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Abstract The desalination of water is a process wherein the brackish water is purified by removing the salts. With increasing demand for fresh water, there is a vast scope for development of sea water desalination process. A number of methods exist for the desalination process, but solar desalination method promises to save energy in today’s energy crunch scenario. A novel solar desalination setup is proposed here. It uses an elliptic hyperboloid concentrator and a helical receiver along with a multi-tray desalination unit to purify water in the most effective manner. The helical receiver proposed in the present work aims at the Dean Flow effect in order to enhance heat transfer in laminar flow. The effectiveness of this property with respect to various physical parameters has been observed and an optimum design has been suggested based on this. The elliptic hyperboloid concentrator is a special design for concentrating solar radiation because of it offers to operate at high efficiency without the requirement of tracking. A detailed ray-tracing code was developed to simulate the radiation incident on the concentrator and an accurate estimation of the optical efficiency was made based on this. The two systems were integrated in order to arrive at a maximum output level for the solar desalination system as a whole.

Photocatalysis by titanium dioxide (TiO2), operational in the UV-A domain with a potential use of solar radiation, could be an alternative to conventional water detoxification and disinfection technologies. However, employing the photocatalyst as a suspension or slurry makes the scaling-up of the process difficult, as the TiO2 has to be removed from the decontaminated water to be reused several times. In this work the photocatalytic activity of different types of TiO2 catalyst (Degussa P-25, Millennium PC-100 and PC-500, Tayca AMT-100 and AMT-600) in suspension or coated on fibrous web were studied in both decontamination and disinfection experiments at laboratory scale. Gallic acid was chosen as the model pollutant for detoxification experiments and Escherichia coli as the model microorganism for disinfection experiments. The influence of the surface area and other characteristics of TiO2 are discussed concerning the photocatalytic properties of TiO2. The role of adsorption is suggested, indicating that the reaction occurs at the TiO2 surface and not in the solution. Gallic acid degradation kinetics were found to be of the same extent for both TiO2 suspended and fixed, whereas for the bacterial inactivation efficiency was significantly less important with coated than with suspended TiO2.

A linear correlation between UV-A and 380 nm was developed by means of the TUV 4.1 radiative transfer model. The prediction error of the correlation was evaluated with data from Buenos Aires, Argentina, 2001, and from 2006, Almeria, Spain. Percent random mean square error (RMSE%) was calculated for intervals of 10° of solar zenith angles, ranging 4.75% at 20° to 37.70% at 90° in clear days and 22.16% at 20° to 26.17% at 90° for cloudy days in Buenos Aires Argentina, and 1.27% at 20° to 11.27% at 90° for clear days in Almeria, Spain. Clouded days were not assessed with the data from Spain. In Argentina, the UV-A radiometer is located in a rural area and the 380 nm radiometer is located in an urban area 6 km away. Hence the real error of the proposed model is closer to that found in Spain were both measurements were performed at the same site. The objective of the work is to achieve a simple and precise method to assess UV-A availability for environmental applications of solar energy, particularly for solar water treatment, at any desired latitude.

Abstract Renewable energy sources (RES) coupled to desalination offers a promising prospect for covering the fundamental needs of power and water in remote regions, where connection to the public electrical grid is either not cost effective or not feasible, and where the water scarcity is severe. Stand-alone systems for electricity supply in isolated locations are now proven technologies. Correct matching of stand-alone power supply desalination systems has been recognized as being crucial if the system is to provide a satisfactory supply of power and water at a reasonable cost. The paper covers plants installed since 1990 on the coupling of the two technologies. The main driver promoting the take up of this technology is that water is a limiting factor for many countries in the Mediterranean region. This paper presents the two technologies, RES desalination, and describes the most promising couplings such as PV–reverse osmosis, wind-mechanical-vapor compression, geothermal-multieffect distillation, etc as well as technologies selection guidelines. Also, included applications and lessons learned from specific applications as well as data on the economics. RES for desalination is an important challenge and useful work has been done. However in order to provide practical viable plants, much remains to be done.

