There geothermal heat pump it is a machine that allows to exploit the ground as a natural resource to reduce energy consumption in the thermal uses of a building: heating, air conditioning and hot water production. Operation is based on the exchange of heat between a cold source, the ground, and a hot source, for example the heating system.
Certainly also there geothermal heat pump to function it needs a share of external 'fuel', which is normally electricity, but the efficiency of the pump drastically reduces the consumption that would occur if the same energy were used directly. On average, the production of 1kWh of thermal energy corresponds to a consumption of 0.25 kWh.
The numbers say that the a heat pump that exploits the ground (technically Ground Source Heat Pump - GSHP) is convenient not only for the end user but also for the entire energy system. In fact, if approximately 2.7 k Wh of primary energy is needed to produce 1 kWh of electricity, with a GSHP system, 1 kWh of electricity corresponds to 4 kWh of thermal energy, that is, an amount greater than that invested.
Compared to heat pumps that use air or water for heat exchange, the geothermal heat pump it has better performances in the summer period (le heat pumps are refrigeration machines and with a cycle inversion system can be used for summer air conditioning) because the ground temperature lower than that of the air makes the heat exchange effective.
In general, to use a system well a heat pump you need a cold source at a not excessively low temperature (the ground is ideal) to be combined with a low temperature heating system. Heat pumps are ideal with radiant floor or wall heating systems or with air systems.
The soil reaches the average external air temperature at a depth of around 20 meters. Beyond this threshold, the temperature increases by 3 ° C every 100 meters. To exploit the heat of the ground the geothermal heat pumps based on heat exchangers use three technologies:
- vertical geothermal probes: heat exchangers installed vertically in the ground with lengths from 50 to 350 meters;
- coils in the ground: heat exchangers placed horizontally 1-2 meters deep in soft ground;
- energy poles: heat exchangers integrated in the foundations of piling constructions with a depth of a few meters.
Only the geothermal probes however, they can be considered an application of geothermal energy. In fact, serpentines and energy poles do not exploit the heat of the subsoil but rather the solar energy that heats the ground up to a few meters deep.
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