air must be lower than the temperature of the chilled water in order for it to chill, it is clear that cooling with outside air is practical only when the set point temperatures in the chilling system can be raised. When the cooling load is low, the system may still operate successfully with the chilling water and the supply air temperatures higher than in normal operation; the extent of which indicates the feasibility of free cooling systems.

D.6.3 Humidity control Chiller efficiency is increased when the chilled water temperature in raised. There are trade-offs when humidity control is required. Reducing the temperature of chilled water reduces space humidity levels as colder chilled water wrings more moisture out of the air at the cooling coils. However, in order for a free cooling system to provide savings, the chilled water temperature needs to be raised as much as possible and so humidity control is reduced. However, in climates with high humidity during cool weather, the dehumidification provided by low coil temperature is as important as cooling and so a high chilled water temperature may not be acceptable.

D.6.4 Weather profiles In cooler climates where the weather is cold enough to cool the chilled water adequately, free cooling systems will have a shorter payback period. There also needs to be cooling demand for a large number of hours for the free cooling systems to be economical. Moreover, free cooling systems are better suited for climates with low relative humidity because most of them use evaporative cooling towers. Evaporative cooling is essential to make free cooling effective. As a ‘rule of thumb’ the feasibility of free cooling requires a large number of hours during which the wet-bulb temperature is below about 7oC. For dry climates, the outside air temperatures should be less than about 15oC. In general, free cooling is more effective in drier climates.



D.6.5 Ability to use heat sinks other than outdoor air A cooling tower is commonly used to reject heat, using the atmosphere as a heat sink. More broadly, free cooling techniques can be adapted to use any other available heat sink, provided that the heat sink has sufficient capacity and a temperature that is low enough. Among these low-temperature heat sources and sinks are ground water, rivers, and lakes.

D.7 Controls It is important to control and limit the operation of the refrigeration system and its major components so that it matches the demand for cooling. The installation of thermostatic controls for evaporator fans in cooled areas and or the installation of variable speed drives for pumps, cooling tower fans etc. can improve the energy efficiency of a refrigeration system considerably.

A scheduling controller can be used to control and optimise a refrigeration unit and its auxiliary equipment.

D.7.1 Scheduling controller A scheduling controller sends the appropriate starting, stopping, and loading signals to the chillers. There are a variety of refrigeration or chiller load schedulers commercially available. The most elementary functions available with the cheaper units is to turn on successive chillers as the previous chillers load up to specified levels and to shut down smaller chillers when they become fully loaded while transferring the load to the larger chillers. The desired compressor loading sequence needs to be inputted. Also, the cooling load can be distributed among modulating chillers at specified ratios.

For complex combinations of chillers, more sophisticated control functions may be needed. Where there are different types and models of chillers with modulating compressors the controller needs to distribute the load in the optimum way throughout the load range and so the controller should be programmed with the efficiency characteristics of each chiller in the plant along with the desired load for each chiller at each chilled water temperature.

D.7.2 Auxiliary equipment scheduling controller In some refrigeration systems auxiliary equipment, such as pumps, fans etc., can account for a large part of the total energy use and yet are often overlooked when considering efficiency. Up to 20% energy savings can be achieved through the use of an auxiliary scheduling controller.

If a refrigeration unit has separate auxiliary equipment the controller will need to be programmed to schedule the optimum combination of auxiliary equipment under all load conditions. Ideally when a central energy management system is available it may be used to optimise chiller sequencing and loading with minimum cost.



D.7.3 Control of chillers and auxiliary equipment After selecting the most efficient combination of equipment for each set of conditions, the following should be considered to achieve optimum efficiency at modest cost.

Heat rejection equipment Fans and/or pumps are used by the heat rejection equipment to dispose of the heat that is collected in cooled spaces or processes. This equipment does not need to operate when the chiller is off; it is not uncommon to find poor control in systems that are assembled from separate components. Also, for more complex heat rejection systems, the equipment may not turn off in a way that minimises energy consumption under all operating conditions.

Chilled water pumps and evaporators Chilled water pumping arrangements that are used in plants with several chillers can be either parallel or in series. With either of these configurations, there are two simple measures to save energy as the cooling load falls; 1) turn off pumps that are not needed to carry the load, and; 2) close valves to stop flow through the evaporators of idle chillers. In addition to saving pumping power the chilling demand is also reduced.

