To understand the whole concept of a geothermal system, read below.
When you are in the market for a heating and cooling system for your home, you should consider geothermal systems. However, most people don't see the benefits of investing in a geothermal system over the cost of a geothermal system installation for their home. Some of this could stem from not knowing the facts of what a geothermal heating and cooling system is and how the system works to heat and cool your home.
Understanding A Geothermal System:
Geothermal units, or equipment, are indeed heat pumps, but they do not use outdoor air, like a traditional air source heat pump, to cool or heat your home.
Geothermal Systems and 3 Main Components:
The system itself, has three main components: A series of pipes in the ground, a heat pump and a heat distribution system. Lengths of high density polyethelyne plastic pipes are buried in the ground, either in a borehole or a horizontal trench near the building to be heated or cooled. Fluid, normally water, absorbs or emits heat to the soil, depending on whether the ambient air is colder or warmer than the soil. In winter, the heat pump removes the heat from the water, upgrades it to a higher temperature for use in the building, typically in forced air heating. A ductwork distribution system is needed to transfer the heat extracted from the ground by the heat pump. The heat is often in the form of hot water or air and is distributed around the dwelling by duct work.
Again, a geothermal heat pump is nothing more than a heat pump. A common misconception is that it uses water from the earth to heat and cool your home. This statement is untrue.It works on the same principles as a regular air to air heat pump.
First, I’m going to explain how a heat pump works.
Compression of any gas to a liquid state generates heat (remember your chemistry and physics classes). In this case the gas we use is called refrigerant. This high pressure refrigerant is then quickly discharged to a vapor state through the use of a nozzle called an expansion valve, the same way hair spray comes out of an aerosol can. That vaporized refrigerant is now really cold. This cold refrigerant is piped through a coil where air blows past it from your air conditioner unit and the cold is what you feel in the summer time coming out of your vents. Once this refrigerant leaves the coil it begins its journey again through the compressor that puts the refrigerant back into a compressed liquid state. Imagine putting the hair spray back into the can and pressurizing it again so that the cycle can start all over again. But wait. The compressor and the refrigerant are now really hot from all this work so the Heat Pump uses a fan to cool everything off. This is what you see sitting outside your house making all kinds of racket out side your bedroom window. In the winter time this process still happens but in reverse.
Water is pumped through a series of closed loop pipes installed (either in a vertical or horizontal position) in the ground. Unlike air, soil doesn’t experience dramatic swings in temperature—it averages about 62 degrees year-round below 20 feet in the Atlanta metro area. So when the temperature outside is 14 degrees, it’s much more efficient for your compressor to extract heat from the 62 degree ground than from the 14 degree air and vice versa in the summer when the temperature is 98 degrees.
Now I need to explain the draw backs to Air to Air heat pumps explained above.
The heat pump is trying to discharge heat to the outdoors in the summer and it’s trying to absorb heat from the outdoors in the winter. This is pretty easy to do on a nice day such as 70 degrees. This is when your Air to Air heat pump is working at its peak SEER rating. Any body bought an 18 SEER unit lately? Ok so imagine you have to go do some yard work on this 70 degree day. Not too bad right? It’s because your body can absorb heat from the outside if needed pretty easily and discharge heat pretty easily if you start sweating if needed. Now imagine you have to do this yard work on a 98 degree day or a 14 degree night, pretty tough. This is when your unit is working at a very poor SEER rating probably in the single digit range. Remember SEER ratings are achieved in a laboratory.
Looking back to the yard work scenario, imagine you finish up the yard work on that 98 degree day and your buddy starts fanning you off. This probably feels better than nothing, but imagine how much better you would feel if you jumped into a swimming pool. That would bring instant relief, right? The same concept happens in the winter if it is 14 degrees outside, jumping in to a 68 degree swimming pool might not feel so bad after all.
Additionally during the summer your geothermal system gradually heats up the ground outside probably 25 degrees by the end of summer. When winter arrives you are going to begin extracting that heat that you have been storing up all summer long and again use it to help your heat pump warm your house. This process gradually cools the earth outside your home by the end of winter and the cycle repeats it’s self over and over, year after year. Just think of your back yard as a giant battery that stores energy in the form of heat. Simply understood, geothermal systems use the constant temperature of the earth for heating and cooling your home.