Dynamic Programming Method to Optimally Select Power Distribution System Reliability Upgrades
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42 ENGINEERING↗
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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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Combined-Accelerated Stress Testing for Advanced Reliability Assessment of Photovoltaic Modules
New and previously undiscovered degradation mechanisms continue to be identified after field exposure in new photovoltaic module designs or materials oftentimes results in significant losses in investment. This is despite passing certification tests. Testing is insufficient largely due to their single-or double-stress nature. A Combined-Accelerated Stress Test (C-AST) has recently been developed. The test combines multiple stress factors of the natural environment to better replicate conditions experienced by modules in the field and detect mechanisms not a-priori known in new materials and designs.
accelerator factor modeling↗
DuraMAT FY 2023 Annual Report: Toward Reliability Forecasting
The Durable Module Materials Consortium (DuraMAT) launched in November 2016 with five years of funding from the U.S. Department of Energy s (DOE's) Solar Energy Technologies Office (SETO). The program renewed in 2022 for an additional 6 years. DuraMAT is a multi-lab consortium led by the National Renewable Energy Laboratory, with Sandia National Laboratories (Sandia) and Lawrence Berkeley National Laboratory (LBNL) as core research labs. DuraMAT's overarching goal is to accelerate a sustainable, just, and equitable transition to zero-carbon electricity generation by 2035. 2023 has been a wild ride in the solar industry. Photovoltaic (PV) manufacturing is coming back to the United States, and deployment is booming again. DuraMAT has a unique opportunity to support flourishing manufacturing and deployment over the next couple of years.
durable module↗
Tearing and reliability of photovoltaic module backsheets
We report that the backsheet in photovoltaic modules belongs to an important class of layered materials where the tearing behavior of the individual layers does not necessarily represent the tearing behavior of the entire backsheet. Such characteristic arises from the interaction between the individual layers during the tearing process, where one layer of the backsheet is mechanically constrained by its neighboring layers and the layers may debond from each other. The mechanical constraint and debonding change the amount of energy dissipated during tearing and affect the overall tearing energy. In this article, we exposed a wide selection of backsheets with polymers including ethylene-vinyl acetate (EVA), polyethylene terephthalate (PET), polyvinylidene fluoride (PVDF), and ethylene tetrafluoroethylene (ETFE) to damp heat (85°C/85%RH) for up to 2000 hours. We report on the effect of damp heat on the tearing energy as a function of damp heat exposure. We developed a model that describes the tearing energy of a layered structure by accounting for the tearing of the individual layers in the backsheet, the effect of mechanical constraint, and the adhesive debonding between the layers. Additionally, we explore the relationship between the microstructural change in the polymers which resulted from the damp heat exposure and the mechanical properties using modulated differential scanning calorimetry (MDSC), small and wide angle X-ray scattering (SAXS and WAXS), and tensile testing.
36 MATERIALS SCIENCE↗
PV Field Reliability Status--Analysis of 100,000 Solar Systems
In this paper, we analyzed annual production data from 100 000 photovoltaic systems as well as comments relating to their performance and maintenance. Our analysis revealed that 80% to 90% of all systems performed within 10% of the predicted production or better. Also, 56% of the systems were still performing above P50 or the median at 5 years. However, a small but significant tail of about 7000 systems perform below P90 expectations. In general, residential systems have a lower rate of failure than utility or commercial systems. Despite higher rates of component failures, utility systems lose less power than residential or commercial systems. This outcome is likely due to closer monitoring and better operations and maintenance practices. Inverters are still the components that reportedly fail most often (4%-6%), but other failures such as unspecified repair and meters cause more production loss. Reported module failures are relatively rare (0.2%) and are within the range of historical values. Installation quality affects performance and safety as indicated by data showing connector, wiring, breaker, and fuse failures due to undersizing, electrical design, and improper connection. Lastly, early detection of degradation and proactive response resulted in less impact on production than reactive, unplanned repairs.
