Common geothermal layout
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Americans usually rely on two familiar systems to heat their homes and
buildings: fuel-powered furnaces or boilers (which burn gas, oil, or
propane) and electric-powered air-source heat pumps or baseboard radiant
heat. These two traditional systems, however, present two drawbacks.
First, even highly efficient models pollute the environment because
fuel must be burned to produce the heat. Second, energy prices! It
has become very apparent that people want cost-effective and long-term
heating and cooling options. Geothermal systems are just the ticket.
They are being installed in homes, businesses, and schools all across
the country.
What’s Wrong With Good, Old-Fashioned Combustion?
Traditional heating systems rely on combustion, the burning of fuel,
either on site or at a power plant. Fuel-powered heating units, such
as gas and boiler systems, burn fuel at the site to produce heat.
Electric-powered heating and cooling systems do not require combustion
at the site of
the furnace but instead, it occurs at the power plants. In 1998,
approximately 80% of U.S. electricity was produced by burning fossil
fuels. Only
nuclear, wind and hydroelectric plants do not burn fossil fuels.
The problem with combustion systems is that the by-products they
produce contain harmful emissions. These emissions degrade air
quality and
contribute to other environmental problems including acid rain
and the greenhouse
effect. For the health of individuals and communities throughout
the world, it makes sense to develop heating and cooling technologies
that
reduce or eliminate fossil fuel combustion.
The application of geothermal heating and cooling has been named "the
most energy-efficient and environmentally sensitive of all space conditioning
systems", by the Environmental Protection Agency. The system's
basic concept takes advantage of the earth's constant temperature,
approximately
55 degrees, to heat and cool a building. By tapping this steady
flow of heat from the earth in the winter, and displacing heat
in the earth
in the summer, a geothermal system can save homeowners 40% to
70% in heating costs and 30% to 50% in cooling costs compared
to conventional
systems.
A typical household can save $1,500, or more, a year. This can
give most systems a payback period of three to five years. Geothermal
units are
more than three times as efficient as the most efficient fossil
fuel
furnace. By moving heat that already exists in the earth, instead
of burning a combustible fuel, geothermal delivers three units
of energy
for every one unit used to power the system.
How Does It Work?
Geothermal works by circulating water, or a water/antifreeze
solution, through a closed loop of polyethylene pipe that
is buried in the
ground or set beneath the water. Geothermal systems can be
laid out in different
orientations, depending on the situation. A closed loop system,
the most popular, can be laid out either vertically in 50
-250 foot deep
holes
drilled like a well, or horizontally in 3-6 foot deep trenches.
The less common open loop system circulates a constant source
of ground water from a stream, well or pond and dispels the
water back to its
origin.
The principle action involves moving heat from a
lower temperature location to a higher temperature location. This
is the
principle of a window air
conditioning unit, where cold air is blown into the
house
and warm air is released out of the back of the unit.
Geothermal works in
a similar
manner, except that its heat source is the warmth of
the earth.
The process of elevating low-temperature heat to over
100° and transferring it
indoors involves a cycle of evaporation, compression,
condensation and expansion. A refrigerant, like Freon, is used as a
heat-transfer medium
which circulates within the pump.
The cycle starts as the cold, liquid refrigerant
passes through a heat exchanger (evaporator) and absorbs heat
from the low-temperature
source
(liquid from the ground loop). The refrigerant evaporates
into a
gas as heat is absorbed. The gaseous refrigerant then
passes through a
compressor where the refrigerant is pressurized, raising
its temperature to over
180°. The hot gas then circulates through a refrigerant-to-air heat
exchanger where heat is removed and pumped into the house at about 100° F.
As it loses the heat, the refrigerant changes back
in to a liquid. The liquid is cooled as it passes through
an expansion valve and begins the
process again. To work as an air conditioner, the flow
is reversed.
Air Distribution Throughout The House
Thermo plastic loops entering into the foundation
4' below grade.
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The ductwork is no different than that of
a conventional forced-air system. The difference is found in the
temperature of the air
flowing from the
registers in the winter. With a conventional
system, the air flow is seldom warmer than 80°. But because
water transfers a greater volume of heat than air,
a geothermal system is able to deliver warmer air,
typically about 110°.
While geothermal systems
require a small amount of electricity to concentrate
the energy and circulate
it through the
system, most
systems acquire
approximately 70% of their energy from a clean,
renewable source, the earth.
Advantages
Since these systems use from 25% to 50% less energy
than conventional systems, users will spend
significantly less on their monthly
energy bills, meaning that most ground source
systems will "pay for themselves" in
3 to 5 years. After this "payback" period,
the owner will simply pay much lower utility
bills.
Other advantages of geothermal systems include
the fact that all components of the unit are
housed inside
the
building, thereby reducing the wear
and tear on the unit by Mother Nature, and
also eliminating the fear of vandalism or theft.
Geothermal
systems
do not require a
flue,
and since there is no on-site combustion, there's
less chance
of fire and
no chance of carbon monoxide infiltrating the
home. Geothermal systems also carry the Environmental
Protection Agency's
Energy Star Label,
which is used to designate energy-efficient
equipment. Often homeowners may
find tax benefits, lower mortgages, or utility
rebates.
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