Progress in Photovoltaics最新文献

The manuscript is a digest, which puts forward findings from previous research papers, combined with new proposals. Approaches comprise two full models' derivation for photovoltaic (PV) systems energy conversion predictability. It brings in several models for key physical observables formulated as functions of the operating conditions. The proposals encompass mean spectral reflectance, coefficient for reflections and spatial geometry, incident angular losses factor, angular losses, and fill factor along with its coefficient of temperature. Applying the superposition principle, these models are integrated into two full approaches for performance predictability. The underlying physics description is mathematically consistent with experimental measurements of the physical observables involved, reported in other studies. To the authors' knowledge, these full models have been reported previously nowhere. Simulation results from the more inaccurate of two full models show good agreement of these findings with the experimental evidence, reported of its performance. The resulting key performance indicators (KPIs), after simulating a grid-connected PV system located in Cuba, yield 1.61%, 13.10%, −1.61%, 2.02%, and 0.81 of MAE, MAPE, MBE, RMSE, and R², respectively, which they confirm the model's good behavior. Approaches formulations, as functions of solar irradiance and module temperature, its derivations, applications, and model's simulation results are considered the main manuscript novelties.

Integration of photovoltaics (PV) into the built environment (BIPV) and infrastructure (IIPV) is required to increase the installed capacity of PV worldwide, while still leaving sufficient area for other land uses. Although BIPV applications have proven to play a significant role in the energy transition, road integrated IIPV concepts are less developed and bring challenges in mechanical and electrical stability and safety that still need to be addressed. In this work, the feasibility of integrating thin-film CIGS (Copper Indium Gallium Selenide) modules into road tiles is investigated. PV road stacks were produced by gluing CIGS laminates onto concrete tiles and covering them with epoxy and glass granulates to form impact- and anti-skid layers. IV (current–voltage) characteristics show that, respectively, a thin and thick epoxy layer results in 2% and 6.6% relative loss in power conversion efficiency. Although a thin protective layer would be beneficial to the power conversion efficiency of road modules, raveling tests show increased risk for electrical failure when a thin top layer is used. Pull-off tests showed that the weakest adhesive strength (0.8 N/mm²) is between the thin-film laminate and concrete, offering sufficient adhesive strength to at least withstand light traffic loading. Raveling and wheel tracking tests show no mass loss and only minor deformation of the stack, respectively, indicating no real risk of raveling or rutting. Thermal cycling and damp heat exposure of the PV road tiles show that yellowing of the top layers can significantly reduce performance over longer periods of outdoor operation. Damp heat exposure after mechanical loading shows no indication of moisture ingress on any of the tested configurations, suggesting the proposed CIGS laminate stack is able to withstand light traffic loading. From the measurement results, it can be concluded that thin-film CIGS modules are mechanically and electrically suitable for road integration. Power conversion efficiencies over 12% can be attained with this technology, indicating its potential for renewable energy generation in road infrastructure. Performance stability can especially benefit from alternative top layer materials that maintain high transparency over long lifetimes. Additionally, pilot tests are required to demonstrate the potential of the technology in a controlled outdoor environment.

Artificial ground reflectors improve bifacial energy yield by increasing both front and rear-incident irradiance. Studies have demonstrated an increase in energy yield due to the addition of artificial reflectors; however, they have not addressed the effect of varying reflector dimensions and placement on system performance and the impact of these parameters on the reflectors' financial viability. We studied the effect of high albedo (70% reflective) artificial reflectors on single-axis-tracked bifacial photovoltaic systems through ray-trace modeling and field measurements. In the field, we tested a range of reflector configurations by varying reflector size and placement and demonstrated that reflectors increased daily energy yield up to 6.2% relative to natural albedo for PERC modules. To confirm the accuracy of our model, we compared modeled and measured power and found a root mean square error (RMSE) of 5.4% on an hourly basis. We modeled a typical meteorological year in Golden, Colorado, to demonstrate the effects of artificial reflectors under a wide range of operating conditions. Seventy percent reflective material can increase total incident irradiance by 1.9%–8.6% and total energy yield by 0.9%–4.5% annually after clipping is considered with a DC–AC ratio of 1.2. Clipping has a significant effect on reflector impact and must be included when assessing reflector viability because it reduces reflector energy gain. We calculated a maximum viable cost for these improvements of up to $2.50–4.60/m², including both material and installation, in Golden. We expanded our analysis to cover a latitude range of 32–48°N and demonstrated that higher-latitude installations with lower energy yield and higher diffuse irradiance content can support higher reflector costs. In both modeling and field tests, and for all locations, the ideal placement of the reflectors was found to be directly underneath the module due to the optimized rear irradiance increase.

