STUDY ON ADAPABILITY OF DIFFERENT AUXILIARY HEAT SOURCES IN RESIDENTIAL SOLAR WATER HEATING SYSTEM IN CHINA

The solar water heating system (SWH) has the potential to reduce household energy usage substantially and also provide external benefits of reducing emissions of CO2 and other pollutants. But SWH is unstable which needs auxiliary heat source to meet continuous hot water demand. There are various types of auxiliary heat sources applied in SWH, such as electricity heater, towngas heater, heat pump and oil-fired heater. Despite previous studies have proposed the suitable solar fraction in different regions of China, the auxiliary heat source form in different regions has less discussion, which should be somewhat different due to geographic variations and local conditions. This paper analyzes the adaptability of the auxiliary heat source in different regions, which helps to guide the applications of SHW in China. In this paper, the optimized solar fraction and regional applicability of auxiliary heat source from aspects of energy efficiency, economic performance and carbon emissions during the life cycle in the typical cities in China are discussed by using Geographical Information System (GIS) mapping techniques and RETScreen software. The residential solar water heating system base model is developed, provincial capital cities with geographic variations in the solar resource, supply water temperature, local energy price, hot water usage, and available incentives are selected for analysis. The results show that the suitable auxiliary heat source form and optimized solar fraction vary in different regions. For example, towngas boosted SWH is appropriate for most regions especially in the west region of China. Meanwhile, it is better to choose electricity boosted SWH in the east part including Shanxi, Shandong, Hebei and Tianjin province. In addition, heat pump boosted SWH is a good choice in the southern coast region. This study may be useful in guiding government decisions and providing suggestions on the design for the solar thermal system.