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Abstract A general procedure for determining the optimum geometry of a reflector-augmented solar collector which produces a desired pattern of flux-augmentation is described. The example used for illustration is a stationary collector whose winter performance is to be improved. Consideration both a flat-plate collector with a bottom reflector and one with a top reflector led to distinct differences in their optimum configuration and performance being identified. Since either systems can be used to augment winter flux, a criterion for selecting the appropriate system is given. This criterion is based on the displacement in collector tilt from latitude inclination.

Abstract In a linear Fresnel reflector field, parallel rows of reflectors in a collector direct the incident sun rays towards a common linear receiver. Some portion of reflector aperture remains unused due to end effect, inter-row shading and blocking. In addition to these factors, cosine effect, cleanliness factor, reflectivity of reflectors, intercept factor, transmissivity of receiver cover, reflectivity of secondary reflector, absorptivity of absorber tube and thermal losses are other factors that contribute to energy losses and thus affect net energy collection by the heat transfer fluid in the absorber, electricity generation and cost of electricity. Conventionally, the collectors are oriented either along North–South or East–West directions in most cases. However the energy collection, electricity generation and cost of electricity need to be found out for all possible collector-orientations lying between North–South and East–West. This can be used in designing collectors for places where the available land strip does not align with any of these two directions. In this work, explicit analytical expressions for energy losses due to cosine effect, end effect, shading and blocking are derived for any desired time interval as functions of length ( L ) and width ( w ) of aperture of reflector-row, spacing between adjacent reflector-rows ( p ), number of reflector-rows in a collector ( n ), height of receiver ( H ), collector-orientation angle ( Ω ) and location. The expressions for the net energy collected by the working fluid, electricity generated by a collector and the cost of electricity are presented. The effects of L , w , p , n , H , Ω and location on energy losses, net energy collection by fluid, electricity generation and cost of electricity are studied. The minimum cost of electricity is found out for different collector-orientations at various locations and relative comparisons have been made. The corresponding collector parameters, annual energy collection by fluid and the annual electricity generation are also found out.

Abstract In this article, we have studied an identical section of a core-shell ZnO Nanorod (NR) based lead-free perovskite solar cell. Various factors affecting the solar cell’s performance have been rigorously investigated for device optimization; specifically, the length and diameter of the ZnO NR core, perovskite shell thickness, thickness of perovskite cap layer, and hole transport layer (HTL) thickness. The defect density of states (DOS) in the perovskite absorber layer and the effect of interface defect density on the performance of the cell are also studied. We obtained power conversion efficiency (PCE) of 14.50%, the open-circuit voltage (VOC) of 0.96 V; short-circuit current density (JSC) of 18.11 mA/cm2 and Fill factor (FF) of 83.35%. We also analyzed the effect of tilt or inclination of NR on the performance of the cell which is a crucial factor toward achieving high performance. By optimizing the device parameters, we have achieved a PCE of 21.27%, VOC of 0.97 V, JSC of 29.56 mA/cm2, and FF of 84.15% at an inclination of 10-degree tilt with respect to the incident light under AM 1.5 illumination. The shadowing mechanism behind efficiency droop is also presented to further realize an optimal design high-performance PSC.

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.

Abstract The depletion of fossil fuel and their impact on the environment due to continual usage for our ever-increasing power needs has forced us to look pro-actively towards other renewable forms of clean energy like wind, solar, ocean energy, etc. Amongst all renewable sources of energy, solar energy is abundantly available throughout the world and can meet the energy needs of our planet if appropriately harnessed. Solar thermal collectors are used to collect solar thermal energy, and then it is transferred to the fluid. The fluid may be air, water, oil, etc. depending on the application. Many researchers are working towards performance enhancement of solar thermal collectors. This article concentrates on solar air collectors and different types of modifications made in the recent past to improve its efficiency. This study is an attempt to summarize and present solar air heaters and various modifications for performance enhancement. The effect of modifications on the Nusselt number, friction factor, and thermohydraulic performance of the solar thermal collector is reported. The present article also discusses the effect of impingement of air on the device thermal efficiency and the geometric modifications. This paper will enable researchers working in this field to get a summary of important work done related to solar thermal collectors.

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%.