Building integrated photovoltaics (BIPV) typically operate under different conditions compared to standard PV due to non-optimal orientations, poor ventilation, or additional losses in coloured modules. In this work, a test site for BIPV curtain wall fa & ccedil;ades was constructed at the Technical University of Denmark (DTU) and monitored for a full year. This data is used to analyze various performance aspects, including operating temperatures, power optimizer efficiencies, and DC performance ratios. In addition, parts of the system are modelled in SAM and results of this simulation are used to identify errors. In addition to this analysis, the underlying data set is published for researchers to use in model validation.

In this work, novel PET-based frontsheet materials with UV-cured coatings were developed and investigated. UV-curing urethane acrylates were selected as innovative, fluorine-free coating systems. Polyurethane coatings exhibit excellent UV resistance, chemical and moisture resistance and, thus, high durability in outdoor applications. A homogeneous application without coating defects such as bubbles, voids or detachments was achieved. Material tests with cross-cut tests showed no separation from the PET substrate. The water vapor transmission rates and the physical (optical and thermal) and chemical properties of the novel polymeric frontsheets were measured and compared with uncoated reference systems and products already on the market. The aging-related changes after irradiation and humid heat storage were investigated and described in detail. Based on this comprehensive study, the newly developed frontsheets can be considered a suitable alternative to polymeric frontsheets with fluorine-containing top layers.

This study explores the thermal behavior of Building Integrated Photovoltaics (BIPV) façades, focusing on the impact of different mounting configurations and colored interlayers. Two experimental setups are analyzed to investigate the operating temperatures of PV modules. The first setup consists of single-cell mini-modules including both colored and uncolored modules operating under ventilated and insulated conditions. The Sandia model is utilized to correlate cell temperatures and module backside temperatures, for which new empirical ΔT coefficients are determined for the different configurations and colored interlayers. The second setup consists of a BIPV container with a south-facing 16-module BIPV curtain wall façade. The modules are mounted with different air gap sizes to examine the effects of rear ventilation on module temperature. The results highlight the significant impact of mounting design and display the complicated nature of temperature distribution of BIPV systems. This research aims to contribute to a broader understanding of the influence that BIPV system integration in architecture has on module operating temperatures.

The demand for building-integrated photovoltaics is constantly increasing, which is reflected in an increasing number of innovative BIPV products on the market and attractively implemented BIPV installations. To support architects, system developers, and other stakeholders involved in the planning of new BIPV projects, the experts of IEA-PVPS Task 15 have developed a multi-dimensional assessment tool based on the experiences and learnings of already installed BIPV-projects. The creation of a comprehensive, interdisciplinary evaluation methodology makes it possible to compare the multi-dimensional performance of existing BIPV systems, to derive strengths and weaknesses and to use this knowledge to plan application-optimized new BIPV systems. In a systematic step-by-step development process, four performance categories were defined: energy-related, economic, environmental and optical/visual. After defining the relevant performance indicators per category, a numerical rating system was established. In addition, a classification scheme for all relevant BIPV installation types was defined. Initial analyses were performed by a group of experts on several case studies of BIPV-roofs, facades and external devices in order to test and validate the methodology and approaches. Multiple iterations were required to optimize the methodology, as issues such as (i) lack of data availability for full project assessment or (ii) objectivity in visual assessments exist and will remain demanding. The research work also identified challenges and limitations in the context of pioneering and pilot building-integrated photovoltaics (BIPV) projects, which often used newly developed, immature or early-stage technologies at the time of their construction. The evaluation results of such lighthouse projects can vary significantly from those of BIPV installations using standardized products and well-established processes.

