AIRAH Energy Efficiency & Green Design in HVAC for ... · example and new site project example. Introduction •What is the meaning of “Green” Design •What is “Good” Design

AIRAH – Energy Efficiency & Green Design in HVAC for Mechanical Engineers

Ken Erbas

Introduction

Ken has over 34 years of mechanical services design experience in a wide range of Commercial, Residential, Hospitals, Laboratory, Education, Council, Government and Special Military projects.

During this time Ken has worked in many countries around the world including US, Germany and Turkey. In Australia, he held several senior positions as Chief Engineer and Associate in prestigious consulting companies.

Introduction

Before We Start

• Would you like to have some ESD with your Mechanical Services Design?

• Some issues to discuss: What is the meaning of “green” design, What is “good” design?, Green ideas & Energy Efficiency measures for mechanical design, existing site project example and new site project example

Introduction

• What is the meaning of “Green” Design

• What is “Good” Design

• Green Ideas & Energy Efficiency Measures for Mechanical Design

• Existing Site Example Project

• New Site Example Project

WHAT IS THE MEANING OF “GREEN” DESIGN

A design that is green is one that is aware of and respects nature. It is a design that minimizes the negative impacts on the natural surroundings. It is not necessarily a concept that denies the need for any human impact and human existence.

It endorses the belief that humankind can exist, multiply, build and prosper in accord with nature and the earth’s natural processes without inflicting irreversible damage to those processes and the long-term habitability of the planet.

WHAT IS “GOOD” DESIGN

The broad characteristics of good building design encompassing both the engineering and non-engineering disciplines might be briefly outlined as follows:

• Meets the purpose and needs of the building’s owners/managers and occupants• Meets the requirements of health, safety and environmental impact as described by

codes• Achieves good indoor environmental quality • Is compatible with and respectful of the characteristics, history and culture of the

immediate surroundings• Creates the intended emotional impact on the building’s occupants and beholders

Thus, we as mechanical engineers choose to make the distinction between the characteristics of good design and green design-but at the same time strongly advocate that buildings should strive to achieve both.

GREEN IDEAS FOR MECHANICAL SERVICES

GREEN IDEA # 1: Night Precooling: Ideal for areas where the ambient night time temperatures are low enough to provide sufficient opportunity to cool the building structure through ventilation air.

GREEN IDEA # 2: Air-to-Air Heat Recovery – Heat Exchange Enthalpy Wheels or Heat pipe systems: Ideal for large amount of outside air intakes and exhausts/spill air situations.

GREEN IDEA # 3: Displacement Ventilation: It offers improved thermal comfort and internal air quality due to increased ventilation effectiveness and reduces energy use.

GREEN IDEA # 4: Chilled Ceiling and Beams: It offers low floor heights, low maintenance and reduces energy use.

GREEN IDEA # 5: Ventilation Demand Control Using CO2: This is best suitable for buildings with a variable occupancy.


GREEN IDEA # 6: Hybrid Ventilation or Mixed Mode Ventilation: This system allows the controlled introduction of outside air ventilation into a building by both mechanical and passive means where extreme outside conditions or a specialised type of building use do not preclude the successful application of this technique.

GREEN IDEA # 7: Variable Flow/Variable Speed Pumping Systems: This saves energy, increases the equipment life due to soft start and quieter than constant systems.

GREEN IDEA # 8: Low-No(x) Burners: Lowers NO(x) and CO emissions and increases energy efficiency.

GREEN IDEA # 9: Ground-Source Heat Pumps: This can reduce the energy usage by as much as 50 %. It has higher capital cost and requires surface area for heat exchanger field.

GREEN IDEA # 10: Water-Loop Heat Pump Systems: It can make use of energy that would otherwise be rejected to the atmosphere.


GREEN IDEA # 11: Thermal Energy Storage for Cooling: It utilises a building’s cooling equipment to remove heat, usually at night, from an energy storage medium for later use as a source of cooling.

GREEN IDEA # 12: Cogeneration: 30% of the power generated in power stations reaches the end user. Cogeneration produces combined heat and power and is 80 % efficient.

GREEN IDEA # 13: Trigeneration: Combined power, heat and cooling with absorption chiller. 80-90% efficiency. 5 ABGR stars compared to 2 stars from grid supply.

GREEN IDEA # 14: Outside Air Cycles: This provides free cooling when the outside air enthalpy is favourable to cool inside by providing 100 % fresh air.

GREEN IDEA # 15: Automatic Controls: Building Management Systems which can start/stop the systems to provide comfort conditions. Fans connected to light switches with a run on timers. After hours switches. Time clocks. CO monitors for carpark fan operations. 2 speed or variable speed fans., etc.


GREEN IDEA # 16: High Efficiency Chillers: Chillers technology are evolved to provide chillers with coefficient of performance of up to 9 compared to air cooled systems of 3-4 and water cooled systems of 4-5.

GREEN IDEA # 17: Building Envelope and building orientation: This is one of the most important tips to save energy. Better roof insulation, wall insulation, less glass, better quality glass with low solar coefficients, double glazing, overhangs and fins to protect direct solar exposure to glass and thermal modelling are being used wide spread to reduce the energy usage of the building.