D.8 Other opportunities for energy savings

D.8.1 Zoning arrangements Many air conditioning systems are set up in ‘zones’ to provide different levels of cooling to specific areas within a building. Whenever building use changes, these zones should be reviewed to ensure that they are still delivering required conditions without wasting energy. In addition, a yearly review of zoning arrangements should be carried out to ensure that systems are operating to peak efficiency.

D.8.2 Temperature dead band The temperature in most work areas will need to be less than 24oC. Also, the system should not provide heating when the temperature is above 18oC. However, it is common that heating and cooling operate at the same time. This wastes large amounts of energy and money. Therefore, a ‘dead band’ between 19 – 24oC is recommended where no heating or cooling is operating. If this is not implemented, there is risk that both systems operate simultaneously and waste energy and money.

D.8.3 Higher efficiency equipment Technological improvements have helped to increase the efficiency of equipment including pumps, motors, and fans. All of the existing components and equipment of the cooling and air-conditioning system should be reviewed in relation to the equipment, application, hours of use and the life cost. When replacing older equipment, it is worth spending time considering the options as it will help make the most energy efficient purchase.


Appendix D – REGRIDGERATION & COOLING

D.9 Refrigeration & cooling checklist Refrigeration and Air Conditioning Systems Walkabout Checklist Compile an inventory of refrigeration and air conditioning systems on site and prioritise according to annual energy use (size x running hours). Conduct the following checks on each system: NOTE: Many refrigeration and air conditioning systems require specialist knowledge about their operation; always seek specialist help where you are uncertain about energy saving measures to implement as this will help prevent unintended outcomes Check Complete Y/N

End Users 1. Check that the temperature of the refrigeration system is well matched to the cooling loads it supplies. 2. Check whether the temperature set-point of secondary refrigerants can be raised. 3. Consider whether any of the users could be switched off at certain times or completely. 4. Consider whether free cooling could be utilised to meet some or all of the cooling loads. 5. Assess whether heat gains of each user could be reduced. Evaporators 1. Check evaporators are in good condition and adequately sized for the application. 2. Check if a deep-clean of the evaporator coils is required. 3. Check defrost controls are optimised to remove any ice without defrosting too often or for too long. 4. Consider installing defrost-on-demand controls. 5. Check if it would be economic to replace thermostatic expansion valves with electronic valves. Condensers 1. Check condensers are clean, in good condition and are adequately sized for the application. 2. Check the condenser is located away from sources of heat and that the air flow to the condenser is unobstructed.

3. For water-cooled condensers, consider whether the cooling water temperature could be reduced. 4. Set the head pressure to the lowest practical level. 5. Assess whether it is possible to operate the refrigeration with a floating head pressure. 6. Check whether current condenser head pressure controls could be improved. Compressors 1. On multi-compressor systems, check compressor suction pressure is set only as low as required. Often

winter set point can be higher than summer. The evaporating temperature (or secondary refrigerant temperature) should be no lower than required to meet the cooling demand of the various users system.

2. Consider replacing pressure switches with an electronic control system to allow better control and a higher average suction pressure to be achieved.

3. Review compressor sequencing controls and check whether it could be improved. 4. Consider installing a smaller compressor or a variable speed drive for one or more compressors. 5. Assess feasibility of heat recovery and/or a desuperheater to recover heat from the refrigeration system. Auxiliaries 1. Consider if the energy usage of any auxiliaries could be reduced by switching off when not required or

improving control.

2. Assess whether it would be cost effective to install a variable speed drive for any secondary refrigerant pumps e.g. chilled water pumps.

Chill/Cold Stores 1. Consider installing rapid closing or automatic doors and fitting strip or insulated curtains. 2. Operate the chill/cold store at the highest possible temperature for the product. 3. Consider installing motion sensors to control the lighting. 4. Check insulation is adequate and in good condition, minimise sources OF heat gain, e.g. direct sunlight. Maintenance 1. Make sure insulation is sufficient at all parts of the cooling system. 2. Ensure that there are routine checks to detect refrigerant leakage and oil leakage.


