ECN publication
Compacte chemische seizoenopslag van zonnewarmte; Eindrapportage
Visscher, K.; Veldhuis, J.B.J.; Oonk, H.A.J.; Ekeren, P.J. van; Blok, J.G.
Published by: Publication date:
ECN Energy in the Built Environment 1-8-2004
ECN report number: Document type:
ECN-C--04-074 ECN publication
Number of pages: Full text:
92 Download PDF  

Compact seasonal storage of solar heatFor a 100% solar heat supply for space heating and tap water heating in the Northern climates it is a necessity to store energy (heat) for a period of at least half a year. In this study candidate materials are searched for reversible thermo chemical heat storage and heat production in a system concept consisting of a solar collector, a chemical reactor with heat exchangers and separate material buffers for the reactants. On basis of a literature search of materials and their thermodynamic properties a "realization potential" derived from seven selection criteria was calculated for each material. The five best scoring candidate materials have been compared with conventional hot water storage through a system simulation or a calculation of the heat storage and production process. The storage of reactant materials was under atmospheric conditions in all cases. From the simulations it follows that magnesiumsulphate-heptahydrate and iron-hydroxide offer the best chances for development of a new autonomous thermo chemical storage system with an effective energy density that is one order of magnitude larger than that of hot water storage. From calculations is follows that silicon dioxide offers a chance for development of thermo chemical storage system with an effective energy density that is two orders of magnitude larger than that of hot water storage. This process is not autonomous because the heat storage part of the process cannot be conducted near residential buildings. It is however suitable for central production of the solid silicon fuel from silicon dioxide on an industrial scale. The high density silicon fuel then can be transported to residential areas and be "burnt" with oxygen or nitrogen from the ambient air. In this study no definite statements could be made about the reaction rate and material conversion of the reversible chemical reactions. Thermal analyses of some model materials showed that the chemical reactions studied usually do not react easily under atmospheric conditions. The list of best scoring candidate materials therefore has to be considered as a first selection of materials that deserve further research. The materials selected follow the required thermodynamic and technical conditions, but their practical application still has to be demonstrated. This can pose many practical problems.

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