We all want to save money heating and cooling our house or office, right? The answer may literally be under your feet. Much of the heating and cooling can come from the ground, below the surface with something called a Geothermal Heat Pump. Below the frost line, about 10 feet down, the earth maintains a nearly constant temperature of 54 degrees. You can tap into this geothermal energy to provide heating in the winter and cooling in the summer.
How Geothermal Heat Pump works:
Here is how it works: bury a loop of pipes, called a heat exchanger just below the surface, and fill them with water, or water and any free solution. During the winter months, the air is usually cooler than the temperature below ground. The solution circulates in a loop underground and absorbs the earth’s heat. This heat is brought to the surface and transferred to a heat pump. The geothermal heat pump warms the air and then your regular heating system warms the air some more to accommodate a comfortable temperature. Finally, ducts circulate the air to the various rooms. A huge benefit is that the geothermal system does not have to work as hard to make people inside comfortably warm, and you save a lot of money on your heating bill.
In the summer time, the geothermal heating and cooling system works in reverse: when its hot outside, the temperature below the surface is cooler than the summer heat. The fluid in the loop absorbs heat in the building and sends it underground. The ground’s lower temperature cools it and it circulates again and again. Now you are saving money on air conditioning. Buildings with large parking longs that use huge geothermal heat pumps to heat and cool the building, can have the system spread out its loop horizontally under the parking lot. However, buildings and homes that do not have all that extra space, can go straight down and use a vertical loop system instead.
Efficiency of geothermal heat pumps:
Getting right down to the bottom line, GHPs use 25%–50% less electricity than conventional heating or cooling systems. This translates into a GHP using one unit of electricity to move three units of heat from the earth. According to the EPA, geothermal energy heat pumps can reduce energy consumption—and corresponding emissions—up to 44% compared to air-source heat pumps and up to 72% compared to electric resistance heating with standard air-conditioning equipment. Geothermal heat pumps also improve humidity control by maintaining about 50% relative indoor humidity, making them highly effective in humid areas. Even though the installation price of a geothermal heating and cooling system can be several times that of an air-source system of the same heating and cooling capacity, the additional costs are returned to you in energy savings in 5–10 years.
Moreover, geothermal heat pump systems have few moving parts, which are housed inside a building, making them highly durable and reliable. The underground piping often carries warranties of 25–50 years, and the heat pumps often last 20 years or more. All the components of the system are easily accessible, which increases the convenience factor and helps ensure that the upkeep is done in a timely fashion. Also, since geothermal pumps (ground source heat pump) have no outside condensing units like air conditioners, there’s no concern about noise outside the home. A two-speed GHP system is so quiet inside a house that users do not know it is operating: there are no tell-tale blasts of cold or hot air.
Another important benefit is that geothermal heat pump systems allow for design flexibility. This means that they can be installed in both new and retrofit spaces. Because the hardware requires less space than the amount required by conventional HVAC systems, the equipment rooms can be reduced in size,freeing space for productive use. GHP systems also provide excellent “zone” space conditioning, where different parts of the building can be heated or cooled to different temperatures. Attesting to the system’s effectiveness, there are approximately 50,000 geothermal heating systems installed in the United States each year, and the number continues to grow as more consumers learn about the benefits of geothermal heat pumps.
Geothermal heat pumps can be used just about anywhere in the US, because all areas have nearly constant shallow ground temperature, although systems in different locations will have varying degrees of efficiency and cost savings. The constant temperature of the earth, just below our feet is a sustainable resource, literally in our own back yard. Geothermal energy is a clean energy source ready for us to use, to heat and cool our homes and offices while lowering our utility bills.
Levchik (Leo) is a renewable energy activist from Boston, MA, and has been involved with alternative energy and green construction since 2004.
In 2009, Leo and his green roofing company (CoolFlatRoof.com) sponsored Boston's Solar Decathlon Team, providing materials and installation labor to install a cool white roof on the top of Curio home (Joint effort by Tufts University and Boston Architecture College) - more info about the project here.
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