Appendix E – ELECTRIC MOTORS & DRIVES

Appendix E ELECTRIC MOTORS & DRIVES Around two thirds of the electrical energy used in a typical industrial plant is used to power electric motor driven systems. These systems are used to power all kinds of processes, examples of which include simple conveyors and material handling, fans, pumps, precision machinery, pressing, crushing and grinding. In many situations the inefficient operation of the motor systems goes by unnoticed as priority is given to the end service / product delivered, and so the energy saving opportunities are overlooked.

Depending on the application the size of the savings opportunities can vary from just 1% or 2%, or extend to over 40%. When taking into account the long running hours of many applications even apparently small opportunities can result in large financial benefits.

Technology overview AC Induction Motor: Also known as asynchronous motor or squirrel cage motor; a type of electric motor powered by an alternating current and where the power is supplied to the rotor by means of electromagnetic induction. Belt Drive: A method of transmission that uses belts and pulleys to transfer power between parallel shafts. High Efficiency Motor (HEM): A motor whose efficiency class is one or more grades higher than that of the market average. Mechanical Transmission: A mechanical device that transfer the rotating mechanical power from the motor output shaft to another device; it can take the form of direct couplings, belt drives, gearboxes, etc. Soft starter: An electronic device that controls / limits the electrical power supplied to an electric motor in order to achieve a predetermined acceleration / deceleration profile on start-up and stop. Variable Speed Drive (VSD): Also known Variable Frequency Drive (VFD), and Adjustable Speed Drive (ASD); is an electronic power converter that in response to a control signal continuously adapts the electrical power supplied to an electric motor in order to control the mechanical power (torque-speed characteristic) output of the motor, by adjusting the three-phase power supply to a variable frequency and voltage supplied to the motor.

Definitions

Alternating Current (AC): An electric current that repeatedly changes its polarity between positive and negative at a given frequency. Full load speed: The maximum output speed of an electric motor at its full rated load. Load: The mechanical burden imposed on a motor by the system. Load Factor: The amount of work a motor does compared with its maximum rated power output. Power (Watt): The capacity to do work. For an electric motor the mechanical output power is a function of the speed (rpm) and turning force applied (torque). RPM: Revolutions per minute Torque (Nm): Measures the turning force applied by a motor and is a function of force and distance.

The size and type of the energy saving opportunity will vary with the application, however many aspects of motor systems are similar; these generic opportunities are addressed in this guide.



The following sections provide background information to assist in the assessment of electric motor driven systems.

E.1 System design and optimisation Energy efficient motor systems: are those that have been designed such that their output closely matches the demands of the process whilst operating for the majority time at or near their best efficiency point.

E.1.1 Minimise the load by reducing process demand. At the outset it is important to examine the process demand and ensure that it is not excessive, for example are water or air supplies being re-circulated unnecessarily, are empty spaces being ventilated, or are pressures in excess of what is actually needed? Look for ways to reduce the process demand and even consider whether the equipment servicing the process is still needed. Only once the real process demand has been established can the system design be optimised to operate at maximum efficiency.

E.1.2 Optimising the system Optimising the whole motor system to reduce the load can realise large energy savings; the following describes measures to consider:

Minimise the load by optimising processes Motor systems comprise different equipment such as fans, pumps, air compressors, refrigeration systems, conveyor belts, etc. Therefore, the methods for minimising the load will depend on the application. Examples include:

Pumping systems:

§ Minimise the number of valves, sharp bends, T’s and other sources of friction loss in the associated pipe work of the system

§ Use low friction coatings

§ Keep the pump well maintained

§ Look for opportunities to reduce velocities in the pipe work

Fans systems:

§ Keep filters clean and clean fan blades

§ Minimise the number of sharp bends, junctions, dampers and other sources of friction loss in the ductwork

§ Select the most efficient / optimise the mechanical power transmission system

§ Ensure unused equipment is suitably isolated.



Conveyor systems:

§ Use low friction belts & rollers

§ Use high efficiency motors and gearboxes

§ Use sensors to detect when a conveyor is not loaded and switch off

§ Consider zoning so that sections that are not used can be switched off

Optimise the components When considering the wider motor driven system, sizing (dimensioning) of the individual components can play a significant role in affecting the overall system efficiency. When selecting components such as pumps, fans, air compressors etc. always opt for the most efficient ones, and ensure their best efficiency operating points are closest to the majority throughput demand of the system. On certain fixed speed centrifugal pumps it may be appropriate to trim the impeller to suit the duty, whereas on fans it may be appropriate to adjust the pulley ratios.

