Efficiency Of Solar Modules Research Articles

Stabilizing vanadyl acetylacetonate using imidazolium Ionic liquids for VO2 thermochromic thin films

This study examines the role of different imidazolium ionic liquids (ILs) on the stabilization of vanadyl acetylacetonate, VO (acac)2, as a vanadium precursor by using UV-Vis spectroscopy. The possible stabilization mechanisms of VO (acac)2 in IL solution were investigated. Furthermore, a fabrication method is proposed to prepare monoclinic vanadium oxide VO2 (M) thin films using a mixture of ionic liquid and poly-ionic liquid (PIL). The ILs 1-ethyl 3 allyl imidazolium bis(trifluoromethansulfonylimide) ( [EAIM] [TFSI]), 1-ethyl 3-methyl imidazolium trifluoromethanesulfonate ( [EMIM] [TFO]) and 1-ethyl 3-methyl imidazolium acetate ( [EMIM] [AcO]) were investigated. It is shown that ( [EAIM] [TFSI]) has the best coordinating ability to VO (acac)2 for protecting the central vanadium atom from oxidation. For thermochromic film formation, the effect of annealing temperature (250°C – 400°C) and time (10 minutes - 120 minutes) on crystallization was studied using X-ray diffraction. The possible role of PIL decomposition on the formation and crystallization of VO2 (M) is discussed. The prepared films showed excellent thermochromic properties with 20.3 % solar modulation efficiency.

System for maintaining optimal temperature modes of solar power plants

Objectives: To ensure efficient operation of solar modules and temperature mode in accordance with standard test conditions range within 20-30◦C. Methods: A mathematical model was developed using the laws of photoelectricity, heat and mass transfer, which provides improvement in the efficiency of solar power plants. Findings: This study presents the theoretical analysis of different embodiment for systems of solar modules using physical and mathematical models. The main design and functional characteristics of solar modules were calculated: temperature and efficiency depending on internal parameters and ambient environment. Dependence between temperature and efficiency of solar modules for different values of air temperature, emissivity factor of solar cells, and efficiency of solar power plants, were determined and presented in the form of diagrams. It was found that solar modules have the highest heating temperature at solar irradiance of Еc=1200 W/m2, air temperature of Тa=50◦C, and that the solar modules have the lowest heating temperature at Тa=30◦C and e =0.8, with a decrease in the heating temperature from 111 to 38oС, the efficiency decreases at an air temperature of 50oС and at the emissivity factor of e =0.8 and 0.3 and makes from 4.2 to 10.3%. The dependences were calculated for different latitudes φ: 56o(Moscow), 45o(Krasnodar), 35.5o(Eslamshahr, Iran), 31.6o(Béchar, Algeria), 13.1o(Chennai, India). Solar modules with cooling devices were installed in the Istra district of the Moscow region and bench tests, to specific calculated parameters, were carried out under full-scale conditions. Conclusions: It was found that the efficiency of solar panels increased significantly due to the use of systems with heat-exchange tubes, and the losses, when using an antigravity heat exchanger for cooling photovoltaic cells, reduced by 6-7 times. Novelty: Usage of an anti-gravity heat exchanger to cool the photovoltaic cells, to maintain the optimal operating temperature prevent electrical distortion due to extreme temperatures. Keywords: Solar panels; air temperature; cooling; emissivity factor; solar irradiance; antigravity tubes; temperature loads; performance improvement

Солнечный трекер с системой самораскрытия

This article provides a brief overview of the state of solar energy in the world. Disadvantages of fossil energy sources are discussed. Low efficiency is considered the main disadvantage of renewable energy sources. A possible way to improve efficiency of solar modules through the use of solar tracking systems (STS) is analyzed. STS is a special device with two drives for horizontal and vertical guidance to ensure that solar modules face the highest light flux source and thereby increase generation of electricity using a special algorithm. The theoretical increase in production for systems under ideal conditions is calculated; working values thereof are given. The disadvantages of the considered type of renewable energy generators are listed. The calculation of wind loads on the STS was carried out according to the presented method. Examples of destruction of solar power plants by natural disasters are given. A new type of solar trackers with a self-deploying system is proposed; these can protect the installation from unfavorable weather conditions. We analyzed accuracy of the positioning algorithm developed for this device. The conclusion contains possible ways of using the installation, its disadvantages, as well as plans for future research.

