Heat pumps: Reducing energy costs in restaurants

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Food service facilities are not allowed to operate without an adequate supply of hot water for sanitation. Moreover, given the current pressure on the electricity grid, it is essential to have a water heating system that meets the hot water needs of your equipment under peak operation in the most energy-efficient way possible.

Restaurant operators expect and seek:

• Unlimited access to hot water• Immediate hot water delivery to faucets and equipment• A water heating system that is reliable with little or no maintenance• Most importantly lower operating costs.

Heat pumps… reducing electricity consumption and lowering operating costs in restaurants

H ot water is the life-blood of restaurants. It is used for three main functions: Preparing and

cooking food, washing dishes and equipment; and washing hands.

Estimated end uses of water in restaurants:

Kitchen – 52%Restrooms – 31%Landscaping – 4%Heating and cooling – 1%Other – 12%

Source: American Water Works Association (AWWA), AWWA Research Foundation, and East Bay Municipal Utility District, Oakland, California.

Evaluate the whole hot water process

Thinking in reverse, starting with equipment that uses hot water and moving back to the water heating system, is an effective thought process to achieve high system efficiency and performance in your restaurant.

Reducing hot water consumption not only results in lower water costs but also in lower energy costs.

• It is advisable to start considering equipment and accessories that use less hot water; the best location in the kitchen to achieve savings is in the washing of dishes, where the largest portion of hot water is used.

Equipment that conserve hot water and fixtures are pivotal in an optimised hot water system, and are the easiest to remove and replace with efficient technology solutions, namely:

- Pre-rinse spray valves: Low-flow, high-performance pre-rinse spray valves are the most cost effective for water and energy savings in commercial kitchens.

- Aerators on hand sink faucets: Aerators are inexpensive devices added to faucets to reduce the water flow rate while maintaining enough force to effectively hand wash and rinse at kitchen sinks and bathroom basins.

- Dishwashers: It is important to know your daily usage (racks per hour) in your establishment to estimate operating costs and assess the value of a more efficient model. Water use per rack is a fundamental measure of efficiency as it correlates to the energy used to heat water and the amount of cleaning chemicals required for each cycle.

• Your hot water distribution system is the second target.

Delivering hot water more efficiently yields permanent energy savings and improved system performance. The placement of sinks, fixtures and equipment in close relation to your water heating system is a key factor in the efficiency and performance of hot water distribution.

Moreover, pipe insulation is by far the most effective solution (if not the most overlooked) to improve the effectiveness of the distribution system that delivers hot water on demand.

Typically, glass wool can be used on hot water piping to prevent heat loss. This saves energy, extends the cool-down time, reduces operating costs and improves the effectiveness of the distribution system to deliver hot water.

• The heart of your hot water distribution system is the water heater. Heat pumps are considered to be the most ideal choice in the provision of hot water in restaurants, since they are flexible and can be scaled up or down to meet varying needs.

The costs incurred in replacing your existing energy-intensive systems – such as electric element geysers – can be broken into the initial capital investment and the daily operating costs.

Factors that impact system size and, therefore, costs, include:• The average ambient air and supplied water temperatures in your area• The humidity levels in your region• The plumbing configuration of your restaurant• The temperature at which water needs to be

delivered• Most importantly, capability to meet peak hot water

demand – system sizing is critical to ensure a sufficient supply of hot water and, therefore, diners’ satisfaction.

Usually, storage tanks are built to cater for 75% of your hot water needs and a heating system that can produce hot water for the remaining period of peak demand. Once peak demand has been met, the system can fill up the storage tank to get ready to cater for the next peak demand period.

Note:

• Peak demand for hot water would vary from restaurant to restaurant, and according to each establishment’s particular food and dining offering – speak to your supplier about your particular period of peak demand when you consider investing in an energy-efficient water heating system for your restaurant.

Note:

• The estimated average daily hot water usage for quick service restaurants – a business that serves its customers essentially a “takeaway” menu, and that does not have dishes or other utensils requiring cleaning in a hot water dishwasher – is 1,890 litres per day.

• The estimated average daily hot water usage of a full service restaurant – a business that serves its customers a “sit-down” menu, and that uses a range of dishes and other utensils requiring cleaning in a hot water dishwasher – is 7,950 litres per day.

Heat pumps use the reverse cycle of a refrigeration plant to heat water. In effect, it transfers heat from a source such as water or air to the water to be heated. (In general the very large commercial units that use water as a heat source). This fact sheet, however, focuses on air sourced units.

As in other refrigeration equipment, heat pumps employ:

• An evaporator• A compressor• A condenser• Refrigerant gas• An expansion valve within a closed circuit.

