Aquifer thermal energy storage (ATES): How much do they cost?

For a successful global energy transition more seasonal thermal energy storage (STES) and district heating and cooling systems are needed. Hence, the economic aspects of STES are essential during the decision-making phase of planning a district heating and cooling system. Until now, only few studies exist on the capital costs of STES and particular aquifer thermal energy storage systems (ATES). Hence, this study aims to identify and analyse the capital costs of 132 existing ATES systems in Europe. Our results show that surface and subsurface installations contribute to 45% and 55% of the total capital costs, respectively. Drilling costs only account for about 8% of total capital costs. The results also illustrate a decrease in capital costs per installed heating and cooling capacity with increasing capacity. Capital costs per installed capacity converge to about 300 €/kW after 2 MW of installed heating and cooling capacity. Hence, larger ATES systems should be favoured. Compared with other seasonal thermal energy storage (STES) systems, ATES systems have the lowest capital costs per storage volume (< 10 €/m³) and the lowest per stored energy (130 – 1630 €/MWh). Hence, if the hydrogeological conditions at a site are favourable for an ATES system, this system should be the preferred STES system. In particular, if cooling and heating are required in equal proportions.