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GEOTHERMAL ENERGY
Geothermal energy is the direct use of geothermal power
for heating and cooling applications. Humans have taken
advantage of geothermal heat this way since the
paleolithic era. Thermal efficiency is high since no
energy conversion is needed.
There are a wide variety of applications for cheap
geothermal heating and cooling. In 2004 more than half
of direct geothermal heat was used for space heating.
A geothermal heat pump can still provide space heating
and air conditioning. Like a refrigerator or air
conditioner, these systems use a heat pump to force the
transfer of heat from the ground to the application. In
theory, heat can be extracted from any source, no matter
how cold, but a warmer source allows higher efficiency.
A ground-source heat pump uses the shallow ground or
ground water (typically starting at 10-12°C, 50-54°F) as
a source of heat, thus taking advantage of its
seasonally moderate temperatures. In contrast, an
air-source heat pump draws heat from the colder outside
air and thus requires more energy.
Closed loop geothermal heat pumps circulate a carrier
fluid (usually a water/antifreeze mix) through pipes
buried in the ground. As the fluid circulates
underground it absorbs heat from the ground and, on its
return, the now warmer fluid passes through the heat
pump which uses electricity to extract the heat from the
fluid. The re-chilled fluid is sent back through the
ground thus continuing the cycle. The heat extracted and
that generated by the heat pump appliance as a byproduct
is used to heat the house. The addition of the ground
heating loop in the energy equation means that more heat
is generated than if electricity alone had been used
directly for heating. Switching the direction of heat
flow, the same system can be used to circulate the
cooled water through the house for cooling in the summer
months. The heat is exhausted to the same relatively
cool soil (or groundwater) rather than delivering it to
the hot outside air as an air conditioner does. As a
result, the heat is pumped over a greater temperature
difference and this leads to higher efficiency and lower
energy use.
This technology makes geothermal heating economically
viable in any geographical location.
ECONOMICS
Geothermal energy is a type of renewable energy that
encourages conservation of natural resources. According
to the U.S. Environmental Protection Agency,
geo-exchange systems can save up to 30-70 percent in
heating costs, and up to 20-50 percent in cooling costs,
compared to conventional systems.
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