In this work, we address the problem of reducing the energy consumption of biofuel plants through their integration with a solar thermal energy system that generates steam. A mathematical model of the solar energy system that includes energy storage is coupled with a rigorous simulation model of the biofuel facility developed in a commercial process simulator. The solar energy system model takes the form of a bi-criteria nonlinear programming (NLP) formulation that accounts for the simultaneous minimization of cost and energy consumption.
We demonstrate the capabilities of this strategy with two case studies in which we address the design of a 12,000 ton/year alkali-catalyzed biodiesel process using vegetable oil modeled in Aspen Plus® and a 120,000 tones/year dry-grind corn-to-ethanol production plant modeled in SuperPro Designer®. In both cases we considered weather data of Tarragona (Spain). A set of Pareto solutions were generated using the epsilon constraint methodology. The results obtained show that is possible to achieve reductions in energy consumption of up to 24.90 % for the biodiesel and 17.24% for the bioethanol with respect to the minimum cost design.
