Life Cycle Assessment of Underground Thermal Energy Storage Systems: Aquifer Thermal Energy Storage verus Borehole Thermal Energy Storage.

Underground Thermal Energy Storage (UTES) systems are energy conservation systems used to buffer the difference between energy supply and energy demand and therefore represent an interesting alternative to energy depletion. At the same time they contribute to cut CO2 emissions by a reduction of energy demand from traditional heating/cooling systems. Even though UTES are relatively environmental friendly solutions they are not completely free of impacts on the underground. They have possible hydro(geo)logical, chemical, thermal or microbiological impacts that are obviously strongly interrelated. The risks of UTES to groundwater quality are insufficiently known, and policies to address this uncertainty are still lacking. In order to improve the understanding and knowledge of UTES techniques, this study aimed to perform a Life Cycle Analysis (LCA) on two different UTES systems: Aquifer Thermal Energy Storage (ATES) and Borehole Thermal Energy Storage (BTES). Even if at present LCA has been mainly performed on products of the industrial and building sector it can be a useful instrument to determine the sustainability of these two possible alternatives of underground exploitation.