Correct motor sizing The amount of work a motor does compared with its maximum rated power output is termed its load factor (or loading). For example, a motor rated at 100kW driving a 90kW load will be operating at a load factor of 90%. In general, motors operate more efficiently when they operate at a loading factor above 50% and peaking between 75% and 90%. In most applications this is not an issue however in some applications motors can be vastly under loaded and here it is worth reconsidering their size or the method by which the motor is controlled.

In some situations an oversized motor can create performance problems with the driven equipment, for example in the form of stress related failures due to excessive torque being applied. In addition large lightly loaded motors often present poor electrical power factor resulting in inefficient use of electrical power.

Conversely undersized motors are at risk of overheating; when a motor is overloaded for sustained periods the temperature in the windings will increase. Overheating the windings shortens the operating life of the motor and reduces its energy efficiency and so the risk of increased maintenance costs will increase significantly.

Optimise the motor controls The way the motor system is controlled is crucial to energy efficient operation. The motor control should be selected such that the output will accurately track the process demands. Motor controls include simple transducers / switches, soft starters, variable speed drives, sequencers and intelligent devices with computing capabilities. These are briefly described below:



The motor control will normally form part of a control loop with other devices such as sensors and transducers. The control may be basic on/off control activated by for example a level switch or it could be via intelligent processor where the motor output is varied in proportion with a pressure or flow demand. Always look to avoid situations where motors are running yet doing no useful work.

E.2 Application of VSDs The following briefly describes the application of VSDs to different technologies in order to achieve energy savings.

E.2.1 Pumps and fans Traditional methods of flow regulation on fixed speed systems such as fans and centrifugal pumps (variable torque loads) include dampers on fans and throttle valves or recirculation circuits on pumps; whilst energy absorbed reduces with the output the overall reduction is not large. Conversely by regulating the speed and hence the output of these devices far greater energy savings can be achieved as the speed is reduced.

Under variable speed control the power absorbed is proportional to the cube of the change in speed, so small reductions in speed will generate significant power savings. To compound matters it is commonplace for motors and equipment installed on industrial and commercial sites to be operating well below full capacity as they will have been sized for the peak output requirements and in addition a small amount of capacity is often added as a safety margin.

On – OFF controls. Simple On – OFF controls are usually implemented through conventional motor starters such as direct on line (DOL) starters. The motor is started and stopped manually or by simple control loops in response to a feedback signal, for example a level switch in a vessel, or where an end point is reached. Manual switched controls are highly susceptible to human behaviour and processes can be left running in idle for long periods without doing any useful work. Soft Starters. These devices are used to reduce start up stresses in motor systems and enable more frequent Stop - Start cycles than would normally be permitted with conventional starters. Variable Speed Drives. A VSD is an electronic controller that in response to a control signal enables a single speed motor to operate at variable speeds. When driving a fan, pump or other device the output can accurately track the process demand. Sequencers. These are intelligent automatic controllers that in large systems with multiple motors performing the same function start and stop the motors in an ordered sequential manner. They are used to achieve a relatively good correlation between the process requirement and the motor system output. Complex Intelligent Control Systems. These can take many forms and will be configured to suit the processes being controlled. Typically they will consist of one or more intelligent controllers with computing and communication capabilities, e.g. Programmable Logic Controller (PLC) and will manage one or more control loops and be able through any combination of the above to control motor starts, stops, speed and torque.



E.2.2 Savings calculation Consider the following where there is opportunity to reduce the flow rate of a pump by 15% through fitting VSD control. The existing operating parameters are given as:

Applying the affinity laws indicates the following operating parameters when the speed has been reduced:

It is then good practice to allow a 5% reduction in the savings to account for additional losses associated with VSD. The savings are then estimated as:

From these calculations it can be seen a 15% reduction in flow and motor speed will result in approximately a 36% reduction in absorbed motor power.

Conveyors Conveyors present a constant torque load. For a horizontal conveyor once the inertia has been overcome the motor torque is essentially independent of the load on the belt and is primarily dependant on friction. Under normal operation the torque and speed of the conveyor motor are constant and the system is controlled by regulation of input quantity. If it is possible to change the system throughput by reducing the conveyor speed there will be corresponding energy savings.

