Volume 52

Research on the thermodynamic performance of a novel power generation system for a natural gas pressure reduction station integrated with cold energy and geothermal energy utilization Qin Yang, Xinli Lu, Wei Zhang, Shuntao Hu, Jiali Liu

Abstract

In this paper, a novel multi-energy complementary power generation system used for natural gas city gate stations (NGCGS) is proposed, which aims at recovering considerable amount of energy (including NG pressure energy and cold energy after expansion) wasted at the pressure regulators in city gate stations (CGS). The proposed system consists of three major subsystems: geothermal water system (GWS), NG expansion power generation system (NGEPGS) and organic Rankine cycle power generation system (ORCGS). GWS works as a heat source to heat the organic working fluid in the ORC’s evaporator and then to heat the NG before it enters the expander for power generation. NGEPGS uses an expander to recover the pressure energy for power generation which replaces the conventional process of NG pressure reduction in the CGS. The ORCGS takes the geothermal energy as heat source and uses the cryogenic NG from the outlet of the expander as ORC’s heatsink for electricity generation. The thermodynamic model of the proposed system is established using EES (Engineering Equation Solver). 9 organic working fluids are selected and compared. Pentane has been chosen as the optimal working fluid in this study because it has the best performance. The proposed system is compared with another system established by previous researchers. The results show that the proposed system in this paper can generate more electricity under the same conditions.

Keywords thermodynamic performance, multi-energy complementary power generation system, natural gas pressure energy, cold energy and geothermal energy, working fluid selection