Building Integrated Photovoltaic Modules Research Articles

Correlating long-term performance and aging behaviour of building integrated PV modules

Because building-integrated photovoltaic (BIPV) modules are fully integrated into a building envelope, the back of the module can be exposed to little or no ventilation, resulting in increased operating temperatures. As the temperature increases, the performance of the modules decreases, and the durability of the module and its polymeric components (e.g., encapsulant and backsheet) may be impacted. Over the years, three different PV test stands were monitored in Canobbio (southern Switzerland) in different configurations: open-rack, BIPV partially-ventilated and BIPV insulated (non-ventilated) to investigate the effect of the operating temperatures on the long-term energy performance of the different BIPV module types. In this study, the PV modules installed in these test stands were thoroughly examined by: (i) evaluating the long-term performance of the modules, and (ii) establishing a correlation between the electrical performance and changes in the properties of the polymers used in the laminate. In general, we observe that: (i) for some bill of materials (BOM), the higher thermal stress of BIPV configurations can accelerate the degradation, particularly of the encapsulant, leading to current losses attributed to the polymer (discolouration); (ii) in some cases, the higher thermomechanical stress can lead to a higher rate of damaged cells and cell interconnects, resulting in fill factor losses; (iii) on the other hand, a careful selection of the BOM and system design (with adequate rear ventilation) may mitigate the issues related to higher thermal and thermomechanical stresses.

Colouring solutions for building integrated photovoltaic modules: A review

As global decarbonisation requires the widespread adoption of solar photovoltaic (PV) electricity, addressing challenges related to land use has become relevant. The conflict between PV installations and other land uses, such as forestry or agriculture, highlights the urgency for alternative solutions. Integrating PV technology into the built environment is a compelling strategy to mitigate these challenges, enabling electricity generation precisely where it is needed. In the context of buildings integrated photovoltaics (BIPV), PV modules serve a dual purpose, functioning both as electricity generators and integral components of the architectural design. Therefore, the architecture requirements — specifically in terms of shape, size, and colour— become relevant for BIPV modules. This paper offers a general overview of the diverse colouring technologies employed for BIPV modules, describing their functioning, challenges, and advantages. An examination of the current landscape of coloured PV products involving considerations of pricing and power output is presented. Additionally, this work addresses the critical topics of reliability and stability in colour solutions, outlining methodologies for quantitative colour characterization. It provides foresight into the potential challenges facing installations in the future and explores the multifaceted social, economic, and environmental implications of this evolving technology.

Large- and small-scale fire test of a building integrated photovoltaic (BIPV) façade system

The number of installed photovoltaic (PV) modules has increased significantly over the last years, and using available building surfaces to generate electricity by integrating PV modules in the construction is an attractive option. Building integrated photovoltaics (BIPV) or other vented claddings can spread fires rapidly to large parts of a building if the fire is allowed to propagate. To investigate this hazard, a large-scale SP FIRE 105 façade fire test was conducted. A façade measuring 4000 mm × 6000 mm covered with BIPV modules was exposed to flames that represent the fire plume from a window in a room at flashover. The results from the test show that critical failures, like falling objects and vertical flame propagation, can be expected in such constructions. These results highlight the importance of details in mounting of BIPV-façades and to require proper documentation from relevant fire tests of such systems. Small-scale cone calorimeter tests were conducted on the studied BIPV module to provide material properties of the combustible parts of the installation. These aspects should be considered when planning new or when retrofitting façades, to prevent escalation of fires. The results presented are, however, only valid for the configuration that was tested. Other BIPV-façades should also be investigated to study how these constructions can be built safely in the future with regard to critical details.

