Photovoltaic Solar Conversion Research Articles

Optimization study on magnetorheological fluid components and process parameters of cluster magnetorheological finishing with dynamic magnetic field for sapphire substrates

Sapphire is used as the base material of high-brightness LED devices, high-speed and high-frequency wireless communication devices, and solar photovoltaic conversion chips. Its surface quality determines the performance of the device. Magnetorheological (MR) finishing can avoid scratches and surface/subsurface damage caused by uneven abrasive particles due to the viscoelasticity of the polishing pad. When MR polishing was used to polish sapphire substrates, the adaptability of the MR fluid components and the rationality of polishing process was the key to quickly obtain high-quality workpiece surface. In this study, sapphire substrates were polished using cluster MR finishing with dynamic magnetic fields formed by multiple synchronous rotation magnetic poles. The components of the MR fluid were optimized by single-factor experiments, and the polishing process parameters were optimized through orthogonal experiment. The results showed that an ultra-smooth surface of Ra 0.27 nm could be obtained when sapphire substrate was polished 8 h by using the optimized MR fluid, which contained 120 nm silica sol with a mass fraction of 8 wt% and W3 carbonyl iron powders with a mass fraction of 16 wt%, also with the optimized process parameters as the machining gap, the workpiece speed, the magnetic pole speed and the rotation speed of the polishing disc were 1 mm, 350 r min−1, 45 r min−1 and 40 r min−1, respectively.

The Fabrication of Micro-/Nano-Structural Antirefraction Coatings Based on the PDMS Film for Solar Cells Application

A simple and low-cost methodology to fabricate micro/nanostructure anti-refraction coatings (ARCs) of solar cells is introduced. The nanostructure ARCs are generated by O2 Plasma surface modification technique for a flexible polydimethylsiloxane (PDMS) polymeric film, the microstructure ARCs are obtained by soft imprint lithography, and the micro-nano complex structure PDMS ARCs are fabricated by soft imprint lithography technique combined with surface modification technique. The measured results show that these PDMS ARCs can decrease reflection loss of light from the solar cells and increase the solar cells photovoltaic conversion efficiency.

Thermal selective coatings and its enhancement characteristics for efficient power generation through parabolic trough collector (PTC)

World climate is an area of concern due to the use of fossil fuels that have been the most commonly preferred resource of energy since the industrial revolution and urbanization. The target to maintain the lowest level of carbon emissions and greenhouse gases has created an urge to look for renewable energy resources. Among the renewable energy resources available worldwide, solar energy is considered as one of the feasible and mature technologies in view of large-scale commercial deployment. Solar photovoltaic and solar thermal conversion (STC) techniques have been implemented so far and are still advancing towards cost-effective solutions. Parabolic trough collector (PTC) is one such economical and feasible STC technology as far as high-temperature thermal applications are concerned and are being widely used for power generation. This paper is an attempt to present the current scenario of PTC technology along with its various advancements over the years. Further in this paper, selective coatings, coating techniques and heat collection element (HCE) or receiver are discussed in detail with regard to their advancements. The present work also illustrates the progressive trends in PTC technology, particularly with respect to various heat transfer fluids, HCE inserts, selective coatings and other performance factors along with some futuristic aspects with respect to coatings and receiver inserts in view of high thermal performance.

Design, development, and implementation of grid-connected solar photovoltaic power conversion system

ABSTRACT In this paper, a detailed documentation revealing the design, development, and implementation aspects of grid-connected solar photovoltaic (SPV) power conversion system is presented. Since the inverter is considered as a key constituent of an SPV system, a laboratory developed three-phase four-legged (3P4L) inverter is employed to diminish the overall cost of the SPV system considerably. The multifunctional inverter controlled SPV system proposed in this work not only injects active power into the electric grid, but it also serves as an active power filter (APF) to provide various power quality (PQ) solutions. This typically includes source current harmonic attenuation, load reactive current mitigation, neutral current elimination, source current balancing, in addition to ensure unity power factor operation. A various hardware circuits including signal sensing circuit, signal conditioning circuit, pulse amplification and isolation circuit, and blanking circuit are fabricated and assembled to develop a complete laboratory prototype model. In addition, the voltage and current controllers, the synchronize reference frame theory (SRFT)-based approach, and the phase-locked loop (PLL) control algorithms are embedded in dSPACE 1104 control platform. Furthermore, an STM32F407VGT microcontroller is employed to implement the incremental conductance based maximum power point (MPP) tracking algorithm. The effectiveness of the developed SPV system is first simulated in MATLAB/Simulink software. In the second step, the efficacy of the proposed configuration is investigated under balanced and unbalanced nonlinear loads on a laboratory developed prototype.

