Geothermal Heating and Cooling System
Geothermal or ground source heating systems operate on the principle of stored energy. The earth at a depth 5 feet or more in this area maintains a constant temperature of 53-54 degrees Fahrenheit. This principle allows geothermal systems to operate by utilizing the energy stored in the earth. By moving energy to and from the ground we are able to both heat and partially cool the structure. Geothermal heating and cooling systems are extremely reliable and energy efficient. Compared to other systems, geothermal technology can save 30-60% on monthly energy bills.
Geothermal heating and cooling systems are the safest, cleanest, and most energy efficient systems you can install providing a 4 to 1 energy return on the electricity used by the system.
System Design:
The design and installation of the geothermal heating system at the Alternative Farming Center was completed by Earth Energy Engineering. The heat pumps were supplied by Water Furnace International. Mountain Electric Cooperative in association with the Tennessee Valley Authority, and the Geothermal Heat Pump Consortium made this innovative heating system a reality.
Five 5-ton Spectra water-to-water units are utilized in regulating the temperature for 90,000 gallons of water in the Tilapia production area. The greenhouse air space is maintained by four Spectra, 17-ton water-to-air units. This allows the facility to be heated and partially cooled, providing a comfortable environment to work in as well as healthy growing conditions for plants.
The Water-To-Water Loop:
The ground loop consists of 2 continuous
operating 1.5 h.p. pumps which circulate 104 gallons of a water based solution per minute
through the lines. The ground loop consists of 3 circuits, each with 5 holes (well
s) dug approximately 300 feet deep, having a total of 2
miles of continuous pipe running through the 15 vertical wells. The water solution
is pumped through the pipe where it equalizes with the ground temperature by transferring
heat energy to and from the ground. The water is then returned to the heat pumps
where the heat is passed to the heating loop. The heating loop runs from the heat
pumps to a plate-frame heat exchanger. It is in this loop where the water is heated
to the desired temperature for the tanks. The heat loop water passes through the
heat exchanger and transfers heat energy to the tank loop. This occurs in the
exchanger without the water from the heat loop or the water from the tank loop contacting
one another. This added feature was included because the long term effects of the
ammonia contained in the fish water coming into contact with the heat pumps was un
known.
The tank loop pumps 60 gallons of water from the raceways per minute through the heat
exchanger and then returns the heated water to the raceways. This allows us to
maintain the desired temperature of 83 degrees needed to support Tilapia production.
Heat or cool is also transferred from the ground loop to the water-to-air pumps.
The Water-to-Air Loop:
The 4 water-to-air heat pumps work on the same
geothermal principles in heating or cooling the greenhouse air space. By using this
method we greatly reduce the energy required to help cool the structure in the
summer. Energy requirements are primarily limited to that needed by the loop pumps
and the fans used to distribute the cool air throughout the structure.
Monitoring:
The Tennessee Valley Authority is presently
using a computer in monitoring every aspect of our system to analyze the energy use and
efficiency patterns. Soon we will have the necessary
information and data over several months to determine how geothermal heating and cooling
systems compare with other conventional heating and cooling systems. The monitoring
will also assist us in improving the overall operation of the Alternative Farming
Center. We hope to show how this innovative geothermal system will be able to
revolutionize the way greenhouse structures are heated and cooled throughout the world.
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