Effects of Power Optimizer Application in a Building-Integrated Photovoltaic System According to Shade Conditions

A building-integrated photovoltaic (BIPV) system produces power using photovoltaic (PV) modules as building exterior materials, whose architectural performance serves the same functions as those of existing building materials. Most relevant studies targeted general PV modules used in the building-mounted and -attached types. This study aims to integrate the building elevation-type BIPV system and exterior materials to secure both exterior material performance and PV electrical performance by embedding a power optimization device in an integrated system of BIPV modules and exterior materials. Thus, the advantages of economy, safety, aesthetics, and ease of maintenance can be achieved. In this study, experiments were conducted on elevation-type BIPV modules with and without a power optimizer, that is, a DC/DC converter, under various shade conditions, and the power loss rate of the BIPV system was analyzed. The power optimizer-equipped BIPV system was experimentally observed to have a PV power-loss rate approximately 2–3 times lower than that of the BIPV system without a power optimizer when the shade ratio of one module was approximately 10–75%. This exterior material-integrated BIPV-specific power optimization device reduces dependence on fossil fuels for power production and improves energy sustainability, contributing to the spread of zero-energy buildings and carbon neutrality.

Analysis of adhesion characteristics of steel back plates and encapsulants for fire-proof BIPV modules

Recently, researchers are actively exploring the use of steel plates as replacements for the backs of building integrated photovoltaic (BIPV) modules to achieve improved workability, reduced weight, and enhanced maintainability. It is crucial to note that the adhesion between steel plates and encapsulants must match the high level observed between conventional backsheets and glass surfaces. In this study, we assessed the adhesion between steel plates and encapsulants and proposed a method to enhance adhesion to the level of existing materials, such as backsheets and glass, by improving the surface of the steel plates and the lamination process. When steel plates were laminated with ethylene vinyl acetate (EVA) encapsulant at 150 °C (as per the preset process), the peel force measured by the 180° peel test was significantly low at 0.045 N/mm. However, it increased nearly 40 times to 1.70 N/mm due to the formation of a structure capable of physical interlocking through surface treatment and an increase in the lamination temperature by 20 °C. Furthermore, we evaluated the adhesion performance of polyolefin elastomer (POE) encapsulant, which demonstrated high adhesion of over 6.0 N/mm, comparable to that between the currently used encapsulants and backsheets. When we examined the surface-treated sample using a confocal microscope and a secondary electron microscope (SEM), the surface-treated sample exhibited a considerably rough surface with a high Rku value of 5 compared to the untreated sample. These modules can maintain high outputs even when exposed to the external environment for extended periods with fire-resistant properties.

Assessment of the Effects of the Cavity in BIPV Applications

As building-integrated photovoltaics (BIPV) become a promising application of decentralized PV systems, it is important to accurately assess their behavior in buildings energy simulations. The module temperature is a major factor in assessing its lifetime and generated power. High module temperatures lead to significant performance deteriorations. The addition of cavity ventilation contributes to decreasing the cavity temperature and is expected to improve the overall performance of BIPV. Thus, the aim of this paper is to explore the impact of the dimensioning of the BIPV cavity and its inlets on the cavity temperature which directly affects the module’s operating temperature. The simulation model developed in previous work was then validated and expanded in order to add an adjustable opening to conduct a sensitivity analysis on the BIPV cavity inlet opening dimension. The projected model consisted of two main parts: a thermal model and an airflow model. These models interact to predict the impact of airflow through the cavity on the cavity’s temperature. The sensitivity analysis included a range of simulations while modifying the dimensions for the ventilation cavity geometry of the BIPV module. The results of the sensitivity analysis revealed that the cavity temperature decreased when the cavity opening was implemented. Different degrees of influence on the cavity temperature were observed by widening or tightening the opening to certain degrees.

Solar Energy Utilization Potential in Urban Residential Blocks: A Case Study of Wuhan, China