14 SOLAR ENERGY↗
Advancing reliability assessments of photovoltaic modules and materials using combined-accelerated stress testing
Previously undiscovered failure modes in photovoltaic (PV) modules continue to emerge in field installations despite passing protocols for design qualification and quality assurance. Failure to detect these modes prior to widespread use could be attributed to the limitations of present-day standard accelerated stress tests (ASTs), which are primarily designed to identify known degradation or failure modes at the time of development by applying simultaneous or sequential stress factors (usually two at most). Here, we introduce an accelerated testing method known as the combined-accelerated stress test (C-AST), which simultaneously combines multiple stress factors of the natural environment. Simultaneous combination of multiple stress factors allows for improved identification of failure modes with better ability to detect modes not known a priori. A demonstration experiment was conducted that reproduced the field-observed cracking of polyamide- (PA-) and polyvinylidene fluoride (PVDF)–based backsheet films, a failure mode that was not detected by current design qualification and quality assurance testing requirements. In this work, a two-phase testing protocol was implemented. The first cycle (“Tropical”) is a predominantly high-humidity and high-temperature test designed to replicate harsh tropical climates. The second cycle (“Multi-season”) was designed to replicate drier and more temperate conditions found in continental or desert climates. Testing was conducted on 2 × 2-cell crystalline-silicon cell miniature modules constructed with both ultraviolet (UV)–transmitting and UV-blocking encapsulants. Cracking failures were observed within a cumulative 120 days of the Tropical condition for one of the PA-based backsheets and after 84 days of Tropical cycle followed by 42 days of the Multi-season cycle for the PVDF-based backsheet, which are both consistent with failures seen in fielded modules. In addition to backsheet cracking, degradation modes were observed including solder/interconnect fatigue, various light-induced degradation modes, backsheet delamination, discoloration, corrosion, and cell cracking. The ability to simultaneously apply multiple stress factors may allow many of the test sequences within the standardized design qualification procedure to be performed using a single test setup.
14 SOLAR ENERGY↗
Assessing the Reliability and Quality of Online Uterine Fibroid Embolization Resources
This study was designed to examine the best internet resources about uterine fibroid embolization (UFE) pertinent to medical trainees, radiologists, gynecologists, family physicians, and patients. The terms 'uterine fibroid embolization,' 'uterine fibroid embolization,' and 'uterine artery embolization' were entered into Google, Yahoo, and Bing search engines; the top 20 hits were assessed. The hits were categorized as organizational or nonorganizational. Additionally, 23 radiological and obstetrical organizations were assessed. The DISCERN instrument and Journal of the American Medical Association (JAMA) benchmarks (authorship, attribution, currency, disclosure) were used to assess the information critically. The scope, strength, weaknesses, and unique features were highlighted for the top five organizational and nonorganizational websites. A total of 203 websites were reviewed; 23 were removed in accordance with the exclusion criteria and 146 were duplicate websites, for a total of 34 unique sites. It was found that 35 % (12/34 websites) were organizational (family medicine, radiology, obstetrics/gynecology) and 65 % (22/34 websites) were nonorganizational (teaching or patient resources). The overall mean DISCERN score was 49.6 (10.7). Two-tailed, unpaired t test demonstrated no statistically significant difference between organizational and nonorganizational websites (p = 0.101). JAMA benchmarks revealed 44 % (15/34 websites) with authorship, 71 % (24/34 websites) with attribution, 68 % (23/34 websites) with disclosure, and 47 % (16/34 websites) with currency. The overall quality of websites for UFE is moderate, with important but not serious shortcomings. The best websites provided relevant information about the procedure, benefits/risks, and were interactive. DISCERN scores were compromised by sites failing to provide resources for shared decision-making, additional support, and discussing consequence of no treatment. JAMA benchmarks revealed lack of authorship and currency.
62 RADIOLOGY AND NUCLEAR MEDICINE↗
Heat-and-Mass Transfer Intensification in Saturated-Steam Generators in NPP with VVER as a Means for Increasing Efficiency and Reliability
The intensification of steam generation in combination with improvement of the temperature regime, specifically, with the elimination of temperature fluctuations of the loaded components of the apparatus (heat-exchange tubes, warming-medium headers) increases the steam-generation capacity and eliminates the factors causing damage to the structural elements of steam generators. The possibility of intensifying heat-and-mass transfer on the basis of the experience gained in operating steam generators in NPP with VVER (horizontal) and NPP in foreign countries (vertical) is examined. It is concluded on the basis of the analysis that it is expedient to develop a domestically produced apparatus of the vertical type, which will make possible well-founded production of steam generators for NPP with VVER in the future.
22 GENERAL STUDIES OF NUCLEAR REACTORS↗
Study on the Reliability of Carbon Nanotube-Reinforced Sn-58Bi Lead-Free Solder Joints
The wettability, microstructure and mechanical properties of multi-walled carbon nanotube (CNT)-reinforced Sn-58Bi composite solder joints were investigated. The results indicate that the wettability of the Sn-58Bi solder is improved and the growth of interfacial intermetallic (IMC) compounds for solder joints is restrained by CNTs. The thickness of the IMC layers is decreased with increasing CNTs concentration. The microstructure of the Sn-58Bi composite solders is refined, the maximum tensile strength and shear strength are obtained by adding the optimum CNTs content about 0.01 wt.%. However, excessive content of CNTs addition can deteriorate the properties. The creep rupture life of Sn-58Bi solder joint and Sn-58Bi-0.01CNTs solder joint is decreased with increasing load, temperature and current density. The average creep rupture life of Sn-58Bi-0.01CNTs composite solder joint is 60% higher than that of the plain solder joint.
