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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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At least 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Correction for Metastability in the Quantification of PID in Thin-Film Module Testing

A fundamental change in the analysis for the accelerated stress testing of thin-film modules is proposed, whereby power changes due to metastability and other effects that may occur due to the thermal history are removed from the power measurement that we obtain as a function of the applied stress factor. In this work, initial thermal treatment of the module is performed before application of the independent variable stress of system voltage so that any temperature-dependent processes (e.g., diffusion) that affect the module power are largely activated beforehand. Secondly, the power of reference modules normalized to an initial state-undergoing the same thermal and light exposure history but without the applied stress factor such as humidity or voltage bias-is subtracted from that of the stressed modules. For better understanding and appropriate application in standardized tests, the method is demonstrated and discussed for potential-induced degradation testing in view of the paralleloccurring but unrelated physical mechanisms that can lead to confounding power changes in the module.

14 SOLAR ENERGY↗
DOE OSTI2021

Representative Modules for Accelerated Thermal Cycling and Static Load Testing

In this work, we explore the influence of module size on the rate of interconnect solder bond thermomechanical fatigue (TMF) damage and the probability of cell fracture. For the solder bond TMF damage evaluation, structural mechanics models of crystalline silicon PV models are created to solve with the Finite Element Method. For the probability of cell fracture evaluation, Weibull analysis and weakest link theory are employed to resolve the probability of crystalline silicon PV cell fracture when measured as bare cells and when stressed in reduced- and full-sized modules. Results conclusively demonstrate that the rate of solder bond TMF damage is independent of module size, interconnect location across the cell and cell location across the module and that smaller, representative, modules must be loaded to a much higher level than their parent full-sized modules to achieve an equivalent driving force for cell fracture.

accelerated testing↗
DOE OSTI2022

Fast External Quantum Efficiency Measurements of Photovoltaic Modules

The external quantum efficiency (EQE) or associated spectral response is widely used to evaluate the performance of photovoltaics, light emitting diodes, photodetectors, photodiodes, semiconductor lasers, laser-induced refrigeration of solids etc. For photovoltaic (PV) devices, The EQE is used to determine the spectral mismatch correction that is used to convert a performance measurement from a non-ideal simulator spectrum to a standard spectrum in PV device calibrations. Moreover, EQE can provide important insight into the physics of a PV device. For instance, the EQE shape can be used to infer mechanisms limiting the performance of the device. However, EQE measurements of full-size PV modules remain a challenge in the PV community due to rare availability of reliable module QE measurement tools worldwide and the size and complexity of module architecture that comprises several cells connected in strings (series or/and parallel). Here, we use a customized nondestructive tool made of high-power light emitting diodes to perform high-throughput EQE measurements on PV modules. Circuit simulations show that the measurement system can safely be used to measure both crystalline silicon and thin film-based PV modules with series connected cells without the risk of damage through reverse bias. In addition, EQE mapping combined with electroluminescence show a strong correlation and provide a way to determine both spatial non-uniformity of the spectral response and defects/degradation effects across the module.

PV module↗
DOE OSTI2018

A Contribution to the Theory of the Interaction of Transient Radiation of a Charged Particle with Periodically Modulated Anisotropic Magnetodielectric Filling of a Waveguide

Transient radiation of a charged particle in a waveguide with modulated anisotropic magnetodielectric filling is considered. It is assumed that the particle moves with a constant velocity perpendicularly to the axis of the waveguide the filling of which is periodically modulated by the harmonic law. Wave equations for the transverse electric (TE) and transverse magnetic (TM) fields in the waveguide have been obtained. Analytical expressions have been obtained for fields in the waveguide in the first approximation by small modulation indices of waveguide filling. Energies of transient radiation of a charged particle have been calculated in the region of weak (nonresonance) interaction between the radiation and modulation waves, in particular, in the case of a rectangular waveguide. It has been shown that radiation energies at the zero harmonic in the region of weak interaction do not depend on the modulation indices and are proportional to the modulation indices in the first power at the plus and minus first harmonics. The mechanism of the appearance of Cherenkov radiation has been analyzed.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Graphene metamaterial modulator for free-space thermal radiation

