Comparative analysis of BTES, ATES, and power-to-hydrogen systems for seasonal storage in public building clusters

Abstract

This study compares three seasonal storage pathways for 44 public buildings with shared rooftop PV in Drammen, Norway. The buildings face a strong mismatch between summer PV surplus and winter heating demand. The three pathways are borehole thermal energy storage (BTES), aquifer thermal energy storage (ATES), and a electricity-to‑hydrogen-to-electricity chain. We use measured hourly data from March 2020 to February 2021. Each pathway absorbs the summer PV surplus, stores it across the season, and returns it during the heating period. BTES and ATES are assessed as thermal storage pathways, while the hydrogen chain is evaluated as an electricity-side storage pathway. BTES injects 10,208 MWh of thermal energy into the ground and recovers 5339 MWh in winter. The seasonal recovery efficiency is close to 52%. ATES at a baseline groundwater velocity of 0.15 m per day recovers 6229 MWh from the same input and reaches 61%, the highest of the three. The hydrogen chain recovers 1452 MWh of electricity from 4455 MWh of summer surplus, giving a round-trip efficiency near 33%. ATES recovery depends strongly on local hydrogeology. Across a sweep of groundwater velocities from 0.02 to 0.30 m per day, recovery ranges from 71% down to 50%. At velocities above 0.25 m per day ATES drops below BTES. Under high‑carbon grid conditions, annual avoided emissions reach up to about 85 t CO₂ per building for BTES and 110 t per building for ATES. The hydrogen chain has the highest annualised cost. Per kWh of electricity delivered it is roughly fifteen times that of BTES. BTES remains the robust thermal option when aquifer conditions are unfavourable, while ATES is preferable where hydrogeology permits.