Energy efficient heat pumps

ENERGY EFFICIENT HEAT

Richmond School District 38 had a decision to make in designing the new Robert McMath Secondary School. Should the district install a conventional heating and cooling system for an annual energy cost of $120,000? Or should it install a geoexchange heat pump system that would cost less than $100,000 a year in operating costs?

The decision was easy: McMath Secondary is now home to a groundcoupled heat pump system that is designed to supply at least 80 per cent of the school's heating needs. On very cold winter days, additional heat is provided by a high-efficiency natural gas condensing boiler. In addition to reduced operating costs, the school district is also enjoying the environmental benefits of less energy use, and a more comfortable indoor environment for students, teachers and staff.

A Smart Choice for Schools Heating and cooling account for the largest portion of a school's energy costs (approximately 70 %) and a significant part of overall operating costs. Because of their lower operating and maintenance costs, energy efficiency and comfort, schools in Canada and the United States are increasingly turning to geoexchange systems as an alternative to conventional HVAC systems.

How Do Heat Pumps Work? Geoexchange systems use geothermal energy, or the energy that is naturally stored as heat in the earth's surface, in the oceans or large water bodies. Almost everywhere in the world, the earth's surface under the frost line maintains a nearly constant temperature between 10 C and 16 C (50 F and 60 F), remaining warmer than the air above it in the winter and cooler in the summer. A geoexchange, or geothermal heat pump system takes advantage of this constant temperature by transferring heat stored in the earth or in ground water into a building during the winter, and transferring it out of the building and back into the ground during the summer. In other words, the ground acts as a heat source in winter and a heat sink in summer.

A geoexchange system consists of three main parts: pipes buried in the ground, a heat exchanger, and ductwork to distribute heat into the building. The series of pipes, commonly called a “loop,” is buried in the ground, either vertically or horizontally, near or beneath the building. The loop circulates a fluid (water, or a mixture of water and antifreeze) that absorbs heat from, or relinquishes heat to, the surrounding soil, depending on whether the building requires heating or cooling.

For heating, heat is removed from the fluid in the loop system, concentrated in the heat exchanger and transferred to the building. This process is controlled by a heat pump that regulates the temperature level. For cooling, the process is reversed. In essence, the system works like an air conditioner, only its sink is underground.

In addition to space conditioning, a geoexchange system can provide hot water heating, using a “desuperheater,” which transfers excess heat from the heat pump's compressor to the building's hot water tank, very common in residential geothermal heat pump applications.

Benefits Electricity savings Typically, heat pump systems reduce heating and cooling costs by 25 to 40 per cent, compared with conventional systems. At McMath Secondary, for

Pumps

example, this translates into savings of $20,000 a year.

“Although the initial cost for the geoexchange system was higher than that for a conventional system, the cost will be quickly offset by lower energy bills,” says Eric Thorleifson, Energy and Projects Manager of Richmond School District.

Increase the scope of the installation, and you increase the savings. In Lincoln, Nebraska, four elementary schools recently installed geoexchange systems. Compared to natural gas HVAC systems that were installed in two other schools at the same time, the four schools had a total energy cost saving of 57 per cent.

Enhanced comfort A major advantage of geoexchange systems for schools is their ability to heat or cool individual classrooms or areas. With zone control, each room can be kept as warm or cool as needed, rather than heating or cooling the entire building uniformly. In addition to being more energy efficient, this boosts occupant comfort.

This has certainly been the case at Paint Lick Elementary School in Kentucky, the first newly constructed school in the state to be heated and cooled by a geoexchange system. Thirty-five separate heat pumps throughout the school allow the library, cafeteria, offices, gymnasium and each classroom to have individual thermostats and zone control. Kentucky now has over 40 schools with geoexchange systems.

And at Swan Lake First Nations School in Brandon, Manitoba, during a winter cold snap, when the outside temperature plunged to -35 C for two days in a row, the auxiliary electric baseboard heaters were not needed.

Environmental and social benefits Geoexchange systems work by concentrating naturally existing heat, rather than by producing heat through the combustion of fossil fuels. By displacing electricity, they reduce associated greenhouse gas emissions, resulting in less air pollution.

Applications Obviously, the best time to install a geothermal system is at the construction stage. However, a heat pump system may also be added during a school retrofit, to replace an HVAC system.

In an effort to decrease operating costs, many provincial education departments limit the amount of floor area that may be cooled. Because of their lower operating costs, however, geothermal systems can improve the economics and the practicality of cooling schools. McMath Secondary, for instance, will be able to use the ground loop to increase the amount of area to be cooled, thereby becoming one of the first schools in B.C. to offer full cooling capability throughout the year. As well, Swan Lake First Nations School was able to provide air cooling due in large part to the decision to incorporate geoexchange units but construction still came in $200,000 under budget.

As well, in moderate climates, during some parts of the year, and for some building types heat removed from spaces requiring cooling is recovered, and reused for heating. For example, community centres can recover heat removed from cooling an ice rink and use it to heat a pool. This heat recovery capability proves effective even in larger systems such as the one provided in West Vancouver Community Centre (as illustrated in the diagram).

BC Hydro Can Help BC Hydro is interested in helping customers apply and test geoexchange technology, and is currently running a demonstration project to look at innovative applications for heat pumps where electric resistance heating would normally be used. School districts may qualify for incentives for geoexchange applications under Hydro's Power Smart Partner program.

In addition, BC Hydro is cohosting

Heat Flow Diagram for West Vancouver Community Centre.

ENERGY FLOW DIAGRAMS

PHOTO COURTESY STANTEC

an international GeoExchange Con fer ence and Tradeshow on March 1718th, 2005 providing an opportunity for participants to learn more about this emerging technology

To find out more about this conference or for more information on how BC Hydro may be able to assist your school district to implement this technology contact: Grad Ilic, P.Eng.,

BC Hydro's New Technology, Dem on strations, and R&D Manager at 604.453.6455 or email grad.ilic@ bchydro.com. BC Hydro also has funding available for quick and easy energy efficiency upgrades that can help your school district reduce costs and save energy. Through the Power Smart Product Incentive Program, your school district could be eligible for funding to install:

• T8 Lighting • CFL Lighting • LED Exit Signs • Pulse Start Metal Halide Lighting • High Pressure Sodium Lighting • Vending Machine Sensors OTHER ENERGY

EFFICIENCY IDEAS To find out how your school can participate in the Product Incentive Program visit, www.bchydro.com/ incentives or call 604 522-4713 in the Lower Main land or 1-866-522-4713 elsewhere.

The case study examples cited in this article are adapted from articles prepared by the US Department of Energy (www.eere.energy.gov) and the Canadian GeoExchange Coalition (www.geo-exchange.ca).

SCHOOLS ARE BECOMING MORE ENERGY EFFICIENT.

JUST LOOK AT THE SIGNS.

Energize your bottom line with LED exit signs

LED (light-emitting diode) exit signs are up to 90% more efficient than incandescent signs and can last up to 10 years. Since exit signs are always on, the energy and maintenance savings add up quickly. Plus switching to LEDs is simple, which makes this an easy way to start saving energy and money.

LED exit signs are just one of the many energyefficient products that are eligible for financial assistance through the Power Smart Product Incentive Program.

To find out how much you can save through the Power Smart Product Incentive Program, visit www.bchydro.com/incentives or call 604 522-4713 in the Lower Mainland, 1 866 522-4713 elsewhere.

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