We proposed and demonstrated a new metamaterial architecture capable of high speed modulation of free-space space thermal infrared radiation using graphene. Our design completely eliminates channel resistance, thereby maximizing the electrostatic modulation speed, while at the same time effectively modulating infrared radiation. Experiment results verify that our device with area of 100 × 120 µm 2 can achieve a modulation speed as high as 2.6 GHz. We further highlight the utility of our graphene metamaterial modulator by reconstructing a fast infrared signal using an equivalent time sampling technique. The graphene metamaterial modulator demonstrated here is not only limited to the thermal infrared, but may be scaled to longer infrared and terahertz wavelengths. Our work provides a path forward for realization of frequency selective and all-electronic high speed devices for infrared applications.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Development of a Visual Inspection Data Collection Tool for Evaluation of Fielded PV Module Condition

A visual inspection data collection tool for the evaluation of fielded photovoltaic (PV) modules has been developed to facilitate describing the condition of PV modules with regard to field performance. The proposed data collection tool consists of 14 sections, each documenting the appearance or properties of a part of the module. This report instructs on how to use the collection tool anddefines each attribute to ensure reliable and valid data collection. This tool has been evaluated through the inspection of over 60 PV modules produced by more than 20 manufacturers and fielded at two different sites for varying periods of time. Aggregated data from such a single data collection tool has the potential to enable longitudinal studies of module condition over time, technologyevolution, and field location for the enhancement of module reliability models.

14 SOLAR ENERGY↗
NASA NTRS2012

W-band Heterodyne Receiver Module with 27 K Noise Temperature

We present noise temperature and gain measurements of a W-band heterodyne module populated with MMIC LNAs designed and fabricated using 35nm InP HEMT process. The module has a WR-10 waveguide input. GPPO connectors are used for the LO input and the I and and Q IF outputs. The module is tested at both ambient (300 K) and cryogenic (25 K) temperatures. At 25 K physical temperature, the module has a noise temperature in the range of 27-45 K over the frequency band of 75-111 GHz. The module gain varies between 15 dB and 27 dB. The band-averaged module noise temperature of 350 K and 33 K were measured over 80-110 GHz for the physical temperature of 300 K and 25 K, respectively. The resulting cooling factor is 10.6.

heterodyne module↗
NASA NTRSDate not supplied

Towers: Critical Initial Infrastructure for the Moon, Such as a Power Module Support

Towers are an efficient structure commonly used to elevate systems against a gravity field, such as above the surface of a planet or the Moon. Towers can be used to elevate antennas, transmitters and sensors for communication, navigation, and observation infrastructure in support of surface operations. Near the Lunar poles, elevation of rotating solar panels enables nearly continuous panel illumination for solar power production despite the Sun remaining near the horizon year-round. Further, once technology is developed for tower assembly, this same technology can be extended to the assembly of a variety of structures including rocket blast containment shields, bridges, shelters, and habitats from either Earth-sourced or Lunar-sourced structural members. Environmental factors on the Lunar surface are vastly different than those found on Earth and have significant impact on the design of towers. Towers designed for the Lunar surface have no heritage nor Earth analog. The designs discussed herein are therefore breaking new ground creating a fundamentally new class of structures outside of current experience and intuition. The purpose of this paper is to: a) describe the unique environmental factors affecting tower design on the Lunar surface compared to Earth-based systems, b) evaluate two structural forms for the tower; telescoping tubes and an assembled truss, as well as c)provide recommendations on when each structural form is most suitable. A major contribution presented in the current paper is to provide parametric plots and supporting equations of mass and volume versus module power level and blanket height above the Lunar surface for the solar array application, to enable system level studies of optimum power module distribution and size. A secondary contribution are plots of the mass and volume of aluminum or structural glass required for assembled truss towers formed from Lunar derived structural members. An objective of achieving 1 MW of total power has been used to enable comparison of structural forms, because the total mass of solar arrays is consistent. It will be shown that for moderate module sizes, up to ~50 kW power modules, based on a telescoping tube tower have advantages, but for power modules from 50 kW to 200 kW an assembled truss tower can be created with half to one third of the tube tower mass. More significantly, when shipped from Earth, an assembled truss tower can be packed into 1/14th to 1/25th of the tube tower volume. Truss designs in the 100 kW to 200 kW range will be shown to be a favorable when assembled from either graphite-epoxy angles shipped from Earth or aluminum angles fabricated from Lunar materials. 50 kW towers are an attractive choice for both a telescoping or assembled tower with the solar arrays elevated 10 m above the Lunar surface, while increased solar array elevation favors 100 kW to 200 kW power modules.