Moisture ingress in photovoltaic (PV) modules is a critical factor for performance degradation, therefore, a low water vapor transmission rate (WVTR) is highly desirable for polymers used to embed the solar cells, including backsheets, frontsheets, and encapsulants. With the advent of glass-free modules for integration in building envelopes and vehicles, there is growing interest in polymer composite structures with embedded glass fibers to enhance rigidity. Furthermore, due to environmental concerns, there is increased interest in fluorine-free polymers for PV applications. In this work, 21 samples with different base polymers, coatings, and/or surface treatments are investigated and their WVTRs are measured. The results show no good alternatives to existing fluoride-based polymers/coatings for reducing WVTRs of backsheets and frontsheets among the investigated samples. In addition, glass fibers embedded within polymers to provide increased stability to backsheets or in composites for lightweight PV are shown to significantly increase WVTRs, especially, when fibers are not properly embedded, providing additional diffusion pathways for moisture ingress. image

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.

Potential glare through reflected sunlight can be a significant hindrance factor for photovoltaic (PV) installations, especially for building-integrated PVs with atypical orientations and tilt angles present. Structured glass surfaces or antireflective (AR) coatings are often used as a solution, however, there is currently no universally recognized method or metric to estimate their impact on glare. This article presents an evaluation of the glare potential of different surface glasses for use in PV modules based on their bidirectional reflectance distribution functions (BRDF). BRDF threshold values for retinal burn damage, flash blindness, and discomfort glare are calculated based on retinal irradiance thresholds from literature. Subsequently, gonioreflectometric measurements on PV minimodules are used to characterize the reflectance profiles of eight different glass surfaces. Results for all measured structured glasses, both satinated and macrotextured, show significant reductions in BRDF compared with smooth glass, largely eliminating the potential for flash blindness as well as discomfort glare at low incidence angles. At high incidence angles, increased potential for discomfort glare as well as forward scattering along the glass surface can be observed. AR coatings, however, are shown to be insufficient to eliminate glare causing flash blindness.

Solid particles in a suspension can be separated effectively through cake filtration where the filter medium is decisive particularly during the initial stage when particle breakthrough can be high. To improve the filtrate quality and throughput, filtration aid additives are used, which are known to alter filter cake structure and thus reduce flow resistance but, in forming clusters, also stabilize fine particles that would otherwise pass through the filter (cake) easily. However, filter aids are costly, increase the complexity of the system and may have adverse effects for subsequent mechanical drying and washing. Instead of supplying additives, four alternative filter media were tested exhibiting an open, three-dimensional structure that reached deeply into the depth of the forming filter cake. An aqueous limestone suspension was investigated in a conventional laboratory test unit. Composite filter medium set-up delivered up to 15% faster filtration. The results indicate that the fiber structures give better performance that reach far into the cake and are oriented not only axially but also radially. In contrary to the initial hypothesis that an axial fiber structure would produce additional drainage channels along the surface of these fibers and thus support but deliquoring, the actual deliquoring performance with air blowing appeared to be slightly less efficient. Although not investigated yet, cake discharge with a 3-D filter layer present poses an additional challenge, rendering the concept of composite filters unpractical.

Background: Soiling can be a major challenge for photovoltaic (PV) installations, depending on their location, as it reduces transmission and can lead to significant losses. Anti-soiling coatings have been demonstrated to reduce soiling losses and thereby increase PV power production. Objective: This article investigates the applicability of a titanium-dioxide-based anti-soiling coating developed by Photocat under the name “ShineOn” for use with PV installations. The main parameter examined is the optical transmission losses, as this directly translates to performance losses during non-soiled operations. Methods: Measurements of transmittance are carried out using both indoor laboratory setups as well as outdoor PV installations, including measurements of the short-circuit current (Isc), incidence angle modifier (IAM) and spectral transmittance. Investigated samples include both full-sized modules and custom-made mini-modules containing a single solar cell. Results: Both indoor and outdoor measurements show minor transmission losses in the range of 0.3 to 0.6 % and negligible effects on the IAM. Additionally, observations indicate that samples should be coated after lamination, as losses for samples coated before lamination are slightly higher. Conclusion: As the transmission losses due to the ShineOn coating are small and no additional angular- dependent losses were observed, the coating is deemed not to be detrimental for PV applications. Proper assessment of the usefulness requires investigations of the anti-soiling properties, for example, through test installations in regions with high soiling rates.