continued safe operation under normal and design basis events (DBE). Normal component and system tests typically confirm the cables can perform their normal operational function. The focus of the cable test program, however, is directed toward the more demanding challenge of assuring the cable function under accident or DBE. The industry has adopted 50% elongation at break (EAB) relative to the un-aged cable condition as the acceptability standard. All tests are benchmarked against the cable EAB test. EAB, however, is a destructive test so the test programs must apply an array of other nondestructive examination (NDE) tests to assure or infer the overall set of cable’s system integrity. Assessment of cable integrity is further complicated in many cases by vendor’s use of dissimilar material for jacket and insulation. Frequently the jacket will degrade more rapidly than the underlying insulation. Although this can serve as an early alert to cable damage, direct test of the cable insulation without violating the protective jacket becomes problematic. This report addresses the range of bulk electrical NDE cable tests that are or could be practically implemented in a field-test situation with a particular focus on frequency domain reflectometry (FDR). The FDR test method offers numerous advantages over many other bulk electrical tests. Two commercial FDR systems plus a laboratory vector network analyzer are used to test an array of aged and un-aged cables under identical conditions. Several conclusions are set forth, and a number of knowledge gaps are identified.

We performed ab initio molecular dynamics (AIMD) simulations to benchmark bulk liquid structures and to evaluate results from all-atom force field molecular dynamics (FFMD) simulations with the generalized Amber force field (GAFF) for organophosphorus (OP) and organochlorine (OC) compounds. Our work also addresses the current and important topic of force field validation, applied here to a set of nonaqueous organic liquids. Our approach differs from standard treatments, which validate force fields based on thermodynamic data. Utilizing radial distribution functions (RDFs), our results show that GAFF reproduces the AIMD-predicted asymmetric liquid structures moderately well for OP compounds that contain bulky alkyl groups. Among the OCs, RDFs obtained from FFMD overlap well with AIMD results, with some offsets in position and peak structuring. However, re-parameterization of GAFF for some OCs is needed to reproduce fully the liquid structures predicted by AIMD. The offsets between AIMD and FFMD peak positions suggest inconsistencies in the developed force fields, but, in general, GAFF is able to capture short-ranged and long-ranged interactions of OPs and OCs observed in AIMD. Along with the local coordination structure, we also compared enthalpies of vaporization. Overall, calculated bulk properties from FFMD compared reasonably well with experimental values, suggesting that small improvements within the FF should focus on parameters that adjust the bulk liquid structures of these compounds.

Characterization of photovoltaic (PV) module materials throughout different stages of service life is crucial to understanding and improving the durability of these materials. Currently the large-scale of PV modules (>1 m2) is imbalanced with the small-scale of most materials characterization tools (≤1 cm2). Furthermore, understanding degradation mechanisms often requires a combination of multiple characterization techniques. Here, we present adaptations of three standard materials characterization techniques to enable mapping characterization over moderate sample areas (≥25 cm2). Contact angle, ellipsometry, and UV-vis spectroscopy are each adapted and demonstrated on two representative samples: a commercial multifunctional coating for PV glass and an oxide combinatorial sample library. Best practices are discussed for adapting characterization techniques for large-area mapping and combining mapping information from multiple techniques.

Soiling can cause large reductions in solar energy system production. To study the spatial variability of soiling, transmission loss and mass accumulation of particulates on photovoltaic (PV) cover plates were measured at five sites across the continental United States. Three sites were in the Front Range of Colorado in rural, suburban, and urban areas representing a semi-arid environment. One site was in Cocoa Florida in a hot and humid environment, and the final site was in Albuquerque, New Mexico, in a hot and arid environment. Total suspended particulate concentrations (TSP) were measured simultaneously at each site. Comparisons between transmission loss and mass accumulation measurements are made. Both mass accumulation and ambient TSP are shown to have some predictive power for transmission loss. Mean deposition velocities of 1.5 cm/s were observed. For every g/m 2 of PM deposited on the PV cover plate, a 2.8% reduction in transmission was observed independent of site. These results provide a method for estimating soiling rates at sites across the United States.

