Exergoeconomic Optimisation of a Novel Tri-Evaporator Solar-Biomass Multigeneration System Coupled with Fuel Cell and Electrolyser

Abstract

This study presents a novel, cost-effective multigeneration system configuration that utilises locally available solar irradiance and biomass resources to produce hydrogen, electricity, heating, hot water, and cooling. The system integrates a range of energy conversion technologies, including non-conventional parabolic trough collectors, conventional biomass gasification, the Kalina cycle, organic Rankine cycle, vapour absorption system, an electrolyser, and a fuel cell. A thermoeconomic analysis was conducted to evaluate system performance, with exergy-based costing applied to determine the operating costs while optimising overall net output. The study also assessed the exergetic sustainability of the system by analysing thermodynamic inefficiencies. It was found that an optimal ambient temperature of approximately 297.4 K maximises the system's exergetic sustainability index, reaching a value of 1.00. The levelized cost of electricity from the Kalina and organic Rankine cycle subsystems was calculated as 0.04308 USD/kWh and 0.0245 USD/kWh, respectively, corresponding to an exergoeconomic factor of 44.51%. When converted to Nigerian currency, these values equate to 69.12 NGN/kWh and 39.31 NGN/kWh − significantly lower than the prevailing electricity tariff in Nigeria, which stands at approximately 209.50 NGN/kWh (0.1306 USD/kWh). Under specified operating conditions, the optimal work outputs of the organic Rankine cycle and Kalina cycle turbines were 47.97 kJ/kg and 435.3 kJ/kg, respectively. The overall energy and exergy efficiencies of the integrated plant were recorded at 52.2% and 16.14%. This multigeneration system demonstrates strong potential as an alternative to fossilfuel- based power generation, particularly in applications and sectors with low energy demand.