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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.

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 This article presents the experiences learned using micro-hydro power at the village level. Site evaluation procedure, financing methods, turbine fabrication, and site construction are discussed. Micro-hydro power provides a decentralized energy source for several of the energy-intensive tasks of villagers. Low-head, small volume hydro potential is common in the Zairian countryside. Often a potential site also serves as the village water source, hence it is located near potential beneficiaries of the power. Over the past three decades, a religous NGO in the Ubangi and Mongala Subregions of northwest Zaire has been developing this small hydro potential as part of its technology transfer and village development program. Local materials and knowledge are used as much as possible in construction. Experiences gained constructing a 370 kW hydro-electric site, as well as building water wheels for water pumping has led to the construction of micro-hydro sites using locally made cross-flow turbines. Four water wheel sites and six micro-hydro sites have been built. The hydropower is used to mill flour and hull coffee. One site also generates 220 V electricity, and two others have 12 V generation planned.

Abstract A given temperature difference across the upper and the lower convective zone of a solar pond is commonly sought in thermoelectric power generation. Based on this consideration, this work is aimed at predicting the lengths of various zones of a solar pond to ensure a minimum temperature potential throughout the year between its upper and lower convective zones. For predicting the critical lengths of various zones of the solar pond, at first, the heat energy conservation-based model available in the literature is modified by accounting the effect of salinity and temperature on various thermal parameters. The model is satisfactorily-validated with similar model and experimental data reported in the literature. Thereafter, considering the requirement of a thermoelectric power generator ( TEG ) , an inverse problem is solved with the aid of a genetic algorithm-based optimization method to predict feasible lengths of various zones satisfying a minimum temperature potential across TEG considering suitable thermal resistances. The present results reveal improved pond dimensions achieving a better temperature profile at a lower total height than that available in the literature. Further, case studies of diverse meteorological conditions of India are carried out and it becomes apparent that, around the year, multiple combinations of convective and non-convective regions of the solar pond can ensure the required minimum (or more) temperature difference across relevant zones of the solar pond. Finally, the present study also reveals that the temperature of the upper convective zone is largely governed by the thickness of this zone, whereas, the thickness of the non-convective zone is largely responsible for the temperature within the storage zone. The present study provides a novel inverse methodology to predict and optimize the suitable dimensions of various regions of a salt-gradient solar pond to ensure a minimum temperature potential across the year for thermoelectric power generation.

Abstract In the present study, the thermal energy balance equations have been taken for N partially covered photovoltaic thermal–compound parabolic concentrator collectors ( N -PVT–CPC) connected in series. An analytical mathematical expression for N th outlet water temperature ( T foN ) and efficiency of solar cell at N th collector ( η cN ) have been derived in terms of climate and design parameters. Numerical computations have been carried out for two Indian climatic condition namely (a) January (winter) and (b) June (summer), respectively. Effect of number of PVT–CPC collectors connected in series, mass flow rate and the percentage of PV coverage on various temperatures, an overall thermal energy and overall exergy have been carried. It has been observed that an overall exergy of proposed system is maximum for winter condition due to less thermal losses.

An experimental saturated solar pond is constructed using magnesium chloride salt. The temperature and concentration gradients are developed by heating the pond from the bottom and adding finely powdered salt from the top. The development of a temperature profile in the pond exposed to direct sunlight and its daily variation are studied. The predictions of the temperature profiles, using the authors' mathematical model, match the experiments better than the concentration profiles.

Current solar hot water (SHW) system modelling techniques, as applied in Australia, are inadequate for the demands of programs and policies that aim at widespread usage of SHW. Two major problems with current modelling techniques are the coarseness of modelling in a spatial context and the use of only two hot water load categories. These problems are described and suggestions are offered for improved modelling processes. Geographical information systems can be used in conjunction with existing SHW performance evaluation tools to produce models with much finer spatial resolution than those currently in use. It is recommended that categories used for evaluating SHW systems should be based upon household size. Methodologies for modelling SHW system performance that conform to these recommendations are described in this paper.

Abstract Solar energy is the natural heating agent for open swimming pools by direct absorption in the water. Because of high heat losses from the surface of the water to the atmosphere the temperature of the pool water does not significantly differ from the mean air temperature. If a suitable transparent plastic cover is placed on the water, the temperature of the water can be raised because the heat losses are reduced while the incident solar radiation can pass through the cover and heat the water. Tests in Melbourne have shown that the swimming season can be considerably extended if an inflated cover made of clear plastic film is used. This method of collection and storage of heat energy from the sun may also find other applications where water of a relatively low temperature can be utilized.

Abstract A large number of industrial processes demand thermal energy in the temperature range of 80–240 °C. In this temperature range, solar thermal systems have a great scope of application. However, the challenge lies in the integration of a periodic, dilute and variable solar input into a wide variety of industrial processes. Issues in the integration are selection of collectors, working fluid and sizing of components. Application specific configurations are required to be adopted and designed. Analysis presented in this paper lays an emphasis on the component sizing. The same is done by developing a design procedure for a specific configuration. The specific configuration consists of concentrating collectors, pressurized hot water storage and a load heat exchanger. The design procedure follows a methodology called design space approach. In the design space approach a mathematical model is built for generation of the design space. In the generation of the design space, design variables of concern are collector area, storage volume, solar fraction, storage mass flow rate and heat exchanger size. Design space comprises of constant solar fraction curves traced on a collector area versus storage volume diagram. Results of the design variables study demonstrate that a higher maximum storage mass flow rates and a larger heat exchanger size are desired while limiting storage temperature should be as low as possible. An economic optimization is carried out to design the overall system. In economic optimization, total annualized cost of the overall system has been minimized. The proposed methodology is demonstrated through an illustrative example. It has been shown that 23% reduction in the total system cost may be achieved as compared to the existing design. The proposed design tool offers flexibility to the designer in choosing a system configuration on the basis of desired performance and economy.