Energy and Exergy Analysis on China's Natural Gas Urban District Heating Systems for Replacing Coal: A Case Study of Beijing

Abstract

China has been vigorously developing natural gas-based urban district heating (UDH) for years to reduce air pollution. Various UDH systems are proposed for a case in the urban area of Beijing. This study investigates the effects of load percentages of different prime movers on the technical performances of several UDH systems at different ambient temperatures. A decrease in the gas turbine load percentage results in an obvious decrease in the exergy efficiency of the UDH system. The calculation results of heating and power outputs, energy and exergy inputs, and exergy efficiency of the UDH systems under different working conditions are presented. The heating association of distributed energy system and on-demand heat pump heating can reach the highest average-exergy-efficiency among the UDH systems. This optimal natural gas-based UDH system should be promoted in China instead of natural gas-fired heating boilers to replace coal-based UDH.