Exergy and Economic Assessment of a Hybrid Solar-Biomass Cogeneration Plant Applied to the Corn Ethanol Industry

Abstract

The present work comprises the thermodynamic and economic performance analysis of a hybrid (solar thermal and biomass) cogeneration cycle applied to a 292.000 m3/year corn ethanol distillery. These analyses aim to assess the technic and economic feasibility of the proposed distillery for its operation in Phoenix (USA) and Barreiras (BRA). A biomass boiler is used parallel with a direct steam generation parabolic trough solar field to produce together the distillery's fixed steam requirement. In this scheme, the solar field is responsible for up to 60% of the produced steam. The study evaluates energy and exergy indexes, for the solar field's design conditions and typical meteorological years, and calculates the net present value for economic evaluation. Annually, the proposed hybrid cycle design achieved biomass savings of 14% in Phoenix and 12% in Barreiras compared to a standard boiler cycle. For both locations, the steam generation processes account for more than 90% of the exergy destruction in the plant. These results show the technical feasibility of the hybrid solution for both locations, with Phoenix performing better due to larger solar resource availability. Furthermore, by finding negative net present values, the economic analysis indicates that the proposed integration is not yet economically feasible.