Experimental Investigations on Charging and Discharging Strategies of Thermal Energy Stores and Their Effect on System Efficiency
Abstract
For solar thermal combisystems, different storages and corresponding charging and discharging concepts are available, e.g. with immersed or external heat exchangers and/or internal or external stratification concepts. In several publications the effect on the system performance is discussed based on simulations and/or test sequences which are representing constricted operating conditions (Han, 2009; Logie, 2010; Lohse, 2010). To achieve a more compelling assessment based on experiments, a combisystem with four different storage and storage integration concepts were tested under realistic load conditions, using the Concise Cycle Test (CCT) method. The common features of all tested systems are the auxiliary heater and the solar collectors as well as the storage volume. Different hydraulic schemes were used for the systems tested to connect these components with the storage. Both immersed and external heat exchangers were used for charging (by the solar collectors) and discharging (domestic hot water preparation) the storage.