ZnO Nanorod Humidity Sensor and Dye-Sensitized Solar Cells as a Self-Powered Device

In this paper, ZnO nanorod humidity sensors with dye-sensitized solar cells (DSCs) were prepared on indium tin oxide conductive glass. The average diameter and length of the ZnO nanorods were ~100 nm and $\sim 1.5~\mu \text{m}$ , respectively. After ZnO nanorods were grown, TiO2 film was coated by TiO2 with a nanoparticle size of approximately 26 nm through the doctor blade method. The sensitizer N3 was used for charge transfer on the DSCs. The solar photovoltaic conversion efficiency of the DSCs was approximately 4.7%. Humidity sensors were used for measurement under ultraviolet (UV) light at 365 nm. During UV illumination, the current increased under low humidity and gradually decreased under high humidity. The integrated device exhibited similar stable and sensitive performance as the traditional ZnO humidity sensor. Experimental results revealed that DSCs could be integrated with ZnO nanorod humidity sensors to create a self-powered integrated device that has potential Internet of Things applications.

Solar Energy a Promising Source for E-Vehicles

The demand and availability of energy is growing day by day in the whole world. Renewable energy resources will play an important role in the future as the conventional energy sources like coal and petroleum are limited and declining. In the present situation, energy crisis is an important very critical problem hence necessary to address. Basically, it is to verify the availability to increase the generation or to install additional generators. Alternatively, load management known as demand side management (DSM) strategy must be adopted. In the current scenario, the uses of fossil fuel for the domestic transport are rapidly increasing and indicate the threat in the near future. The adverse effects of the practice of such vehicles and means leads to the environment pollution and health issues related to the living habitats. In line with this the upcoming mode of transport is E-vehicles keeping concerned about the environment pollution. The drawback of this mode of transport is the use of electric energy for the propulsion and going to create additional burden on the existing power system setup and infrastructure. But the use of power electronics and controls in Electric vehicles (EVs) along with latest technologies is fostering and supporting the green transportation systems.E-Vehicle charger is the role player in reducing the dependence on fossil fuels and is the natural evolution of our energy infrastructure significantly. Consumer incentives are also important to make the purchase of an electric vehicle and home fast-charging station more affordable and attractive. To address this issue most of the developed countries have taken up an initiative to extract solar photovoltaic conversion systems to store and transfer to the grid.The present rate of use of E-vehicles is 70% compared to the earlier decade. From the perspective of solar energy basically, it is extracted as either heat or light energy. But the storage system is the bottle neck issue in this regard due to technical, economic barriers and challenges. The power electronics interfaces male E-vehicle battery to get charged from the grid if there is no source solar energy known as grid to vehicle (G2V). The other mode is to transfer the stored energy from the storage battery to grid (V2G) as and when grid finds the deficit of energy to meet its loads. Then the solar PV systems installed on the roof top of the vehicle generate the electricity and is used for their operation by the battery support.Therefore, the E-vehicles fitted with solar PV panels can even transfer electricity to the grid (V2G). Hence, the suitable design and implementation can prove the solar photovoltaic source as a promising source for such E vehicle application in the very near future. This creates an opportunity to the engineers and enterprises.

Monitoring the performances of a maximum power point tracking photovoltaic (MPPT PV) pumping system driven by a brushless direct current (BLDC) motor

Nowadays, water pumping systems powered by solar-cell generators are one of the most important applications. It’s a promising alternative to conventional electricity and diesel based pumping systems, especially for applications like community water supplies and irrigation. This study presents a monitored standalone photovoltaic solar direct pumping system using the Maximum Power Point Tracking (MPPT) algorithm to optimize the solar photovoltaic conversion efficiency. It was done at ISET-Rosso in Mauritania. The experimental setup based on Lorentz PS1200C-SJ8-5 pumping system consists of four photovoltaic (PV) panels, inverter PS1200, BLDC motor, centrifugal pump and a storage tank. The system has been monitored, in order to determine the relationship between: the DC power produced by the PV generator and the solar radiation; the water flow and the DC power and by then the relationship between the water flow and the solar radiation. The effect of ambient temperature and solar radiation on the PV panels was also done under Matlab/Simulink environment and compared to the experimental results. ©2019. CBIORE-IJRED. All rights reserved