Hydraulic packs Hydraulic packs are used to generate high pressure oil for motive power in extruders, presses and other high force applications. Whilst the operation of the process is cyclic it is commonplace for the hydraulic packs to operate continuously with a single speed motor where during the unloaded part of the cycle the excess oil pressure is relieved via bypass valve. In some of these systems depending on the response time required and the proportion of the cycle that is unloaded, it is possible to fit VSDs on the positive displacement pumps and implement control based on a constant pressure control loop.

(22-13.5) x 0.95

New motor speed 2,900 x 0.85 = 2465 rpm New system pressure 4 x (0.85)2 = 2.9 bar New absorbed power 22 x (0.85)3 = 13.5 kW

Motor speed 2,900 rpm Electrical power absorbed 22 kW



Limitations to the application of VSDs for energy savings Cases for the application of VSDs for the purposes of realising energy savings should always be accompanied by technical assessments and examination of the business fundamentals to ensure they are safe to implement and there is a satisfactory return on the investment. The following describe some of the limitations that may be considered:

E.3 Motor running costs and higher efficiency motors The efficiencies of electric motors vary widely and in many situations it is both good practice and makes economic sense to opt for the highest efficiency possible. Review all the significant energy using motors on site and evaluate the case for upgrading them. Use the following information to inform the review.

E.3.1 Motor efficiency labels The widely adopted IEC motor labeling standard (IEC 60034-30) classifies AC induction motors according to their energy performance. It defines three classes of motor efficiency namely, IE1, IE2 and IE3, where IE3 is the highest. This standard superseded the previous EU / CEMEP motor labeling scheme which used the labels EFF3, EFF2 & EFF1. The table below shows a broad comparison of these labeling schemes:

Systems operating at or near full load conditions: there will be little opportunity to reduce speed and so the energy loss associated with the VSD electronics (assume 5%) are additional and may actually reduce the overall efficiency. Where static head / pressure makes up the majority of the output pressure requirement: there will be little opportunity to reduce speed as the majority energy requirement is to overcome the static head / pressure requirement. Where no flow conditions are required: this can only be achieved by control valves or similar. Where high speed responses are required: in specialist applications which require a near instantaneous response this can only be achieved through the use of a properly selected control valve. VSDs can only offer a dynamic response to changing operating conditions. Equipment speed limitations: at reduced speeds (>50%) the motor and equipment cooling fans lose their effectiveness and so other forms of cooling may be required. In other applications especially conveyors or materials handling interaction with other equipment may be compromised and so the potential impact should be evaluated beforehand. Where single speed changes are required: it may be more cost effective to install parallel equipment that has been matched to the different duty requirement and operate this only when required. Lubrication requirements: certain types of air compressors and gearboxes may experience a reduction in their ability to deliver adequate lubrication at reduced speeds.



Motor labelling schemes

Efficiency IEC EU (CEMEP)

Highest IE3

IE2 EFF1

IE1 EFF2

Lowest EFF3

E.3.2 Loading and power absorbed The power output rating of electric motors is always quoted as their maximum rated load, in practice however motors rarely run at their full load. The actual mechanical load that a motor is subject to is normally referred to as its ‘loading’ and is presented as a portion of the full rated load, for example, 0.75 represents a motor that is loaded to 75% of its full rated capacity.

Whilst the name plate on a motor declares its output power at the shaft the actual electrical input energy drawn will be the output power at the shaft plus the power lost due to the motor inefficiency.

The actual electrical power absorbed is calculated as:

E.3.3 Annual running costs The annual running cost is derived from the actual power drawn times the annual running hours times the electricity cost and can be summarized as follows:

kW drawn = (Rated kW x loading)/efficiency

So, for a motor rated at 37kW with a loading of 0.6 and an efficiency of 91.2% the electrical power absorbed will be: (37 x 0.6) / 0.912 = 24.3kW



E.3.4 Estimating life costs In a simple calculation the life cost equals the initial capital cost and disposal cost plus the annual operating cost times the anticipated life expectancy.

E.3.5 The cost of migrating to higher efficiency motors Depending on the number of annual operating hours the purchase costs of electric motors typically represent between 1% and 5% of their whole life costs. The initial capital cost premium of higher efficiency motors is usually easily justified when taking into account the whole life costs of electric motors and in many cases the additional premium for a higher efficiency motor can be paid back within one to two years.

