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This energy can be used to heat buildings indirectly.
Pipe is buried in the ground, either in a borehole
or a horizontal trench. The pipe is usually a closed
circuit and is filled with a mixture of water and
antifreeze, which is pumped round the pipe, absorbing
heat from the ground. In winter the ground is warmer
than the air and buildings above. The anti-freeze
mixture absorbs heat from the ground, which is then
concentrated and transferred to the buildings. This
heat can be used to heat domestic water and a low
temperature heating system such as underfloor heating.
Air source heat pumps use the refrigeration process
to transfer low grade energy from the air outside
into high grade energy used for heating and domestic
hot water. Even at temperatures as low as -20?C, an
air source heat pump can supply significantly more
energy than it uses - and with no local C02 emissions,
it helps reduce impact on the environment.
The refrigerant then passes through a condenser where
energy is transferred to the heating system water
and the refrigerant is turned from a high pressure
vapour into a high pressure liquid. The liquid refrigerant
then passes through an expansion valve that lowers
its pressure and temperature. With the refrigerant
evaporating and at a very low temperature it passes
through a heat exchanger. At this stage the refrigerant
collects large amounts of low grade energy from the
air, causing it to boil and return to a vapour form.
This continuous cycle of changing the state of the
refrigerant from liquid to vapour allows the heat
pump to extract energy.
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