Theoretical Analysis of Pressure Retarded Membrane Distillation (PRMD) Process for Simultaneous Production of Water and Electricity

This study proposed and investigated a new pressure-retarded membrane distillation (PRMD) for simultaneous production of water and electricity. The PRMD process was designed by combining the concepts of direct contact membrane distillation (DCMD) and pressure-retarded osmosis (PRO) processes in a single membrane module. A mathematical model for the PRMD process was developed, and the performances of energy generation and water production were estimated and compared to the results of the DCMD process. It was found that the PRMD process can save energy by producing electricity from a hydro-turbine, but the water production rate is slightly less than the DCMD process. Also, the effects of operating conditions and membrane properties were analyzed, and the best conditions were investigated. By applying the best available membrane technology, the PRMD process can save about 0.1738 kWh/m³ with about only 3% sacrifice of fresh water production compared to the DCMD process at the same basis. Thus, the PRMD process can be used as a multifunctional system for producing water as the DCMD process and electricity as the PRO process at the same time, so it can be a self-sustained process when low-grade heat energy could be supplied.