Energy from the earth
Geothermal energy uses the subsoil or the water present in it (hydrothermal) as a thermal source to heat and cool buildings and, at the same time, to produce domestic hot water.
From a depth of about 15 m, the temperature of the subsoil is constant and no longer depends on the external climate, just as the temperature of the groundwater is stable. One can therefore define “low-enthalpy” (or low-temperature) geothermal energy an inexhaustible and renewable source of energy because it is always available.
The heat pump allows heat to be transferred from a lower temperature source (ground, groundwater, air) to the environment to be heated (heating system, domestic hot water or process water) by raising its temperature. In the cooling phase, the plant represents the cold source from which heat is extracted in order to obtain even lower temperatures so as to inject coolness into the environment.
Heat exchange with the subsoil takes place mainly in two ways:
– open-circuit systems, in which the heat pump carries out the heat exchange with groundwater drawn from and returned via a hydraulic circuit with separate wells (hydrothermal);
– closed-circuit systems, where the heat pump carries out the heat exchange with the ground indirectly, by means of a unified hydraulic circuit (inserted up to 100 ÷ 120 metres underground) in which a heat transfer fluid flows.
to the core.
the advantages of being more sustainable
The energy and economic advantage of heat pumps is the ratio between the amount of heat supplied the
building and the amount of energy (usually electricity) used: this ratio is called COP (Coefficient Of Performance). Heat pumps are inherently much more efficient than a boiler because they do not ‘produce’ the energy needed to run the system through combustion, but rather ‘transport’ it. To make 100 units of thermal energy available in the room to be heated, boilers
burn about 120 units of chemical energy of fossil fuel or biomass; the heat pump, on the other hand uses 70-80 units of renewable energy, requiring only 20 to 30 units of electricity. Compared to using air as the ‘source’ of the heat pump, the choice of sources such as the ground or groundwater (characterised by higher average temperature values and, above all, less variability than air) allows for higher average seasonal energy performance and greater stability of the heat output of the heat pump
The choice of source (air, ground, water) and the relative seasonal trends are therefore of utmost importance in determining the performance of a heat pump and are reflected both on the energy performance of the system and on the sizing of the heat pump.