New medium-low temperature hydrothermal geothermal district heating system based on distributed electric compression heat pumps and a centralized absorption heat transformer

Abstract

Development of geothermal heat for district heating has attracted considerable attention in China. However, transporting geothermal heat for long distance has become the bottleneck for developing large-scale medium-low temperature hydrothermal geothermal fields that located far away from heat load areas. To solve this problem, a new medium-low temperature hydrothermal geothermal district heating system based on distributed electric compression heat pumps and a centralized absorption heat transformer is proposed and evaluated both from the aspects of thermodynamic performance and economic benefit. Analysis of the results may lead to following main conclusions: (i) for the proposed system, its cost-effective main line length of the primary heating network is about 10 km. (ii) The annual coefficient of performance, annual product exergy efficiency, and heating cost of the proposed system are found to be 24.5, 61.4% and 55.62 ¥/GJ, respectively. The centralized absorption heat transformer can reduce irreversible loss of the heating station and improve performance of distributed electric compression heat pumps. (ⅲ) Unlike the conventional medium-low temperature hydrothermal geothermal district heating system with longer distance of transporting geothermal heat, the annual coefficient of performance and annual product exergy efficiency of the proposed one can be improved by about 4.34 and 7.4%, respectively.