https://phys.org/news/2018-10-future-energy-combined-storage-key.html > Heat accumulators, where the thermal energy is stored, form the second component of the new storage concept. Thanks to its high specific heat capacity, water serves as an additional thermal energy storage medium for the underground pumped storage power plant. Renewable energy is used to heat the water to up to 90°C. Thermal energy is stored and used by means of heat exchangers installed in the underground reservoirs. When demand for heat is high, it can be supplied directly to consumers via district heating transmission lines. > Franz Georg Pikl also integrated district cooling technology into the concept – this method of cooling buildings is becoming increasingly significant – in the shape of absorption chillers. When required – in other words, on warm days – the hot water drives the chillers, which produce cooling energy that is distributed to customers along district cooling transmission lines. To ensure a constant supply of cooling energy to various temperature zones, this system can be modified by cooling the water of the underground pumped storage hydropower scheme – which could then be labelled a "cold-water pumped storage hydropower plant."