Abstract Summary
• Thermal energy storge performance of tunnels is enhanced by increasing underground temperature, as induced by climate change. Specifically, thermal loss to the environment is reduced, resulting in improved storage efficiency. • Tunnel environments with convection heat transfer are discouraged for underground thermal energy storage, even in case of comparatively warm air. In fact, best performance is achieved in absence of convection. • In optimal tunnel environmental conditions, storage efficiencies up to 60% can be reached.
