Within the frame of two projects funded by the German Federal Ministry for Research and Technology (BMFT) a thermochemical energy storage system for solar application and a sensible/latent hybrid storage system for industrial application were investigated. The thermochemical energy storage system utilizes the heat of reaction of the reversible reaction of magnesium and hydrogen. The operation temperature range is between 280°C and 480°C. The storage capacity amounts to about 54 MJ. The combination of the MgH_2/Mg system with an appropriate low-temperature alloy/hydride offers the option of producing cold below 0°C in the heat retrieval cycle. The hybrid storage system uses a salt/ceramic which consists of a micro-porous MgO matrix, the pores of which are filled with a salt (85 wt% NaNO_3, 15 wt% NaNO_2). The sensible heat of both the ceramic and the salt and the phase change enthalpy of the salt in the temperature range 250°C to 290°C can be utilized. The experimental storage bed was operated in the temperature range of 150°C to 450°C, the storage capacity was about 400 MJ. Air was used as the heating and cooling heat transfer medium.
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