The texture or patterning of soil on PV surfaces may influence light capture at various angles of incidence (AOI). Accumulated soil can be considered a microshading element, which changes with respect to AOI. Laboratory deposition of simulated soil was used to prepare test coupons for simultaneous AOI and soiling loss experiments. A mixed solvent deposition technique was used to consistently deposit patterned test soils onto glass slides. Transmission decreased as soil loading and AOI increased. Dense aggregates significantly decreased transmission. However, highly dispersed particles are less prone to secondary scattering, improving overall light collection. In order to test AOI losses on relevant systems, uniform simulated soil coatings were applied to split reference cells to further examine this effect. The measured optical transmission and area coverage correlated closely to the observed I SC . Angular losses were significant at angles as low as 25°.

The texture or patterning of soil on PV surfaces may influence light capture at various angles of incidence. Accumulated soil can be considered a micro-shading element, which changes with respect to AOI. While scattering losses at this scale would be significant only to the most sensitive devices, microshading could lead to hot spot formation and other reliability issues. Indoor soil deposition was used to prepare test coupons for simultaneous AOI and soiling loss experiments. A mixed solvent deposition technique was used to consistently deposit patterned test soils onto glass slides. Transmission decreased as soil loading and AOI increased. Highly dispersed particles are less prone to secondary scattering, improving overall light collection.

The Advanced Measurement and Analysis of PV Derate Factors project focuses on improving the accuracy and reducing the uncertainty of PV performance model predictions by addressing a common element of all PV performance models referred to as “derates”. Widespread use of “rules of thumb”, combined with significant uncertainty regarding appropriate values for these factors contribute to uncertainty in projected energy production.

The sheet resistance of three soil types (Arizona road dust, soot, and sea salt) on glass were measured by the transmission line method as a function of relative humidity (RH) between 39% and 95% at 60°C. Sea salt yielded a 3.5 orders of magnitude decrease in resistance on the glass surface when the RH was increased over this RH range. Arizona road dust showed reduced sheet resistance at lower RH, but with less humidity sensitivity over the range tested. The soot sample did not show significant resistivity change compared to the unsoiled control. Photovoltaic modules with sea salt on their faces were step-stressed between 25% and 95% RH at 60°C applying -1000 V bias to the active cell circuit. Leakage current from the cell circuit to ground ranged between two and ten times higher than that of the unsoiled controls. Degradation rate of modules with salt on the surface increased with increasing RH and time.

Initial results from a study examining spatial variations of soiling are presented. Soiling from five sites is examined. Three sites in the area surrounding Denver, Colorado and two additional sites, one in Albuquerque New Mexico, and one in Cocoa Florida at US Department of Energy Regional Test Centers. These locations represent a diverse array of climates in which solar energy may be utilized. These locations represent a diverse array of climates in which solar energy may be utilized. Results highlight similarities and differences between soiling at locations across the United States. In addition to soiling data, ambient particulate data is also collected at the five sites, and results from these measurements, and how they relate to soiling, are presented.

Soiling losses on high concentrating photovoltaic (HCPV) systems may be influenced by the spectral properties of accumulated soil. We have predicted the response of an isotype cell to changes in spectral content and reduction in transmission due to soiling using measured UV/vis transmittance through soil films. Artificial soil test blends deposited on glass coupons were used to supply the transmission data, which was then used to calculate the effect on model spectra. The wavelength transparency of the test soil was varied by incorporating red and yellow mineral pigments into graded sand. The more spectrally responsive (yellow) soils were predicted to alter the current balance between the top and middle subcells throughout a range of air masses corresponding to daily and seasonal variation. (C) 2013 Elsevier Ltd. All rights reserved.

Soil accumulation on photovoltaic (PV) modules presents a challenge to long-term performance prediction and lifetime estimates due to the inherent difficulty in quantifying small changes over an extended period. Low mass loadings of soil are a common occurrence but remain difficult to quantify. In order to more accurately describe the specific effects of sparse soil films on PV systems, we have expanded upon an earlier technique to measure the optical losses due to an artificially applied obscurant film. A synthetic soil analog was sprayed onto glass coupons at very brief intervals with a high-volume, low-pressure pneumatic sprayer. Light transmission through the grime film was evaluated using a quantum efficiency test stand and UV/vis spectroscopy. A 0.1-g/m(2) grime loading was determined to be the limit of mass measurement sensitivity, which is similar to some reports of daily soil accumulation. Predictable, linear decreases in transmission were observed for samples with amass loading between 0.1 and 0.5 g/m(2). A similar change was observed for soiled coupons from an outdoor monitoring station. Collected soil from the field coupons was analyzed to develop a compositional analog for indoor studies. Natural and synthetic soils produced similar decreases in transmission.

