Advanced Control Strategy Combined with Solar Cooling for Improving Ethanol Production in Fermentation Units

This work proposes the use of solar radiation as energy source to support energy demands in the optimal control process for ethanol production. The control system proposed for the reactor has two layers: the local one composed by PID (Proportional-Integrative-Derivative) controllers for the pH, level, and temperature loops of the reactor and the master controller which uses an advanced MIMO (Multiple-Input and Multiple-Output) MPC (Model Predictive Control) strategy. The control of the solar cooling system is performed by means of a switching control scheme. Since there is no availability of a practical system which integrates the experimental solar cooling plant and a fermentation unit, the Hardware in the Loop technique has been performed on the plant of Centro de Investigación de Energía Solar (CIESOL), located at the University of Almería (Spain), interconnected with a simulator that represents the ethanol fermentation in Brazilian factories. Three scenarios are analyzed in detail, in which the increments in ethanol production are shown.