77 NANOSCIENCE AND NANOTECHNOLOGY↗
Combining physics-based and data-driven techniques for reliable hybrid analysis and modeling using the corrective source term approach
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97 MATHEMATICS AND COMPUTING↗
A review of examples and opportunities to quantify the grid reliability and resilience impacts of energy efficiency
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24 POWER TRANSMISSION AND DISTRIBUTION↗
Assessing the reliability of SiC MOSFET through inverter-like accelerated test vs. power cycling test
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14 SOLAR ENERGY↗
Optimizing the impacts of solid additives on the operational stability and processing reliability of organic solar cells
Previous reports have revealed that by leveraging solid additives, organic solar cells (OSCs) can surpass the device’s performance beyond the intrinsic limitations of host photoactive molecules, a remarkable advancement. However, the impacts of more complex interactions introduced by solid additives are not yet well understood. Herein, optimizing the fabrication process based on the traditional efficiency-guided approach fails to represent the ideal and most practical devices. In particular, achieving superior operational stability while minimizing the device performance scattering was found to require processing solvent evaporation to be synchronized with the volatility of the chosen solid additive. However, this may be challenging since most organic photoactive materials display excellent efficiencies only with selected solvents. Accordingly, this work also demonstrates the potential of dual and complementary solvents selection, consisting of low boiling point (primary) and high boiling point (secondary). This strategy allows for the suppression of any potential trade-offs in efficiency. Meanwhile, the operational stability and precision of device performance are substantially enhanced. Additionally, solid additives have demonstrated that the singlet exciton dissociation rate does not limit the free charge generation yield. Finally, these findings are expected to reformulate OSC device fabrication strategies towards more practical devices.
36 MATERIALS SCIENCE↗
A unique molten salt reactor feature – The freeze valve system: Design, operating experience, and reliability
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73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Reliability of tandem solar cells and modules: what's next?
Hybrid tandem photovoltaic (PV) technology development has gained momentum in the last few years. This has been motivated by a need to push module efficiencies beyond what is theoretically capable with single-junction technologies to further accelerate total global PV deployment. Significant advances have been made with multiple material systems achieving tandem efficiencies over 30% in the last decade. All of the highest record efficiencies have been from laboratory-scale devices, with areas of 1 cm2 or less. Interestingly, there are multiple material combinations and terminal configurations that have demonstrated promising results. Despite these high laboratory efficiencies, reasonable service lifetimes (a useful operating lifetime of at least 25 years) are needed for tandems to compete with the levelized cost of energy (LCOE) of traditional single junction PV technologies. Existing commercial Si PV products have demonstrated performance in the field with an average of less than 1% relative annual degradation in module and system performance, and many manufacturers now provide 30 year warranties on their products.
14 SOLAR ENERGY↗
Accelerated reliability tests of n + and p + poly-Si passivated contacts
We report on the stability of encapsulated, low-pressure chemical vapor-deposited phosphorus (n + poly-Si) doped and boron (p + poly-Si) doped poly-Si/SiO x passivated contacts by exposing the samples to three different accelerated tests: damp heat test, thermal cycling and ultraviolet exposure, adhering closely to the IEC 61215 standard. Outdoor testing was also performed by exposing the samples in the outdoor testing field at the National Renewable Energy Laboratory, and preliminary data accumulated for 1000 h from February to April of 2021 is reported. We studied non-metallized, thermally-metallized, and screen-printed n + and p + poly-Si by monitoring the effective minority carrier lifetime at the implied maximum power point using a Sinton lifetime tester, and recorded photoluminescence images before and after the exposure. Furthermore, the samples were found to be stable under all test conditions, which is encouraging for incorporation of these contacts in next-generation industrial silicon solar cells.
14 SOLAR ENERGY↗
Reliability studies on Si PIN photodiodes under Co-60 gamma radiation
Silicon PIN photodiodes were fabricated with 250 nm SiO{sub 2} antireflective coating (ARC). The changes in the electrical characteristics, capacitance-voltage characteristics and spectral response after gamma irradiation are systematically studied to estimate the radiation tolerance up to 10 Mrad. The different characteristics studied in this investigation demonstrate that Si PIN photodiodes are suitable for high radiation environment.
36 MATERIALS SCIENCE↗