E.3.6 Repair and rewinding vs. replacement decisions An electric motor can be quick and cheap to repair so having it rewound and reconditioned can be the obvious choice when it fails. However, a rewound motor could typically suffer a drop in efficiency of around 0.5 - 2%, unless the work is carried out to a high standard. This means a rewound motor may well have an efficiency several percentage points lower than that of a new high-efficiency (IE3) motor. While the initial repair cost may be lower, the reduced efficiency means the increased running costs will quickly outweigh the initial capital cost saving. Furthermore, a rewound motor will rarely be offered with the same guarantee period as a new product and could cost more in breakdowns and lower reliability.

In considering whether to replace or repair a failed motor, it is therefore important to understand the total lifetime cost, combining the purchase and installation cost with running costs. Generally the larger the motor, the more likely for it to be economic to repair, and so the decision to repair or replace can be reduced to a consideration based on motor size and annual running hours.

It is good practice to set up motor policies containing guidance on this issue and to tailor them to the local circumstances. Broadly speaking, the cost difference between repairing and replacing a smaller motor (typically below 5.5kW to 11kW) is sufficiently small that replacement should be the

Life cost = Capital cost + disposal cost + (n x Annual running cost)

Where n is the time frame in years over which the payback is assessed. The disposal costs are likely to be the same for all motor efficiency classes and so can be excluded from costing comparisons.

Annual running cost = (kW/eff) x L x hrs x £elec

Where kW is the rated kW of the motor, eff is the motor efficiency (%), L is the typical loading (use 0.75 as a default), hrs is the annual operating hours and £elec is the cost of electricity (£/kWh).



automatic choice, irrespective of running hours. Conversely, for larger motors, repair is usually more economic, depending on the running hours. In between there is a ‘grey area’ which usually requires some thought or calculation before the right choice can be made.

E.4 Optimise mechanical power transmission systems An important part of any motor driven system is the mechanical power transmission system which transfers the rotary motion of the motor shaft to the driven equipment. There are a number of forms of transmission including direct drive couplings, belts and pulleys and gearboxes; each usually selected to suit the application. The energy efficiency of transmissions varies according to the type of transmission and their condition.

A direct drive transmission system is made when the load is connected directly to the motor shaft with a simple in-line coupling device. This method is probably the simplest and the most energy efficient as very little power is wasted on friction.

Belts and pulleys are used to transfer power between parallel shafts that are not axially aligned and can achieve a different shaft speed at the driven end. Their efficiency varies with the type of belt used and the level of maintenance; for example whilst efficiencies of V belts can reach 97% - 98% they can rapidly drop by 10% or more as belts and pulleys wear, tension reduces or alignment is not true.

Gearboxes are used to deliver speed and torque changes, or mechanical power transmission between shafts set at different orientations. The efficiency of gearboxes varies widely and it is good practice to ensure the most efficient gearbox for the application has been selected and that it is correctly maintained.

E.5 Rectify voltage imbalances Motors supplied from three-phase electrical supplies require the voltages to be balanced in order to operate efficiently. Imbalances in the supply voltages are a primary cause of motor overheating and premature failure, and reduce overall energy efficiency.

In a three-phase system the voltage imbalance is defined as 100 times the absolute value of the maximum deviation of the line voltage from the average voltage on the three phases, divided by the average voltage.

For example in a 400 volt system, if the measured line voltages are 405 volts, 408 volts, and 390 volts, then the average is 401 volts, and the imbalance is:

100 x (401 – 390)/401 = 2.74%



An imbalance of 3.5% in the supply voltage can decrease motor efficiency by up to 2%. As part of annual maintenance activities it is good practice to check the supply voltage to motors and where the imbalance exceeds 1% carry out corrective reallocation of single phase loads at the site to restore the balance.

E.6 Monitoring

E.6.1 Electrical monitoring There are a number of direct electrical power measurements that can be undertaken on electrical motors to assess their performance and general operational efficiency:

E.6.2 Condition monitoring Condition monitoring techniques are used to predict potential failure risks of mechanical equipment and analyse trends in energy use. Common techniques include:

These techniques tend to be used on large equipment or where breakdown of equipment would be a significant issue.

