Thermodynamic modelling of a combined polygeneration system with sustainability analysis for power, cooling and hydrogen production

Abstract

The study presents the thermodynamic modelling of a combined polygeneration system with sustainability analysis for power, cooling and hydrogen production. The study’s objective includes producing multiple products from a single energy source from an adapted polygeneration plant and comparable cooling rate production from the condensate of one evaporator system. The system’s sustainability was also evaluated based on some considered thermodynamic parameters. The system was modelled component by component, and the thermodynamic models developed were analysed using an engineering equation solver software (EES). The results show that total energy and exergy efficiencies obtained from the operating parameters were 47.2 and 38.32%, respectively, with total cooling rate production of approximately 25 kW. The cooling rate decreases by about 3% for one one-degree rise in the dead state temperature, while for an increase in the gasifier temperature, the high-power turbine work somewhat decreases by about 5%. The maximum hydrogen production rate was about 135 kg/h obtained at 80°C of the electrolyser temperature. The system was sustainable as the exergy-based indicators showed approximately 1.66, 0.87 and 0.65 for the sustainability index, exergetic impact index and thermal exergy index, respectively. Suggestions are made for optimisation for ideal parameters that will bring the system close to ideality.