ECONOMIC-POWER GENERATION FROM LOW-TEMPERATURE GEOTHERMAL RESOURCES USING ORGANIC RANKINE-CYCLE COMBINED WITH VAPOR ABSORPTION CHILLER

Power generation with low temperature geothermal resources is not economically viable due to the poor thermal efficiency of organic Rankine cycles (ORC). A novel idea is proposed where a vapour absorption chiller (VAC) can be employed to lower the ORC condensing temperature, thus increasing its power output. This paper presents detailed analysis of a VAC that operates with water-lithium bromide to extract-heat from the geothermal brine leaving the ORC vaporizer. The evaporator of the VAC serves as the ORC condenser. A computer program is coded to simulate the combined ORC VAC performance and compare it with that of the conventional ORC. The results indicate that the ORC VAC option would render power generation more economical. The organic fluid flow rate in the ORC per unit power output is cut by at least 50% in this case, thus reducing the ORC size and turbine cost. Moreover, even though the ORC-VAC includes more components, the total heat exchange area requirement per unit power output remains practically unchanged.