Integration of Membrane Distillation and Solar Thermal Systems for Coproduction of Purified Water and Heat

Abstract: In the Middle East and North Africa region fresh water resources are very scarce and theexisting sources are depleting rapidly. Desalination is the method to fulfill increasing waterdemand, and people depend mostly upon bottled water for drinking purposes. Bottledwater is resource and energy demanding, hence there is a need for supplying drinkablewater in a sustainable way. The main objective of this research is to develop solutions forproviding potable water to urban communities through integrating membrane distillationwater purification units with solar driven hot water installations. A single-cassette Air GapMembrane Distillation (AGMD) unit was tested on laboratory scale to investigate theinfluence of various operating parameters on the distillate production. Particular attentionwas given for identifying process conditions relevant to the design of solar energyintegrated systems. In parallel, a simplified empirical model using response surfacemethods was developed and validated against bench scale experimental results. Thedeveloped model for performance indicators was later employed in dynamic simulations ofa solar thermal integrated membrane distillation system. A pilot plant was designed andinstalled at RAK Research and Innovation Center in UAE. Experimental investigations wereconducted on this integrated system for co-production of pure water (around 15-25 l/day)along with hot water production equivalent to the needs of a family of five. A dynamicsimulation model was developed in TRNSYS to analyze optimum operating conditions ofthe system. Economic analysis showed an impressive payback period and savings for theintegrated system as compared with standalone counterparts. A second pilot facility using alarger multi-cassette AGMD module and absorption cooler was designed and installed.Performance of this solar co-production system for heat, cooling, and pure water is analyzedfor various integration modes.