Design and applicability analysis of a new district heating system combining the conventional district heating network with renewable energy

In recent years, China has experienced serious air pollution, and people have realized that it is due to the unreasonable energy consumption structure. The current situation is that the coal consumption accounts for about 69% of total energy consumption. Therefore, improving the energy utilization efficiency and adjusting the energy structure have become the most important tasks at present. In this paper, a new district heating technology which combining the conventional district heating system with renewable energy is presented. The doing work ability of the primary pipe network is used to drive the absorption heat exchanger (AHE) in the substation to extract the geothermal energy and the solar energy. Thus, the heating capacity of the heating source can be incremented by 25%. Solar seasonal thermal storage is considered for the annual ground thermal balance and three operation modes of the system are presented. The design method is given and through the case studies of several typical northern cities, the applicability of the system is analyzed. The results show that the system has better economy in the area where the fuel price is high and the soil temperature as well as the solar radiation is higher. The relative energy efficient ratio is 20% to 21% compared with the conventional district heating system.