Heat pumps can save up to 67% of your energy consumption. How does this energy-efficient technology work?

Latent heat is given off when the refrigerant gas is liquefied through the condenser and transferred to surrounding water, effectively raising the temperature of the water to 55°C. In some circumstances even higher temperatures can be attained. Generally there is a need for a hot water booster pump to achieve this result.

It may seem strange that an electro-mechanical device with moving parts – an electric motor driving a compressor – can be a more energy-efficient method to heat water than a typical resistance element geyser. In fact, a heat pump can be up to three times more efficient – for every kWh of electricity supplied to the heat pump, more than three kWh of thermal energy in the form of hot water is produced. A thermostat will keep the hot water at a constant temperature of 55°C.

Note:Your dishwashing unit should have a built-in booster heater that heats water to the required 82°C for dish sanitisation.

The other benefits of heat pumps

Apart from being energy-efficient and reducing energy costs, these include:

• The cooling system of a heat pump can be used to simultaneously cool a building, or a specific area of a building. This is especially useful in restaurants where cool air can be channeled into the dining areas, thereby reducing electricity use and saving on the cost of a separate stand-alone air conditioning system.

If both the hot and cold sides of an installation are used, capital amortisation can occur over a shorter period.

• Reduction in your restaurant’s maintenance costs.

• Reducing your restaurant’s carbon footprint because no combustible gas is burnt in the heating process.

• Ensuring a longer lifespan for the boiler tank due to the lack of chemical interactions between the element, and the other metals such as copper used in the plumbing process.

• Although initial equipment and installation costs are higher than those of gas or electric geyser systems, these are offset by lower operating costs. In South Africa, a typical payback period on a commercial system would be three to five years at current electricity costs – as electricity costs increase this time frame will become shorter.

• Systems can vary in size from small to very large commercial applications with heating and a storage capacity for thousands of litres of water.

• Although bulkier than traditional boilers, heat pumps can usually be accommodated in existing spaces and do not always require additional buildings to house these.

• Restaurants that depend on standby generators can use heat pumps during power outages to produce hot water as they are more efficient than directly heating water with gas.

Heat pumps are internationally recognised as eco-friendly, contributing to lowering

greenhouse gas emissions by between 200 and 400%.

Heat pumps in commercial premises – such as restaurants –

are typically mounted at ground level.

Which electricity source is required for installations?

The majority of large commercial heat pumps use three-phase electricity supply.

Should heat pumps be serviced?

Yes. Your preferred technology supplier will provide details of these requirements – heat pumps typically need less servicing than more conventional water heating systems.

Are heat pumps noisy?

This depends on the size and design of your system. Noise is usually produced by the compressor and the air blown through the evaporator radiator as it flows through the unit.

Air noise is marginally higher than ambient background noise and is usually not distracting, especially as heat pumps will be located far away from your dining areas. On very large systems the noise level could cause distraction and, therefore, need to be housed appropriately.

Eskom Energy Advisors

Restaurants can dramatically reduce electricity consumption and cut operating costs by installing energy-saving technologies such as heat pumps. Eskom Energy Advisors are on standby to assist you with your restaurant – they excel at giving advice on how to:

• Reduce energy usage

• Do walk-through energy assessments to identify energy usage patterns, energy needs, areas of energy wastage and energy-saving opportunities

• Optimise operations and maintenance

• Improve electrical systems and processes

• Measure and verify energy savings (and where to find a SANAS approved Measurement & Verification Authority).

Understanding the latest energy-efficient electro-technologies, drawing on outside technical assistance and having a variety of tariffs on hand to work with, Eskom’s Energy Advisors are equipped to make specialist energy efficiency recommendations with regards to tariffs and appropriate energy sources – whether electrical, fossil fuelled or renewable – based on anin-depth energy assessment of your establishment.

Call 08600 37566, leave your name and number and one of our advisors will contact you, alternatively, ask for a specific advisor to contact you.

Visit www.eskom.co.za/idm for more information.

Credits: • AmericanWaterWorksAssociation(AWWA),AWWAResearchFoundation,andEastBayMunicipalUtilityDistrict,

Oakland, California• www.epa.gov/watersense/commercial• DesignGuide–EnergyEfficientWaterHeating,DeliveryandUse–3.26.1043;2010Fisher-Nickel,inc.• eTundra.com• CaseStudiesinRestaurantWaterHeating,DonaldFisher,Fisher-Nickel,Inc.WilliamPietrucha,PacificGasandElectric

Company;http://acee.org

IssuedbyEskomIntegratedDemandManagementOctober2015EskomHoldingsSOCLtdRegNo2002/015527/30