Synthesis of Monoclinic Vanadium Dioxide via One-Pot Hydrothermal Route

Pure monoclinic vanadium dioxide nanoparticles (VO2 NPs) with a controlled uniform size are considered essential for the preparation of thermochromic smart window coatings on desired substrates. Herein, we report a facile one-step hydrothermal synthesis of VO2(M) NPs without post-treatment of annealing, which may induce unwanted aggregation of NPs. In contrast with the annealed sample, the one-step processed VO2(M) NPs exhibit superior thermochromic performance with the solar modulation efficiency of 11.8% and luminous transmittance of 37.3%.

THE INFLUENCE OF DUST AND TEMPERATURE ON THE EFFICIENCY OF SOLAR PHOTOVOLTAIC MODULES

At present, the use of solar photovoltaic (PV) modules plays an important role in the field of utilization of solar energy and transformation of this energy into electricity. The main characteristic of PV modules is the work efficiency. It strongly depends on external influences such as the degree of contamination on the glass surface and the operating temperature of the PV modules. Accumulation of dust particles on the surface of PV modules has a very negative effect on their efficiency. At high ambient temperatures, solar PV modules heat up, and the efficiency of modules is reduced. This problem is very substantial for the countries with high temperature conditions and dusty climate. In this paper, the influence of dust and temperature on the efficiency of solar PV modules is investigated. The new-type economically viable system for cleaning and cooling PV modules is used during the experiments. The conducted experimental studies under actual operating conditions during the rainiest period of the year in Yerevan, have shown that due to the cleaning of dust, the efficiency of PV modules is increasing on average by 6.7%. Due to rapid cooling by water in two minutes, the efficiency of PV modules is increased by 2.5%. To improve the operation efficiency, the PV modules must be cooled periodically, taking into consideration the quantity of the consumed water in order to get the maximal economic effect.

Layup-only modulization for low-stress fabrication of a silicon solar module with 100 μm thin silicon solar cells

Despite the predominance of solar modules with bulk crystalline silicon solar cells as a result of their high photoconversion efficiency, long-lasting durability, and low cost per electrical watt, the competitive market has elevated the necessity of thinner silicon solar cells to further reduce direct material costs. However, the tabbing and stringing process using high melting temperature soldering in the conventional fabrication method of a silicon solar module is required to alternatingly interconnect adjacent silicon solar cells, which entails significant thermomechanical stress. The lifting up-and-down motions in the layup process of serially stringed silicon solar cells also lead to an unfavourable interfacial stress between metal ribbons and silicon solar cells. Consequently, a considerably poor yield of silicon solar modules with the unbearable breakage loss of thin silicon solar cells is ascribed to such processes. Herein, an innovative solution to interconnect thin silicon solar cells through virtually no thermomechanical stress is proposed by using encapsulants pre-attached with low melting temperature metal ribbons at 139 °C, which allow the interconnection of pre-laid silicon solar cells in the course of the vacuum lamination at 160 °C. The resulting silicon solar modules exhibit a photoconversion efficiency of 19.1 ± 0.1%, which represents 99.9 ± 0.6% of the benchmark photoconversion efficiency of conventional silicon solar modules. The presented layup-only modulization succeeds in fabricating silicon solar modules with 100 μm thin silicon solar cells and it is anticipated to curtail the breakage loss of thin silicon solar cells as well as elevate fabrication productivity by simplifying the fabrication steps of silicon solar modules.

