Materials for thermochemical storage: characterization of magnesium sulfate

Magnesium sulfate hepta hydrate (MgSO4.7H2O) was studied as possible thermochemical material for seasonal storage of solar heat. Both hydration and dehydration were investigated and it was found that the material was able to take up and release almost 10 times more energy than water of the same volume. The amount of water taken up and energy released by the material turned out to be strongly dependent on the water vapor pressure and temperature. Unfortunately, the material was not able to release all the stored heat under practical conditions. Despite this problem, valuable information on the dehydration and hydration behavior of MgSO4.7H2O was acquired and the characterization procedure will also be used for future characterization of other salt hydrates for thermochemical materials