Energy and economic savings using geothermal heat pumps in different climates

A technical and economic feasibility study is performed on residential buildings, heated and cooled by geothermal heat pumps (GHPs) equipped with energy piles. The analysis is carried out for two different climate locations and building energy needs, which have been evaluated following the current European standard ISO 13790. The energy pile system performance coupled with the GHP has been numerically calculated by using the PILESIM2 software over 20 years of operation. The Primary Energy Saving (PES) indices were calculated comparing the actual GHPs systems with traditional cooling and heating systems, together with their sensitivity to thermal and cooling loads for two different climate locations. Also, economic savings and greenhouse gases (GHG) reduction have been calculated resulting from the GHPs use. The results show that in mild climates, where the GHPs are mainly used as HP, the annual average temperature of the ground around the energy piles can increase up to about 10 °C after many years of operation, whereas in cold climates the increase is nearly negligible. Thus, the economical profit of GHPs is more difficult to achieve in mild climates than in cold ones. Conversely, GHG emission reduction is found to be larger in mild climates than in cold ones.