Moderating oxygen deficiency induced better thermochromic properties of monoclinic vanadium dioxide thin films

Monoclinic vanadium dioxide (M-VO2) is a kind of typical thermal phase change materials, but its relatively high phase transition temperature (68 °C) and low solar modulation efficiency greatly hinder the applications as energy materials. In this work, well-crystalline M-VO2 were prepared by pulsed laser deposition (PLD) under the adjustable oxygen pressure range. By fine adjusting the low oxygen pressure (0.1–0.9 Pa), VO2 maintain the monoclinic crystal and excellent photoelectrical properties, even if oxygen deficiency and other defects exist. Results indicate that the phase-transition temperature (Tc) decreases with the decrease of oxygen pressures while the solar modulation efficiency (ΔTsol) increases with the decrease of oxygen pressures. Moreover, the M-VO2 thin films prepared with 0.3 Pa oxygen pressure showed the best photoelectric performance, in which the sheet resistance changes up to three orders of magnitude, the phase-transition temperature is 61 °C and the ΔTsol is as high as 8.3%. This work has demonstrated the role of moderate oxygen defects in optimizing the photoelectric properties of M-VO2, also provided a feasibility study on how to deposit pure M-VO2 by PLD.

VO2-based composite films with exemplary thermochromic and photochromic performance

Vanadium dioxide (VO2) is one of the best candidates for thermochromic smart windows, which undergoes a metal–insulator transition at a critical temperature (Tc) of ∼68 °C, accompanied with a huge transmittance contrast in the near-infrared range. However, the application of VO2-based smart windows is limited by the poor luminous transmittance (Tlum) and low solar modulation efficiency (ΔTsol). Besides, the intrinsic yellow–brown color of the VO2 film does not change before and after the phase transition, which is not satisfactory. In order to solve the above-mentioned issues, a photochromic material [6-nitro-1′,3′,3′-trimethylspiro-[2H-1-benzopyran-2,2′-indoline] (spiropyran)] has been employed to combine with VO2 nanoparticles to form a hybrid composite film. This newly designed nanostructure demonstrates exemplary solar modulation efficiency (ΔTsol = 23.58%) along with color change from yellow to pink as the light sources change. Moreover, this hybrid composite could block ultraviolet radiation, a crucial index to evaluate the performance of the VO2-based smart windows, which will be promising for industrial applications.

VO2/ZnO bilayer films with enhanced thermochromic property and durability for smart windows

VO2 films are widely considered as one of the most suitable material to act as smart windows. Although this system is able to function, the durability of the film has been an issue as the surface of the films may oxidize by converting V4+ to V5+. To overcome this problem, attempt is made to coat the VO2 film with ZnO, which can assist by creating a resistance layer to prevent further oxidation of VO2. Here, VO2/ZnO bilayer film was prepared by a facile method comprised of spin-coating and dip-coating process and shows excellent durability, and in particular. the solar modulation efficiency (△Tsol) maintaining ca 89.9% (from 17.8% to 16.0%) after 300 days in a humid environment, however, the △Tsol of pure VO2 film is decreased from 11.8% to 4.1%. Also, the VO2/ZnO bilayer exhibits an enhanced thermochromic property of visible transmittance (Tlum = 55.7 ± 2.1%) and △Tsol (17.1 ± 1.4%) which is 1.49 times higher than that of pure VO2 film (△Tsol = 11.5 ± 0.4%). The enhancement in the thermochromic performance and durability is probably attributed to the anti-reflection and protection of ZnO layer. Therefore, this work can provide an effective way to optimize thermochromic property for practical application of VO2-based smart windows.

Thermal management of solar PV module by using hollow rectangular aluminum fins

Some of the recent challenges encountered in research and development of the solar photovoltaic (PV) industry include the decrease in electrical output efficiency of a conventional solar PV module due to the rise in its surface temperature. The main objective of this research work is to enhance and improve the electrical output efficiency of a common silicon-based solar PV module by lowering the operating temperature of the PV module, which was accomplished by attaching hollow rectangular aluminum tubes as a fin to the rear surface of the solar PV panel. The proposed geometrical configuration of tubes helped to increase the PV module heat transfer rate to the surrounding air by increasing the effective heat transfer area without increasing the overall weight of the PV module. In this experimental study, a comparative analysis has been presented for PV modules with fins and without fins. The results obtained from experiments demonstrated that the attached fins reduced the average temperature of the front and rear surfaces up to 8.97% and 8.41%, respectively. The cooling effect produced due to fins improved the open circuit voltage up to 12.97% and the electrical output efficiency up to 2.08%. Furthermore, the results are thoroughly compared with other published studies, which revealed that the proposed configuration is cost effective and structurally sound.