assembly↗
DOE OSTI2012

Development of a Visual Inspection Checklist for Evaluation of Fielded PV Module Condition (Presentation)

A visual inspection checklist for the evaluation of fielded photovoltaic (PV) modules has been developed to facilitate collection of data describing the field performance of PV modules. The proposed inspection checklist consists of 14 sections, each documenting the appearance or properties of a part of the module. This tool has been evaluated through the inspection of over 60 PV modules producedby more than 20 manufacturers and fielded at two different sites for varying periods of time. Aggregated data from a single data collection tool such as this checklist has the potential to enable longitudinal studies of module condition over time, technology evolution, and field location for the enhancement of module reliability models.

14 SOLAR ENERGY↗
DOE OSTI2015

Bottom-Up Cost Analysis of a High Concentration PV Module; NREL (National Renewable Energy Laboratory)

We present a bottom-up model of III-V multi-junction cells, as well as a high concentration PV (HCPV) module. We calculate $0.65/Wp(DC) manufacturing costs for our model HCPV module design with today’s capabilities, and find that reducing cell costs and increasing module efficiency offer the promising pathways for future cost reductions. Cell costs could be significantly reduced via an increase in manufacturing scale, substrate reuse, and improved manufacturing yields. We also identify several other significant drivers of HCPV module costs, including the Fresnel lens primary optic, module housing, thermal management, and the receiver board. These costs could potentially be lowered by employing innovative module designs.

$/W↗
DOE OSTI2015

In-Situ Measurement of Power Loss for Crystalline Silicon Modules Undergoing Thermal Cycling and Mechanical Loading Stress Testing: Preprint

We analyze the degradation of multi-crystalline silicon photovoltaic modules undergoing simultaneous thermal, mechanical, and humidity stress testing to develop a dark environmental chamber in-situ measurement procedure for determining module power loss. From the analysis we determine three main categories of failure modes associated with the module degradation consisting of: shunting, recombination losses, increased series resistance losses, and current mismatch losses associated with a decrease in photo-current generation by removal of some cell areas due to cell fractures. Based on the analysis, we propose an in-situ module power loss monitoring procedure that relies on dark current-voltage measurements taken during the stress test, and initial and final module flash testing, to determine the power degradation characteristic of the module.

14 SOLAR ENERGY↗
DOE OSTI2025

In‐Scribe Silane Bonding for Mechanical Reinforcement of Perovskite Photovoltaic Modules

Despite the extraordinary rise in power conversion efficiency over the last decade, metal halide perovskite (MHP) photovoltaics remain more mechanically fragile than other PV technologies. In this work, the scribe area, created by the monolithic interconnection of thin-film solar cells, is used to extrinsically reinforce the mechanical robustness of packaged MHP solar modules. In contrast to the epoxy-based chemistries often leveraged in the MHP literature, silane-grafted polyolefin encapsulants are designed to form strong covalent bonds to oxide surfaces, specifically to glass and the transparent conductive oxide at the base of the scribe line. Pseudo-modules encapsulated with silane-grafted polyolefin are measured with more than an order-of-magnitude enhancement infracture energy from 0.27 ± 0.01 J·m −2 (no scribes) to 5.97 ± 0.42 J·m −2 (scribes perpendicular to delamination directioncovering ≈2.2% of the module area). The silane-grafted polyolefin retains strong adhesion even after undergoing an accelerated IEC 61215 thermal cycling test consisting of 250 cycles. We find that the in-scribe bonding allows perovskite modules to have adhesion strength comparable to commercial c-Si and CdTe technologies with only 5% reduction in the active module area. This manufacturing-compatible approach offers a practical solution to address the mechanical integrity challenges in MHP solar modules, regardless of cell architecture.

