Applied Solar Energy最新文献

Solar Liquid Flat Plate Collector (LFPC) system used for low-temperature domestic water heating has wide applications. However, the conversion efficiency is observed to be poor since losses from collector surface is higher. Mostly heat transfer augmentation in solar collectors is one of the key issues in energy saving, compact designs and different operational temperatures. The present work focusses on coining an appropriate Heat Transfer Fluid (HTF) and internal grooves to the Heat Transfer Fluid (HTF) ducts to enhance the performance of LFPC, taking Mumbai as site for analysis. Experimental feasibility study at Mumbai city for four months unrolled maximum global radiation of 800 W/m² and 32.5°C of ambient temperature. Thermophysical analysis of three distinct base fluids namely Molten Salt, Dowtherm A and Therminol VP-1 showcased significant performance of therminol VP-1 with specific heat, density and thermal conductivity of about 1688.8 J/kg-K, 1351.6 kg/m³ and 20.99 W/mK respectively at 50°C. Similarly, three different internal groove profiles (plain, rectangular and trapezoidal) where analysed, of which trapezoidal profile showed improved system performance with maximum of 51.6°C as outlet temperature and 1478 W useful heat gain. The efficiency of trapezoidal profile (77.3%) was found to be 1.01 and 1.003% upfront of plain and rectangular groove profiles. Experimental values for LFPC system with water and plain duct was recorded to compare with other combinations. The enhancement achieved is helpful for addressing various green-house gas emissions and clean energy sustainability.

The aim of this paper is to assess the thermal performance of a parabolic trough collector where the thermophysical characteristics of the heat transfer fluid, the glass envelope, and the absorber pipe are temperature dependent for which we have created our own mathematical correlations. The structure of a parabolic trough collector consists of a reflecting mirror, a heat transfer fluid circulating in an absorber tube that is covered by a glass envelope. The studied model has been subjected to seasonal variations (solstices and equinoxes days) of solar radiation along with the concentrated heat flux reflected from the parabolic trough mirror for conditions at Tetouan city, Morocco. The amount of diffuse and beam solar radiation required has been modelled using the solar load model under Ansys Fluent software environment. The estimation of the heat transfer mechanism of our model has been done by solving Navier Stokes equations, also, the solar discrete ordinate model (DO) has been used to simulate radiation heat exchange on the receiver. The results have shown that the temperature of the heat collector element reaches its maximum values at equinoxes days compared to solstices days, also, it is found that the use of temperature-dependent properties enhances the thermal performance of the model by 1.4%.

Fault detection in photovoltaic (PV) arrays is one of the prime challenges for the operation of solar power plants. This paper proposes an artificial neural network (ANN) based fault detection approach. Partial shading, line-to-line fault, open circuit fault, short circuit fault, and ground fault in a PV array have been investigated, and a data set is synthesized to evaluate the impact on maximum power amplitude and number of power peaks under various exposure of irradiance and temperature. The ANN model has been trained considering irradiance, temperature, maximum power, and the number of power peaks corresponding to the different faulty conditions and non-fault situations. The considered ANN model has been optimized in order to increase the accuracy of fault identification. A particle swarm optimization-based algorithm has been employed to find the optimum number of neurons in the hidden layers to achieve the highest possible prediction accuracy on the test data set. The performance of the optimized neural network has been further cross-validated by an arranged data set containing all the types of faulty conditions. The effectiveness of the proposed technique is verified by comparing the results with existing methods.

Kesterite Cu₂ZnSnS₄ thin films were synthesized by the spray pyrolysis method with subsequent annealing at temperatures in the range from 425 to 525°C. To understand the impact of Ag on the Cu₂ZnSnS₄ structural properties, changes in the elemental and phase composition, as well as microstructure were studied by electron microanalysis, X-ray phase and Raman analysis, scanning probe microscopy and scanning electron microscopy. The obtained samples have a compact morphology without appreciable voids and pores and crystallize in the tetragonal structure of kesterite CZTS. Phase analysis indicated incorporation of Ag in different concentrations without formation of other impurity compounds. An increase in the annealing temperature leads to an increase in the coherent scattering region, while the stoichiometric ratio of metals to chalcogen approaches 1, remaining close to that upon Ag alloying.