Application of compound parabolic concentrators to solar photovoltaic conversion: A comprehensive review

The use of concentrating systems has been proposed as a way to reduce the cost of electrical energy from photovoltaic (PV) module. Since 1970s, different solar collector designs have been used to increase energy flux on the PV module. This study aims at providing a comprehensive review of development in the application of compound parabolic concentrators (CPCs) to solar photovoltaic conversion for the past five decades. By narrowing down the application of CPCs to electrical energy only gives a reader an opportunity to clearly understand the detail development stages, challenges, and research opportunities for further improvement. From this review, it has been found that during 1970s, all studies on the application of CPCs to solar photovoltaic conversion were mainly focused on establishing technical feasibility and cost effectiveness. Thereafter (1981-May 2018), extensive studies were carried out to resolve challenges that were observed during the establishment stage. However, it has been found that even though the power output of the PV modules with the CPC was always higher than similar modules without the CPC, the values were less than the expected (theoretical) results. This was due to optical losses, series resistance losses, non-uniform illumination effect, and high operating cell temperature effect. In addition, high cost of the PV-CPC systems and low concentration ratio of the CPCs were also the main concerns of various researchers.

Self-Powered ZnO Nanorod Ultraviolet Photodetector Integrated with Dye-Sensitised Solar Cell

In this study, ZnO nanorod ultraviolet (UV) photodetectors (PDs) with dye-sensitised solar cells (DSSCs) were prepared on ITO conductive glass. The average diameter and length of the ZnO nanorods were ∼99 nm and ∼1.6 μm, respectively. After the growth of the ZnO nanorods, the TiO2 film with the TiO2 nanoparticle size of ∼25 nm was coated using doctor-blade method. Then, sensitiser N3 was used for the charge transfer in the DSSCs. The solar photovoltaic conversion efficiency of the DSSCs was approximately 4.75%. The performance of the UV PDs was also measured by exposing it with UV light at 365 nm. Results showed that the transient responses of the ZnO nanorod UV PDs integrated with DSSCs were stable and reproducible.

Sol-gel preparation and near-infrared emission properties of Yb3+ sensitized by Mn4+ in double-perovskite La2ZnTiO6

Yb3+/Mn4+ co-doped La2ZnTiO6 (brief as LZT:Yb3+/Mn4+) phosphors with xYb3+ (x = 0–0.12) and yMn4+ (y = 0–0.01) doping concentrations have been synthesized via a sol-gel method. X-ray diffraction (XRD) and photoluminescence spectra were employed to characterize the properties of final products. The LZT:Yb3+/Mn4+ material can efficiently convert the short-wavelength sunlight in wide spectral ranges (250–600 nm) into near-infrared emission around 990 nm which matches the higher photosensitivity region of Si-based solar cells. A dipole-dipole interaction plays an important role for the energy transfer process from Mn4+ to Yb3+ ions, which has been verified by Dexter's theory. Under the 390 nm excitation, the energy transfer efficiency is 38.6% in the La1·9ZnTi0·998O6:0.1Yb3+/0.002Mn4+ co-doped sample. Due to the effective absorption of Mn4+ in the visible region and charge transfer transitions (O2−→Yb3+ and O2−→Mn4+) in the UV region for LZT and the efficient energy transfer to Yb3+, this material can be developed as spectral convertors to improve silicon solar cell photovoltaic conversion efficiency.

Deep-level traps and recombination centers effects on photovoltaic conversion efficiency of GaAs based crystalline solar cell

In this work, we proceed to analytical and numerical resolutions, using finite difference method, of semiconductor four equations system governing the variations of electrostatic potential, electrons and holes densities, density profile of occupied levels associated to deep-level traps as well as concentration profile of occupied levels related to recombination centers, in one-dimensional thin-film crystalline solar cell based on Gallium Arsenide (GaAs). In addition to physical quantities mentioned above, the problem resolution, achieved using Maple computer algebra software, enables us to retrieve electrostatic field, electrons and holes current densities as well as energy band diagram throughout the device. Ultimately, particular attention is devoted to specific phenomena related to semiconductors such as the presence of deep-level traps or recombination centers whose levels are in the middle of the gap. In this way, we show that the presence of deep-level traps or recombination centers leads, via Shockley-Read-Hall mechanisms, to a decrease of solar cell photovoltaic conversion efficiency. We also show that these effects are dependent on energy levels of traps and defects, on traps and defects concentrations as well as their electron and hole capture cross sections.

