Heat Pumps & Geothermal
What is a Heat Pump?
A Heat Pump is heating and cooling system for your home. It uses a basic refrigeration cycle—evaporation, compression, condensation, and expansion—to capture and pump heat from one area to another. Super-efficient geothermal heat pumps provide clean, quiet heating and cooling while cutting utility bills by up to 70%. Heat pumps eliminate noisy outdoor compressors and fans, and reduce greenhouse gas emissions by the equivalent of planting 750 trees or taking two cars off the road. Check out what rebates SCI REMC offers for members installing heat pumps.
2 Types of Electric Heat Pumps: Air-Source and Ground-Source
Air-Source Heat Pump
This looks similar to an outdoor air conditioner. To heat a house, it gathers heat from the outside air, and moves that heat inside a house to keep it warm. To cool the home, it gathers the heat from inside and gets rid of it by sending it outside. In the winter (when temps go below 32 degrees), air-source heat pumps can have trouble gathering heat from the cold winter air, and in the summer, sending warm air out into warm air.
Ground-Source (Geothermal) Heat Pump
A ground-source, or geothermal, heat pump functions like a conventional heat pump, moving heat between indoors and out, but is difference in geothermal heat pumps transfer heat to and from the ground, via long loops of liquid-filled pipe buried in the ground.
The temperature underground stays around 50 degrees no matter how hot or cold it gets outside. So while an air-source heat pump struggles to scavenge heat from freezing winter air or to dump it into the summer swelter, its ground-source counterpart has the comparatively easy job of extracting and disbursing heat through the 50-degree liquid circulating in its ground loop.
Geothermal systems are twice as efficient as the top-rated air conditioners and almost 50 percent more efficient than the best gas furnaces.
What it costs
$15,000–$20,000 installed for the system, including ground loops, heat pump, and controls. The Database of State Incentives for Renewable Energy (www.dsireusa.org) provides up-to-date information on state incentive programs.
What is a geothermal closed-loop heat pump (geothermal system)?
There are two main components to the geothermal system: the buried closed-loop (a loop of pipe buried in the ground) and the indoor unit which is tied into a proper ductwork system. There is no outdoor unit used with this system as you would find with an air-source heat pump system.
Heat is exchanged with the earth by using a buried earth loop and a small circulating pump. Only two types of pipe are acceptable for the earth loop – polybutylene and high-density polyethylene pipe. This earth loop must be installed by a certified contractor. The loop is carefully assembled on location using “heat fusion” to join the pipes where necessary. Once this is done, the loop system becomes “one piece” of pipe with parallel circuits. The integrity of this loop is such that a virtual lifetime of trouble-free use can be expected. Installation by any other means may cause a failure of the pipe because of the unique conditions below the ground.
Water, with an antifreeze solution, is circulated through the earth loop. In the heating mode, the indoor unit extracts heat from the solution in the loop, and with a refrigeration process, intensifies that heat and delivers it through the duct system at temperatures ranging from 95 to 105 degrees F. Since heat is being transferred – not produced – the geothermal system is delivering over three units of energy for every unit of energy it consumes. This is possible due to the fact that it takes advantage of below ground temperatures that are warmer in the winter and cooler in the summer than the outdoor air. Since the earth loop is buried in the ground, where temperatures are constant, the outdoor temperature does not adversely affect the high efficiency of the geothermal system.
In the cooling mode, the indoor unit extracts heat from the air inside the home, and transfers that heat into the solution circulating through the loop. The heat is then rejected to the earth. It is much easier to transfer heat into the cooler earth than trying to transfer it into the 90-100 degree outdoor air.
Domestic Hot Water (Desuperheater)
Most manufacturers offer an option, which is becoming a standard, that produces a large percentage of the annual hot water requirements. A “Desuperheater” is installed with a small circulating pump between the existing water heater and the geothermal system. During the winter, when the geothermal system is operating in the heating mode, hot water is being produced at the same high efficiency. In the summer, the heat that is being rejected by the geothermal system is transferred to the water heater at little or no cost.