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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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Shingled solar cells overlapping along non-linear edges

Solar devices and methods for producing solar devices are disclosed. In some examples, a solar device includes solar cells arranged in a shingled manner such that adjacent long edges of adjacent ones of the solar cells overlap. The adjacent long edges have a non-linear shape that has protruding portions. The solar device includes contact pads arranged in the protruding portions of the adjacent long edges such that the contact pads of the adjacent ones of the solar cells are electrically connected.

Caswell, Nathaniel Alexis↗

Systems and methods for reworking shingled solar cell modules

A high efficiency configuration for a solar cell module comprises solar cells arranged in a shingled manner to form super cells, which may be arranged to efficiently use the area of the solar module, reduce series resistance, and increase module efficiency. Removing a defective solar cell from a super cell may be difficult, however. It may therefore be advantageous to bypass defective solar cells in a super cell rather than remove and replace them. A bypass conductor may be applied to the rear surface of the super cell to bypass one or more defective solar cells in a super cell or in a solar module comprising super cells.

Caswell, Nathaniel Alexis↗

Analysis of electrically conductive adhesives in shingled solar modules by X-ray imaging techniques

The failure mechanisms of electrically conductive adhesives (ECAs) in solar modules are difficult to study since the ECA layer is not easily accessible within the module package. In this work, we present two complementary imaging modalities—X-ray radiography and X-ray microcomputed tomography (XCT)—that reveal important morphological features of the ECA within a shingled module. X-ray radiography uses single X-ray projections to provide fast and non-destructive imaging of the shingled interconnection, illuminating the alignment of the ECA relative to the busbars, the size and shape of the ECA, and the presence of voids within it. Through X-ray radiography, we observed, for example, that the average void coverage area of ECA segments reduced from 36.7% to 4.4% when an ECA was cured for 60 s prior to module lamination. XCT is a three-dimensional imaging technique that can identify regions in which the ECA makes electrical contact to busbars on cells and regions in which the ECA has cracked, among other features. XCT can also be used to image the individual metal particles within ECA, from which the metal volume fraction of an ECA was found here to be 70.4%. This is a quantity that is not often reported by ECA manufacturers but is important to ensure isotropic conduction. As X-ray projections can be performed non-destructively on full modules, the technique may be used to pinpoint ECA failures in accelerated degradation testing. XCT is complementary and is suited to forensic analysis of failing modules.

14 SOLAR ENERGY↗

Method and apparatus of fabricating a solar cell device

Solar cell devices as well as method and apparatus for producing solar cell devices are disclosed. Aspects of the disclosure provide a solar cell device that includes a string of solar cells. The string of solar cells are conductively connected in series and arranged in a shingled manner with sides of adjacent solar cells being overlapped. A first metal ribbon segment is conductively bonded to a front surface of an end cell, the front surface being configured to face a light incoming direction to receive energy from a light source.

Caswell, Nathaniel↗

System and method for shingling wafer strips connected in parallel

A solar device includes a first string of first solar wafers, wherein a plurality of the first solar wafers each overlap with at least one vertically adjacent solar wafer from the first string. Additionally, the solar device includes a second string of second solar wafers, wherein a plurality of the second solar wafers each overlap with at least one vertically adjacent solar wafer from the second string, wherein a plurality of the first solar wafers overlap with one or more of the plurality of second solar wafers to electrically connect horizontally adjacent solar wafers in parallel.

Caswell, Nathaniel Alexis↗

System and method for shingling wafer strips connected in parallel

A solar device includes a first string of first solar wafers, wherein a plurality of the first solar wafers each overlap with at least one vertically adjacent solar wafer from the first string. Additionally, the solar device includes a second string of second solar wafers, wherein a plurality of the second solar wafers each overlap with at least one vertically adjacent solar wafer from the second string, wherein a plurality of the first solar wafers overlap with one or more of the plurality of second solar wafers to electrically connect horizontally adjacent solar wafers in parallel.

Caswell, Nathaniel↗

Solar panel

A high efficiency configuration for a solar cell module comprises solar cells arranged in an overlapping shingled manner and conductively bonded to each other in their overlapping regions to form super cells, which may be arranged to efficiently use the area of the solar module.

Lin, Yafu↗

Solar panel

A high efficiency configuration for a solar cell module comprises solar cells arranged in an overlapping shingled manner and conductively bonded to each other in their overlapping regions to form super cells, which may be arranged to efficiently use the area of the solar module.

Lance, Tamir↗

Solar panel

A high efficiency configuration for a solar cell module comprises solar cells arranged in an overlapping shingled manner and conductively bonded to each other in their overlapping regions to form super cells, which may be arranged to efficiently use the area of the solar module.