Anti-reflectance investigation of a micro-nano hybrid structure fabricated by dry/wet etching methods

Black silicon fabrication and manipulation have been well reported by institutes around the world and are quite useful for solar absorption and photovoltaic conversion. In this study, silicon micro-nano hybrid structures were fabricated, and the morphologies of the hybrid structures were analyzed. This paper studied nanostructures formed on tips, pits and a flat surface using a dry etching method and a wet etching method. In terms of nanostructure morphology, nanostructures etched by the wet etching method (13 μm) were taller than those etched by the dry etching method (1 μm), but the wet etched morphology was less organized. After the nanostructures were grown, six samples with nano sturctures and three samples with micro sturctures were measured by a photometer for reflectivity testing. The nine samples were compared and analyzed using the integral of reflectivity and solar emissivity at the earth’s surface. The results show that the nanostructures grown on a tip surface using the wet etching method had the minimum reflectivity in the wavelength range of 300 nm–1100 nm, in consideration of the forbidden energy gap of silicon.

Effect of the depth base along the vertical on the electrical parameters of a vertical parallel silicon solar cell in open and short circuit

Abstract This article presented a modeling study of effect of the depth base initiating on vertical parallel silicon solar cell’s photovoltaic conversion efficiency. After the resolution of the continuity equation of excess minority carriers, we calculated the electrical parameters such as the photocurrent density, the photovoltage, series resistance and shunt resistances, diffusion capacitance, electric power, fill factor and the photovoltaic conversion efficiency. We determined the maximum electric power, the operating point of the solar cell and photovoltaic conversion efficiency according to the depth z in the base. We showed that the photocurrent density decreases with the depth z. The photovoltage decreased when the depth base increases. Series and shunt resistances were deduced from electrical model and were influenced and the applied the depth base. The capacity decreased with the depth z of the base. We had studied the influence of the variation of the depth z on the electrical parameters in the base.

Influence of process parameters on the gallium composition of a CuIn1−xGaxSe2 solar cell on the efficiency of non-vacuum blade coating stacking

The distribution of an energy gap gradient can influence photovoltaic conversion, which in turn influences the performance of solar cells. On the other hand, controlling the energy gap gradient can influence the range of the absorption spectrum, and thus the overall solar photovoltaic conversion efficiency is affected. To control the energy gap of a CuIn1−xGaxSe2 (CIGS) solar cell, this study employs a non-vacuum stack coating technique. The chemical composition of the ink is regulated and a multilayer stack is coated to investigate (1) the distribution range of the energy gap and (2) the variability of conversion efficiency in multilayer stack and single-layer composition conditions, in order to determine the feasibility of using a coating stack design to change and control an energy gap. The effect of film composition on crystallinity is tested through high-temperature selenylation. Finally, a miniature solar module is prepared and the conversion efficiency is found to improve from 5.02% to 7.08%, and the feasibility of energy gap control is demonstrated.

Experimental investigations into low concentrating line axis solar concentrators for CPV applications

Solar photovoltaic conversion systems with integrated, low concentration ratio, non-imaging reflective concentrators, could be on south facing building roofs used to generate power at a lower cost than currently available proprietary systems. The experimental investigation presented by this research provides information on the optical and energy conversion characteristics of two geometrically equivalent non-imaging concentrators; a compound parabolic concentrator and a V-trough reflector. The aim was to investigate the assumption of uniform cell illumination when PV cells located on the receiver surface with their central axes are aligned parallel with the focal line of the line-axis concentrator. Solar radiation incident was measured at the aperture and the PV cell surface using respectively a pyranometer and photodiodes at six different collector tilt angles of 0°, 10°, 20°, 30°, 40° and 52°. The analysis of the collected experimental data presented demonstrated that the V-trough system had a more even distribution of solar radiation than the CPC and a higher optical concentration ratio (ratio of solar radiation incident on the aperture cover to that incident on the receiver) though the geometrical concentration ratio of the two collectors was equal to 2.2×. Also, the V-trough concentrator had an electrical power output up to 17.2% higher than the CPC system at a specific tilt angle of 30°. The V-trough had a consistently higher receiver plate temperature as it was reflecting larger quantities of solar radiation than the CPC. Over 17 consecutive typical summer days’ similar performance was observed over the range of tilt angles studied. The development of V-trough concentrators should be preferred due to higher power production, reduced complexity, increased uniformity of illumination and lower manufacturing costs compared to CPCs.

