Efficiency Analysis Of Binary Cycle Power In Distributed Geothermal Energy System And Experimental Investigation Of Cascaded Heating System

With the energy challenge for sustainable development, the geothermal energy would play a key role in promoting renewable energy utilization in the future energy structure of the world. The large-scale utilization of medium-low enthalpy geothermal resources would have great market potential in China. It is necessary to study the cascaded use of medium-low enthalpy geothermal power generation and district heating system. The core of this dissertation is thermodynamic performance study through expression derivation, numerical computation and experimental data analysis, which have essential technical guidance to medium-low enthalpy geothermal system design and performance evaluation.In this dissertation, the exergy analysis method was employed to evaluate the thermodynamic performance of Organic Rankine Cycle (ORC) geothermal power generation system. The method has improved exergy efficiency model of the main equipments in conventional binary power plant. The overall thermal efficiency and exergy efficiency are calculated under different reference conditions based on a conceptional medium-low enthalpy geothermal binary power plant in China. A computed model was established using EES engineering software, the influence of inlet high pressure of turbine and environmental dead temperature on the cycle efficiency was optimized, and some technical measures of improving binary cycle efficiency was analyzed.The dissertation puts forward the novel conception of Distributed Geothermal Energy System (DGES), and gives thermoeconomic analysis on the given geothermal Kalina Cycle Power & District Heating System. Simultaneously, according to the structural method of thermoeconomic optimazation, the Coefficient of Structural Bond (CSB) values of key heat exchangers in the DGES plant were estimated.The dissertation established a research platform of cascaded geothermal district heating system with relatively larger heating scale in China. Through collecting the operation data of representative heating days in the heating period, the geothermal utilization factor and total energy efficiency ratio are analysed, and influencing trendancy on the system performance index was studied due to the reinjection water temperature variation. The exergy analysis model of the selected geothermal cascaded district heating system was given, from which the heat exchanger value distribution, exergy losses and exergy loss ratios in heat exchanger process between geothermal water and secondary recirculating water were determined from those analysis to find corresponding energy & exergy loss parts or system components aiming to promote the overall energy utilization efficiency. The study could afford technical support for domestic large-scale geothermal district heating system design.The dissertation studied the variation relationship among sustainability, environmental impact and exergy efficiency of energy system, analysed the geothermal reinjection technology of doublet-well system popular in geothermal engineering. The environmental benefits and environmental impacts of geothermal energy utilization were assessed comprehensively.