This study aims to examine available avenues to improve thermo-economic performance of a hybrid solar-biomass organic Rankine cycle (ORC) cogeneration plant. The ORC unit is rated at about 630 kWe, and it is related to a real solar-ORC plant which currently runs in Ottana (Italy). The implemented hybrid configuration had been conceived as an efficient way to improve dispatchability and operating hours in the aforementioned existing concentrated solar power (CSP) plant and other similar ones, through biomass retrofit. Beyond what is available in literature on hybrid solar-biomass systems, enhanced exergoeconomic analysis is performed in this study, by considering intrinsic irreversibilities and cost rates in the respective components, which are imposed by the assumptions of systemic and economic constraints, and can thus not be eliminated. Results show that relative cost rates of between 2% and 73% of total cost rates could be theoretically avoided. Also, it was obtained that investment cost rates of solar field, thermal energy storage tanks, furnace heater, recuperator and ORC preheater need be reduced, for acceptable economic performance of the hybrid plant. This type of information is highly essential for improved design and quicker market penetration of fully-renewable energy systems.
Keywords organic Rankine cycle (ORC), enhanced exergoeconomic analysis, hybrid solar-biomass plant, avoidable investment