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Abstract Combining the advantages of low temperature (below 50°C) solar energy collection and high temperature thermal energy conversion into electrical power, a scheme for continuous power generation is proposed. This scheme is based on the concept of “concentration difference energy system” proposed by Isshiki. Make-up steam generated at about 6 kPa by flashing water at 45°C and exhaust steam from a turbine are fed to a cascade of absorber-boiler units to produce steam at a turbine inlet pressure of 2.4 MPa. The absorber-boiler cascade operates along the saturation line of CaCl 2 solution taking advantage of b.p. elevation of aqueous CaCl 2 solution. Large inexpensive solar farms are used to obtain hot water and to concentrate effluent dilute CaCl 2 solution taking advantage of the low humidity conditions prevalent in arid zones. Based on a detailed study of the performance of various components of the scheme, its economic feasibility is evaluated. Preliminary cost estimates show that power production cost is about 0.25 $/kWh and 0.04 $/kWh for plant capacities of 1 and 100 MW, respectively.

Abstract Cu2ZnSnS4 solar cell has been fabricated with a non-toxic buffer layer and Al doped ZnO transparent conducting layer. A detailed material study on each layer of the solar cell has been carried out independently. The precursor films prepared by spin coating were sulphurized at different temperatures to optimize the conditions to obtain phase pure CZTS films. X-ray diffraction, Raman spectroscopy and rietveld refinement studies confirmed the phase purity of the film sulphurized at 500 °C. The optimum CZTS properties like band gap of 1.45 eV, high absorption coefficient ~2 × 105 cm−1 and dense surface morphology were obtained for films sulphurized at 500 °C. Carrier concentration, mobility and resistivity of these films were ~1 × 1019 cm−3, 0.23 cm2 V−1 s−1 and 2.7 Ωcm, respectively. The efficiency measurements of the cells with device structure SLG/Mo/CZTS/ZnS/AZO/Ag were carried out using absorber films with three different thicknesses. The optimized CZTS absorber layer with thickness of ~1.8 µm exhibited solar cell conversion efficiency of 3.02% for an active area of 0.21 cm2 with open-circuit voltage of 0.38 V, short-circuit current density of 17.19 mA/cm2 and fill factor of 46%.

Oxide volatility of silicate melts at high temperatures and pressures by vapor fractionation

Abstract Until recently, the advances in hydrogenated amorphous silicon (a-Si:H) solar cell performance and stability have been achieved materials prepared with hydrogen dilution following primarily empirical approaches. This paper discusses the recently obtained insights into the growth, microstructure and nature of these materials. Such protocrystalline Si:H materials are more ordered than the a-Si:H obtained without dilution and evolve with thickness from an amorphous phase into first a mixed amorphous–microcrystalline and subsequently into a single microcrystalline phase. The development of deposition phase diagrams, characterize their microstructural evolution during growth which can be used to guide the fabrication of solar cell structures in a controlled way. Examples are presented and discussed of their application in solar cell fabrication to obtain a fundamental understanding of the properties of the phase transitions as well as the systematic optimization of cell performance.

Abstract Cell to module (CTM) conversion loss, during Solar Photovoltaic (SPV) module manufacturing, in terms of wattage losses, at critical process steps Tabbing and Stringing (T&S) and Lamination have been analyzed and a comprehensive electrical and optical model presented. The relation between efficiency of the starting cells and CTM loss has been established. The optimization criteria of the T&S process, in terms of ribbon dimensions and the cell parameters, has also been described. CTM conversion loss/gain for lamination process has been modeled using refractive index and thicknesses of various thin film layers on cell with and without lamination. A guideline for selecting these parameters for obtaining optimized efficiency for laminated cells has been presented. The effect of added electrical resistance due to junction box and change of optical property due to anti reflection coating (ARC) on cover glass have also been presented in brief for completeness. Indoor as well as outdoor test data have been used for modules with ARC on cover glass. During outdoor test, measurements have been carried out with varying intensity and angle of incident of the light. T&S and lamination models have been validated by experiments conducted on single cell coupons. The power loss due to junction box and power gain due to ARC on cover glass has been done on full 60 cell modules. The models described here have been successfully used by the author for minimizing CTM conversion loss for two types of cells with known cell process parameters.