Nanostructured Ni(x)Co(3-x)O4 films serve as effective electrocatalysts for both the oxygen reduction and oxygen evolution reactions in alkaline electrolyte.

This manuscript is intended to serve as a practical guide to conducting repeatable indoor soiling experiments for PV applications. An outline of techniques, materials and equipment used in prior studies [1-3] is presented. Additional recommendations and practical guidance has been presented. Major sections include techniques to formulate soil simulants, ('standard grime') and feedstocks from traceable components, spray application, and quantitative measurement methodologies at heavy and minimal soil loadings.

In this study we examine the role of the support for selective hydrogenation of acetylene. Palladium (Pd) nanoparticles with a narrow size distribution were deposited on three supports, carbon, alumina and magnesia. The Pd particles ranged from 0.5 to 1.0 nm in diameter. A novel synthesis based on room temperature alcohol reduction of the Pd acetate precursor allowed us to deposit similar sized Pd particles on all three supports. We used electron microscopy and X-ray absorption spectroscopy (EXAFS) to characterize these samples and to confirm the similarity of the distribution and the size of the nanoparticles on all three supports. The carbon-supported Pd yielded a higher selectivity to ethylene at 100% acetylene conversions (from acetylene/ethylene mixtures) when compared to the oxide-supported samples. This work provides clear evidence that the support can play an important role in the selective hydrogenation of acetylene. While alumina is extensively used in industry as the support for Pd and Pd alloys, considerable improvements in selectivity could be made by the use of carbon supports. (C) 2014 Elsevier B.V. All rights reserved.

Effective evaluation and prediction of photovoltaic performance loss due to soiling require consistent test methods. Natural soil accumulation is time-consuming and location specific, and thus does not provide reproducible results across different geographic regions. Therefore, we have demonstrated a laboratory technique to artificially apply soil to a specimen and quantify the resulting effects of the film on the transmission of incident light. An artificial soil analogue was formulated with NIST-traceable components and applied to the specimen using an aerosol spray gun. This approach produced consistent soil coatings, which were directly correlated to electrical performance loss of multicrystalline Si cells in a laboratory setting. Two independent measurement techniques were used to quantify the influence of the layer of artificial soil on the spectral transmission of light. It was found that the performance loss due to deposited soil could be effectively predicted over a range of mass loadings. Furthermore, it was demonstrated that the composition of the blend, termed "standard grime," had a significant and repeatable influence on performance loss. The methods presented here provide the basis for further study of the influence of specific soil types on the performance loss of PV systems. It is envisioned that these laboratory studies could be coupled with field studies to better understand these effects.

Soil accumulation on photovoltaic (PV) modules presents a challenge to long-term performance prediction and lifetime estimates due to the inherent difficulty in quantifying small changes over an extended period. Low mass loadings of soil are a common occurrence, but remain difficult to quantify. In order to more accurately describe the specific effects of sparse soil films on PV systems, we have expanded upon an earlier technique to measure the optical losses due to an artificially applied obscurant film. A synthetic soil analogue consisting of AZ road dust and soot in acetonitrile carrier solvent was sprayed onto glass coupons at very brief intervals with a high volume, low pressure pneumatic sprayer. Light transmission through the grime film was evaluated using a QE test stand and UV/vis spectroscopy. A 0.1 g/m2 grime loading was determined to be the limit of mass measurement sensitivity, which is similar to some reports of daily soil accumulation. Predictable, linear decreases in transmission were observed for samples with a mass loading between 0.1 and 0.5 g/m2. Reflectance measurements provided the best means of easily distinguishing this sample from a reference.

