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.

The aim of this paper is to evaluate optimum design criteria for developing solar thermal integrated membrane distillation system for cogeneration of pure water and heat. The temporal and seasonal variability of the driving variables, such as ambient temperature and solar irradiance requires dynamic simulation of combined system using tools such as TRNSYS. Dynamic simulation and parametric analysis enables to design a functional system and then optimizes the design. In this study, the application of cogeneration system for residential households in United Arab Emirates is considered for per capita production of 4l/day of pure water and 50l/day of domestic hot water. The performance of cogeneration is optimized by varying various design parameters such as collector tilt angle, thermal storage volume and area of the solar collector field. Cogeneration solar fraction and payback period are considered as performance indicators for energetic and economic optimization. Further simulations are extended from small to large family application and for utilizing either flat plate (FPC) or evacuated tubular collector (ETC) systems. Optimized cogeneration system utilizes more than 80% of the available solar energy gain and operates at 45% and 60% collector efficiencies for FPC and ETC systems respectively Also, combined and system efficiencies of the cogeneration system are compared with standalone operational efficiencies for solar heaters and solar membrane distillation systems. Results show that, cogeneration operation reduces 6–16% of thermal energy demand and also enables 25% savings in electrical energy demand. Payback period could be reduced by 2.5–3 years by switching from regular solar water heating to cogeneration systems along with 4-fold increase in net cumulative savings.

The demands for space air-conditioning and clean drinking water are relatively high in Middle East countries. A sustainable and innovative approach to meet these demands along with the production of domestic hot water is discussed in this chapter. A solar thermal polygeneration (STP) system is designed and developed for the production of chilled water for air-conditioning using absorption chiller, pure water with membrane distiller, and domestic hot water by heat recovery. The STP system has four major components: (i) evacuated tube collector field, (ii) 10TR absorption chiller, (iii) air-gap membrane distillation units, and (iv) heat exchangers integrated together to operate in four different modes for complete solar cooling, cogeneration of pure water and domestic hot water, trigeneration of cooling, pure water and domestic hot water, and cogeneration of cooling and pure water. Experiments on different modes and the analyzed results show the advantages of combined operation through effective utilization of heat lost in the process operation.