From thermodynamics to sustainability: 4E analysis and parametric insights into solar-assisted organic Rankine cycle systems under resource constraints

• 4E and parametric analysis of three solar-assisted ORC–NG hybrid configurations. • Cascaded dual-loop ORC achieves 10 % energy and 13.1 % exergy efficiency. • Parametric analysis reveals key trade-offs in HTF temperature and collector size. • n-Butane and isobutane identified as optimal fluids for high/low temp cycles. • Up to 503 tCO 2 -eq avoided annually, equal to 46 ha of forest carbon capture. This study investigates three solar-driven Organic Rankine Cycle configurations integrated with a natural gas burner as auxiliary heat source. These configurations include (i) preheating of the heat transfer fluid before the solar collector, (ii) a regenerator for turbine waste heat recovery, and (iii) a cascaded dual-loop system. Dynamic hourly-based comparative simulations were performed in TRNSYS with thermodynamic properties evaluated in EES, and performance assessed through a comprehensive 4E framework with updated Chemical Engineering Plant Cost Index (CEPCI) normalized cost data and experimentally validated collector performance, ensuring realistic and reproducible results. Results show that the cascaded ORC offers the most favorable performance, with energy and exergy efficiencies of 10 % and 13.1 %, and the lowest levelized cost of electricity ($0.16/kWh) despite the highest net present cost. Environmentally, it avoids about 503 tons of CO 2 -eq annually, equivalent to the carbon capture capacity of 46 ha of forest. Following the 4E evaluation, detailed parametric analysis was conducted to optimize energy, exergy, economic, and environmental performance and operation in resource-constrained regions. Parametric analysis identified the optimum collector area balancing efficiency, exergy destruction, and fuel savings, with oversizing causing diminishing returns and undersizing increasing natural gas dependence. For the ORC subsystem, n-Butane and isobutane were confirmed as the most suitable fluids with significantly lower Global Warming Potential (GWP) for the high- and low-temperature cycles, respectively. Moreover, it was shown that integrating the monetary value of avoided CO 2 emissions could shift system economics, make larger solar fields more attractive and align designs with long-term sustainable development goals.