English

A solar photovoltaic (SPV) system generating power to run a 53-m3 storage for indirect air-cooling combined with evaporating cooling (IAC+EC) for providing a cool environment for storage of tomatoes under small-scale farming was evaluated. The experiment consisted of nine 330 W solar modules, twelve 230 AH Gel batteries, 145 VDC solar charge controller, 5 kW inverter, 290 W ventilation fan, 260 W water pump, psychrometric unit, and a 3.8-ton tomato storage chamber constructed and assembled on site. The psychrometric unit consisted of three-cooling pad layers and a 1760 W indirect heat exchanger. The solar modules were arranged in three series-three strings and were used in conjunction with a three string-48V bank facility. The performance evaluation of the system was conducted with full recirculation of air inside the storage chamber using solar module yield and efficiencies of inverter, battery and charge controller. Based on the experiment data the SPV system produced 2873.5 W that is 98% of the design power output at 80% probability of exceedance. The power yield of 2873.5 W was 24% higher than the power required in running the electrical appliances for IAC+EC system. Tracking the SPV system under ambient conditions with an average daily generation during the period of the experiment, the electrical power efficiency was 14.9%. The power output of modules increased with temperature of the module to 24°C and declined thereafter. The power generated by the SPV system depended on the solar irradiance availability, ambient temperature at the site and the time of the day. It was found that the SPV system could power the IAC+EC during daytime for the summer season, and the excess power stored in the battery could run the system until 22.00 h at night when temperatures were low enough for storage of tomatoes and SPV system was then switched off. Key words: Small-scale farming, design power, theoretical power, efficiencies, actual power.

In-Plane Residual Stress Map for Solar PV Module: A Unified Approach Accounting the Manufacturing Process

The photovoltaic (PV) cell fracture reduces the efficiency of solar PV modules and the residual stresses generated in the silicon cells by various stages of manufacturing process are attributed as one of the primary reasons among others. In this study, a unified approach to investigate the residual stresses present across the PV module owing to differing material properties and thermal cycles during manufacturing process is attempted. In particular, an in-plane residual stress map for different layers of solar PV module and the stress jump across the layered structure arisen during the manufacturing process are quantified through finite element method by considering ethylene vinyl acetate encapsulant as a linear viscoelastic material. The maximum residual stress presence in the cell is observed during the encapsulant curing cycle of lamination process. The predictions on the stress pattern and magnitudes from the simulations collaborate well with the experimental observations reported in literature.

High-Pressure Nitrogen-Extraction and Effective Passivation to Attain Highest Large-Area Perovskite Solar Module Efficiency.

Slot-die coating holds advantages over other large-scale technologies thanks to its potential for well-controlled, high-throughput, continuous roll-to-roll fabrication. Unfortunately, it is challenging to control thin.film uniformity over a large area while maintaining crystallization quality. Herein, by using a high-pressure nitrogen-extraction (HPNE) strategy to assist crystallization, a wide processing window in the well-controlled printing process for preparing high-quality perovskites is achieved. The yellow-phase perovskite generated by the HPNE acts as a crucial intermediate phase to produce large-area high-quality perovskite film. Furthermore, an ionic liquid is developed to passivate the perovskite surface to reduce surface defect density and to suppress carrier recombination, resulting in significantly increased efficiency to 22.7%, the highest for large-area fabrication. The strategies are successfully extended to large-area device fabrication, making it possible to produce a 40×40 mm2 module with stabilized PCE as high as 19.4%, the highest-efficiency for a large-area module to date.

