The optimization of tank-volume-to-collector-area ratio for a thermosyphon solar water heater

Through the use of the TRNSYS simulation program, the performance of a domestic solar water heating system operating with natural circulation (thermosyphon) and a daily hot water load has been analysed. The effect of tank height on the annual solar fraction of the system has been investigated for different hot water load temperatures and storage tank volumes. Optimum values (values which maximize the annual solar fraction of the system) for storage tank height and volume are calculated for operating temperatures ranging from 50 to 80°C. The response of the system to the ratio of the storage tank volume to the collector area is investigated. The dependence of the solar fraction on tank height was observed to be more notable in the case of large tank volumes and high load temperatures. The results indicate the existence of an optimum value for the tank volume at a given tank height and a high load temperature. At lower temperatures, the solar fraction rises rapidly with tank volume to a nearly constant level. An optimum value of the storage-tank-volume-to-collector-area ratio was also observed at high load temperatures.