Local separation of heat extraction and icing in ice stores

The contribution of renewable energies in the global energy market is increasing. With this Energiewende the energy system needs to become more flexible while the importance of energy storage comes to the fore. An ice store represents a possibility locally to store thermal energy. Ices stores utilise enthalpy of solidification of water. Heat is extracted from the water in the store through heat exchangers. The water temperature decreases until nucleation temperature is reached and ice growth is initiated. Further heat extraction results in ice layer growth around the heat exchanger pipes while the water temperature remains constant. The growing ice layer increases the heat conduction resistance. As a result, more heat exchangers are needed to freeze the water in the ice store.

The objective of this project is to test the impact of surface coatings for heat exchanger surfaces on the local nucleation temperature. It is possible to decrease the local nucleation temperature and to super-cool the water in the ice store through surface modifications. The aim is to uncouple the initiation of ice growth and the heat extraction. Therefore, a higher loading performance and storage capacity of the ice store will be achieved with smaller heat exchangers.