EVALUATION OF STORAGE CONFIGURATIONS WITH INTERNAL HEAT-EXCHANGERS

An international standard, ISO/DP 9459-4A, 1996 has been proposed to e stablish a uniform standard of quality for small solar heating systems . In this proposal, system components are tested separately and total system performance is calculated using system simulations based on val idated component model parameter values. Another approach is to test t he whole system in operation under representative conditions, where th e results can be used as a measure of the general system performance. Component testing and system simulation is flexible, but requires an a ccurate and reliable simulation model. The advantage of system testing is that it is not dependent on simulations and that it shows the actu al system performance. Its disadvantage is that it is restricted to th e boundary conditions for the test. The heat store is a key component concerning system performance. Thus, this work focuses on the storage system consisting of store, electrical auxiliary heater, internal heat exchangers (solar and load loops) and tempering valve. Four different storage system configurations with a volume of 7501 were tested in an indoor system test using a statistically generated six-day test seque nce and a solar collector simulator. A store component test and system simulation was carried out on one of the four configurations, applyin g the proposed standard for stores, ISO/DP 9459-4A, 1996 and the MULTI PORT store model. Three test sequences for internal load side heat exc hangers, not in the proposed ISO standard, were also carried out. This paper discusses the results of the indoor system test, the store comp onent test, the validation of the store model parameter values and the system simulations. (C) 1998 Elsevier Science Ltd. All rights reserve d.