14 SOLAR ENERGY↗
DOE OSTI2018

Evaluating and predicting molecular mechanisms of adhesive degradation during field and accelerated aging of photovoltaic modules

Extending photovoltaic (PV) module lifetimes beyond 30 years is a goal of significant priority. A challenge that must first be addressed, however, is the development of a predictive reliability model that captures the synergy of terrestrial stressors on module degradation, particularly at encapsulant interfaces. Using a metrology designed specifically for PV modules, a comprehensive study of the widely used ethylene vinyl acetate encapsulant was performed in which encapsulant adhesion was evaluated as a function of environmental stressors (UV exposure, temperature, and humidity) for modules aged both under accelerated lab and internationally located field conditions for months to nearly 3 decades. Mechanical and chemical characterization methods are combined with fundamental polymer reaction engineering to unravel the degradation processes active at the molecular scale that lead to encapsulant delamination. An analytical and modular model framework is put forward enabling the prediction of long-term PV module durability, starting from fundamental principles at the molecular level and explicitly accounting for bond rupture events in the bulk encapsulant and at the encapsulant interfaces. Successful parameter tuning to adhesion data indicates a dominant occurrence of deacetylation, β-scission, and hydrolytic depolymerization, respectively. The model contributes to the longstanding challenge of predicting module lifetimes in any geographic location while minimizing time-consuming and costly aging studies.

14 SOLAR ENERGY↗
DOE OSTI2021

Electrochemical Degradation Modes in Bifacial Silicon Photovoltaic Modules

Motivated by the rapidly rising deployment of bifacial monocrystalline-silicon photovoltaics (PV), we investigate the durability of various PV module packaging configurations with transparent coverings on both the front and rear sides of the module. We use a series of bifacial passivated emitter and rear cell (p-PERC) mini-modules with systematically varying outer cover materials (glass/glass, G/G, or glass/transparent backsheet, G/TB) and encapsulant chemistries (poly [ethylene-co-vinyl acetate], EVA; or polyolefin, POE). We study degradation modes over 1,000 hours of combined damp heat (DH) exposure and high system voltages that can cause potential-induced degradation (PID) under positive, zero, or negative 1,000 V cell-to-frame bias. We analyze the degradation modes using a combination of current-voltage measurements, impedance spectroscopy, external quantum efficiency, and spatially resolved luminescence and thermal imaging. Our results highlight various types of degradation including shunting, enhanced recombination, and series resistance increases, and we use spatially resolved characterization to separately identify the localized effects. We show that multiple PID and moisture-ingress degradation modes severely affect EVA-containing modules, with previously reported PID processes under negative-bias DH and a unique observation of rear-side surface recombination in G/EVA/G modules under positive-bias DH. We observe significantly less degradation in POE-containing modules, where the G/POE/G configuration exhibits minimal degradation under all stress conditions that we employ.

14 SOLAR ENERGY↗
DOE OSTI2024

Field‐representative evaluation of PID‐polarization in TOPCon PV modules by accelerated stress testing

Abstract Potential‐induced degradation‐polarization (PID‐p) can reduce module power, but how to project the extent to which PID‐p may occur in field conditions considering the factors of system voltage, condensed moisture, temperature, and illumination has not been clarified. Using tunnel oxide passivated contact (TOPCon) modules, this work demonstrates a method to test full‐size crystalline silicon PV modules for PID‐p to provide field‐representative results. In initial screening tests with positive or negative 1000 V electrical bias applied at 60°C for 96 h using Al foil electrodes on the glass surfaces, the module type exhibited reversible PID‐p only on the front face when the cell circuit was in negative voltage potential. No PID was detected on the rear after testing in either polarity. We then evaluated the PID‐p sensitivity on the front side under different UV irradiances while maintaining the glass surface wet to estimate real‐world susceptibility to PID‐p. The magnitude of the observed behavior was fit using a previously developed charge transfer and depletion by light model. Whereas power loss with −1000 V applied to the cell circuit at 60°C for 96 h in the dark was about 30%, testing the module front under 0.051 W·m −2 nm −1 at 340 nm UVA irradiation using fluorescent tubes, the mean degradation was only 3%. When the modules were tested in the dark for PID‐p with in situ dark current–voltage (I‐V) characterization, the thermal activation energy for degradation was 0.71 eV; for recovery in the dark, it was 0.58 eV. Whereas recovery from the degraded state at 60°C in the dark without voltage bias was 5% absolute in 38 h, rapid recovery of about 5% absolute was observed with 1000 W·s/m 2 exposure at 25°C using a flash tester.