The development of transparent electron-selective contacts for dopant-free carrier-selective crystalline silicon (c-Si) heterojunction (SHJ) solar cells plays an important role in achieving high short-circuit current density (J_SC) and consequently high photoelectric conversion efficiencies (PCEs). This becomes even more important when focusing on the development of bifacial solar cells. In this study, bifacial SHJ solar cells using a transparent-conductive-oxide-free and dopant-free electron-selective passivating contacts are developed, showing a J_SC bifaciality of up to 97%. Intrinsic ZnO_X layer deposited by atomic layer deposition was used in this structure, which simultaneously provides negligible passivation loss after annealing and enables a low contact resistivity on the electron-selective contact. With both side finger metal electrodes contact, this bifacial solar cell shows an efficiency of 21.2% under front-side irradiation and 20.4% under rear-side irradiation, resulting in an estimated output power density of 24.1 mW/cm² when considering rear-side irradiance of 0.15 sun.

Within this work, we investigate the potential to optimize the screen-printed front side metallization of silicon heterojunction (SHJ) solar cells. Three iterative experiments are conducted to evaluate the impact of the utilized fine mesh screen configurations and grid layout adaption (finger pitch) for the front side metallization on silver laydown and electrical performance of the solar cells. With respect to the screen configuration, we compare the performance of a fine-mesh knotless screen to a conventionally angled screen demonstrating an additional gain of Δη = +0.1%_abs due to reduced shading losses. Additionally, a grid layout is improved by increasing the number of contact fingers from 120 to 156. Furthermore, the current possibility to push the fine-line printing process for low-temperature pastes to the limit is investigated by reducing the nominal finger width w_n to 20, 18, and 15 μm. It is shown that even the smallest nominal width of w_n = 15 μm can be printed with high quality, leading to an additional efficiency gain of Δη = +0.15%_abs as well as a reduction of silver paste laydown by −5 mg. Finally, a batch of champion cells is fabricated by applying the findings of the previous experiments, which results in a maximum efficiency of η_max = 23.2%. Compared to the reference group without optimization, this corresponds to a gain of Δη = +0.17%_abs, which comes along with an additional decrease of the silver paste laydown by approximately −2 mg. This emphasizes the significance of consistent optimization of the screen-printing process in terms of cell performance and resource utilization for SHJ solar cells.

Daylight photoluminescence imaging of crystalline silicon photovoltaic modules is demonstrated for modules embedded in rooftop and utility-scale systems, using inverters to electrically switch the operating point of the array. The method enables rapid and high-quality luminescence image acquisition during the day, unlocking efficient performance and quality monitoring without the need to connect specific electrical hardware or to make any modifications to the system wiring. The principle of the measurement approach is discussed, and experimental results from a 12-kW_DC residential rooftop system and from a 149 MW_DC utility-scale photovoltaic power plant are presented. Measurements were performed using commercial inverters without modifications to the inverter hardware or firmware. In the case of the utility-scale power plant, the daylight photoluminescence image acquisition of modules connected to a central inverter was obtained from a remote piloted aircraft. Data analysis includes the conversion of photoluminescence image data into implied voltage differences.

