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[en] A one-dimensional nonstationary three-element distributed thermal model of a flat-plate collector with allowance for time variation of the temperatures through the “thickness” of the elements and along the length of the solar collector (SC) has been developed and software-implemented. The main data in this model consist of the thermophysical and overall parameters of the collector elements, heat carrier inlet velocity, solar radiation density, and ambient and sky temperature. To decrease the calculation variants, the variation ranges of mass flow of the heat carrier and its flow velocity were estimated for the characteristic parameters of the heat-removal channels of flat-plate SCs. It has been found that the specific mass flows of water in flat-plate SCs are 2.5–10 g/(s m2), and the water flow velocity is 0.0005–0.002 m/s. It is shown that the instantaneous efficiency coefficient and temperature of the heat carrier can fall outside stationary values within 1–3 h. However, the daily efficiency coefficients of the SC do not fall outside the stationary values even within a day. The developed flat-plate SC model can be used to estimate the influence of the thermophysical and overall parameters of the elements, as well as the parameters of the environment, on its thermophysical characteristics when developing flat-plate SCs and methods for experimentally determining their characteristics.
[en] This paper studies the experimental and exergy analysis of solar still with the sand heat energy storage system. The cumulative yield from solar still with and without energy storage material is found to be 3.3 and 1.89 kg/m2, respectively for 8-h operation. Results show that the exergy efficiency of the system is higher with the least water depth of 0.02 m (mw = 20 kg). Competitive analysis of second law efficiency shows that the exergy efficiency improves the system by 30% than conventional single slope solar still without any heat storage. The maximum exergy efficiency with energy storage material is found as 13.2% and it is less than the conventional solar still without any material inside the basin.
[en] The current work represents the simulation results of the thermal performances of flat-plate solar collector with heat transfer fluid–nanofluid (SiO2 + water with 5% concentration) which is obtained experimentally . The dependence of the outlet temperature and gained useful energy of heat transfer fluid (nanofluid) on the flow rates (10, 15 and 20 L/h) at different ranges of incident solar radiation (500–1000 W/m2) was obtained.
[en] The annual supply of total solar irradiation (SI) to the surface of a randomly oriented photovoltaic panel (PVP) is considered; on this basis, the optimal horizontal tilt for seasonal or annual use is found. A flow diagram is proposed for determining the global total irradiation (GTI) on the surface of PVPs installed in variously oriented positions. Surkhandarya region is considered as an example. The actinometric findings obtained from the Sherabad station, as well as the PVP test results, are provided.
[en] The paper presents the results of calculated research on determining the thermal technical indicators of a combined solar desalinization and drying plant. The structure of the plant is developed and proposed. A mathematical model is developed that describes the thermal processes occurring in the plant based on heat-balance equations solved using the Laplace method.
[en] The objective of this paper is to improve the power conversion efficiency of HIT solar cell using amorphous materials. A high efficiency amorphous material based on two dimensional heterojunction solar cell with thin intrinsic layer is designed and simulated at the research level using Synopsys/RSOFT-Solar Cell utility. The HIT structure composed of TCO/a-Si:H(p)/a-Si:H(i)/c-Si(n)/a-Si:H(i)/a-Si:H(n+)/Ag is created by using of RSOFT CAD. Optical characterization of the cell is performed by Diffract MOD model based on RCWA (rigorous coupled wave analysis) algorithm. Electrical characterization of the cell is done by Solar cell utility using based on Ideal diode method. In addition, optimization of the different layer thickness in the HIT structure is executed to improve the absorption and thereby the photocurrent density. The proposed HIT solar cell structure resulted in an open circuit voltage of 0.751 V, a short circuit current density of 36.37 mA/cm2 and fill factor of 85.37% contributing to the total power conversion efficiency of 25.91% under AM1.5G. Simulation results showed that the power conversion efficiency is improved by 1.21% as compared to the reference HIT solar cell. This improvement in high efficiency is due to reduction of resistive losses, recombination losses at the hetero junction interface between intrinsic a-Si and c-Si, and optimization of the thicknesses in a-Si and c-Si layers.
[en] A practical fault detection approach for PV systems intended for online implementation is developed. The fault detection model here is built using artificial neural network. initially the photovoltaic system is simulated using MATLAB software and output power is collected for various combinations of irradiance and temperature. Data is first collected for normal operating condition and then four types of faults are simulated and data are collected for faulty conditions. Four faults are considered here and they are: Line to Line faults with a small voltage difference, Line to line faults with a large voltage difference, degradation fault and open-circuit fault. This data is then used to train the neural network and to develop the fault detection model. The fault detection model takes irradiance, temperature and power as the input and accurately gives the type of fault in the PV system as the output. This system is a generalized one as any PV module datasheet can be used to simulate the Photovoltaic system and also this fault detection system can be implemented online with the use of data acquisition system.
[en] Traditional design of Hybrid photovoltaic thermal (PV/T) system has the solar cells fixed on the top of the absorber. A new PV/T system in which the solar cells are pasted on the bottom of the glass cover is suggested with the aim of realizing higher electricity output considering the lower temperature of glass cover compared with that of absorber. A numerical analysis model is set up to compare the performances of the traditional PV/T and the new PV/T in this study. It is found that compared to the traditional PV/T, the new PV/T shows higher daily electric efficiency. But this superiority is not as apparent as expected. The key point to increase the daily electric efficiency of a PV/T lies in increasing the solar energy transfer efficiency of the solar cell. The total energy gain of the new PV/T is about 7% lower than that of the traditional PV/T because of smaller mass rate and more energy loss from glass cover with higher temperature.
[en] The Multi-layered Thermal Energy Storage (TES) tank consists of three regions–top and bottom part is packed with suitable Phase Change Materials (PCM) and low-cost pebbles are placed in the middle region, whereas entire tank portion is filled by solid fillers in Single-layered tank system. For a storage tank operating between 563 and 663 K with bed dimensions of 12 and 14.38 m using Solar salt as Heat Transfer Fluid (HTF), it is observed that the duration of discharge for multi-layered tank is 5.32 h whereas it is 4.19 h for single-layered tank with a Reynolds number of 10. The effect of intermediate melting temperature range of PCMs are also analyzed by taking PCMs with sharp as well as intermediate melting ranges. Further, comparison of single and multi-layered systems is carried out by analyzing the temperature profiles and width of both PCM layers. The width of top and bottom PCM layers of tank is varied from 0 to 30% to analyze its effect on the discharging duration. It is observed that multi-layered system provides extra discharge of 1 h with introduction of PCM at top and bottom with a width of 10%. Discharge duration increases with increase in PCM width whereas the percentage increase in duration of discharge with increase in PCM width is comparatively less. It is also seen that PCMs with sharp melting point performs better compared to one having intermediate range of melting temperatures. Multi-layered configuration concept offers best possibilities as integration to CSP plants with desired efficiency.
[en] The paper presents the results of an experimental study of the efficiency of the integrated controllers of PWM and MPPT PV/batteries, which are part of an autonomous photovoltaic power plant. The dependences of the efficiency on the hourly sums of solar radiation are represented, which can be used to calculate the productivity of autonomous photovoltaic systems with an hourly integration step. The operational features of the controllers during low-level periods of solar radiation are considered.