Lin, Yafu↗

Characterization of Interconnects

Combined-accelerated stress testing (C-AST) simultaneously combines stress factors of the natural environment (including UV radiation, temperature, humidity, electrical current, and external mechanical force) into a single test that requires fewer modules, fewer chambers, and makes it possible to discover weaknesses in new designs that are not known a-priori. C-AST reduces risk, accelerates time to market, and improves bankability by reducing costly overdesign using test levels not exceeding those seen in the natural environment. This project seeks to evaluate strengths and weaknesses of modern cell interconnect designs with combined-accelerated stress testing (C-AST) to screen multiple climates along with finite element and failure analysis to determine the potential for a 50-year life. Supporting this, we seek to develop methods of characterization to assess the degradation of interconnects, enable predictive rate models with material forensics and FEA and show C-AST's ability to find interconnect failures and benchmark it relative to other accelerated stress test methods like temperature cycling and cyclic dynamic mechanical loading. Examples of modern interconnect designs covered are Canadian Solar Hetero Technology ribbon enabling closer cell interconnections, SmartWire (eg. Meyer-Berger technology), and shingled cells with new interconnect materials.

C-AST↗

Solvari SR, Simplifying Residential Solar to 1 SKU, with Extended Testing

Accelerated weathering and material compatibility testing for polymeric and asphaltic materials. NLR will be testing the durability of the polymeric materials proposed for use in the supporting structures designed by TESCI solar. This will include the bare materials and coupons attached to asphalt shingles. The exposure will be in damp heat and separately heat, humidity and UV light, all followed by mechanical evaluation. Modification 1 is an extension of the first round of testing with both a continuation of some of the same testing and addition of new testing methods and materials. The testing of materials in the condition of A3 looking at mechanical durability will be continued looking at the materials used in the mounting brackets. We will be adding in testing of the silicone adhesive to the module and of the module itself. For the mounting brackets, testing will also be conducted at multiple temperatures and humidity levels to allow for extrapolation to the field.

14 SOLAR ENERGY↗

United States cool surfaces deployment plan

Solar-reflective building envelope surfaces, such as cool roofs and walls, can be especially helpful in disadvantaged communities that often have poorly insulated older homes, aging or absent air conditioning units, steep utility bills, polluted air, and high vulnerability and exposure to extreme heat. With support from the U.S. Department of Energy, our project seeks to dramatically increase the climate-appropriate deployment of cool surfaces across the United States with an emphasis on their application to disadvantaged communities. First, we sought to identify cool-surface deployment barriers, opportunities, and models by (a) reviewing the history of cool-surface deployment activities, (b) interviewing cool-surface stakeholders, (c) researching successful energy-efficiency/green building deployment models; and (d) interviewing the actors who have implemented these models. Second, we conducted a workshop to engage stakeholders in development of a deployment plan. Third, we asked several U.S. federal agencies (a) how cool surfaces and cool surface stakeholders could support their missions and (b) how agency activities could support cool-surface deployment. Fourth, we identified a set of transformative ideas that form the core of the deployment plan. Transformative ideas include but are not limited to initiatives to (a) launch an educational campaign to make the general public and building professionals aware of how cool roofs and walls exclude unwanted solar heat; (b) create a “Cool Roof Prize” stimulating the development of affordable, high-performance cool asphalt roofing shingles; (c) conduct high-profile, large-scale demonstration programs that bring cool surfaces to disadvantaged heat-vulnerable communities; and (d) support local, regional, and state climate action (heat mitigation) plans with cool surfaces.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

Performance and durability of electrically conductive tape for shingled Si heterojunction technology cells

We report electrically conductive tape (ECT) was characterized and used to assemble shingled cell strings at low temperature to achieve high reliability Pb- and Ag-free interconnections. The volume resistivity for two considered ECTs are 0.13 ± 0.06 mΩ·cm and 0.47 ± 0.20 mΩ·cm and specific contact resistances, 6.85± 2.00 mΩ·cm 2 and 6.30 ± 0.37 mΩ·cm 2 using the emerging IEC 62788-8-1 Technical Specification for assessment of electrically conductive adhesives (ECA). Durability and performance of the technology in glass–glass mini modules were evaluated with temperature cycling, damp heat testing, and combined-accelerated stress testing (CAST). Through temperature cycling (-40°C to 85°C) applying five times the mini module short-circuit current in forward bias and in the multi climate CAST protocol, there was negligible degradation of fill factor after replacing connectors at the modules' cable leads; however, CAST resulted in short circuit current loss attributed to degradation in light collection by the cells, not the ECT. The IEC 61215-2 85°C, 85% relative humidity damp heat testing showed susceptibility of the HJT cells to effects of humidity in the electroluminescence intensity around the module perimeter that degraded power performance by 4% (relative). Contrasting the IEC 61215-2 qualification testing-based damp heat testing with CAST, factors such as the optical stress of CAST may precipitate the degradation of the modules whereas the humidity levels and duration of IEC 61215-2 damp heat testing may lead to excessive levels of humidity diffused into the modules, potentially resulting in degradation that is unrepresentative of the field.

