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Abstract Periodically adjusted parabolic mirror/evacuated tube absorber combinations are evaluated using computer simulation methods. The results show that a 4–6 X reflector adjusted 10–15 times per year, operating at 150°C, competes favourably in cost-effective terms with a fixed reflector CPC collector operating at 50°C. Periodically adjusted collectors are advocated for medium temperature industrial applications below 200°C.

Abstract Maximally concentrating collectors include the class of ideal concentrating collectors, but are a more general class offering many more practical possibilities. By evaluating such configurations using the concept of maximal flux concentration, based upon average radiation flux concentration over the acceptance angle, clear ray trace comparisons may be made between different collector configurations. These comparisons allow the most effective configuration to be selected for a given application. An example of a comparatively simple and practical two-stage concentrator having equal or better maximal performance than previous work for high rim angle primaries is given. This uses an unusual straight section of reflector and allows rays to cross from one reflector segment of the secondary to another. Versions which allow concentration up to 90% of maximal are described, as are versions achieving 80% with high collection efficiency. Use of the 1 sin θ max geometrical concentration criterion based upon aperture ratios is suggested to be inappropriate for comparisons.

Abstract The values of series and shunt resistances play an important role in the modelling behaviour of a photovoltaic cell. The authors proposed in earlier work a new method to determine these values numerically at maximum power point using the Newton–Raphson method and equations based on the Lambert W -function. Here, an experimental investigation has been carried out to further validate this method and observe its behaviour over the entire current–voltage curve. Current–voltage curves from a single multi-crystalline cell were obtained under outdoor testing in Hamilton, New Zealand under three levels of illumination (800, 900, and 1000 W/m 2 ). In addition to the method of Ghani and Duke (2011) , two other methods were also used to calculate series and shunt resistances based on the parameters extracted from the experimental data. A comparative study of each methods output current vector using a root mean square error analysis revealed that greatest accuracy was achieved with the proposed approach.

Abstract Solar energy is a potential clean source of energy to meet our thermal and electrical energy demands but its penetration is hindered by the factors such as intermittency of solar radiation, lower thermal efficiency, and capital requirement for the solar energy systems. Improving the thermal performance of the solar collectors and effectively collecting the thermal energy from photovoltaic panels can pave the way to promote clean energy utilization. Heat pipe, being a passive energy system with a high heat transfer rate ability, can aid in ameliorating the performance of solar collectors as well as photovoltaic panels. This review study is proposed to discuss the theoretical and experimental aspects of the design and integration of heat pipes with various solar applications including solar thermal, freshwater production, and photovoltaic-thermal systems. In addition, numerical models relevant to heat pipe and solar energy systems are highlighted. An elaborate analysis of various influencing factors on the thermal performance of heat pipe integrated solar energy systems is also presented. The critical observations from experimental aspects are elucidated, and the future scope of heat pipe systems are also substantiated. This review encourages the selection of a particular heat pipe and the heat transfer enhancement method to attain higher energy conversion rate and the productivity corresponding to various solar energy systems.

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

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.

A solar thermal power project that makes use of a compact linear Fresnel reflector array to concentrate solar radiation onto a stationary absorber cavity suspended above the array has been proposed. The cavity is trapezoidal in cross-section. The upper surface of the cavity is a flat plate absorber with steam tubes running behind it. The lower surface is a glass window that allows solar radiation, focused by the mirror array, to enter the cavity. Heat loss from the absorber occurs via a complex interaction between radiation, convection and conduction within the cavity, and then from the cavity to the surroundings. This paper describes the experimental techniques used to investigate the heat losses from the absorber, and the flow visualization technique used to capture the flow patterns within the cavity. It then goes on to compare the experimental results with predictions obtained from a model developed using FLUENT, a commercially available computational fluid dynamics package. Excellent agreement is achieved between the flow patterns observed in the experiment and those predicted by the computational model. Reasonable agreement between the experimentally determined heat losses and those predicted by the computational model are also shown to exist.