Modelling and optimising of MED-TVC seawater desalination plants assisted with electric heaters

Abstract

One major issue with MED-TVC systems, a widely used thermal-based desalination technology, is their high energy consumption and carbon emissions. This underscores the importance of optimising and integrating these thermal-based desalination technologies with sustainable energy systems to utilize their waste heat and enhance the performance of these plants effectively. This research aimed to optimize and address the environmental challenges of MED-TVC desalination plants in areas with insufficient sunlight, unstable weather conditions, and limited economic resources. To this end, a model of an electric heater for generating thermal energy coupled with an optimized MED-TVC desalination plant was proposed. The MED-TVC section was optimized by incorporating an additional ejector in the final stage of MED-TVC demonstrating an increase of over 11 % in evacuating non-condensable gases from the last effect and increasing the product water by up to 14.89 %. Regarding the design of the electric heating elements used in electric heaters, the use of one-plus-two U-tubes with helical baffles was more efficient than multi-layer U-tubes with segmental baffles as improved the pressure loss of the thermal fluid by 25 % and increased the heat transfer coefficient of the heating elements to 18 %. The power section was also equipped with an off-grid system to provide the necessary power for the equipment of the proposed model. In the economic analysis of employing a parabolic trough solar collector and electric heaters, not only were the direct costs of the electric heaters almost equal to just 40 % of the direct costs of the parabolic trough solar collector approach but also the required thermal fluid was 50 % of the solar case.