Heat-pumps (ground source heat-pump)
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A heat pump system works in a very similar way to a domestic refrigerator. A long
loop of pipes situated outside collects low grade energy from the
environment. For instance 1.5m below ground the temperature remains
constant at ~15C all year round. The evaporation/ compression,
condensation/expansion cycle in the heat pump concentrates the heat energy,
boosting the available temperature to 60C.
This is then used for space heating via under-floor heating, or radiator
central heating.
Heat Pump FAQs.
This diagram above shows the Energy Fence type
collector. See our
collectors page
to see the different types of collectors and discussion of their merits.
A geothermal
heat pump or ground
source heat pump (GSHP) is a central
heating and/or cooling system
that pumps heat to or from the ground. It uses the earth as a heat source
(in the winter) or a heat sink (in
the summer). This design takes advantage of the moderate temperatures in the
ground to boost efficiency and reduce the operational costs of heating and
cooling systems, and may be combined with solar
heating to form a geosolar system
with even greater efficiency. Geothermal heat pumps are also known by a
variety of other names, including geoexchange,
earth-coupled, earth energy or water-source
heat pumps. The engineering and scientific communities prefer the term
"ground source heat pumps" because geothermal
power traditionally refers to heat originating from deep in the earth's
mantle. Ground source heat pumps
harvest a combination of geothermal power and heat from the sun when
heating, but work against these heat sources when used for air conditioning.
Like a refrigerator or air conditioner, these systems use a heat
pump to force the transfer of
heat. Heat pumps can transfer heat from a cool space to a warm space,
against the natural direction of flow, or they can enhance the natural flow
of heat from a warm area to a cool one. The core of the heat pump is a loop
of refrigerant pumped through a vapor-compression
refrigeration cycle that
moves heat. Heat pumps are always more efficient at heating than pure
electric heaters, even when extracting heat from cold winter air. But unlike
an air-source
heat pump, which transfers heat to or from the outside air, a ground
source heat pump exchanges heat with the ground. This is much more
energy-efficient because underground temperatures are more stable than air
temperatures through the year. Seasonal variations drop off with depth and
disappear below seven meters due to thermal
inertia. Like a cave,
the shallow ground temperature is warmer than the air above during the
winter and cooler than the air in the summer. A ground source heat pump
extracts ground heat in the winter (for heating) and transfers heat back
into the ground in the summer (for cooling). Some systems are designed to
operate in one mode only, heating or cooling, depending on climate.
System life is estimated at 25 years for inside components
and 50+ years for the ground loop.
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