Taguchi optimization of solar thermal and heat pump combisystems under five distinct climatic conditions

Solar domestic hot water systems worldwide generally combine solar collectors and heat pumps. The utilization of heat pump as the auxiliary heat generator of solar combisystem is a common solution of the last decade. Atmospheric factors such as solar radiation, ambient temperature, and relative humidity influence the performance of such systems; therefore, optimizing the flow rates in the solar and heat pump loops, as well as the volume of the water tanks, is essential to obtain maximum heating performance. In this study, the Taguchi method was applied to determine the optimal operating parameters for two solar combisystems (single- and dual-tank) by determining the higher-the-better characteristics of the signal-to-noise ratio. Moreover, five metropolitan areas were selected to investigate the effect of divergent climatic conditions on the Taguchi optimizations. The results demonstrated that the predominant parameter affecting performance varied for the two hydraulic layouts, but was identical across the five cities. In addition, the payback periods of the solar combisystems in the five cities were investigated. The combined results provide practical guidelines for choosing the best type of solar combisystem to implement under varying climatic and economic conditions.