Three Bypass Diodes Architecture at the Limit

In this work, we demonstrate that partial shading of one solar cell in a state-of-the-art monocrystalline photovoltaic module with three bypass diodes results in hot cells with critical peak temperatures of 164 $^\circ$ C. We examine two solar modules in the IEC 61215-2 MQT 09 hot-spot endurance test, one with 367.3 W $_\text{P}$ featuring 72 full-cells and the other with 388.6 W $_\text{P}$ featuring 144 half-cells. For the solar module with 72 solar cells, we measure a maximum temperature of 164 $^\circ$ C, which results in a degradation of the encapsulation material and increases the risk of solar module failure. The high temperature results from the hot cell effect due to the power dissipation in the reverse-biased solar cell caused by partial shading. Our experiments show that the half-cell solar module is advantageous in terms of solar cell shading compared to the full-cell solar module. Although the half-cell solar module has a higher power output than the full-cell solar module, we measure a cooler peak temperature of 150 $^\circ$ C. However, under certain shading conditions, the half-cell solar module can exhibit similar temperatures as the full-cell solar module. Based on our experimental results, we develop an electrical and a thermal model to predict the temperature of novel high-power solar modules with solar cells from larger silicon wafer formats in case of partial cell shading. Our predictions consider the trends of further increasing solar cell and module efficiencies, larger silicon wafer formats, and larger solar modules. We simulate a maximum peak temperature of 176 $^\circ$ C at the solar module's surface, which significantly increases the risk of solar module failure. Our results show that new high-power solar modules employing solar cells that are made from larger silicon wafer formats need a new protection against overheating. Three bypass diodes per solar module are no longer sufficient.

Perovskite modules with 99% geometrical fill factor using point contact interconnections design

AbstractThin‐film photovoltaic technology, based on hybrid metal halide perovskites, has achieved 25.2% and 16.1% certified power conversion efficiencies for solar cell and solar module devices, respectively. Still, the gap between power conversion efficiency of small area solar cells and large area solar modules is greater than for any other photovoltaic technology. Analysis of loss mechanisms in n‐i‐p solution processed devices defined layer inhomogeneity loss and inactive area loss as the two most prominent loss mechanisms in upscaling. In this study, we focus on minimizing inactive area loss. We analyze the point contact interconnections design and demonstrate it on perovskite thin‐film solar modules to achieve a geometrical fill factor of up to 99%. Numerical and analytical simulations are utilized to optimize interconnections and solar module design and balance inactive area loss, series resistance loss, and contact resistance loss.

Reduced Self-Doping of Perovskites Induced by Short Annealing for Efficient Solar Modules

Summary Controlling of doping in semiconducting light absorber can minimize the charge recombination and maximizing power output from solar cells; however, it is challenging for perovskites due to lack of controlled doping. Here, we report that a short post-annealing of less than 3 min for facilitating high-throughput manufacturing of perovskite solar modules in an ambient environment maintains the stoichiometric composition of perovskites, encouraging a spontaneous de-doping of perovskites during aging. The reduced self-doping results in less charge recombination and, thus, higher device efficiency. The stabilized open-circuit voltage of sub-cells in the CH3NH3PbI3 minimodules with an area >20 cm2 reaches 1.19 V on average. The aperture efficiency reaches 17.8% under one sun and 18.7% under a quarter sun illumination, deriving an averaged efficiency >20.0% for each sub-cell with an area >3 cm2, demonstrating the excellent uniformity of the films by this scalable process. The minimodule also works as uniform light-emitting devices.

Experimental characterization of a photovoltaic solar-driven cooling system based on an evaporative chimney

Abstract Photovoltaic systems combined with electrical compression chillers offer a high potential for energy efficient cooling with a high economic feasibility. They can significantly reduce the energy consumption in the building sector. The main goal of this study is to analyse the performance of a PV solar driven water-water chiller. The novelty of the work relies on the use of a novel system, called photovoltaic evaporative chimney, which aims to increase the efficiency of solar photovoltaic modules by evaporative cooling. The complete solar cooling system consists of four PV panels (1.02 kWp) and a 3.8 kW refrigeration capacity water-cooled chiller. A systematic study was undertaken and nine sets of experiments were conducted in summer conditions of a Mediterranean climate (Spain). The system’s ability to convert the solar energy into refrigeration capacity was observed to be 0.49 on average for the tests performed. The solar contribution (ratio of PV energy consumption to total absorbed energy) was 64.40%. The system produced on average 11.32 cooling kWh per each kWh consumed from the grid. The influence of the ambient conditions on the key performance indicators has been assessed and global correlations for use in more detailed energy analyses have been developed.