1. Vibration analysis: Increased vibration or noise can be an indication of problems including, bearing failure, poor shaft alignment and lubrication problems. To monitor vibration levels a suitable probe is attached to the motor, gearbox or drive system, a data logger will record vibration levels at different frequencies, and analysis of the vibration profile will then highlight any potential problems.

2. Oil Analysis: Samples of gearbox oil can be taken and analysed to identify potential problems. The presence of excessive quantities of metal particles could indicate that there is a high level of wear within the gearbox and the potential for failure has increased. The condition of the oil can be determined by measuring its viscosity; if it is too far from specification it can be replaced. The oil can also be tested for the presence of contaminants, such as water, that may reduce lubrication efficiency.

3. Thermographic surveys: - Portable Infrared imaging systems can be used to scan electric motors and associated equipment. The thermal images can then be converted to visible pictures displaying qualitative temperature analysis. Amongst others motor overheating, potential bearing failure, poor shaft alignment, and electrical faults such as loose connections can then be clearly highlighted.

1) The supply voltages and currents should be assessed to ensure they are in balance. 2) The supply voltages should be assessed to ensure they are within tolerance and preferably as near to the motors nominal rated values as possible. 3) Where electrical tariffs penalise poor power factor, the power factor should be corrected (with power factor correction capacitors) such that the overall site power factor

is around 0.95 or better. 4) On larger high value motors an analysis of the power quality (including harmonics) can indicate impending electrical failure.



E.7 Electric motor driven systems checklist Electric Motor Driven Systems Walkabout Checklist Compile an inventory of motor systems on site and prioritise according to annual energy use (size x running hours). Conduct the following checks on each system: NOTE: Many motor systems require specialist knowledge about their operation; always seek specialist help where you are uncertain about energy saving measures to implement as this will help prevent unintended outcomes. Check Complete Y/N Review the process demands Review each system and determine the process demands including throughput rates of the system. 1. Identify opportunities to reduce the overall process demand. 2. Check if process set points can be reduced. Review the service that the system is delivering 1. Check whether the service delivered is necessary. 2. Investigate whether the service can be delivered by some other more energy efficient means. 3. Check the throughput of the system matches and tracks the demands of the process. Look for opportunities to optimise the whole system 1. Determine whether the system can be optimised. 2. Review the throughput of the system and look for ways to ensure it is working near its peak efficiency. Optimise the performance of components Once the throughput is right, look for ways to optimise the performance of components in the system, for example: 1. Is the pump / fan the correct size and working at its best efficiency point? 2. Can high efficiency motors and other higher efficiency equipment be installed? 3. Is the equipment in good condition; does it need repair / upgrading? 4. Are components redundant, can they be removed (e.g. valves, dampers)? Improve the way the system is controlled 1. Where motor / equipment runs for long periods without doing useful work look for opportunities to implement

automatic switch off (Stop - Start) controls. Implement manual switch off procedures where appropriate.

2. Replace control by dampers / throttle valves: a. where loads are constant, by reducing the input speed to fans / pumps, or; b. where loads are variable, by controlling the speed of fans / pumps with variable speed drives.

3. In other systems where loads are variable / include bypasses: a. Use variable speed drives to match the speed to the load or; b. Use sequencers to switch banks of parallel equipment.

Review mechanical power transmission systems 1. Check belts and pulleys in good condition, correctly tensioned & aligned. 2. Check gearboxes in good condition and correctly maintained. 3. Look for opportunities to change technologies, e.g. switch to direct couplings. Check electrical supplies 1. Are the supply voltages within 10% of the rated nominal values for the motor? 2. Are the phases balanced to within 1%? 3. Is the electrical power factor within acceptable limits for the site? (Different sites set different limits; optimum

motor performance will be attained when it is between 0.95 and 1).

Look out for persistent faulty equipment 1. Identify faulty equipment, establish the cause of the faults & recommend corrective actions where appropriate.

Look at the overall health of the system 1. Are ductwork and pipes clean? 2. Are filters clean? 3. Have all leaks (including leaky valves) been repaired? Review and amend the site maintenance schedule Ensure maintenance schedule includes measures to maintain / enhance efficiency of motor system operation.



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2. how to use this guide