In dense, energy-demanding urban areas, the effective utilization of solar energy resources, encompassing building-integrated photovoltaic (BIPV) systems and solar water heating (SWH) systems inside buildings, holds paramount importance for addressing concerns related to carbon emission reduction and the balance of energy supply and demand. This study aimed to examine the interplay between urban residential blocks and their solar energy potential, with the objective of promoting environmentally sustainable development within urban residential areas. The primary focus of this study was the hot summer and cold winter zone of China, which serves as a representative case study. Methodologically, we employed Rhinoceros and Grasshopper (GH) software version GH6.0 tools to simulate the solar radiation potential within residential blocks and translated this information into the potential utilization of BIPV and SWH systems. Subsequently, our focus was directed towards identifying optimal locations for mounting BIPV modules and water heaters on roofs and building façades. The study results revealed the following: (1) The floor area ratio (FAR), building density (BD), average building height (ABH), and space layout (SL) exerted substantial influences on the solar potential of a residential block, with correlations of up to 75%, 71%, 78%, and 50%, respectively, concerning the overall solar potential of the entire plot. (2) It is essential to emphasize that, with regard to the BIPV installation potential, façades account for 80% of the overall residential block potential, whereas rooftops contribute only 20%. Both south- and west-facing façades exhibited a BIPV installation ratio of approximately 34%. (3) In the realm of solar water heating, the potential for installations on building façades accounted for 77% of the total living area of the residential blocks, 23% on the rooftops, and 35% on the south-facing façades. This study furnishes practical guidelines for harnessing the potential of BIPV and SWH systems within residential blocks, thereby contributing to the advancement of sustainable urban development practices.

Modeling reflection by structured building-integrated photovoltaics

Evaluating the reflection of solar radiation by Building Integrated Photovoltaics (BIPV) with structured front-glass is challenging for two reasons. First, the resulting irregular scattering of light cannot be accounted for by simple reflection models. Second, the locations where the evaluation needs to take place cannot be predicted by simple geometric considerations, as in the case of mirror-like reflection. The detailed modelling of a BIPV module featuring a periodical, linear structure based on the scanning of its surface is described. The application of the model is demonstrated in the assessment of solar reflection by a concave array of the modules. The stochastic sampling of the BIPV modules from each location in a dense sensor grid, that is required to ensure that no local concentration of reflected solar radiation is missed, is supported by re-orienting the sensors. Rather than relying on a data-driven Bidirectional Reflectance Distribution Function (BRDF) model of limited directional resolution, the geometric structure of the front-glass is modelled by modulating the normal of a mirror-like surface. The method allows an accurate and dense simulation with moderate computational demand.

Highly efficient color-control technique for building-integrated photovoltaics using optical dielectric thin film

A color-control technique based on optical thin films on glass is investigated by means of numerical simulation and experiment, with a particular focus on building-integrated photovoltaic (BIPV) applications. We show that white-colored BIPV modules can be realized with a minimum optical loss by applying optical thin films that have multiple reflection peaks in a complementary color relationship, like the emission spectrum of white LEDs. The angular dependence of hue, which is an inherent drawback of optical thin film systems, is suppressed by modifying the design of the film to maintain the complementary color relationship of multiple reflection peaks. The simulated thin film design is confirmed by an experiment with a silicon solar cell, resulting in a white color and a low short-circuit current density loss (ΔJ SC) of 5.9%. These results indicate that our approach is a promising way to realize fascinating colors and a high energy yield simultaneously in BIPV modules.

Aesthetically Appealing Building Integrated Photovoltaic Systems for Net-Zero Energy Buildings. Current Status, Challenges, and Future Developments—A Review

With the sharp increase in global energy demand, industrial and residential buildings are responsible for around 40% of the energy consumed with most of this energy portion being generated by non-renewable sources, which significantly contribute to global warming and environmental hazards. The net-zero energy building (NZEB) concept attempts to solve the global warming issue, whereby a building will produce, on-site, its required energy demand throughout the year from renewable energy sources. This can be achieved by integrating photovoltaic (PV) building materials, called building-integrated photovoltaic (BIPV) modules, throughout the building skin, which simultaneously act as construction materials and energy generators. Currently, architects and builders are inclined to design a building using BIPV modules due to the limited colors available, namely, black or blue, which result in a monotonous building appearance. Therefore, there is an increasing demand/need to develop modern, aesthetically pleasing BIPV green energy products for the use of architects and the construction industry. This review article presents the current stage and future goal of advanced building integrated photovoltaic systems, focusing on the aesthetically appealing BIPV systems, and their applications towards overcoming global challenges and stepping forward to achieve a sustainable green energy building environment. Additionally, we present the summary and outlook for the future development of aesthetically appealing building integrated photovoltaic systems.

