Design, optimization, and experimental validation of a hybrid biomass–solar multigeneration system for methanol, electricity, and freshwater production

The current methods for desalination and fuel production use lots of energy and rely on fossil fuels. To address this, this work proposes a biomass–solar hybrid polygeneration system that combines biomass gasification and pyrolysis with parabolic trough collectors, aiming to meet some of the thermal needs of both the Rankine cycle and the gasifier's steam generation. Freshwater is produced through a four-stage Multi-Effect Distillation (MED) unit, while methanol is synthesized in a catalytic reactor. Experimental validation of the developed model against laboratory data from methanol synthesis showed deviations consistently below 5% across a wide range of operating conditions, confirming the robustness of the model. The simulation results indicate that at a solar irradiance of 1.2 kW/m², the system produces 720 ton/h of freshwater, generates 31.5 MW of electricity with a turbine efficiency of 72.5%, and achieves a methanol production cost of 284 $/ton. Furthermore, the system attains energy and exergy efficiencies of 67.45% and 59.35%, respectively. The economic assessment results in a net present value (NPV) of 283.8 M$, an internal rate of return (IRR) of 19.5%, and a payback period of 5.1 years. Optimization using Sequential Quadratic Programming enhanced energy efficiency by 6%, significantly reducing energy waste; cut biomass operating costs by 12%, saving a noticeable sum; and decreased the levelized cost of water to a new low of 1.49 $/m³ . Through sensitivity analysis, it was determined that expanding the solar share significantly reduces CO₂ emissions to 0.35 ton/MW while boosting profitability.