Solar sailing is a unique form of propulsion where a spacecraft gains momentum from incident photons. Since sails are not limited by reaction mass, they provide continual acceleration, reduced only by the lifetime of the lightweight film in the space environment and the distance to the Sun. Practical solar sails can expand the number of possible missions that are difficult by conventional means. The National Aeronautics and Space Administration’s Marshall Space Flight Center (MSFC) is concentrating research into the utilization of ultra lightweight materials for spacecraft propulsion. Solar sails are generally composed of a highly reflective metallic front layer, a thin polymeric substrate, and occasionally a highly emissive back surface. The Space Environmental Effects Team at MSFC is actively characterizing candidate sails to evaluate the thermo-optical and mechanical properties after exposure to electrons. This paper will discuss the preliminary results of this research.

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 Conventional jaggery making process utilizes the bagasse for boiling of sugar cane juice which releases pollutants into the atmosphere and high particulate matter from these emissions causes air pollution. In this article, solar powered jaggery industry with freeze pre-concentration is proposed with conventional and modified heating pans. The system performance, environmental impacts and economic feasibility were assessed by carrying out 4E (Energy-Exergy-Environment-Economic) analyses using the developed mathematical model. These systems were designed to produce 300 kg of jaggery per day when operated for 7.5 h in 3 batches with average solar direct normal irradation of 662 W/m2 and 343 °C. These systems are integrated with auxiliary heating for uninterrupted production in the absence of sunlight. These systems can mitigate nearly 2015.95 to 3062.15 tons of CO2 emission during its 25 years of lifespan under 300 clear days of operation each year. Jaggery produced by this technique is rich in its colour and completely safe for human consumption as no artificial clarificants are used. Amount invested in these systems can be recovered in a span of 12.03 to 13.45 years for jaggery selling price of USD.0.514/kg or INR.36/kg.

Abstract Estimation of solar radiation is of considerable importance because of the increasing requirement for the design, optimization and performance evaluation of the solar energy systems. This paper presents the development of pattern similarity based clustering algorithm and its application in solar radiation estimation. In the present work continuous density, Hidden Markov Model (HMM) with Pearson R model is utilized for the extraction of shape based clusters from the input meteorological parameters and it is then processed by the Generalized Fuzzy Model (GFM) to accurately estimate the solar radiation. Instead of using distance function as an index of similarity here shape/patterns of the data vectors are used as the similarity index for clustering, which overcomes few of the shortcomings associated with distance based clustering approaches. The estimation method used here exploits the pattern identification prowess of the HMM for cluster selection and generalization and nonlinear modeling capabilities of GFM to predict the solar radiation. The data of solar radiation and various meteorological parameters (sun shine hour, ambient temperature, relative humidity, wind speed and atmospheric pressure) to carry out the present work is taken from the comprehensive weather monitoring station made at Solar Energy Centre, Gurgaon, India. To consider the effect of each meteorological parameter on the estimation of solar radiation the proposed model is applied on 15 different sets comprising of various combinations of input meteorological parameters. The meteorological data of three years from 2009 to 2011 (915 days) is used to estimate the solar radiation. Out of these 915 days data, the first 750 days data is used for the training of the proposed paradigm and rest 165 days data is used for validating the model. The results of estimation using all the sets of various combination of meteorological parameter are analyzed and it is found that the sunshine duration is the prime parameter for the estimation of solar radiation. The next important parameter, which influences the estimation of solar radiation, is temperature followed by relative humidity, atmospheric pressure and wind speed. It is interesting to note that worse results are obtained for the sets which are not using sunshine duration as an input. The best performance is achieved by the set which uses all the parameters except the wind speed. The Root Mean Square Error (RMSE), Mean Absolute Percentage Error (MAPE) and correlation co-efficient ( R -value) of the proposed paradigm for the best performing combination of meteorological parameter are 7.9124, 3.0083 and 0.9921 respectively which shows that the proposed model results are in good agreement with the actual measured solar radiation.