Large-scale building-integrated photovoltaics installation on building façades: Hourly resolution analysis using commercial building stock in Tokyo, Japan

The installation of photovoltaic (PV) modules is one of the most effective measures for decarbonizing urban building stock. The considerable potential of the process has been demonstrated using building-integrated PV (BIPV) modules. Earlier studies have provided significant knowledge about the PV potential of buildings, but a detailed investigation of the large-scale installation of BIPV modules on building façades has not been undertaken. In the present study, a model for estimating the hourly PV potential of building surfaces on a regional scale was developed and applied to commercial building stock in Tokyo, Japan. Analytical results showed that the generated PV power would be capable of satisfying 15%–48% of the annual electricity demand of the building stock in 2050, based on the extent to which the PV potential of building surfaces, especially façades, was exploited. This demonstrates the usefulness of BIPV for achieving a decarbonized society. Additionally, hourly estimation results showed that, if a higher economic efficiency is pursued, the use of large-scale installation of BIPV together with rooftop-mounted PV could increase the PV power generation without altering the hourly PV power fluctuation. However, electricity demand and generation analyses revealed the negative impacts of the larger-scale BIPV installation on the power system: The reduction in asset utilization and the increase in the need for flexibility. The findings of this study promise to be useful to policymakers in formulating guidelines for the use of BIPV modules.

Experimental evaluation of the impact of pigment-based colored interlayers on the temperature of BIPV modules

While colored photovoltaics are gaining popularity in the market for building-integrated photovoltaics (BIPV), several specific properties are not accounted for in standard PV performance models. This work shows how relying on the coloration efficiency alone can lead to significant errors regarding module temperatures. By comparing measured temperature data from a test installation featuring BIPV façade elements in multiple colors, little correlation is found between total optical losses (reflection and absorption losses) and module temperature. Instead, better correlation is found with total reflectance. This is attributed to the light absorbed in the pigment-based colored layers contributing to module heating, whereas reflected light does not. This is especially relevant for colors with high lightness, such as gray or beige, for which reflection losses are dominating absorption losses. When modelling colored BIPV products, it is therefore recommended to only consider reflection losses for the irradiance contributing to module heating, while continuing to also include absorption losses for the effective irradiance used in electrical performance modelling.

Overview of the Fundamentals and Applications of Bifacial Photovoltaic Technology: Agrivoltaics and Aquavoltaics

Bifacial technology is attracting the attention of the photovoltaic community. Although considered premature, research and development activities still need to be carried out to improve bPV performance. In addition, the need for a standard test reference will aid bankability and increase confidence in this technology. This article describes the state of the art of bifacial technology, going through the bPV cell and its difference compared to conventional monofacial cells and listing the different sources of limitations, with an identification of different parameters that characterize the performance of the bifacial. Then, the paper reviews the different modeling methods that allow predicting the performance of bPV systems, and ends with the most important applications, whether for dual use of land to produce energy and food (agrivoltaic) or for placing bPV modules on water bodies instead of on the ground (aquavoltaics), or for vertical use as solar fences, acoustic barriers, or building-integrated photovoltaic modules.

Study on thermal characteristics and electrical performance of a hybrid building integrated photovoltaic (BIPV) system combined with vacuum insulation panel (VIP)

Renewable energy systems are key technologies towards realizing reduced carbon footprint and sustainable architecture. Building integrated photovoltaics (BIPV) are renewable energy systems that function as integral building envelope components and simultaneously produce electricity. Not only is it essential to install BIPV for energy rebates, incentives or to cut down dependence on grid, but it is equally important that BIPV satisfies relevant building energy codes. Thus, thin high-performance insulation is needed to meet strict codes. Of all kinds of insulation materials presently available, vacuum insulation panel (VIP) has the highest thermal resistance per unit thickness. Therefore, VIP is a viable solution as an insulator for BIPV. In this study, the thermal characteristics and electrical performance of a hybrid BIPV module combined with VIP was investigated. The study is largely based on experiments carried out in a test building facility and supplemented with essential numerical simulations using Physibel BISCO/TRISCO building physics software. Data analysis was carried out for winter season. Results indicated that temperature at the back of the hybrid BIPV module (directly in contact with indoor air) was about 4 °C warmer than the heating setpoint temperature, which is advantageous for winter season. The maximum electrical efficiency was estimated to be 12.3 %. Compared to manufacturer specified electrical efficiency of 15 %, the peak efficiency realized is somewhat acceptable, factoring losses and winter weather conditions. Integrating BIPV and VIP yields an overall hybrid product that is compact and portable, and thermally more efficient from a building envelope perspective. As far as the authors know, this study is the first covering BIPV combined with VIP as a unitized module. Finally, current challenges and future research opportunities are explored.