GREEN IDEA # ….: Other Ideas to be discussed for future presentations (Electrical, hydraulic, photovoltaic, rainwater harvesting, etc.)

Example Project 1 – Existing Building

How can we improve comfort conditions, energy efficiency & flexibility while catering for a diversely used existing building for up to 800 people and still save money on capital cost and running cost???

PROJECT:

Recently, we were engaged in the mechanical services upgrade of site used for a variety of activities varying from Exhibitions, Theatre usage, Formal Functions to Rock Concerts (seating up to 800 people). The entire area (approximately 2000m2) consists of four main areas with Hall dividing into two areas, Function room and Stage. The Function Room and both of the Hall areas are designed to operate separately if required.

MAIN SCOPE OF WORK:

Replacement of the existing air conditioning system and other mechanical systems ensuring building compliance with the Building Code of Australia (BCA).

• EXISTING SYSTEMS:

• Existing air conditioning systems are Air Cooled Chiller, Heating Hot Water Boiler, Hot Water and Chilled Water Pumps, Air Handling Units & Fans.

• PROPOSED SYSTEMS:

After the initial investigation, we proposed to provide the following to our Client and advise the advantages instead of direct replacement of existing equipment:

• Air Cooled Reverse Cycle 100% Fresh Air Packaged Units with Heat Recovery for the Hall.

• Air Cooled Reverse Cycle Packaged Air Conditioning Units for the Function Room.

• A combination of Packaged Air Conditioning Unit for the lower part of the Stage and Natural Ventilation system for the upper part of the Stage.

• Mechanical Ventilation for Wet Areas.

• New Smoke Exhaust Fans.


Existing Systems Erbas & AssociatesProposed Systems

- Air Cooled Chiller, Heating Hot Water Boiler, Hot Water and Chilled Water Pumps, Air Handling Units & Fans.

- Air Cooled Reverse Cycle 100% Fresh Air Packaged Units with Heat Recovery for the Hall.

- Air Cooled Reverse Cycle Packaged Air Conditioning Units for the Function Room.

- A combination of Packaged Air Conditioning Unit for the lower part of the Stage and Natural Ventilation system for the upper part of the Stage.

- Mechanical Ventilation for Wet Areas.- New Smoke Exhaust Fans.


EXISTING SYSTEMS TO PROPOSED SYSTEMS

• ADVANTAGES:

100% Fresh Air systems with Heat Recovery will improve air quality within the Hall Areas used. Conventional air conditioning systems would require 501 kW total cooling load. Innovative design systems require 327 kW total cooling load. The saving is 174 kW cooling load per hour when the whole building is fully occupied. This is approximately equal to 60 kW savings of electrical load per hour only from the Hall systems.

– Independent Air Conditioning systems serving independent areas will improve energy efficiency (due to

not running chiller, boiler & pumps continuously as required from the current system).

– Reduced energy consumption for the Stage Air Conditioning by utilising an independent Air Conditioning

system in combination with Natural Ventilation for the Stage Upper Area. Stage upper area is unoccupied

and does not require comfort conditions. Total cooling load requirement has been reduced from 120 kW

to 60 kW. The saving is 60 kW total cooling load. This is approximately 21 kW of electrical load per hour.

– Improved serviceability due to deletion of Chiller, Pumps and Boiler.

– Improved redundancy by having two air conditioning units per half Hall and not dependency on central

chilled water and boiler systems.

– Estimated Saving on Capital Cost: $ 100,000


• CONCLUSION:

– Estimated Total Cooling Load reduction: 234 kW.– Estimated Total Electrical Load Reduction: 81 kW per hour.– Estimated Total Running Cost Reduction: $ 11/hour or $ 11,000/year assuming a full capacity usage of

approximately 1,000 hours per year.– Estimated Total Capital Cost Reduction: $ 100,000 (Total Allocated Budget was $ 710K, i.e 15 % saving)– Life Cycle Cost: Similar– Service/Maintenance Cost: Much Less compared to Chiller/Boiler Cost

• WHO IS THE WINNER:

Everyone is a winner.

– Client is a winner by spending less capital cost and less running costs and improved redundancy of the plant for breakdowns.

– User of the Hall is a winner by getting 100 % fresh air at all times for improved comfort conditions and better air quality

– Environment is a winner by saving energy and production of less greenhouse gases.


Example Project 2 – New Building

SCOPE:

Investigations in terms of capital cost, energy usage, water usage, life cycle analysis and fit for purpose for a large bulk storage type shopping centre (Approximately 30,000 m2).

The two systems analysed are:

Option 1: Water Cooled Base Option andOption 2: Air Cooled Plant Option.

Option 1: Water Cooled Base Option

Advantages

• Long life cycle of equipment;

• Good energy efficiency; and

• Flexibility for any fit-out changes as new fan coil units can easily be added to chilled and hot water systems.

