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Geothermal pumps heat, cool homes year-round
Babette Fasolino • For the Poughkeepsie
Journal• October 31, 2010
Many homeowners are turning to their property's soil as a source of home heating and cooling by installing geothermal energy systems.
Through a government incentive program, residents can save 30 percent off installation costs. According to the U.S. Environmental Protection Agency, geothermal heat pumps are the most energy-efficient, environmentally clean and cost-effective systems for temperature control. Although most homes still use traditional furnaces and air conditioners, geothermal heat pumps are becoming more popular.
Geothermal pumps work by using energy stored in the Earth.
According to the federal Department of Energy website, "while temperatures above ground change a lot from day to day and season to season, temperatures 10 feet below the Earth's surface hold nearly constant between 50 degrees and 60 degrees Fahrenheit."
For most areas, the Energy Department says, the resulting effect is that soil temperatures are usually warmer than the air in winter and cooler than the air in summer. Geothermal heat pumps can be used year-round by using the Earth's constant temperatures to heat and cool buildings.
The Energy Department notes "because they move heat rather than generate heat, heat pumps can provide up to four times the amount of energy they consume." High-efficiency heat pumps, the feds say, also dehumidify better than standard central air conditioners, resulting in less energy usage and more cooling comfort in summer months.
Pleasant Valley resident Joe Cardella lost his home and Christmas tree farm to a fire two years ago. When he rebuilt his house and farm, he decided to install a geothermal system for heating and cooling.
Cardella worked with Sam Johnston, an expert on geothermal technology who serves as program manager for Terraclime Geothermal in Connecticut. Cardella said a big benefit of the geothermal systems is that there are no large heating bills.
"There are no fuel bills whatsoever — no gas bills, no oil bills," he said.
Cardella noted that he did see an increase in his electric bill of approximately $50 for two months. "I'll take my $50 increase in electric anytime," he said. "There's virtually no maintenance," Cardella said of the geothermal system. "There's just a filter that you clean."
A minor downside to geothermal systems that Cardella experienced is that it takes a little longer for the thermostat to respond to manual changes in temperature, but otherwise he has been very pleased with the system. Johnston said, "Geothermal heat pump systems use fluids that can easily change from a liquid to a vapor and back again."
The energy stored in the Earth's subsurface, Johnston said, is absorbed by the fluid, called refrigerant, and causes the refrigerant to change states. This is done through pipes, called a loop, drilled or buried in the ground. The pipes use the circulating fluid to ultimately transfer the heat of the ground to the building.
"The refrigerant has a very low boiling temperature and changes to an excited gaseous state when underground," he said. Once the gas is pumped up to the building, a compressor concentrates the energy to a higher temperature. This energy is then sent via a water-heat exchanger or air handler to heat the building's air and water.
The geothermal process is reversed to cool the house.
Johnson said that geothermal systems offer several distinct benefits over traditional heating and cooling systems. "First, there's no fossil fuel burning and there's no carbon monoxide," Johnson said.
Geothermal systems also use renewable energy from the sun, and the electricity component is alterable and could come from sources such as wind energy.
Costs for installing a geothermal system generally vary, Johnston said, from $5,000 to $10,000 for an average 1,800-square-foot home, and installation is completed in about a week. Homeowners can receive a 30 percent tax credit, Johnston said, for geothermal systems through the American Recovery and Reinvestment Act of 2009.
The act created tax incentives for residential renewable energy installations; homeowners who install geothermal heating or cooling systems before Dec. 31, 2016, are eligible for the tax credit.
According to the DOE, although they may cost more to install than traditional heating or cooling systems, geothermal heat pumps have low operating costs because they take advantage of relatively constant ground or water temperatures. However, the DOE says the installation depends on the size of a homeowner's lot, the subsoil and landscape.
Ground-source or water-source heat pumps can be used in more extreme climates.
The Energy Department states that the specific geological, hydrological and spatial characteristics of a homeowner's land will help a system supplier or installer determine the best type of ground loop for the site.
Geology
Factors such as the composition and properties
of soil and rock, which can affect heat transfer rates, at the installation site require consideration when designing a ground loop.
The amount of soil available contributes to system design as well — system suppliers in areas with extensive hard rock or soil too shallow to trench may install vertical ground loops instead of horizontal loops.
Hydrology
According to the DOE,
ground or surface water availability also plays a part in deciding what type of ground loop to use.
Depending on factors such as depth, volume and water quality, bodies of surface water can be used as a source of water for an open-loop system, or as a repository for coils of piping in a closed-loop system.
The DOE also notes that groundwater can be used as a source for open-loop systems, provided the water quality is suitable and all groundwater discharge regulations are met.
Land availability
Factors such as the amount and layout of the property, the landscaping and the location of underground utilities or sprinkler systems also contribute to a system's design, according to the Department of Energy.
Cardella researched alternatives for heating and cooling and found many to be cost-prohibitive.
After discovering that he could take advantage of the government tax break, Cardella found the geothermal system to be a viable option.
"The tax break makes it very affordable and very intelligent to do," he said.
Babette Fasolino is a freelance writer. Reach her at life@poughkeepsiejournal.com.
