Solar energy for combined production of electricity and industrial process heat

Industrial process heat represents a large part of energetic demand in industries. A parabolic-trough collector solar power plant working on cogeneration mode may meet the thermal and electrical demand of these industries, especially at average and low temperatures (<250 degrees C). Simulations were performed to attend the demand of a food processing plant installed at three locations in Northeastern Brazil with different Direct Normal Irradiances (DNI). The solar power plant was simulated using different receiver settings with and without vacuum for the generation of 1 MWe and the supply of industrial process heat. A comparison between organic Rankine cycle (ORC) and steam Rankine cycle (SRC) was also performed to confirm the best power cycle to be applied to those plants. The results showed that the ORC allows higher efficiencies than the SRC, regardless of the receiver used (i.e. evacuated or not). When evacuated receivers are used, the ORC allows a gain in solar-to-electric efficiency of 1.2-1.3 percentage point (i.e. from 10% to 13% in relative value) as well as a correspondingly lower land footprint. Furthermore, the study showed that the design with non-evacuated receivers covered with glass tubes is feasible despite its lower efficiency.