While the economic advantages are significant, the environmental impact of a geothermal heating and cooling system can be even more convincing.
Energy conservation and renewable energy
The U.S. Department of Energy forecasts that by the year 2030, geothermal heat pumps can provide as much as 2.7 quads per year of renewable energy. This is very significant, as our annual energy appetite in the U.S. is 81 quads per year and growing.
According to the U.S. Environmental Protection Agency, geothermal systems average 40 percent greater efficiency than air-source heat pumps, 48 percent better than natural gas furnaces and 75 percent better than oil furnaces.
Geothermal systems currently in use help to remove more than 1.5 million metric tons of carbon emissions from the atmosphere every year.
In one study, a 3.5-ton residential system in Indiana reduced the power needed for heating, cooling and water heating by more than 17,000 kWh per year compared to electric resistance heat.
This equates to more than nine tons of coal that would have been burned at a power plant. Annual carbon dioxide emissions alone were cut by 12 tons. The savings increase with larger systems.
Wells and water issues
For years, geothermal heat pumps have been connected to wells in coastal areas with high water tables.
In these open loop systems, the water is pumped from the well, used once, then pumped out. The only change in the water was a slight temperature difference.
The rejected water is returned to a surface well, lake or stream, continually removing water from the aquifer. Other systems use a recharge well to return the water into the ground.
Environmental concerns have been raised since aquifers can be depleted if the water is not reinjected. Also, the risk of contamination is an increasing concern. Improperly installed wells can be a path for surface water run-off that carries pesticides, fertilizers, organic materials and other contaminants into underlying aquifers.
Properly installed and maintained systems pose relatively few problems. But because the potential for abuse exists, some states and communities have prohibited the use of open loop systems. Check local codes for water discharge regulations.
Refrigerants and CFC issues
Geothermal heat pumps on the market today use modern refrigerants. The Environmental Protection Agency considers this refrigerant as part of the interim solution to the CFC issue.
Field connections of refrigerant piping are potential sources of leaks. No field connections are required with geothermal heat pump systems. They are sealed at the factory, just like your refrigerator.
The ground loop is made of durable high-density polyethylene pipe, which carries a warranty of 20 to 50 years. This helps eliminate the possibility of leaks into a nearby water table. The same type of pipe and pipe fusion methods have been safely used for more than 30 years in natural gas distribution systems.
Chemically, HCFC-22 is chlorofluoromethane, CHCIF2. No health or safety concerns have been identified; it is classified in the A1 Safety Group, the safest group, in the American National Standard ANSI/ASHRAE 34-1992.
The toxicity group A indicates no toxicity identified at concentrations of less than or equal to 400 parts per million. Group 1 indicates there is no flame propagation.
As with any refrigerant, it should be handled carefully. It should never be vented to the atmosphere, and all equipment should be properly installed and maintained by a certified technician.