Environmental Footprint of High Temperature Aquifer Thermal Energy Storage

Abstract

High Temperature Aquifer Thermal Energy Storage (HT-ATES) systems are a form of shallow geothermal energy application, which can be used in seasonal applications to buffer heat production and demand from a variety of heat sources. This function enables HT-ATES to improve the efficiency of large-scale heat sources by facilitating heat production to function at maximum capacity throughout the year, irrespective of fluctuations in demand. However, HT-ATES cannot be said to be free of impacts. In order to determine marginal effects of HT-ATES to heat sources, this research carries out one of the first attempts to quantify the environmental and energy footprints of ATES by means of a life cycle impact assessment (LCIA) and life cycle cumulative energy demand (CED) analysis through the investigation of two systems: a geothermal heat plant delivering heat for direct use in greenhouse farms, and a waste-to-energy incinerator delivering heat to a municipality. Analysis is carried out considering environmental effects and energy demand of the final delivery of 1 GJ of heat as the comparison basis. This is analysed using the ReCiPe midpoint method with European normalisation, and the single issue CED method – both accessible in SimaPro 8. ReCiPe midpoint assesses environmental effects within the life cycle of a product without weighing into damage categories, whereas CED analyses the life cycle for primary energy demand. Outcomes of the analysis reveal that marginal effects of HT-ATES on heat sources are unsubstantial compared to the benefits they provide, and that compared with conventional heat delivery by natural gas incinerator in the Netherlands, HT-ATES/heat source systems exhibit fossil fuel savings and climate change reduction. However, analysis also reveals that primary energy demand is higher for HT-ATES/heat source systems than for conventional means of heat delivery. This paper shows how boundary conditions may influence the extent of life cycle effects of such systems, and highlights the environmental categories in which ATES benefits or hinders heat supply.