Using Green Energy Sources in Trigeneration Systems to Reduce Environmental Pollutants: Thermodynamic and Environmental Evaluation

Abstract

With rising electricity demand and environmental concerns, renewable energy is increasingly important. Geothermal power plants offer an opportunity to utilize natural energy sources advantageously. These systems can be coupled with other power cycles, like gas Brayton cycles, to maximize their potential output. Biogas is considered a viable replacement for fossil fuels such as natural gas to further mitigate pollutant gas emissions. In this paper, a biogas-fueled gas turbine coupled with a double-expansion geothermal cycle is proposed that uses, for heat recovery, combustion product gases to run a Kalina cycle. After heating the geothermal fluid twice for double expansion, the product hot gases also heat water in a domestic water heater. Also, three thermoelectric generators are utilized to increase the overall output. Using the geothermal cycle’s waste heat, a humidifier–dehumidifier desalination unit is considered for freshwater production. Green energy, freshwater, and heat are the system’s products, all of which are useful. The proposed system is examined from a thermodynamic perspective using EES V.10.561 (Engineering Equation Solver) software. For the considered input parameters, energy and exergy efficiencies of 36% and 44% are achieved.