Abstract A combination of heat pump and humidification-dehumidification (HDH) process is a suitable choice to obtain fresh water for small-scale desalination applications, especially when the solar energy is used as the auxiliary heat source. In this paper, a novel two-stage solar assisted heat pump (SAHP) desalination system based on HDH, in which the humidifiers are connected in parallel, is proposed. A mathematic model is developed to improve the system performance by optimizing the operating parameters such as process air flow rate and cooling seawater flow rate, and it is also validated by the experimental results. Analysis results indicate that there exists an optimal process air flow rate in the desalination system, which does not vary with the hot seawater flow rate. However, it will be increased with the increase of cooling seawater flow rate. When the flow rates of process air and cooling seawater are 350 m3/h and 0.55 m3/h, respectively, the maximum fresh water yield is 17.94 kg/h. The corresponding gained-output-ratio (GOR) is 2.02. However, the system performance is constrained by a bottleneck: increasing dehumidifying capacity can result in a reduction in the performance of lower-temperature (LT) humidifier. Consequently, a modified system is then proposed to solve this bottleneck effectively. The maximum fresh water yield can be increased by 16.70% to 20.54 kg/h, and the corresponding maximum GOR is also increased by 18.05% to 2.42.

Abstract Wind data for eleven stations along the east coast of the Arabian Peninsula have been analysed. Monthly average wind speeds were determined for each station. They range from 2.5 to 7.0 m/s, with a peak between February and July and a low during the August–October period. Maximum extractable monthly and annual average wind powers were derived. They vary between 20 and 250 W/m 2 , 40 and 150 W/m 2 , respectively. An application of wind power, i.e. the production of freshwater with a wind-driven reverse osmosis desalination plant, is suggested.

Abstract The effective utilization of solar energy is a big challenge as global energy demand is increasing sharply. In this paper, we present the details of design of an extremely concentrated solar energy delivery system (ECoSEnDS) and its possible utilization in daylighting and sustainable wastewater treatment. The EcoSEnDS is made with double mirror based solar concentrator coupled with pure silica optical fiber bundle. This device is capable to deliver 96 suns concentrated sunlight in first stage of testing where efficiency of the primary mirror is 50%. This device can distribute light equivalent to 813 incandescent bulbs of 60 W or 149 LED bulbs of 15 W. Therefore, this device can be used as daylighting system in the building and underground car parking area. Using appropriate semiconductor nanophotocatalysts, this device can be used for sustainable rapid wastewater purification process. We have used BiVO4 nanoparticles for photocatalytic methylene blue degradation and the complete (100%) purification of methylene blue stained wastewater was achieved within one hour using only 7 suns concentrated sunlight. Therefore, the ECoSEnDS will open new technological aspects for sustainable fastest wastewater treatment process using solar energy.

Abstract Phase effect of bismuth vanadate (BiVO4) nanostructured catalysts for the photoelectrochemical (PEC) solar water oxidation, removal of toxic organic pollutants from wastewater, and electrochemical storage were reported. The monoclinic (BV-M) and tetragonal (BV-T) crystal structured BiVO4 photocatalysts were synthesized using a facile hydrothermal route without the support of any template. The BV-T photoelectrode also exhibits lower charge transfer resistance compare to BV-M photoelectrode. The BV-T photoelectrode showed a remarkable photocurrent density (0.4249 mAcm−2) over BV-M photoelectrode (0.0702 mAcm−2), which is about 6 times greater than BV-M photoanode. Furthermore, BV-T sample showed 17 times superior electrochemical capacitance over BV-M sample at the scan rate of 10 mVs−1. The photocatalytic analysis has also shown that the BV-T photocatalyst revealed greater photocatalytic activity for the methyl orange under visible light, about 87.8% of the MO was degraded within 80 min.

Abstract In this study, a typical rice paddy in Guilan province of Iran is considered and the technical and economical feasibility of the solar powered pumping system is studied. The monthly mean daily solar irradiance has been studied for this area and the measured data is compared with European Photovoltaic Geographic Information System (EU PVGIS) model for Middle East, including Iran. The investigations imply that the average monthly mean daily solar irradiance in irrigation months are reported equal to 5.92 kW h/m2/day by Guilan Meteorological Administration and 5.95 kW h/m2/day by EU PVGIS. A mean monthly clearness index from 0.54 to 0.57, in irrigation period, gives Guilan province a good potential to employ photovoltaic (PV) pumping system. In this study, the appropriate size of the PV panels and the lifecycle cost estimation of PV pumping system in comparison with conventional systems are presented. Also, the area of the PV solar panel to supply required power of the pumping system for a rice paddy with specified area is calculated. Results show that though the initial outlay of the PV system is about 9 times of the conventional systems but the total lifecycle costs of the PV pumping system is just 65.6% costs of the conventional pumping system. Also in spite of high initial costs of the PV pumping system, it is found that after around 9 years, the total costs of both systems would be equal to conventional one i.e. gasoline pumping system and after this time, the costs of the conventional pumping system will exceed the PV solar panel system.