Tunable and angle-insensitive structural coloring of solar cell modules for high performance building-integrated photovoltaic application

Building-integrated photovoltaics (BIPV) is desired to reduce carbon emissions from residential and commercial buildings. In this application, the controlling the visual impact of BIPV module with preserving PV performance remains a great challenge since the appearance of conventional PV modules is not favorable for building skins in most cases because of their dark colors. In this paper, we report on the color control of crystalline silicon (c-Si) PV modules by introducing the structural colors based on the interference effect. We apply the structural colors to the cover glass of PV minimodules with textured surfaces. The glass texturing is realized by sandblasting technique that allows us to form various textured surfaces depending on sandblasting conditions. High flexibility of structural colors is demonstrated by realizing various colors including violet, cyan, green, and orange using dielectric multilayers deposited on planar and textured glass sheets. These colored glass sheets are applied to c-Si PV minimodules, which exhibit high efficiencies (>18%) with distinct colors. The efficiency of colored PV minimodules depends strongly on their colors, as the efficiency loss originates solely from the optical loss by the colored glasses. In addition, the color difference at various view angles is evaluated by reflectance measurement with an integral sphere and compared in a CIE color system. It clarifies that surface texturing by sandblasting mitigates the angular dependence of structural colors substantially, which is also observable by our eyes. Besides, surface texturing is effective to mitigate the glare effect as well. Therefore, the combination of structural colors and surface texturing is a promising way to realize fascinating colors and a high energy yield simultaneously in BIPV modules. • We investigate the structural color technology to develop colorful building-integrated photovoltaics (BIPV). • Violet, cyan, green, and orange modules are achieved with high efficiencies over 18%. • The efficiency loss originates solely from the optical loss by the colored glasses. • The textured colored glasses mitigate the angular dependence of colors substantially as well as the glare effect.

Performance evaluation of sputter-coating based color BIPV modules under the outdoor operational condition: A comparative analysis with a non-color BIPV module

Building integrated photovoltaic (BIPV) modules with color-cover glasses have been developed to overcome design limitations in building applications. Although several current studies have presented informative outcomes through experimental analysis, understanding the long-term operating performance of color BIPV modules is still insufficient, especially when considering the transmittance features of the color-cover glass. Therefore, this study evaluates the operational performance of color BIPV modules based on comparative analysis under outdoor experimental conditions. A typical BIPV module (i.e., a non-color BIPV module) and color BIPV modules are used for this comparative analysis. The transmittance characteristics of general low-iron tempered glass (LTG) and LTG with the color coating are considered to evaluate the effect of performance degradation according to the transmittance reduction by the color coating. The thickness differences of the coating layer make different color patterns of gray, blue, and orange. In addition, the color modules are installed on the inclined (30°) and the vertical (90°) plane to assess power performance on different angle positions. Compared to the ratio of transmittance reduction (RTR) by the color coating and the percentage of efficiency reduction (RER) by the color-cover glass, the RER is less than the RTR. The RER of operational efficiency for blue and orange modules is similar to the RER in STC. Still, the RER of the gray module’s operational efficiency is about 5% greater than RER in STC. , the voltage and current characteristics for the gray module using operational data are analyzed to investigate the effect of color differences on the power efficiency. Based on the result, it was confirmed that the active efficiency reduction of the gray module is expected from the decrease in the current.

