地热驱动的新型冷热电三联供系统的热力学与热经济学分析

THERMODYNAMIC AND ECONOMIC ANALYSIS OF NOVEL SYSTEM COMBINED COOLING,HEATING AND POWER DRIVEN BY GEOTHERMAL ENERGY

针对地热能源的梯级利用问题,以170℃地热水为热源提出一种联合闪蒸-Kalina发电循环和吸收式制冷循环的新型冷-热-电三联产系统,并验证系统的可行性及优越性。对系统进行热力学与热经济学计算,详细分析蒸发压力,氨水浓度和分流比等关键参数对系统热力学性能的影响。结果表明:提高氨水浓度和Kalina循环中汽轮机的进口压力均能使系统的热效率增加;闪蒸-Kalina循环部分的净发电量和效率在闪蒸压力为0.3 MPa时存在最优值,分别为601 kW和43.9%;使系统安全运行所需的氨水浓度范围为0.89~0.68;吸收式制冷系统的能效比(COP)与精馏塔入口温度成正比例关系;系统的总效率随冷凝器出口处分流比的增加,呈先减小后增大的规律。通过热经济分析得到的结果表明:汽轮机是投资成本最大的部件,较高的分流比可使系统投资回收年限减小。

Aiming at the cascade utilization of geothermal energy,a novel system combined cooling,heating and power which combined flash-Kalina power generation cycle and absorption refrigeration cycle is proposed using geothermal water at 170℃as the heat source,and the feasibility and superiority of the system are verified.The thermodynamic and economic calculations of the system are carried out,and the effects of key parameters such as evaporation pressure,ammonia concentration and split ratio on the thermodynamic performance of the system are analyzed in detail.The results show that the thermal efficiency of the system can be increased by increasing the ammonia concentration and the inlet pressure of the turbine in the Kalina cycle.The net power generation and exergy efficiency of the flash-Kalina cycle part have optimal values when the flash pressure is 0.3 MPa,which are 601 kW and43.9%,respectively.The ammonia concentration required to safe operation of the system ranges from 0.89 to 0.68.The coefficient of performance(COP)of the absorption refrigeration system is proportional to the inlet temperature of the fractionating column.The total exergy efficiency of the system decreases first and then increases with the increase of the split ratio at the outlet of the condenser.The results obtained through the economic analysis show that the steam turbine is the component with the largest investment cost.A higher split ratio can reduce the payback period of the system investment.