The optimization of III-V-based photovoltaic cells involves addressing the trade-off between optical losses due to grid shading and electrical losses due to series resistance. In this work, we overcome the boundary conditions of this optimization problem by increasing the grid line height. Contrary to a few micrometer high evaporated metal grid lines, distributed circuit modeling of 1-cm² GaAs photonic power converters suggests that 15-μm high grid lines yield the best performances, especially for high-current operation in the 1 to 10 A cm⁻² range. We have successfully implemented a silver plating process into the fabrication scheme of these devices. Current–voltage measurements under intense illumination demonstrate fill factors above 80% at currents up to 35.8 A, highlighting the capability to extract such high currents without major series resistance losses. Under equivalent monochromatic input power of 62.6 W, this results in a maximum power output of 35.5 W from the 1-cm² single-junction photovoltaic cell. This development enables optical power links with largely increased power densities, reducing the material demand of precious semiconductors and associated costs.

The delamination of encapsulants in photovoltaic (PV) modules is a common issue that leads to power loss due to optical losses. Encapsulant debonding is usually examined under monotonic loading conditions subsequent to environmental exposure such as damp heat. Service-relevant, superimposed environmental-mechanical fatigue loads are not considered adequately. Hence, the environmental fatigue delamination resistance of thermally toughened double glass laminates with an ethylene vinyl acetate copolymer (EVA) adhesive layer was investigated in this study. Focus was given to the melting range of EVA, in which the non-crosslinked crystalline phase fraction is already in the partly molten state. Double cantilever beam specimens were tested on an electrodynamic test machine at temperatures of 60, 70, 80, and 90°C and relative humidity (rh) levels of 2%, 30%, 50%, and 80%. The fractured surfaces were characterized by digital microscopy, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and differential scanning calorimetry (DSC). The cyclic fatigue tests revealed a decay in delamination resistance at elevated temperature and humidity levels. At 70°C, the delamination resistance was low, regardless of the relative humidity. Most of the laminates failed by debonding. XPS analysis showed a reduction of the C=O and C–O content, along with an increase in Si–O content with increasing relative humidity. For laminates tested at 60 and 70°C, an EVA recrystallization peak was observed in DSC experiments. This peak was shifted to significantly higher temperatures at 80% rh. XPS and DSC indicated local hydrolysis within the porous fracture process zone ahead of the crack tip. Consequently, acetic acid formation led to a decrease in delamination resistance, resulting in lower fatigue threshold values. The investigations confirmed the significant impact of environmental conditions on the fatigue delamination resistance within glass/encapsulant laminates. Notably, acetic acid formation and a significant reduction in delamination properties were observed after around 100 h of environmental fatigue exposure.

In May 2022, the European Commission adopted a new European Union (EU) Solar Energy Strategy [1] aiming to ensure that solar energy achieves its full potential in helping to meet the European Green Deal's climate and energy targets. A goal of the strategy is to reach nearly 600 GW of installed solar photovoltaics (PV) capacity by 2030. While Europe is a pioneer in the definition of new policy requirements to ensure the circularity and sustainability of PV products, its manufacturing capabilities are limited. The EU mostly imports PV modules from China, which for the last decade has remained the global leader in PV manufacturing across the supply chain. This article aims to provide insight into the solar PV industry and the surrounding policy context, focusing on the manufacturing phase and its climate impact. It provides a comparative overview of the key players in the European and Chinese PV markets with an overview of the whole supply chain (i.e. production of polysilicon, cells, wafers and modules). Having in mind the net-zero commitments across the globe, and a central role of the solar PV in the energy transition, the demand for PV products is expected to grow exponentially in the next decades. With this in mind, the authors look into environmental impacts from the PV manufacturing. A simplified analysis concludes on the suitability of the PV manufacturing process today and indicates the opportunities for the net-zero transition in the future. While the focus is on the carbon impacts of the solar PV industry, the authors also identify other relevant aspects (such as circularity), laying the ground for a future research.