Single crystalline rutile TiO₂ nanorods were synthesized by using low temperature hydrothermal synthesis method. Activity of the TiO₂ nanorods in the visible light range was achieved by introducing low bandgap semiconductor materials, such as CdS, CdSe, and CdS/CdSe and their photoelectrochemical performances were comparatively investigated. Morphological, microstructural and photocatalytic characterization results revealed that TiO₂/CdS/CdSe composite photoelectrode demonstrated superior photocatalytic performance compared to others owing to single crystalline TiO₂ core component as well as favorable band alignment of the sensitized CdSe/CdSe nanoparticles.

This paper presents a detailed performance analysis of multilevel inverter for both stand-alone and grid connected PV systems. Here, converter circuit is not only tested for parameters like total harmonic distortion (THD), power output and system efficiency by connecting the non-linear load but the variations of power factor is also considered which is not found commonly. First the simulated results for THD, power output and efficiency are tabulated with variation of load power factor individually for both systems and best operating power factor is found with respect to distortions and efficiency respectively. For Stand-alone system, circuit efficiency as high as 96.8% is achieved when operated at 0.85 power factor. Then the analytical analysis has been carried out for grid connected system where efficiency of 84.3% is achieved for 60^o grid phase angle and 75.8% for 10^o and thus proposing operation at higher grid phase angle. Harmonic components have been further reduced and brought below 5% level by means of passive filters. Finally, to validate the proposed outcome, simulated results have been compared with analytical results and corresponding plots have been shown.

Assessment of wind potential at a certain site requires an accurate estimate of wind speed at different heights other than that at the measured altitudes. Extrapolating wind data is affected, among other parameters, by the spacing height of the measured wind data. An estimate of the wind shear coefficient (WSC) is needed in order to develop the predicted wind speed profile. In this paper, the effect of spacing height of wind speed measurements on the WSC estimation is investigated using the power-law model, while taking into consideration the effect of the atmospheric stability. Estimation of WSC that would give the nearest value of the extrapolated wind speed to the measured value was performed at three different terrains and promising wind farm locations in Libya. The obtained results indicate the undeniable fact that WSC depends on time, altitude and the spacing height. The value of WSC of the lower measuring spacing height of 20–40 m gives best estimate to wind speed profiles for all atmospheric stability conditions for the two southern cities, while the second spacing height (40–60 m) gave best estimate of wind speed profile for the coastal site. Adopting the proposed WSC instead of the value of seventh in wind potential assessments, leads to an increase in the productivity of wind turbines at rates of 8 and 16% at hub heights of 50 and 100 m, respectively. This in turn will reduce the levelized cost of energy (LCOE) and enhance the competitiveness of wind energy in the energy market.

Nanofluid-based spectral splitting photovoltaic/thermal (SSPV/T) system is an emerging means of achieving full-spectrum utilization of solar energy. In this paper, one-dimension models for nanofluid-based spectral splitting photovoltaic/thermal collectors designs are presented and validated by the experimental results. The energy performance of SSPV/T collectors of different structural designs is analyzed and compared with conventional collectors. The results show that for SSPV/T or conventional photovoltaic/thermal collectors, an insulated cover is very important, especially for thermal efficiency. The thermal efficiency of Design C (cover-insulated SSPV/T) is nearly four times of Design A (non-cover-insulated SSPV/T), while the electrical efficiency is only reduced by 0.7%. The analysis indicates that at present technologies, the spectral splitting PV/T collectors have no obvious advantages than conventional PV/T collectors whether for non-cover-insulated or cover-insulated PV/T collectors. Additionally, Design F (conventional cover-insulated PV/T with low-e coating) performs better than Design C (cover-insulated SSPV/T), low-e coating (high transmittance) is very promising in improving PV/T thermal efficiency.