Progress in Photovoltaics最新文献

Desert regions have emerged as ideal places for GW utility-scale photovoltaic (PV) module installations because of their ultra-large spaces, abundance of high-irradiance sunshine hours, and clear sky. However, the harsh desert climate presents challenges to the reliability and bankability of PV modules. This review provides an in-depth understanding of the unique desert parameters impact, desert-induced degradation modes, status, and required properties of the bill of materials (BOMs) and suggestions for the development of desert standards. The review reveals that the climatic conditions in the desert are considerably harsher than those in the moderate climate. The main degradation mechanisms caused by the desert are ultraviolet (UV)-induced discoloration, thermomechanical flaws of interconnects, and glass abrasion (because of soiling). The development of desert modules may necessitate the use of new-generation modules with low-temperature coefficients, high efficiency, high bifaciality, stability under UV light, and elevated temperatures. For the desert module application, options include advanced back sheets and encapsulants that are thermally and UV stable, free of acetic acid groups, and have a low water vapor transfer rate. The degradation modes induced by desert climate are not sufficiently addressed by the present environmental and safety standards through accelerated aging tests. As a result, this article provides a summary of current standards and recommends creating a new testing proposal called the “Hot Desert Test Cycle (HDTC)” sequence that is specific to the desert climate. This comprehensive review catalyzes the PV community to explore novel designs and develop desert PV modules while adhering to localized standards.

Modeling of solar modules and their components is essential to quantify geometrical, optical, and electrical losses and to improve the designs and technologies in terms of performance. In most loss analysis models, the current share among the busbars of the solar cell is assumed to be equal since a symmetrical distribution of the metallization is given. The impact of string terminal connection on the current distribution among the ribbons and the resulting changes in ohmic losses has not been studied yet. In this study, a MATLAB model is developed to consider the impact of the string connector terminal position on the current distribution and the ohmic losses in the ribbons and in string connector. The model allows for the analysis of the impact of contact defects scenarios in ribbons and string connectors on the current distribution. Results show that the highest current flows at the closest busbar to the string connector terminal while the current decreases at the busbars farther away from the terminal due to higher ohmic resistance of the current path. The higher the ohmic resistance of the string connector, the more inhomogeneous the current share at busbars. Simulating a 9 busbar M6 half-cell with 1 × 0.08 mm² string connector, positioning the string connector terminal at the leftmost or rightmost ribbon results in 0.4 W less power compared to center connection configuration, where the string connector terminal is positioned at the center ribbon. Furthermore, simulation results show that inhomogeneity of current causes about 2.1% reduction in module power compared to the case of evenly distributed cell current, considering a 120-haf-cell module with the same string connector. Regarding contact defect analysis, exemplary simulations show the impact of the position of detached ribbons on the power or efficiency loss. Considering left or right connection configuration, detaching the leftmost or rightmost ribbon results in higher power loss compared to other ribbons. Detaching one cell ribbon completely from the string connector results in about 0.2%_abs decrease in cell efficiency, while detaching the outer ribbon along all strings of a 120-half-cell module results in power loss of about 0.8%. The developed model is validated by performing magnetic field imaging (MFI) measurements, in which the magnetic flux density induced by the current carried by the ribbons is measured.

This work presents a practical approach to designing an optical filter for thermal management for photovoltaic modules. The approach emphasizes the practicality of manufacturing over optical performance. Simulation work demonstrates that, for an interdigitated back contact solar cell architecture, complete rejection of infrared radiation offers limited thermal benefits requiring highly complex optical filter designs. An alternative approach consists of reducing thermalization losses by providing reflectance at lower wavelength values. An optical filter design that fulfills this requirement is possible using simple structures based on two materials and taking advantage of the harmonics present in quarter wavelength optical thickness designs. The filter is later optimized for angular performance via second-order algorithms, resulting in a device consisting of only 15 thin-film layers. Performance simulations on two locations, Delft (the Netherlands) and Singapore, estimate a temperature reduction of 2.20°C and 2.45°C, respectively. In a single year, the optical loss produced by the filter is not compensated via temperature reduction. However, improvements in the annual degradation rate show that in Singapore, the overall effect of the filter on the lifetime DC energy yield is positive.

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.

The fabrication process of interdigitated-back-contacted silicon heterojunction (IBC-SHJ) solar cells has been significantly simplified with the development of the so-called tunnel-IBC architecture. This architecture utilizes a highly conductive (p)-type nanocrystalline silicon (nc-Si:H) layer deposited over the full substrate area comprising pre-patterned (n)-type nc-Si:H fingers. In this context, the (p)-type nc-Si:H layer is referred to as blanket layer. As both electrodes are connected to the same blanket layer, the high lateral conductivity of (p)nc-Si:H layer can potentially lead to relatively low shunt resistance in the device, thus limiting the performance of such solar cells. To overcome such limitation, we introduce a thin (<2 nm) full-area molybdenum oxide (MoO_x) layer as an alternative to the (p)nc-Si:H blanket layer. We demonstrate that the use of such a thin MoO_x minimizes the shunting losses thanks to its low lateral conductivity while preserving the simplified fabrication process. In this process, a novel (n)-type nc-Si:H/MoO_x electron collection contact stack is implemented within the proposed solar cell architecture. We assess its transport mechanisms via electrical simulations showing that electron transport, unlike in the case of tunnel-IBC, occurs in the conduction band fully. Moreover, the proposed contact stack is evaluated in terms of contact resistivity and integrated into a proof-of-concept front/back-contacted (FBC) SHJ solar cells. Contact resistivity as low as 100 mΩcm² is achieved, and fabricated FBC-SHJ solar cells obtain a fill factor above 81.5% and open-circuit voltage above 705 mV. Lastly, the IBC-SHJ solar cells featuring the MoO_x blanket layer are fabricated, exhibiting efficiencies up to 21.14% with high shunt resistances above 150 kΩcm². Further optimizations in terms of layer properties and fabrication process are proposed to improve device performance and realize the efficiency potential of our novel IBC-SHJ solar cell architecture.