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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 This study evaluates the mechanical behaviour of a ceramic disk which makes up an innovative volumetric absorber design. The new receiver design is formed by a group of disks which are rotating inside a cavity, distributing the radiation absorbed in the aperture to the whole cavity. This research studies the stress fields due to thermal gradients and its effect in the crack propagation in the disks. The complete analysis has been carried out in three steps: the mechanical characterization of the material, in order to know its fracture properties, the computational fluid dynamics (CFD) analysis of the disk, in order to know the temperature distribution in the disk and the finite element model (FEM), which uses as inputs the results of the two previous steps and solves the stress fields in the disk and the fracture behaviour. Fracture and crack growing in the disk have been modelled by using a cohesive element, which, from the fracture properties of the material, allows simulating the crack growing in the disk. This investigation, by means of stress fields and crack propagation analysis, demonstrates the mechanical viability of the disks concept.

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 Previous computer simulations and bench-scale experiments showed that the heat pipe assisted solar wall had the potential for significantly improved performance relative to conventional passive space heating systems. To further test this potential, a full-scale prototype of the heat pipe system was designed, built and installed in a classroom on the University of Louisville campus in Louisville, KY. During the spring heating season of 2010 (January–April), maximum daily peak thermal efficiency was 83.7% and average daily peak thermal efficiency was 61.4%. The maximum hourly average room gain achieved during the season was 163 W/m2. On days with good solar insolation, the thermal storage was heated to temperatures sufficient to provide significant energy to the classroom – even during the coldest days of the season. During the longest period (4 days) of low insolation during the season, average hourly heat delivery to the room from storage remained positive, and was never less than 16.6 W/m2. During good insolation days following a period of consecutive low insolation days, thermal storage temperature was quickly restored to levels comparable to those obtained during consecutive good insolation days. Estimated heat removal factor * transmittance absorptance product FR(τα) and heat removal factor * overall loss coefficient FRUL values for the system were comparable to those for glazed liquid active collectors.

Abstract This paper deals with improving the effectiveness of the control system for the DC/AC grid connected photovoltaic (PV) inverter. The three-phase DC/AC grid connected PV inverter control system consists of two main control loops: (i) external loop to control the DC link voltage. (ii) An internal control loop for regulating the inverter current by controlling both direct and quadrature currents (Id, Iq) that are provided by the inverter phase-locked loop (PLL). The main component of each control loop is the proportional-integral (PI) controller, whose optimal gains are challenging tasks. The optimal PI controller gains should be selected to achieve multi-objectives such as increasing inverter efficiency, stability and power factor while decreasing the total harmonic distortion (THD) in the inverter output current as well as voltage. For this purpose, various meta-heuristic techniques (MHTs) are suggested with a comprehensive comparative study such as: (i) Whales Optimization Algorithm (WOA), (ii) Grey Wolf Optimization (GWO) algorithm, (iii) Antlions Optimization algorithm (ALO) and (iv) Moth Flame Optimization (MFO) algorithm. The numerical results attained through MatlabTM-Simulink reveal that the WOA technique is more superior than the three others studied MHTs in enhancing the inverter efficiency, stability and power factor with minimum THD.

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.

The design of a solar trough is described which reflects solar radiation onto the bottom of a black metal tray which holds fruit to be dried. Drying results using this solar trough dryer were compared for several fruits with conventional dryers, indicating a 40 to 45% decrease in the required drying time to reach 50% moisture content. (SPH)