The intermittent and seasonal characteristics of solar water heating systems motivate the development of auxiliary heating equipment. In this study, an experimental study was carried out on a solar water heating system in Xiangtan with hot summers and cold winters. The effects of meteorological parameters such as local solar irradiance and ambient temperature on the heat storage capacity of the system were tested, and the economy and carbon emissions of three types of coupled auxiliary solar heating equipment were comprehensively analyzed. The experimental results reveal that the hot water generated by solar water heating system meets the needs of residents in summer and autumn ; the remainder of the season requires the support of auxiliary heating equipment. Among the three integrated systems, the carbon emission of the biomass-coupled solar water heating system is 188. 26 kg/year, and the net present value is 259 in 18 years. A sensitivity analysis of the three integrated systems revealed that the electric water heater coupled with solar water heating system and the natural gas coupled with solar water heating system are more sensitive to the service life, whereas the biomass coupled with solar water heating system is more sensitive to the discount rate. The policy environment is very important for the development of a biomass-coupled solar water heating system.
Yan et al. (Sun,) studied this question.