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Powerful cold thermal energy storage with vacuum ice slurry

By Mathias Safarik, ILK Dresden

Cold thermal energy storage can be applied in air-conditioning and industrial cooling systems. Efficient cold thermal energy storage with high energy density can make an important contribution for the integration of high shares of renewables, e.g. solar thermal, PV, wind. 

For cold thermal energy using ice as phase change material has several advantages: 

  • The storage temperature (0 °C) is close to the applications temperatures commonly used, e.g. 6 °C
  • The storage density is much higher compared with sensible chilled water storage (about 7…8 times)
  • The storage temperature / phase change temperature is constant 

In order to overcome the drawbacks of conventional block ice storages the vacuum ice slurry technology has been developed by ILK Dresden and demonstrated in a first pilot installation.

In the vacuum ice process a pumpable mixture of water and ice is generated by direct evaporation of the refrigerant water near triple point conditions (0 °C, 6 mbar) – a very interesting process where water boils and freezes at the same time. This direct evaporation process allows a considerably higher efficiency (~30 %) compared to conventional block ice storage. 

Vacuum ice generation is connected to a chilled water system or water chiller. That means, it can be connected with solar thermally or solar electrically driven chillers.

First pilot installation of a vacuum ice slurry cold thermal energy storage connected to the chilled water network of Zwickau University of Applied Sciences

The main parameters of the first commercial pilot installations are: 

 

  • charging capacity (ice generation): 50 kW
  • Discharging capacity (ice melting): 100 kW
  • Storage capacity: 350 kWh

Within the second pilot project the ice generation capacity has been increased to 180 kW. The ice generator is connected with a 1 MWh storage. The plate heat exchangers and pumps installed allow a discharging capacity of 350 kW. 

The next step will be the further increase of the ice generation capacity to 500 kW per module. This will reduce the specific cost and enhance the economy. This step will be done within the WindNODE project as part of the German Sinteg initiative to develop and demonstrate solution for the integration of high shares of renewables. 

Partners interested in applying the full scale demonstrator in their cooling system are welcome to cooperate.

Further information is available here.

Please click here to download the project presentation.

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