The U.S. Department of Energy and the U.S. Environmental Protection Agency have acknowledged that a geothermal heating system is the most energy efficient, environmentally clean, and cost-effective space conditioning system available. Geothermal heat pumps (GHPs) have been in use in the U.S. since the late 1940s. A geothermal heating system can heat, cool, and supply a house with hot water. They use the constant temperature of the earth as the exchange medium instead of the outside air temperature. Just below the “frost line”, (which in the US is between 0 and 6 feet), ground temperatures range from 45°F (7°C) to 75°F (21°C).
The equipment costs about the same as conventional gas furnaces and needs to be replaced less often. The cost to run a geothermal heating system is 40-60% less than a conventional furnace due to its efficiency. Where a fossil fuel furnace may be 78-90 percent efficient, a geothermal heat pump is about 400 percent efficient. For every unit of energy used to power the system, 3-4.5 units are supplied as heat. Why then isn’t this heating system more popular in the US? Probably because the initial cost is about twice the cost of a conventional system. Fifty percent of the total cost is the underground loop field. If this cost could be reduced it would make geothermal a very popular HVAC choice.
There are four basic types of ground loop systems. The first three are closed-loop systems; horizontal, vertical, and pond/lake. Horizontal and vertical closed loop systems are the most expensive types of ground loop systems since they require digging trenches and laying pipes that circulate refrigerant or water thru an area in the ground to exchange heat. Horizontal systems require more land area than many home owners have. If a home owner is lucky enough to live by a lake or pond, the cost of the loop is less since pipes can be circulated in the water to exchange heat.
The least expensive option for a ground loop systems is called an “open loop”. If there is an available aquifer that can be tapped into, only a few square feet of real estate are needed. The water is returned to the aquifer after passing over a heat exchanger, so it is not “used” or otherwise negatively impacted. Our company is investigating how to make an open loop system more accessible to home owners. MEC systems LLC is exploring the use of its current Woda-Sci Green Tech Sump Controller to use the ground water under many homes as an open loop. The water in a home’s foundation drainage system would be accessed thru the sump and a secondary shallow well pump to use as an open loop heat sink for geothermal HVAC applications. While this application would only be applicable in high water table areas, it would reduce the cost of geothermal heating for many customers and make it a more viable choice when building a home or replacing an existing heating system.