Technical and economic performance analysis of large flat plate solar collector coupled air source heat pump heating system

Abstract

In rural areas of China, clean energy heating in winter is important for coal replacement. Winter temperatures in northwest China are usually below 0°Celsius and the heating season lasts for a long time, which is a huge expense for local residents. Solar energy, air source heat pumps(ASHP), and other energy-saving technologies are known to be effective in reducing heating expenses. However, due to the intermittent and unstable nature of solar energy itself, relying on solar heating is difficult to ensure stable heating and is certainly not economical. ASHP adds a financial burden to local residents due to the relatively high cost of winter heating. In response to the above problems, a new idea of ASHP coupled with solar energy for stable heating is proposed, and a large flat plate solar collector-air source heat pump(LFPSC-ASHP) heating system was established in Green Village, Lanzhou City. Experimental and simulation studies were conducted for this system to reveal the performance and economic benefits of the system for the heating season in three modes: solar collector heating, solar heat pump heating, and air source heat pump heating. The results show that the ASHP-assisted solar heating system is a great technical and economical improvement over the use of solar collectors or ASHP heating throughout the heating season. The LFPSC-ASHP system can continuously and stably heat the target building and has excellent economic and environmental benefits. In the operation of the whole heating season, the average collector efficiency of LFPSC is 0.42, the average COP of solar heat pump heating season is 3.75, and the average COP of ASHP heating season is 2.94. The solar fraction of the system in the whole heating season is 31.8 %, and the system energy efficiency ratio is 3.08. The system can save 7,690.5 CNY by running the whole heating season with a dynamic payback period of 6.58 years. ​Sensitivity analysis of the dynamic payback period shows that lower coal prices extend the dynamic payback period, while lower electricity prices and system costs reduce it. The primary energy saving rate of the system in the whole heating season is 67.5 %. The system can conserve 4,700.06 kg of standard coal in a whole heating season, which is equivalent to a reduction of 12,323.55 kg of CO2.