14 SOLAR ENERGY↗

PV Lifetime Project - 2025 NLR Annual Report

DOE's PV Lifetime project was initiated in 2016 with the goal of accurately characterizing the early-life evolution of photovoltaic (PV) field performance. Different PV cell and module technologies result in different initial degradation rates due to effects like light-induced degradation (LID) and light and elevated temperature-induced degradation (LeTID). To accurately characterize the initial field degradation of maximum power (Pmp) requires the use of high-accuracy indoor IV curve measurements at standard test conditions. Therefore, PV modules involved in this study are removed from the field once or twice per year and brought indoors for measurement under constant temperature and irradiance conditions. Overall annual degradation rates are as follows: our first modules to be deployed (Jinko, Trina, QCells) have annual median degradation rate between -0.4%/yr and -0.5%/yr mainly concentrated in the first year. Mission Solar, LG and Panasonic modules are all displaying modest degradation, better than -0.3% / year. Indeed, Mission Solar fielded modules degraded less than their control modules which remain indoors and un-exposed. This is also true for the LONGi monofacial modules, which had some field degradation, but not as much as the degradation of the indoor control modules. The LONGi bifacial modules on the other hand have degraded more in the field than their monofacial counterparts, although still a modest amount (-0.4 %/yr). Of the four newest module types in the study, only one has had better than average degradation. REC360NP2 (N-type TOPCon) had a slight performance increase over the first year and a half of field deployment. For the other three new module types (plus one older module type), degradation was more rapid. In our study of 16 module types, four have demonstrated degradation faster than -1%/yr: two N-type Heterojunction, one PERC bifacial and one PERC shingled module. The two heterojunction modules in our study are degrading the most rapidly. Sunpreme n-HIT bifacial modules are showing a loss rate around -1.5%/yr, for over -10% total to date. This is largely attributed to loss in front-side Isc. This is distinct from the REC 405AA-Pure modules which have degraded -6.8% in only a year and a half, for an annualized decline of -3.9 %/yr. For this module type, the decline is roughly half in Voc, with the remaining split between FF and Isc. Of the remaining two module types, Prism Solar PERC bifacial has declined -5% total since 2019, although this loss appears to have stabilized in the most recent measurement. The Solaria PowerX-400R Shingled module type has also lost around -3.2% in the first 1.5 years of field deployment. It remains to be seen if these losses will continue with time.

14 SOLAR ENERGY↗

Observations and Lessons Learned From Installing Residential Roofing-Integrated Photovoltaics

Building-sited solar photovoltaics (PV) could play a key role in decarbonizing the building sector either through racked and mounted PV or through Building-integrated PV (BIPV). BIPV is installed into the building envelope itself, with solar cells and/or modules forming the outer layer of a building structure, thus transforming a single-purpose structure into one that serves the dual purposes of the building envelope and electricity. BIPV can be applied to building roofs, facades, awnings, pergolas, windows, skylights, balustrades, and other external surfaces. Given BIPV products vary widely, the focus of this research is residential roofing integrated PV (RIPV), where solar is incorporated into or otherwise replaces the roofing material. Previous research suggests that residential RIPV could reduce customer acquisition, labor, supply chain, and equipment costs. These products have yet to realize these cost savings and deployment remains significantly less than conventional rooftop PV as a relative share of the addressable market in the US. One potential barrier to broader residential roofing integrated PV deployment may be higher costs relative to conventional rooftop PV, primarily because the design and installation of these products is still evolving. Here, we explore residential RIPV cost-reduction opportunities by analyzing installation processes. Our study documents residential RIPV installations at 2 reroofing sites and the equivalent of 9 new construction sites in California through a methodology known as time and motion study. We also conducted interviews with subject-matter experts to identify barriers and solutions to maximize these products' market penetration. Our time and motion study breaks the RIPV installation process into four steps: 1) staging, unloading, and roof preparation; 2) fire resistant underlayment(s) (synthetic material laid between roof shingles and roof deck); 3) flashings and PV installation; and 4) wiring and monitoring. We measure the time required for each step in terms of worker-hours, representing an hour of labor from a single worker. We further normalize process time by dividing worker-hours by kilowatt (kW) of system capacity. The most time-intensive step was flashings and PV installation, taking around 2.4 worker-hours per kW on average and accounting for around 60% of the process time for an average installation. The total installation process took on average about 6.4 and 3.5 worker-hours per kW at the reroofing sites and new construction sites, respectively. For comparison, a previous time and motion study documented a time of 6.9 worker-hours per kW for conventional rooftop PV. The shorter RIPV installation times are consistent with previous studies suggesting that RIPV could be installed faster than conventional rooftop PV. The time and motion results and feedback from interviewees provide insights into potential residential RIPV cost reduction opportunities. Several interviewees suggested that these products would be more efficient if PV installation was more fully integrated into the roofing/construction industries, which currently use separate supply chains and skillsets. Further integration could reduce supply chain delays and labor force redundancies. Future research could explore specific ways to integrate these industries to help realize the cost savings potential of RIPV.

14 SOLAR ENERGY↗