Integrated concentrating photovoltaic-thermal solar collector and membrane distillation system for desalination and vinasse treatment

Abstract

This study presents the evaluation to integrate hybrid Concentrating Photovoltaic Thermal (CPVT) collectors with a Vacuum Membrane Distillation (VMD) module as a green alternative to produce freshwater. The CPVT collector provides the thermal and electrical energy required for the VMD to desalinate water. The performance of these integrated solar-assisted desalination technologies is numerically evaluated using TRNSYS. Parametric studies were conducted to find optimal operating conditions regarding the collector’s surface area and the brine’s set point temperature, from which a configuration using 4-collector units and a set point temperature of 55°C was chosen for a multi-city study. Annual weather conditions and specific information about the characteristics and operating conditions of a real CPVT collector and VMD module are considered in the dynamic simulation for 4 coastal cities: Acapulco, MX; La Paz, MX; Nadi, FJ; and Singapore, SG. The system can convert almost 50% of the solar radiation it receives into useful energy (8.2% into electricity and 41.4% into heat). The permeate production varied from 170.365 m3/m2_VMD in Singapore, SG, to 209.415 m3/m2_VMD in Acapulco, MX, showing a clear correlation between the solar radiation received and the performance of the system. Moreover, in a comparative study against a non-solar system, the specific energy cost for every m3 of freshwater produced could be decreased by 80% by implementing the CPVT collector. Additionally, an alternative application for this innovative system was tested, simulating the treatment of vinasses from the tequila production process. During the months with larger incident solar radiation, the performance of the system was optimal, with the peak specific permeate production achieved was 17.33 m3/m2_VMD during May, while the lowest SEC was 0.50 kWh/m3. The results of the simulations showed the exciting potential to use solar energy from hybrid CPVT collectors for a VMD process, not only for desalination in coastal cities but also as a viable technology to contribute to the production of freshwater demanded by industry and society.