Comparison of two different approaches for a geothermal heating system

Abstract

This project compares two different design approaches for achieving a geothermal district heating system in Huang Hua city, HeBei province. The Jinxiuhuacheng building project, with a heat load of 4.6 MW for more than 116,000 m2, has been used to assess these design approaches. This project presents the specificity of having buildings heated with only floor-heating or with only radiators grouped together and located nearby the heat central. The first design approach is based on the traditional Chinese way with two distribution systems in the heat central. Hot water is produced via heat exchangers connected in series, using return water from the radiators heat exchanger as supply water for production of floor-heating hot water. In this case, radiators are designed for 65/50°C supply/return temperatures and floor heating for 45/35°C. The other design approach has only one distribution system carrying supply water produced at 70°C via one heat exchanger at the heat central. Radiators are designed for 70/35°C supply/return temperatures. Floor-heating, requiring lower supply temperature, is directly connected to the supply pipelines and equipped with mixing devices to mix (cold) return water to the district heating supply water. Results of the assessment are discussed in three parts, the production system, the distribution system and the space heating system. Finally, an economic analysis of the two different approaches is made. The main conclusions are that the new approach allows simplification of the control system, reduces the distribution system cost and yearly operational cost. On the other hand it increases the indoor system investment cost. On the whole, it seems to be more economical, with more attractive and space efficient radiators. In addition, it can supply good quality domestic hot water heating.