14 SOLAR ENERGY↗
DOE OSTI2019

Power distribution and BER in indoor VLC with PPM based modulation schemes: a comparative study

Visible light communication (VLC) uses an intensity-modulation and direct-detection scheme to transmit data. The light source utilized in VLC structures is constantly switched on and off rapidly, resulting in flickering. Furthermore, most of illumination systems exclude dimming support to permit customers to dim the light source to the desired stage. Therefore, the modulation scheme for information transmission in VLC should consist of flicker mitigation and dimming manage abilities. Double inverse pulse position modulation (DIPPM), sub-carrier pulse position modulation (SC-L-PPM), and M-ary variable pulse position modulation (M-VPPM) are recommended for minimizing the flicker issues and supporting an excessive degree of dimming for VLC systems. In this paper, a comparison is introduced between DIPPM, SC-L-PPM, and M-VPPM according to error performance and bit rate. In addition, a simulation is carried out to measure the optical power distribution for a LED lamp in an indoor room topology for each modulation technique. The obtained results indicated that SC-L-PPM is the best choice regarding the bit error rate (BER) and optical power distribution compared to the other two schemes. A 10{sup −6} BER is achieved with a very low power requirement at L = 8, while a remarkable power distribution of 1.5–6.5 dBm is observed from 3 × 5 × 5 m{sup 3} room corners to the center, respectively. According to the bit rate, it is noticed that, M-VPPM is the most efficient one compared to the two other schemes. It achieves 2.3 × 10{sup 7} bps at a signal to noise ratio (SNR) of 22 dB and M = 8.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Development and case study of the liquid desiccant system module in sorption system simulation program (SorpSim)

Liquid desiccant systems (LDS) have recently seen an increase in research interest as they can utilize low-grade heat resources and separate the sensible and latent cooling loads by efficiently removing moisture in the air without cooling it to the dew point. Yet, simulation and analysis of LDS had remained complex and demanding due to the limited resources of LDS simulation tools. This work presents the new LDS module developed in the Sorption system Simulation program (SorpSim), which is an open-source and flexible platform for steady-state simulation and analysis of various sorption systems. First, the new LDS module containing a finite-difference model and an effectiveness-NTU model for the heat and mass transfer in LDS dehumidifier/regenerator component was introduced. Then the simulation results of the new module were verified using data from the literature. Lastly, a case study was carried out in SorpSim where an LDS cycle was built and simulated using the new module. The impacts of design and operating parameters on the simulated LDS performance were investigated. The parametric study revealed that a high source temperature improved moisture removal rate (MRR) but reduced the system coefficient of performance (COP); the COP increased monotonically with the desiccant solution recirculation ratio, while the MRR peaked at a ratio of 85%; and an internal solution heat exchanger with UA of 800 W/K was found to be sufficient for optimal performance under high recirculation ratios. The case study demonstrated the LDS module’s capability to facilitate the analysis of LDS design and operation. The LDS module can be further coupled with other component models in SorpSim to simulate and analyze various liquid-desiccant-based systems.

42 ENGINEERING↗
DOE OSTI2012

Development and Impact Evaluation of an E-Learning Radiation Oncology Module

Purpose: Radiation oncologists are faced with the challenge of irradiating tumors to a curative dose while limiting toxicity to healthy surrounding tissues. This can be achieved only with superior knowledge of radiologic anatomy and treatment planning. Educational resources designed to meet these specific needs are lacking. A web-based interactive module designed to improve residents' knowledge and application of key anatomy concepts pertinent to radiotherapy treatment planning was developed, and its effectiveness was assessed. Methods and Materials: The module, based on gynecologic malignancies, was developed in collaboration with a multidisciplinary team of subject matter experts. Subsequently, a multi-centre randomized controlled study was conducted to test the module's effectiveness. Thirty-six radiation oncology residents participated in the study; 1920 were granted access to the module (intervention group), and 17 in the control group relied on traditional methods to acquire their knowledge. Pretests and posttests were administered to all participants. Statistical analysis was carried out using paired t test, analysis of variance, and post hoc tests. Results: The randomized control study revealed that the intervention group's pretest and posttest mean scores were 35% and 52%, respectively, and those of the control group were 37% and 42%, respectively. The mean improvement in test scores was 17% (p < 0.05) for the intervention group and 5% (p = not significant) for the control group. Retrospective pretest and posttest surveys showed a statistically significant change on all measured module objectives. Conclusions: The use of an interactive e-learning teaching module for radiation oncology is an effective method to improve the radiologic anatomy knowledge and treatment planning skills of radiation oncology residents.

62 RADIOLOGY AND NUCLEAR MEDICINE↗