Parametric analysis and multi-objective optimization of biomass-fired organic Rankine cycle system combined heat and power under three operation strategies

Biomass-fired organic Rankine cycle (ORC) systems for combined heat and power (CHP) generation are a feasible technology to provide carbon-neutral power production. In this study, the parametric analysis and multi -objective optimization of a biomass-fired ORC-CHP system under three operation strategies are conducted. The thermodynamic, exergoeconomic, environmental and sustainability models are established, while the effects of seven operation parameters on exergy efficiency (riex), unit cost of exergy (UCE), equivalent carbon emission (ECE) and ecological life cycle cost (ELCC) are examined. A further four-objective optimization problem is addressed using NSGA-II and the Pareto-optimal solutions for the three operation strategies are derived and compared. The results indicate that evaporation temperature, condensation temperature and heat source inlet temperature present positive effects on riex and UCE, whereas opposite effects are imposed by degree of superheat and pinch point temperature difference. System B yields a 0.21% higher riex and a 0.41 tons higher CO2,eq than system C. The Pareto-optimal solutions of riex, UCE, ECE and ELCC for system A using TOPSIS decision-making are 12.380%, 0.183 $/kWh, 10.250 tons CO2,eq, and 13.677 x 10-3 $/kWh, respectively. System A may be regarded as the preferred operation strategy for biomass-fired ORC-CHP systems due to its moderate performance.