Assessment of a novel geothermal powered polygeneration system with zero liquid discharge

Energy, exergy, economic, exergoenvironmental, and environmental analyses are reported for a novel polygeneration system consisting of a geothermal cycle, a CO2 cycle, a reverse osmosis unit, an electrodialysis unit, a lithium bromide absorption chiller, and a liquefaction unit for natural gas. The proposed system is able to produce electricity, cooling, desalinated water, sodium hydroxide, and hydrogen. To study the environmental aspects of the proposed facility, the associated social cost of air pollution is determined. This parameter implies a comparison between nonrenewable and renewable energy systems to produce the same amount of electricity, while the amount of air pollutants generated and their associated costs are considered. Three scenarios are introduced. The results indicate that the system produces 631 GWh/year electrical energy, 465 GWh/year cooling, 6.22 left-to-right markton/year NaClO, 1.57 x 10(8) m(3)/year hydrogen, and 386,000 m(3)/year potable water for a geothermal working fluid supplied with mass flow rate of 100 kg/s at a temperature of 150 degrees C and a pressure of 457.5 kPa. Also, the calculated values of the energy and exergy efficiencies are 58.3% and 94.2%, respectively. The payback period is determined to be 5.3 years. The net present value left-to-right markis found to be left-to-right mark113.6 million US$ which is lower than that for all the nonrenewable-based scenarios considered.