Thermo-economic assessment of hybrid solar-driven supercritical CO2 cycle for multi-generation system

Concentrated solar power (CSP) connected to a thermodynamic power cycle is used to convert solar energy into electricity. This study investigates a combination of two power generation cycles, where the topping cycle utilizes supercritical carbon dioxide (sCO₂), and the organic Rankine cycle (ORC) serves as the bottoming cycle. The diesel engine exhaust is utilized as a backup source when solar energy is not available. An additional hydrogen production unit is connected to the system for producing hydrogen through the steam methane reforming (SMR) method process and operated when available heat is obtained from the hybrid system. This experiment was carried out in Rangpur, Bangladesh. Due to a higher coefficient of performance, Therminol VP-1, CO₂, and R245fa were selected as working fluids in parabolic trough collectors (PTC), sCO₂, and ORC, respectively. The comparison of standalone sCO₂ with the combination of sCO₂-ORC has been conducted in terms of efficiency. The optimal results for the hybrid model have been found as a mass flow rate of 82 kg/s, net power output of 6062 kW, and specific investment cost (SIC) of 5237 $/kW at the pressure of 250 bar. The results also showed that the developed hybrid model achieved 68.5 % higher efficiency than standalone sCO₂. On the other hand, through the SMR method, 288 kg/h is found to be the ideal mass flow rate of methane, with a corresponding cost of $ 100.8/h, which produces hydrogen efficiently at a rate of 62.87 kg/h. The output of the hybrid model shows multiple outcomes, such as electricity and hydrogen, making this system a multi-generation system.