Presented at: 5th International Renewable Energy Storage Conference IRES 2010, Berlin, Germany, 22-24 november 2010.
The heat demand in the summer can be completely fulfilled using solar heat, but in the winter the heat demand is exceeding the solar supply. A solution is to store the excess of solar energy in the summer, and to use it to fulfill the heat demand in the winter.
Water is traditionally used for storing heat (e.g. solar boiler), but seasonal heat storage requires large water tanks (>40m3) that are too large to be placed inside a family building. An alternative option is to store heat by means of chemical processes using the reversible reaction: A+B?C+heat. With thermochemical heat storage, energy storage densities can be reached that are ten times higher than for heat storage in water. Additionally, after the thermochemical material has been charged, the heat can be stored for a very long time without losses. Interesting materials are cheap, non-toxic, non-corrosive, have sufficient energy storage density and have reaction temperatures in the proper range. A large materials inventory by ECN identified a number of interesting materials, including magnesium chloride hexahydrate (MgCl2.6H2O) as one of the most promising materials for seasonal heat storage (Zondag, 2007).
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