When a discussion comes up about heat pumps for buildings, people often have a hard time grasping the particulars. That’s a shame, because this technology is probably the most efficient and growing sector of the market and everyone should have a shot at reaping the benefits.

A basic principle of thermodynamics is that heat always flows toward cold whenever there is an opportunity. An air conditioner and a refrigerator are heat pumps; pulling heat from a room or from food items by a refrigerant cooling source which attracts the heat and replaces it with cool air. I think people get confused about refrigerants, compressors, expansion valves, evaporators, heat exchangers, etc.; but it is really just a way to get heating and cooling values to move in one direction or the other. The refrigerant changes easily from a liquid to a gas. Heat causes the refrigerant to boil or turn into a gas. When that gas is compressed mechanically, it gives up most of its heat and returns to a liquid. The process is reversed to create cooling. By this means the desired temperature is extracted and moved from one place to another. So an air conditioner is like a heat pump, except that there is a reversing valve in a heat pump that allows refrigerant to flow in two different paths, one for heating and one for cooling.

Heat can be extracted and moved around from air and water sources. The typical “air to air” heating and cooling system can consist of an outside and inside unit, or be a through the wall “split system” that is more self-contained, cheaper and somewhat more efficient if the situation is right. Air to air heat pump systems make up about 85 percent of the units in use. Another type of heat pump uses ground water to work with. This is known as geothermal heating and cooling. Pipes are bored or layed into the earth in various depths and configurations, to gather the constant earth temperature of approximately 55 degrees Fahrenheit. This temperature can be raised or lowered by the refrigerant moving that heat around through compression and expansion. In geothermal, the water can be “closed loop” as it comes in contact with the ground; meaning that a water and antifreeze mixture flows over and over again through a system of pipes. An “open loop” system draws water up through a heat exchanger and then it is pumped back down into the same level of the aquifer. Sometimes geothermal temperature sourcing is achieved from pipes in the bottom of a lake or pond. Once the heating or cooling values of the ground contact water is received, it can be transferred to air for duct distribution or water for baseboard, radiator or in-floor piping distribution. There is even an option with geothermal to use some of its extracted heat for domestic water heating.

All of this is accomplished without direct fossil fuel burning, although a power plant may use such fuels to make the electricity that powers the pumps and motors of these units. As alternative energy becomes more available, it is possible for these residential or commercial systems to be much more pollution free.

There are many rebate programs for such equipment available for homes and other buildings through the New Jersey Clean Energy Program at NJCleanEnergy.com. For more guidance in Galloway, contact the Office of Sustainability at 609-652-3700 ext. 209; or contact an HVAC provider who offers an energy audit as well as the supply and installation of this type of equipment with rebates !

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