A holistic approach to interface stabilization for efficient perovskite solar modules with over 2,000-hour operational stability

The upscaling of perovskite solar cells to module scale and long-term stability have been recognized as the most important challenges for the commercialization of this emerging photovoltaic technology. In a perovskite solar module, each interface within the device contributes to the efficiency and stability of the module. Here, we employed a holistic interface stabilization strategy by modifying all the relevant layers and interfaces, namely the perovskite layer, charge transporting layers and device encapsulation, to improve the efficiency and stability of perovskite solar modules. The treatments were selected for their compatibility with low-temperature scalable processing and the module scribing steps. Our unencapsulated perovskite solar modules achieved a reverse-scan efficiency of 16.6% for a designated area of 22.4 cm2. The encapsulated perovskite solar modules, which show efficiencies similar to the unencapsulated one, retained approximately 86% of the initial performance after continuous operation for 2,000 h under AM1.5G light illumination, which translates into a T90 lifetime (the time over which the device efficiency reduces to 90% of its initial value) of 1,570 h and an estimated T80 lifetime (the time over which the device efficiency reduces to 80% of its initial value) of 2,680 h. The upscaling of layer treatments and processing that afford high efficiency and stability in small-area perovskite solar cells remains challenging. Liu et al. show how the efficiency and stability of perovskite modules can be improved using an integrated approach to interface and layer engineering.

Luminescent down-shifting natural dyes to enhance photovoltaic efficiency of multicrystalline silicon solar module

The short wavelength photons (below 500 nm) of the solar spectrum are under-utilized in multicrystalline silicon (mc-Si) solar modules because of their high surface recombination losses. The application of luminescent down-shifting (LDS) materials is an effective way to utilize the short wavelength photons to enhance the efficiency of a mc-Si solar module. This study utilized four ‘natural’ dyes extracted from the wheat husk, rice husk, turmeric rhizomes (Curcuma longa L.), and Moringa Oleifera leaves for LDS application. These natural dyes showed absorption in the UV and blue range, and emission in the visible range which is effectively utilized by the silicon solar cell. Optimum concentrations of the natural dyes were incorporated in the front ethylene vinyl acetate (EVA) layers which were used to encapsulate bare Si cells into photovoltaic (PV) modules. The mc-Si PV modules which had the front encapsulation of EVA films containing the turmeric and moringa dyes showed relative enhancement of ~ 6.8% (±3.6) and ~ 9% (±4) respectively, in their efficiencies with respect to that of the corresponding bare silicon cells. The gains in the photovoltaic efficiency obtained with the turmeric and moringa dyes were found to be comparable to (or slightly greater than) the values reported in the literature using various Eu3+ based lanthanide complexes as LDS materials. Finally, the inclusion of natural LDS dyes in the encapsulating EVA layer would offer an economical and pro-environmental solution at high volume manufacturing to improve the utilization of short-wavelength photons.

A facile one-step annealing route to prepare thermochromic W doped VO2(M) particles for smart windows

W doped VO2 is a promising thermochromic material for smart windows but its preparation process is usually complicated and time-consuming. In this work, W doped VO2 (V1-xWxO2) particles were synthesized via a novel and facile one-step annealing method where V2O5 and (NH4)10H2(W2O7)6 composite powders were used as precursor. The solid state reaction between the products (VO2 and WO3) was considered to promote the diffusion of W elements into VO2 lattice during the annealing process which was confirmed by the XPS and EDS results. As increasing the content of (NH4)10H2(W2O7)6, the phase transition temperature of V1-xWxO2 was significantly reduced from 62.7 °C to 46.7 °C, meanwhile the corresponding V1-xWxO2/WO3 composite based films showed a same trend in the solar modulation efficiency from 10.7% to 7.8%. In addition, these films exhibited satisfactory visible transmittance of 56%–62%. Especially, the film based on the sample with V/W molar ratio of 8:1 showed a good thermochromic performance (TMIT = 55.6 °C, ΔTsol = 9.7% and Tlum = 60.8%) for smart windows. Therefore, this method based on the traditional solid-based reaction could provide a new way for elements doping into VO2 to promote application of VO2 in smart windows due to its low cost, repeatability and scale production.