The accumulation of soil on photovoltaic (PV) modules may introduce a spectral loss due to the color profile of the accumulated material. In order to compare the spectral and total losses experienced by a cell, soil analogs were formulated to contain common mineral pigments (Fe2O3 and gothite) with previously developed "standard grime" mixtures. These mixtures simulated a wide range of desert soil colors and were applied to glass test coupons. The light transmission through the deposited film was evaluated by UV/vis/NIR spectroscopy and by placing the coupon over a test cell in a 1-sun simulator and quantum efficiency test stand. Distinct peaks in the 300-600-nm range were observed by UV/vis/NIR spectroscopy corresponding to the Fe2O3 and gothite. Approximately analogous features were noted in the QE measurement. Overall comparisons were made by integrating the response of a soiled coupon relative to a clean reference. Soils rich in red pigments (Fe2O3) caused a greater integrated response than soils rich in yellow pigment (gothite). The yellow soils caused a greater attenuation in a specific region of the spectrum (300-450 nm), which may have significant implications to specific devices, such as multijunction and CdTe technologies.

Effective evaluation and prediction of photovoltaic performance loss due to soiling requires consistent test methods. Natural grime accumulation is time-consuming and location-specific, and thus does not provide reproducible results across different geographic regions. Therefore, we have demonstrated a technique to apply artificial soiling with NIST-traceable components using an aerosol spray technique. This approach produces consistent soil coatings which were directly correlated to performance loss of multicrystalline Si cells in a laboratory setting. By tailoring the composition of the test blend, termed `standard grime', the loss due to soiling can be effectively predicted over a range of mass loadings and soil types.

This paper describes efforts to characterize different aspects of photovoltaic connector reliability. The resistance variation over a population of connections was examined by measuring 75 connectors from three different manufacturers. The comparison shows differences in average resistance of up to 9% between manufacturers. The standard deviation of resistance among the same manufacturer ranged from 6%-11%. In a separate experiment, the corrosive effects of grime on the connector pins during damp heat accelerated testing at 85 ° C/85% RH were studied. We observed a small resistance increase in the first 100 hours of damp heat and no further changes up to the current 450 hours of available data. With the exception of one connector, the effects of grime on connector performance during accelerated testing could not be measured during this time period.

A series of modified, hafnium tert-butoxide ([Hf(OBu(t))4]) compounds (1-26) were crystallographically characterized, and representative species were then used to produce HfO2nanoparticles. This systematically varied family of [Hf(OR)4] compounds was developed from the reaction of [Hf(OBu(t))4] with a series of (i) Lewis basic solvents, tetrahydrofuran, pyridine, or 1-methylimidazole; (ii) simple phenols, HOC6H4(R)-2 or HOC6H3(R)2-2,6 where R = CH3, CH(CH3)2, or C(CH3)3; and (iii) complex polydentate alcohols, tetrahydrofuran methanol (H-OTHF), pyridinecarbinol (H-OPy), and tris(hydroxymethylethane) (THME-H3). The solvent-modified products were crystallographically characterized as [Hf(OBu(t))4(solv)n] (1-3). The phenoxide (OAr)-exchanged [Hf(OBu(t))4] products isolated from toluene were characterized as dimeric [Hf(OAr)n(OBu(t))4-n]2 (4 and 5) or [Hf(μ-OH)(OAr)3(HOBu(t))]2 (6 and 7) for the less sterically demanding OAr ligands and [Hf(OAr)n(OBu(t))4-n(HOBu(t))] (8 and 9) monomers for the larger OAr ligands. When Lewis basic solvents were employed, solvated monomers of varied OAr substitutions were observed as [Hf(OAr)n(OBu(t))4-n(solv)x], where solv = THF (10, 11, and 13-15) and py (16 and 19-21). The nuclearities of the remaining complex polydentate alcohol derivatives ranged from monomers (24, OPy) to dimers (22, OTHF; 23, OPy) to tetramers (25 and 26, THME). On the basis of their nuclearities, select members of this family of [Hf(OR)4] compounds (monomer, [Hf(OBu(t))4], 8; dimer, 19a, 22; tetramer, 25) were used to determine the validity of using [Hf(OR)4] precursors for the production of hafnia (HfO2) nanoparticles under solvothermal (oleylamine/oleic acid) conditions. After a 650 °C thermal treatment, the resulting powder X-ray diffraction pattern for each powder was found to be consistent with HfO2 (PDF 00-040-1173), and after a 1000 °C treatment, larger particles of HfO2 (PDF 00-043-1017) were reported. Transmission electron microscopy images confirmed that nanomaterials had formed. Because identical processing conditions had been employed for each HfO2 nanomaterial, the morphological variations observed in this study may be attributed to the individual precursors ("precursor structure affect").