Environmental and exergoeconomic analysis of a low-carbon polygeneration process based on biomass energy, a geothermal source and a high-temperature fuel cell

By combining renewable energy resources, we can expect higher efficiency from energy systems, which in turn can facilitate their commercialization. In addition, fuel cells are among the clean devices that provide superior performance with zero environmental pollution. Fuel cells can improve the stability of the energy conversion system by storing energy. This paper introduces and analyzes a polygeneration system driven by a biomass fuel and a geothermal source. The system consists of a high-temperature fuel cell coupled with a gasification cycle. In addition, a triple-flash geothermal cycle, a refrigeration unit, and a proton-exchange membrane (PEM) electrolyzer are used in the bottoming cycle. Accordingly, power, hydrogen, and cooling and heating capacities are considered as products of the system. Energy, exergy, environmental and economic analyses have been applied to evaluate the system. Besides that, the optimal working conditions of the system based on two decision-making methods have been identified. According to the findings, the outputs of power and hydrogen from the polygeneration system were equal to 3880.8 kW and 0.356 kg/h. Also, cooling and heating capacities of 2168.1 and 1534.5 kW can be obtained. Accordingly, the system will be 33.16% and 60.39% efficient in terms of energy and exergy. Further, the total emitted CO2 and product unit cost are 57.75 kg/GJ and 5.802$/GJ. According to the TOPSIS decision-making method, more optimal environmental and cost findings can be achieved than using the LINMAP method.