Geothermal
Glossary
Homeowners in virtually every region of
the United States are enjoying a high level of comfort and
significantly reducing their energy use today with geoexchange
(geothermal) heating and cooling.
This
marvelous technology relies primarily on the Earth's natural
thermal energy, a renewable resource, to heat or cool a
house or multi-family dwelling. The only additional energy
geoexchange systems require is the small amount of electricity
they employ to concentrate what Mother Nature provides and
then to circulate high-quality heating and cooling throughout
the home.
Homeowners who use geoexchange systems give them superior ratings because of their ability to deliver comfortably warm air, even on the coldest winter days, and because of their extraordinarily low operating costs. As an additional benefit, geoexchange systems can provide inexpensive hot water, either to supplement or replace entirely the output of a conventional, domestic water heater.
Heating and Cooling System Benefits.
Geoexchange heating and cooling is cost
effective because it uses energy so efficiently. This makes
it very environmentally friendly, too. For these reasons,
federal agencies like the Environmental Protection Agency
and the Department of Energy, as well as state agencies
like the California Energy Commission, endorse it.
Owners of geoexchange systems can relax
and enjoy high-quality heating and cooling year after year.
Geoexchange systems work on a different principle than an
ordinary furnace/air conditioning system, and they require
little maintenance or attention from homeowners. Furnaces
must create heat by burning a fuel--typically natural gas,
propane, or fuel oil.
With geoexchange systems, there's no
need to create heat, hence no need for chemical combustion.
Instead, the Earth's natural heat is collected in winter
through a series of pipes, called a loop, installed below
the surface of the ground or submersed in a pond or lake.
Fluid circulating in the loop carries this heat to the home.
An indoor geoexchange system then uses electrically-driven
compressors and heat exchangers in a vapor compression cycle--the
same principle employed in a refrigerator--to concentrate
the Earth's energy and release it inside the home at a higher
temperature. In typical systems, duct fans distribute the
heat to various rooms.
In summer cooling
mode, the process is reversed in order to cool the
home. Excess heat is drawn
from the home, expelled to the loop, and absorbed by the
Earth. Geoexchange systems provide cooling in the same way
that a refrigerator keeps its contents cool--by drawing
heat from the interior, not by injecting cold air.
Geoexchange systems do the work that ordinarily requires two appliances, a furnace and an air conditioner. They can be located indoors because there's no need to exchange heat with the outdoor air. They're so quiet homeowners don't even realize they're on. They are also compact. Typically, they are installed in a basement or attic, and some are small enough to fit atop a closet shelf. The indoor location also means the equipment is protected from mechanical breakdowns that could result from exposure to harsh weather.
Geoexchange works differently than conventional
heat pumps that use the outdoor air as their heat source
or heat sink. Geoexchange systems don't have to work as
hard (which means they use less energy) because they draw
heat from a source whose temperature is moderate. The temperature
of the ground or groundwater a few feet beneath the Earth's
surface remains relatively constant throughout the year,
even though the outdoor air temperature may fluctuate greatly
with the change of seasons. At a depth of approximately
six feet, for example, the temperature of soil in most of
the world's regions remains stable between 45° F and
70° F. This is why well water drawn from below ground
tastes so cool even on the hottest summer days.
In winter heating
mode, it's much easier to capture heat from the soil
at a moderate 50° F than from the atmosphere when the
air temperature is below zero. This is also why geoexchange
systems encounter no difficulty blowing comfortably warm
air through a home's ventilation system, even when the outdoor
air temperature is extremely cold. Conversely, in summer,
the relatively cool ground absorbs a home's waste heat more
readily than the warm outdoor air.
Studies show that approximately 70% of the energy used in a geoexchange heating and cooling system is renewable energy from the ground. The remainder is clean, electrical energy which is employed to concentrate heat and transport it from one location to another. In winter, the ground soaks up solar energy and provides a barrier to cold air. In summer, the ground heats up more slowly than the outside air.
