Evaluation Procedure for Storage Tank Tests Using the Combination of TRNSYS with GenOpt and New Proposal for Holistic Error Estimation
Abstract
The Fraunhofer Institute for Solar Energy Systems (ISE) has been operating a test center for solar thermal systems since 1997. Within this test center in- and outdoor test stands are operated for performance and functional testing of solar collectors and for prefabricated solar thermal systems for hot water preparation. Custom built solar thermal systems can have a large number of possible combinations of the various components. Therefore, it is appropriate to have component-wise performance evaluation of solar systems for domestic hot water and/or for space heating according to CEN/TS 12977-2:2010 (CTSS - component testing system simulation). According to the CTSS method controller, storage tank and collector will be tested individually. Based on the determined parameters of the components, a simulation for calculating the energy output of the whole system is performed later. In this way, a lot of different combinations can be evaluated within acceptable costs. To test the component store, Fraunhofer ISE established a test stand and implemented an evaluation procedure with TRNSYS and GenOpt to determine the storage parameters according to EN 12977-3:2008 (domestic hot water storage tank) and CEN/TS 12977-4:2010 (combistores). With this method, parameters such as heat loss rate can be determined on basis of the measurement data (measured input and output) of the tested store. A parameter identification procedure is used to determine the parameters. The “Generic Optimization Program” GenOpt performs iterative TRNSYS (TRaNsient SYstems Simulation Program) simulations continuously adjusting parameters of the storage tank model and comparing simulated output with measured output. When the difference between measured and simulated outputs, which is calculated in a target function called “objective”, is minimized to a certain degree, the simulation represents the thermal behavior of the store with sufficient accuracy and therefore the store parameters are identified.