Study on performance of clean heating systems for energy-saving small households

Abstract: Rural areas in China is potential for installing clean heating system. Considering the distribution of rural population and housing, if we use the common central heating as the heating method, it will lead to low-density heating demand, high initial investment and high hot water transmission energy consumption, and rural buildings are facing the problem of relocation in the process of urbanization, thus decentralized heating is more suitable for rural areas in northern China. Multi-energy combination utilization, as a common means of clean heating, has few experimental studies in typical cold regions of China. The technical, economic and environmental assessments of different combined heating systems lack comparative analysis. Taking small-scale energy-saving heating system for farmhouse in Tianjin as an example, this paper proposes a method to asses technical, economic and environmental impact of different cleaning heating systems using meteorological data. We compared and analyzed the applicability and operation of three systems: the air-source heat pump combined with solar collector system, the condensed gas furnace combined with solar collector system, and air-source heat pump combined with condensed gas furnace system. The hot water load under different standards was calculated using an energy simulation software based on the heating load calculated for typical small household. The key equipment was selected based on the load level, and a test platform using floor radiation as terminal heating equipment was established to obtain the essential heating characteristics of the key equipment. Experiment based on the standards was conducted, and the relationship between the performance parameters of the key equipment and the outdoor environmental parameters were obtained. The primary energy consumption and primary energy rate of each system was evaluated based on typical annual meteorological data. Economic assessment of the three systems was based on the annual cost of their energy consumption and the existing energy policy; the environmental impact was assessed based on the annual energy consumption and the CO2, SO2 and NO2 emissions. The results show that the primary energy ratio and the consumption of the air-source heat pump water heater combined with solar collectors were equivalent to those of the solar collectors combined with gas furnace. The initial investment and operating cost of the air-source heat pump water heater combined with solar collector system were the lowest, with an annual cost of ￥1 638.29, but its heating quality was low when ambient temperature was below -6 °C. The subsidy provided from the clean heating policy accounts for 45.07% of the annual operating costs, indicating that the policy plays an important role in promoting the clean heating system. In terms of environmental impact, the pollutant emission of the scheme 2 was the lowest. The CO2 emissions of Scheme 2 were 65% and 59% of Scheme 1 and Scheme 3, respectively. The SO2 emissions of Scheme 2 were 9% and 8% of Scheme 1 and Scheme 3, respectively, and the NOx emissions of Scheme 2 were 26% and 23% of Scheme 1 and Scheme 3, respectively. This study provides technical reference for the application of clean heating in rural areas.