Power Generation Prediction of Building-Integrated Photovoltaic System with Colored Modules Using Machine Learning

The building-integrated photovoltaic (BIPV) system is provoking mention as a technology for generating the energy consumed in cities with renewable sources. As the number of BIPV systems increases, performance diagnosis through power-generation predictions becomes more essential. In the case of a colored BIPV module that has been installed on a wall, it is more difficult to predict the amount of power generation because the shading loss varies based on the entrance altitude of the irradiance. Recently, artificial intelligence technology that is able to predict power by learning the output data of the system has begun being used. In this paper, the power values of colored BIPV systems that have been installed on walls are predicted, and the system output values are compared. The current-voltage (I–V) curve data are measured to predict the power required changing the intensity of the irradiance, and the linear regression model is derived for the changes in the voltage and current at a maximum power operating point and during irradiance changes. To improve the power prediction accuracy by considering the shading loss of colored BIPVs, a new model is proposed via neural network machine learning (ML). In addition, the accuracy of the proposed prediction models is evaluated by comparing the metrics such as RMSE, MAE, and R2. As a result of testing the linear regression model and the proposed ML model, the R2 values for the voltage and current values of the proposed ML model were 5% higher for voltage and 2% higher for current. From this result, the proposed ML model of the RMSE about real power improved by more than 50% (0.0754 kW) compared to the simulation model (0.1581 KW). The proposed model demonstrates high-accuracy power estimations and is expected to help diagnose the performance of BIPV systems with colored modules.

Building-Integrated Photovoltaic (BIPV) products and systems: A review of energy-related behavior

This paper reviews the main energy-related features of building-integrated photovoltaic (BIPV) modules and systems, to serve as a reference for researchers, architects, BIPV manufacturers, and BIPV designers. The energy-related behavior of BIPV modules includes thermal, solar, optical and electrical aspects. Suitable standardization to evaluate heat transfer and solar heat gain by BIPV modules still need to be developed further since BIPV elements behave differently to the building elements they substitute. The optical properties of BIPV modules, such as light transmittance or color rendering, also play a role in the search for a good balance between energy saving, electricity generation, aesthetics and visual comfort. However, architecturally adapted BIPV design may affect the electrical performance also, by reducing the efficiency of BIPV modules and systems compared to standard photovoltaic (PV) ones. This is not the sole challenge for the electrical designers, as the special operating conditions of BIPV systems such as non-homogeneous irradiance complicate the electrical design and the forecasting of BIPV performance. The aim of this review is to present the current state of knowledge of the aspects mentioned above, to promote continued progress in BIPV and to inform suitable standardization efforts.

Building-Integrated Photovoltaic Modules Using Additive-Manufactured Optical Pattern

This paper suggests a novel way to manufacture power-efficient building-integrated photovoltaic (BIPV) modules that are aesthetically acceptable for use in zero-energy buildings (ZEBs). An optical pattern is formed using additive manufacturing (AM) to maximize the number of sunrays that reach the solar cells and to hide cells beneath the pattern. The optical pattern was optimized by simulation, then selected PV modules were fabricated to ensure that they met the optimal optical pattern conditions. Increase in pattern angle and lens space yielded increase in the output power of the PV module, but reduced the aesthetic functionality. This color BIPV technology is expected to help expand the BIPV market and reduce carbon for “net zero” objectives.

Nonthermal laser ablation of high-efficiency semitransparent and aesthetic perovskite solar cells

Abstract Perovskite solar cells (PSC) offer a promising solution for building integrated photovoltaics (BIPVs) due to its high photoelectric conversion efficiency (PCE). However, increasing the transparency of their functional layers dramatically decreases the PCE. Here, a computer controlled laser patterning method was proposed to directly turn PSC modules into semitransparent and with aesthetic artificial pattern, without additional complexities to the conventional PSCs fabrication process. A structured ST-PSC achieving a champion PCE of 17.5% with average visible transparency (AVT) of 18.2%, and a mini-module with 5 × 5 cm2 delivering a PCE of 9.1% with AVT of 37.7% were demonstrated. Rationally designed aesthetic patterns were imprinted on mini-modules, achieving a PCE of 14.4%. These results reveal a new route for low-cost facile fabricating high performance large-area aesthetic BIPV modules, and represent a big step forward toward the fabrication of solar cells with high efficiency and high transparency.