Free Cooling Energy from the Ground
A very good practice is to directly cooling the building using the soil as cold thermal source. This mechanism is known as free ground cooling (FGC). It can be easily implemented in GCHPs, only circulating the fluid through the GHX and by passing the heat pump. V-GHXs are preferred for FGC applications, since soil temperatures are lower at deep depths in summer, when cooling energy is generally required. Indeed, FGC effectiveness depends on the inlet set point temperature of the indoor cooling energy distribution system. It increases incrementing the inlet set point temperature. Thus, for very low inlet temperatures FGC is not applicable. When applicable, building space cooling (SC) requirements can be satisfied only consuming a small amount of electricity (Wang et al. 2010; Wu et al. 2014). This makes FGC technique worth of investigation in the design phase of GCHPs, although not all the locations are suitable for FGC application.
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