A Numerical Simulation Of A Combined Heating System With Solar Energy And Ground Source Heat Pump In Lanzhou Area

In recent years, the rapid economic development results in a fact that the demand for energy increases continuously. In the meantime, air pollution caused by using traditional fossil fuel has become a serious worldwide problem. Especially during the heating period in winter in China, atmospheric haze occurs more and more frequently, which has seriously affected the normal life, work, and study for people and their health. In order to reduce the use of traditional fossil fuels and realize the requirements of environmental protection and energy conservation, people seek new energy and new technologies of energy conservation, such as solar energy and heat pump technology. Solar energy is considered as the representative of renewable energy due to its characteristics of energy-saving, environmental protection, utilization of renewable energy, etc. The solar water heating systems that can afford the heating loads of buildings in winter have been widely applied in architectural regions. However, because of the influence of the weather condition, a single solar water heating system may lead to the phenomenon of not providing the heat continuously, even interruption. As for the cold north area, a heating system using a single ground source heat pump can absorb the amount of heat from soil during the heating period in winter, which exceeds the hotfix capacity of soil during the non-heating period. Thus, the soil temperature of buried pipes of a ground source heat pump unit(GSHPU) can decline gradually, and the COP value of the GSHPU decreases and its running power increases conversely.In order to overcome the above problems and make full use of the abundant solar energy resources in Lanzhou area, the design idea, technological process, and operating modes for a combined heating system with solar energy and ground source heat pump are proposed in this paper by synthesizing the technologies of solar energy and heat pump and the requirements of heating process. Based on TRNSYS software, this hybrid heating system is feasible in theory by the numerical simulation and performance analysis. The main research results in this paper are as follows.1. Based on the technologies of solar energy and heat pump and the requirements of heating process, the corresponding technological process for this hybrid heating system is proposed. In addition, its operating modes including heating method A, heating method B, and the method C for heat clawback to soil are analyzed.2. The working mechanism of each main component for this combined heating system with solar energy and ground source heat pump is described mathematically and the type choosing and calculation of main equipments are carried out.3. An office building in Lanzhou area is selected as the applied objective of this hybrid heating system and this hybrid heating system for this office building is configured by TRNSYS software. The numerical simulation of change regularities of main running parameters during heating period is executed by means of TRNSYS software. The results indicate that the proposed hybrid heating system can meet the requirement of heating load for this office building. Similarly, another numerical simulation of the method C for heat clawback to soil for the buried pipes of a GSHPU is carried out during the non-heating period. The results show that the method C for heat clawback to soil can recover the soil thermal balance and overcome the problems of the soil temperature drop and the fall in COP value of the GSHPU.4. On the basis of indexes of technology, economy, energy saving, and environmental protection, etc, a comparison of this hybrid heating system with other traditional heating system is carried out. The results indicate that the proposed hybrid heating system has some advantages of low operation cost, advanced technology, the effect of energy conservation and reduction of pollutant emissions, etc.The research in this paper verifies the feasibility of the combined heating system with solar energy and ground source heat pump, which exploits a new path to solve the heating problem in the cold north areas in winter and offers a certain reference role for the comprehensive utilization of the solar energy and shallow geothermal energy.