Comparison of Multi-Tank and Large Single Tank Thermal Storages for Solar DHW Applications

The performance of a multi-tank water storage was studied by experiment and computer simulation. The unit investigated consisted of three 270 L storage tanks connected in series and was charged through individual side-arm, natural convection heat exchangers. Laboratory tests were conducted on a specially instrumented prototype to characterize its performance in terms of temperature stratification, heat transfer and energy storage rates. Based on these tests, a computer model of a complete multi-tank solar thermal system was created. With this model, the performance of a multi-unit storage was compared to a single-tank system of equal total storage volume for a multi-family solar domestic hot water (SDHW) system application. Data were produced for two U.S. locations representative of differing climatic locations. Results show that a reasonably insulated multi-tank system can be used in place of a large single tank with only a small reduction in delivered solar energy.