Testing of solar hot water stores by means of up- and down-scaling algorithms

For the characterisation of the thermal behaviour of a heat store in conjunction with a numerical store model it is necessary that the appropriate modelling parameters are known. According to the present version of ENV 12977-3 (Thermal solar systems and components- Custom built systems- Part 3: Performance characterisation of stores for solar heating systems) it is required that every store has to be tested in order to determine its parameters. This is even the case, if the stores belong to a series with identical design and only vary in size or volume, or with regard to the heat exchangers. In order to reduce costs for testing, it is favourable if store parameters within one store series can be determined from measurements of certain stores from the same series. In order to develop such a procedure, appropriate investigations have been carried out. Therefore several hot water store series of different manufacturers were tested and their parameters were determined by means of parameter identification. Afterwards, algorithms have been developed for calculating certain store parameters based on the parameters of larger or smaller stores with identical basic design. In order to verify these algorithms, yearly simulations with the simulation program TRNSYS were carried out using the parameters obtained by testing the store on one hand, and on the other hand using the parameters determined by up- and downscaling, in order t