A solvothermal route to synthesize kesterite Cu2ZnSnS4 nanocrystals for solution-processed solar cells

Cu2ZnSnS4 (CZTS) has been proposed as an alternative earth-abundant absorber material for thin film solar cells. In this paper, we report a facile solvothermal method to produce impure-free kesterite CZTS nanocrystals. Optical band gap of the obtained high quality CZTS nanocrystals is 1.52 eV determined by UV–VIS–NIR absorption spectrum, which is match well with the optimum for photovoltaic solar conversion in a single-band-gap device. We closely systematically investigated both the concentration of Sulfur (S) and the species of precursor Tin (Sn) and their impact on the final products. Furthermore, CZTS nanocrystals based layers hybrid junction solar cells were fabricated by a layer-by-layer dip-coating method. The enhancement in photovoltaic performance was also explore through the solid state ligand exchange which was used 1, 2-ethanedithiol (EDT) to treat the CZTS nanocrystals layer. We achieved the best power conversion efficiencies (PCE) of 1.73% fabricated with the EDT treated CZTS nanocrystals layer, which is approximately 5 fold than the comparative devices without treatment.

Al2O3:Cr3+/tellurite glass composites: An efficient light converter for silicon solar cell

Al2O3:Cr3+ nanocrystals have been developed as spectral converters for improving silicon cell photovoltaic conversion efficiency. In the Al2O3 lattice, Cr3+ ions act as broadband spectral acceptors by absorbing UV–vis (320–670nm) photons, which are effectively converted into the strong red emission centered at around 696nm, indicating Al2O3:Cr3+ can be a good material for overcoming the so-called spectral mismatch in the silicon solar cell. The Al2O3:Cr3+ nanocrystals are successfully introduced into tellurite glass to form transparent composites with good optical performance which can be characterized by photoluminescence (PL) spectra. These tellurite glass composites open a brand new field for the research of improving silicon solar cell photovoltaic conversion efficiency.

Measuring complex for studying cascade solar photovoltaic cells and concentrator modules on their basis

The design and implementation of several measuring complexes intended for studying cascade solar photovoltaic converters are considered. The complexes consist of a solar simulator and an electronic unit with an active load. The high-aperture light source of the complex reproduces solar intensity over wide spectral range λ = 350–1700 nm with an angle of divergence of ±0.26°, which are characteristic of solar radiation. The active load of the electronic unit allows taking both dark and illuminated I-V characteristics of test objects within about 1 ms during the quasi-stationary part of the irradiation pulse. The small size and low power consumption of the complexes hold out the hope that they will be widely used in designing, refining, and testing cascade efficient photovoltaic converters made of III–V materials and solar modules integrating these converters with concentrator modules.

Solvothermal synthesis of CZTS nanoparticles in ethanol: Preparation and characterization

In this work, a low-cost, non-toxic and convenient one-pot solvothermal route to synthesize Cu2ZnSnS4 (CZTS) nanoparticles is reported. The effects of solvothermal temperature and reaction time on the structure, morphology and optical properties of the as-synthesized product were investigated by using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX) measurements and X-ray photoelectron spectroscopy (XPS). The results showed that the crystallinity of the CZTS powders was influenced by the solvothermal temperature and reaction time. The band gap of selected CZTS samples was near the optimum value for photovoltaic solar conversion in a single-band-gap device.

YAG中Cr3+和Yb3+的发光特征以及Cr3+和Yb3+之间的能量传递过程

室温下观察了YAG∶Cr^3＋,Yb^3＋材料在近红外区域的发光特性,并通过对Cr^3＋：4T2和Yb^3＋：2F5/2能级辐射跃迁寿命以及它们布居时间的比较研究,提出了从Cr^3＋到Yb^3＋的能量传递机制,同时借助于能级图描述了从Cr^3＋到Yb^3＋的能量传递以及Cr^3＋和Yb^3＋的近红外发光过程。