Performance comparison of a natural gas and renewable-based power and desalination system for polygeneration

Conventional district energy supply (DES) systems have relatively lower efficiencies when compared to polygeneration systems. The use of fossil fuels as a primary energy source in DES generates high levels of CO₂ emissions, degrading their environmental performance. On the other hand, renewable energy systems are generally integrated into the energy portfolio mix to improve the overall efficiency and sustainability, whilst curbing the overall greenhouse gas (GHG) emissions. In this study, an alternative renewable energy polygeneration system design based on biomass and solar energy is proposed. A thermodynamic analysis of the system was carried out, and the energetic and exergetic efficiencies were subsequently compared against the reference case. The results indicate that the alternative system only demonstrates slightly improved efficiencies over the reference system on the basis of cogeneration. However, when implemented for polygeneration, the alternative system offers a clear advantage with estimated energy and exergy efficiencies of 62.9% and 41.9%, respectively.