The earth absorbs almost 50% of all solar energy and remains a nearly constant temperature of 50°F to 70°F depending on geographic location. Working with an underground loop system, a Water Furnace geothermal unit utilizes this constant temperature to exchange energy between your home and the earth as needed for heating and cooling.
In winter, water circulating inside a sealed loop absorbs heat from the earth and carries it to the unit. Here it is compressed to a higher temperature and sent as warm air to your indoor system for distribution throughout your home.
In the summer, the system reverses and expels heat from your home to the cooler earth via the loop system. This heat exchange process is not only natural, but is a truly ingenious and highly efficient way to create a comfortable climate in your home.
What is Geothermal Heating and Cooling?
The pre-packaged explanation you will hear the most is that geothermal is an HVAC (Heating, Ventilation and Air Conditioning) system that uses the earth’s energy to help heat and cool your home. This obviously doesn’t paint a very vivid picture, so think of the earth as a giant solar battery that absorbs nearly half of the sun’s energy and stores it as heat. This keeps the ground a relatively constant temperature throughout the year, providing a warm heat source in the winter and a cool heat sink in summer. Geothermal HVAC systems provide a mechanism for transferring heat in the winter and cool in the summer from the ground to your house.
How Do Geothermal HVAC Systems Work?
You need to go about 60 feet under the surface of the earth in order to take advantage of the earth’s stable temperatures. Geothermal HVAC systems use geothermal ground loops made of high-strength polyethylene pipes that are filled with water or in the north, anti-freeze. These are buried in the ground and then the liquid is circulated through them and into the geothermal unit in your home, extracting or dumping heat from or into the ground in order to heat or cool your house.
This geothermal HVAC setup differs from the typical HVAC system that utilizes an indoor unit that contains a fan and cooling coil. Typical HVAC units use the fan to push air over the coil. The coil then heats or cools that air and then distributes it through the duct system and on into the home. However, there is more to these systems than just the inside unit. The second half of the typical HVAC system is the large compressor outside of the home which functions to dissipate the warm or cold air out of the house.
A geothermal HVAC system can also be thought of as a two stage system. You’ll still have an indoor unit, but now it will contain your coil, fan and compressor, while the big compressor outside will be replaced with a pump and geothermal ground loop which takes over the job of dissipating heat or cold.
Can I Install Geothermal Anywhere?
Yes, Geothermal is suitable for most areas and climates though the liquids used in the ground loops as well as the specific optimal loop configurations may vary. There are a number of geothermal ground loop configurations to choose from. The main closed loop geothermal systems include horizontal trenches, vertical trenches and pond loops. There are also open loop geothermal systems that can be used with a standing column well that reaches potable water, or with a combination of a well and pond or lake. With both the horizontal and vertical closed loop geothermal configurations there are even more options available, including slinky type loops with horizontal trenches. Geothermal ground loop configuration need not be driven strictly by geography, available space on your land plays just as important of a role.
Geothermal Technology is Unproven, Right?
Not at all! It is estimated that there are already at least one million geothermal units installed in the United States today. In fact, the principle of utilizing water and the earth’s constant temperature to help heat and cool our homes has been along much longer than many realize. The oldest ground source system was a water driven compressor installed in 1855 in Austria. In the United States, Oklahoma State University is among the leaders in researching and developing the geothermal industry and has been at it since 1974. International Ground Source Heat Pump Association, IGSHPA , is a non-profit organization established in 1987 to help advance ground source heat pump technology. IGSHPA is headquartered at Oklahoma State University where they can take advantage of the incredible state-of-the-art facilities the campus has created for research and installation training.
Why Choose Geothermal?
The direct heat transfer provided by geothermal systems is much more efficient than a traditional HVAC system's air to air heat transfer. In addition, you can choose to recapture heat instead of dissipating it and transfer it using a desuperheater to your hot water heater, giving you hot water for free. Geothermal HVAC systems also run quieter and last longer with lower maintenance costs than traditional HVAC systems. Most importantly, geothermal HVAC systems lower energy consumption during heating cycles by 25-50% and during cooling cycles by 25-30%.
One drawback, however, is that geothermal HVAC systems do cost more than traditional HVAC systems. But, if you are looking at new construction and you can roll the initial cost into a mortgage, the monthly energy savings will generally more than offset the increased cost giving you an immediate return on your investment. This means that even though the cost to install geothermal is higher than a traditional HVAC, your overall outgoing monthly expenditures will still be lower. In an example from Oklahoma State University, a 2,539 square foot house in Stillwater, Oklahoma was able to reduce their annual utility costs by $1,170 using a geothermal system.