Disadvantages

• Large quantities of water used by heat rejection with cooling towers and condenser water system;

• Capital outlay significantly higher;

• Plantroom required to accommodate central plant;

• Higher level of maintenance than air cooled option; and

• Over engineered system for application.

Example Project – New Building

Option 2: Air Cooled Plant Option.Advantages

• Improved energy efficiency for air cooled systems for equipment proposed with large Packaged Units serving the majority of areas having a turn down ratio of 4 to 1 (or 25-100% capacity range) so seasonal energy efficiency is maximised. These units are also provided with high efficiency EC (electronically commutated) plug fans, EC outdoor condenser fans and an optimised refrigeration circuit;

• Capital outlay significantly lower;

• Ability to shut down completely air conditioning to unoccupied spaces (with the water cooled system the water would still need to be pumped throughout the system);

• No plantroom required;

• No water utilised; and

• Lower level of maintenance when compared with water cooled.

Disadvantages• Shorter life cycle of equipment than water cooled option;

and

• Lack of flexibility (modifications or additions are likely to require new air conditioning system).

Advantages & Disadvantages of both options

Example Project – New BuildingENERGY MODELLING OF PROPOSED OPTIONS/SYSTEMS

SUMMARY OF ENERGY USAGE

kWhr MJ %

______ _______ ____

Lighting 1270555 61.8

Equipment 243878 11.9

TOTAL (Light + Equip) 1514433

Chiller Plant 196480 9.6

Heating Plant 239899 3.2

Heating Plant Aux 47640 2.3

Chiller Plant Aux 229536 11.2

TOTAL (HVAC) 473656

_______ ________ ____

TOTAL (mixed) 1,988,089.00 239,899.00

TOTAL (kWh equiv) 2,054,728

per square metre 81 293

project floor area (m²) 25260

Option 1 Water Cooled (Base Option)

SUMMARY OF ENERGY USAGE

kWhr MJ %

______ _______ ____

Lighting 1270555 54

Equipment 243878 10.4

TOTAL (Light + Equip) 1514433

Unitary Cooling 811357 34.5

Unitary Heating 10735 0.5

Unitary Fan and Aux 15903 0.7

TOTAL (HVAC) 837995

_______ ____

TOTAL 2,352,428 kWh

per square metre 93

project floor area (m²) 25260

Option 2 Air Cooled

Energy simulation software was used to estimate the energy consumption of the store taking into account the site location, the building

structure and the type of building services installed. Utilising the program we made energy comparisons for the air conditioning systems

using actual measured climatic data.

The complete results of the energy simulation are tabulated on the following page. For ease of comparison we have broken down the usage

into similar headings.


LIFE CYCLE COMPARATIVE COST ANALYSIS

From the above table and from our experience we believe that typically the Air Cooled Option will require replacement in

15 years and the Water Cooled in 25. To allow for a variation in different items requiring replacement we allowed 30% of

cost of Air Cooled Infrastructure in year 15 and 40% of Water Cooled Infrastructure in year 25 (both with escalation costs

included).

For the 30 year period life cycle cost for the Air Cooled Option is $17.9M versus $26.1M for the Water Cooled. It should be

noted though that at the end of 30 years (not shown) the Air Cooled would again require replacement which would be an

outlay of approximately $3.6M while the water cooled would have another 15 years life.


Over the life of the project we estimate that Water Cooled Option will use 61,000 MWhr of energy and the

Air Cooled Option 71,000 MWhr.

LIFE CYCLE COST ANALYSIS

LIFE CYCLE ENERGY CONSUMPTION OVER 30 YEARS

The above graph demonstrate that the initial outlay of the water cooled option (blue) is higher but the ongoing

costs are slightly lower and in year 15 a large capital outlay must be spent on the air cooled (orange) system and

in year 25 for the water cooled system. The grey line indicates the return of investment of 4% on the $1.5M saving

in selecting the air cooled initially and has a significant impact on the life cycle cost analysis.


LIFE CYCLE ACCUMULATED OPERATING COST

• Both options are fit for purpose and they should both provide a pleasant and suitable environment for the future staff and customers.

• In terms of overall life cycle analysis the Water Cooled Option offers ongoing savings to the client and longer plant life. However as the

initial capital outlay is significantly higher the client need to consider whether this saving now is better in the long term for their

requirements. If the capital cost saving was invested at a low interest rate of 4% this negates the financial energy savings though not

the greenhouse gas emissions.

• If the store is not to remain operational for more than 15 years when the Air Cooled Option would need replacement then potentially the

air cooled option is more appropriate and if the store intends to remain operational for 30 years then the water cooled option would

need careful consideration.

• Client decided to spent $ 500K on photovoltaic collectors with the savings they had for $ 1.5 M capital cost in air conditioning system

which will bring the energy usage of the whole building down considerably.


CONCLUSIONS…..

References

• ERBAS Engineers Projects Library

• ASHRAE Green Guide – David L. Grumman

• AIRAH Publications

Questions

Documents

AIRAH Energy Efficiency & Green Design in HVAC for ... · example and new site project example. Introduction •What is the meaning of “Green” Design •What is “Good” Design