Water is the most desirable and sparse resource in Gulf cooperation council (GCC) region. Utilization of point-of-use (POU) water treatment devices has been gaining huge market recently due to increase in knowledge of urban population on health related issues over contaminants in decentralized water distribution networks. However, there is no foolproof way of knowing whether the treated water is free of contaminants harmful for drinking and hence reliance on certified bottled water has increased worldwide. The bottling process right from treatment to delivery is highly unsustainable due to huge energy demand along the supply chain. As a step towards sustainability, we investigated various ways of coupling of membrane distillation (MD) process with solar domestic heaters for co-production of domestic heat and pure water. Performance dynamics of various integration techniques have been evaluated and appropriate configuration has been identified for real scale application. A solar combi MD (SCMD) system is experimentally tested for single household application for production 20 L/day of pure water and 250 L/day of hot water simultaneously without any auxiliary heating device. The efficiency of co-production system is compared with individual operation of solar heaters and solar membrane distillation.

Membrane distillation is a novel process that could be adapted effectively for many water purification applications. In recent years, several bench, pilot and commercial scale membrane distillation systems with production capacities ranging from 20 L/d to 50 m(3)/d were developed and tested. In this work, a single cassette air-gap membrane distillation (AGMD) module was characterized to identify the effect of process parameters on distillate flux and thermal efficiency. Favorable conditions to obtain distillate flow rate of 1.5-3 kg/h were determined on a bench scale experimental setup. Factorial design of experiments was conducted and response surface methodology (RSM) was applied to develop an empirical regression model relating operating parameters with AGMD system performance indicators. Operating parameters including hot feed inlet temperature (T-Hin), cold feed inlet temperature (T-Cin), feed flow rate (V-f) and feed conductivity (C-f) were considered. Distillate flux (J(d)) and specific performance ratio (SPR) were selected as the performance indicators for the modeling. The developed regression model using RSM was tested by analysis of variance. Regression analysis showed agreement with the experimental data fitted with second-order polynomial model having determination coefficient (R-2) values of 0.996 and 0.941 for J(d) and SPR, respectively. Numerical optimization has been carried out to identify optimal set of operating conditions for achieving desired operation. Also, dynamic simulation of the membrane distillation module integrated solar thermal system has been reported along with validation of the system model by comparing with the experimental data obtained from a pilot scale setup located in UAE.

The demands for space air conditioning and clean drinking water are relatively high in Middle East North African (MENA) countries. A sustainable and innovative approach to meet these demands along with the production of domestic hot water is experimentally investigated in this paper. A novel solar thermal poly-generation (STP) pilot plant is designed and developed for production of chilled water for air conditioning using absorption chiller, clean drinking water with membrane distillation units and domestic hot water by heat recovery. The STP system is developed with a flexibility to operate in four different modes: (i) solar cooling mode (ii) cogeneration of drinking water and domestic hot water (iii) cogeneration of cooling and desalination (iv) trigeneration. Operational flexibility allows consumers to utilize the available energy based on seasonal requirements. Performance of STP system is analyzed during summer months in RAKRIC research facility. Energy flows in STP pilot plant during peak load operations are analyzed for all four modes. STP system with trigeneration mode utilizes 23% more useful energy compared to solar cooling mode, which improves overall efficiency of the plant. Economic benefits of STP with trigeneration mode are evaluated with fuel cost inflation rate of 10%. STP plant has potential payback period of 9.08 years and net cumulative savings of $454,000 based on economic evaluation.

A novel solar thermal cogeneration system featuring the provision of potable water with membrane distillation in combination with domestic hot water supply has been developed and experimentally analyzed. The system integrates evacuated tube collectors, thermal storage, membrane distillation unit, and heat exchangers with the overall goals of maximizing the two outputs while minimizing costs for the given design conditions. Experiments were conducted during one month's operation at AURAK's facility in UAE, with average peak global irradiation levels of 650 W/m2. System performance was determined for three integration strategies, all utilizing brackish water (typical conductivity of 20,000 μs/cm) as a feedstock: Thermal store integration (TSI), which resembles a conventional indirect solar domestic hot water system; Direct solar integration (DSI) connecting collectors directly to the membrane distillation unit without thermal storage, and Direct solar with thermal store integration (DSTSI), a combination of these two approaches. The DSTSI strategy offered the best performance given its operational flexibility. Here the maximum distillate productivity was 43 L/day for a total gross solar collector area of 96 m2. In terms of simultaneous hot water production, 277 kWh/day was achieved with this configuration. An economic analysis shows that the DSTSI strategy has a payback period of 3.9 years with net cumulative savings of $325,000 during the 20 year system lifetime.

Scarcity of fresh water sources, rapid industrial development and increase of urban population in arid regions like UAE lead to tremendous increase in bottled water dependency for drinking purpose. The bottling process right from treatment to delivery is highly unsustainable and hence we focus on the issue of providing pure drinking water in a sustainable way through solar domestic hot water (SDHW) systems. The shift towards sustainability in the oil rich region and recent growth of interest on Membrane Distillation (MD) technique at small scale application development by coupling with solar energy source has motivated us to develop a combined SDHW-MD pilot unit for feasibility analysis. Present application is to co-generate 20 l/day of drinkable water and 250 l/day of domestic hot water for a single family house/villa in UAE region. Experiments are performed for municipal water purification and compared with empirical equation based model developed using laboratory experimental data along with PolySun simulations. Monthly energy consumption and water production profiles have been obtained which would form a basis for detailed dynamic simulation and optimization of system performance.

Tri-generation is one of the most efficient ways for maximizing the utilization of available energy. Utilization of waste heat (flue gases) liberated by the Al-Hamra gas turbine power plant is analyzed in this research work for simultaneous production of: (a) electricity by combining steam rankine cycle using heat recovery steam generator (HRSG); (b) clean water by air gap membrane distillation (AGMD) plant; and (c) cooling by single stage vapor absorption chiller (VAC). The flue gases liberated from the gas turbine power cycle is the prime source of energy for the tri-generation system. The heat recovered from condenser of steam cycle and excess heat available at the flue gases are utilized to drive cooling and desalination cycles which are optimized based on the cooling energy demands of the villas. Economic and environmental benefits of the tri-generation system in terms of cost savings and reduction in carbon emissions were analyzed. Energy efficiency of about 82%-85% is achieved by the tri-generation system compared to 50%-52% for combined cycles. Normalized carbon dioxide emission per MW.h is reduced by 51.5% by implementation of waste heat recovery tri-generation system. The tri-generation system has a payback period of 1.38 years with cumulative net present value of $66 million over the project life time.