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ECN publication
Inventarisatie warmte-opslag-concepten
Published by: Publication date:
ECN Energy Efficiency in Industry 1-12-1999
ECN report number: Document type:
ECN-I--99-016 Other
Number of pages: Full text:
126 Download PDF  

Heat storage can improve the exploitation of renewable energy in thebuilt environment. The storage of thermal energy can be subdivided in short and long-term storage, in active and passive systems and in working principles (sensible, latent and chemical heat). In this report an overview of heat storage systems is presented. Usually, storage systems are insulated tanks filled with water. Small tanks are used in combination with solar collector systems and large tanks in greenhouses. For a better stratification vertical systems are preferred to horizontal tanks. Disadvantages are the heat loss and the requirement of a large temperature difference to unload the system. Phase Change Materials (PCM) have a large storage capacity in a small melting range. Examples are salt hydrates and paraffines. A great deal of research has been carried out to improve the heat conduction and heat transfer. To avoid oxidation of the salt and loss of material, some PCMs are encapsulated. These macro-encapsulated PCMs can be used in water tanks or a water bag to increase the storage density. For passive systems in buildings it is also possible to use organic or micro-encapsulated PCM in building materials like wallboard and plasters. These building materials are not commercially available yet. Chemical reactions like hydratation make it possible to store energy without loss of heat and to transform the heat to another temperature level. ECN is carrying out investigations on the Na2S.nH2O system in the SWEAT project. In many locations in the Netherlands, energy is stored in aquifers for large scale cooling and heating demand. It is also possible to use small size closed systems with horizontal or vertical heat exchangers in the ground. They are mostly used as a source for heat pumps. 66 refs.

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