Heat storage materials for the energy transition
Space heating accounts for more than half the energy consumption in Germany, and therefore plays a crucial role in the energy transition. In addition to minimizing thermal losses, effective utilization of heat requires suitable storage to bridge the temporal gap between generation and demand. Zeolite heat-storage systems promise great flexibility and high storage capacity. Energy in the form of water vapor is absorbed in the interior of this highly porous material. One problem of this storage concept that has not yet been solved is the heat transfer between the storage material and the heat exchanger. High thermal transmission resistance between metalic structures (heat exchangers) supplying and removing heat to and from the granulated zeolite hinder its effective thermal loading and thermal discharge.
Fraunhofer FEP is taking a new approach in the ZeoMet project: Zeolite granules are metalized in a rotary drum process under vacuum. They thereby acquire a thin aluminum layer (< 0.1 mm) that has high thermal conductivity while at the same time still exhibiting enough porosity that the zeolite base material remains accessible to water vapor molecules, therefby maintaining the absorption capacity of the granules. This ensures good heat transfer at the loading and unloading point as well as heat and mass transport between the metallized pellets in the bed. Sintering of the individual metalized pellets to form larger aggregated units is also possible.