3E Comparative Analysis of Brayton–ORC Cycle Using Two Thermal Sources: Solar Energy and Coconut Shell Biomass

Abstract

Solar energy and biomass offer sustainable alternatives to meet the energy demand and reduce the environmental impact of fossil fuels. In this study, through mass and energy balances, a comparative analysis of energy, exergy, and environmental impact (LCA) was conducted on two renewable thermal sources: solar energy and coconut shell biomass, both coupled to a supercritical CO2 Brayton cycle (sCO2) with an organic Rankine cycle (ORC) for waste heat recovery. The sCO2–ORC–biomass configuration showed higher exergy efficiency (41.1%) and lower exergy destruction (188.88 kW) compared to the sCO2–ORC–solar system (23.76% and 422.63 kW). Thermal efficiency (50.6%) and net power output (131.73 kW) were similar for both sources. However, the solar system (204,055.57 kg CO2-equi) had an 85.6% higher environmental impact than the biomass system (109,933.63 kg CO2-equi). Additionally, the construction phase contributed ~95% of emissions in both systems, followed by decommissioning (~4.5%) and operation (~0.1%). Finally, systems built with aluminum generate a higher carbon footprint than those with copper, with differences of 2% and 3.2% in sCO2–ORC–solar and sCO2–ORC–biomass, respectively. This study and an economic analysis make these systems viable thermo-sustainable options for clean energy generation.