Thermal Storage (HTES)

Efficiency of the energy system is down to the combined efficiency of the components in the system. With the transition to a fossil-free society, we have to rely on the efficiency of nature’s ‘green’ sources such as wind, earth and sun. Storage of energy will in the near future become an important part of the total Danish energy system as part of the necessary leveling out variations in energy production and consumption.

The solution is to build buffers into the energy system. The project ‘HTES’ (High Temperature Energy Storage) aims at demonstrating a new seasonal storage technology. The project will store energy in the subsurface limestones (~600m depth) beneath the greater Copenhagen area, look at integration into a practical context in the DH sector and gaining operational experiences with the technology for subsequent commercialisation.

The principle of the system is whenever there is surplus production of heat – typically during the summer season – the heat is stored in the reservoir. The advantage of the HTES is the size of the storage system and its almost unlimited capacity to receive surplus energy. When demand – e.g during winter - exceeds normal supply, the storage is activated and the heat is produced back via a heat exchanger into the district heating system.

The heat supply for the HTES system will originate from surplus production from CHP units, industrial surplus heat and not least surplus heat from sun farms.