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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 847 records · Page 47
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

GaP/GaNP Heterojunctions for Efficient Solar‐Driven Water Oxidation

The growth and characterization of an n‐GaP/i‐GaNP/p + ‐GaP thin film heterojunction synthesized using a gas‐source molecular beam epitaxy (MBE) method, and its application for efficient solar‐driven water oxidation is reported. The TiO 2 /Ni passivated n‐GaP/i‐GaNP/p + ‐GaP thin film heterojunction provides much higher photoanodic performance in 1 m KOH solution than the TiO 2 /Ni‐coated n‐GaP substrate, leading to much lower onset potential and much higher photocurrent. There is a significant photoanodic potential shift of 764 mV at a photocurrent of 0.34 mA cm −2 , leading to an onset potential of ≈0.4 V versus reversible hydrogen electrode (RHE) at 0.34 mA cm −2 for the heterojunction. The photocurrent at the water oxidation potential (1.23 V vs RHE) is 1.46 and 7.26 mA cm −2 for the coated n‐GaP and n‐GaP/i‐GaNP/p + ‐GaP photoanodes, respectively. The passivated heterojunction offers a maximum applied bias photon‐to‐current efficiency (ABPE) of 1.9% while the ABPE of the coated n‐GaP sample is almost zero. Furthermore, the coated n‐GaP/i‐GaNP/p + ‐GaP heterojunction photoanode provides a broad absorption spectrum up to ≈620 nm with incident photon‐to‐current efficiencies (IPCEs) of over 40% from ≈400 to ≈560 nm. The high low‐bias performance and broad absorption of the wide‐bandgap GaP/GaNP heterojunctions render them as a promising photoanode material for tandem photoelectrochemical (PEC) cells to carry out overall solar water splitting.

Kargar, Alireza↗
DOE OSTI2017

Investigation of Pristine and (Mo, W)-Doped Cu 11 V 6 O 26 for Use as Photoanodes for Solar Water Splitting

The development of new and inexpensive semiconductor electrodes that possess suitable bandgap energies and band positions for solar water splitting is of great interest in the field of solar fuel production. In this study, n-type Cu 11 V 6 O 26 that has a bandgap energy of 1.9 eV was produced as a pure, high quality photoanode and its properties and stability for photoelectrochemical water splitting were systematically investigated in pH 9.2 and pH 13 solutions. As Cu 11 V 6 O 26 photoanodes appeared to suffer from poor charge transport properties, Mo and W-doping into the V site were also examined, which considerably improved the photocurrent generation of Cu 11 V 6 O 26 . Furthermore, the bandgap energy, band edge positions, flatband potential, photocurrent generation, and photostability of pristine and doped Cu 11 V 6 O 26 electrodes are discussed in comparison to elucidate the effect of Mo- and W-doping and to evaluate the promise and limitations of Cu 11 V 6 O 26 as a photoanode for use in a water splitting photoelectrochemical cell.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Flexible Boundary Design for a Chattanooga Microgrid Powered by Landfill Solar Photovoltaic and Battery Storage

Landfill based microgrids powered by renewable energy aid reliability and resiliency while promoting environmental and energy justice. This paper aims to design a flexible boundary algorithm for a proposed Chattanooga landfill microgrid with the ability to shrink or expand its boundaries based on the available power from the solar PV and battery storage. This helps to improve resiliency unlike the conventional fixed boundary microgrids. The flexible boundary algorithm determines the combination and switching status of the intellirupter ® which changes the microgrid boundaries to achieve power balance by dropping or energizing specific load sections. Finally, the microgrid with flexible boundary was simulated in MATLAB/Simulink and performed satisfactorily when tested under various scenarios.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2025

Data for Attributing Differences of Solar-Induced Chlorophyll Fluorescence (SIF)-Gross Primary Production (GPP) Relationships between Two C4 Crops, Corn and Miscanthus

Information to characterize the solar-induced chlorophyll fluorescence (SIF)-gross primary production (GPP) relationship in C4 cropping systems remains limited. The annual C4 crop corn and perennial C4 crop miscanthus differ in phenology, canopy structure and leaf physiology. Investigating the SIF-GPP relationships in these species could deepen our understanding of SIF-GPP relationships within C4 crops. Using in situ canopy SIF and GPP measurements for both species along with leaf-level measurements, we found considerable differences in the SIF-GPP relationships between corn and miscanthus, with a stronger SIF-GPP relationship and higher slope of SIF-GPP observed in corn compared to miscanthus. These differences were mainly caused by leaf physiology. For miscanthus, high non-photochemical quenching (NPQ) under high light, temperature and water vapor deficit (VPD) conditions caused a large decline of fluorescence yield (ΦF), which further led to a SIF midday depression and weakened the SIF-GPP relationship. The larger slope in corn than miscanthus was mainly due to its higher GPP in mid-summer, largely attributed to the higher leaf photosynthesis and less NPQ. Our results demonstrated variation of the SIF-GPP relationship within C4 crops and highlighted the importance of leaf physiology in determining canopy SIF behaviors and SIF-GPP relationships.

Feedstock Production↗
DOE OSTI2017

The Effects of Interplanetary Transport in the Event-intergrated Solar Energetic Particle Spectra

Previous investigations on the energy spectra of solar energetic particle (SEP) events revealed that the energy spectra observed at 1 au often show double power laws with break energies from one to tens of MeV/nuc. In order to determine whether the double power-law features result from the SEP source or the interplanetary transport process from the Sun to 1 au, we separately analyze the SEP spectra in the decay phase, during which the transport effect is minimum. In this paper, we reported three events observed by the Interplanetary Monitory Platform 8 spacecraft, which occurred on 1977 September 19, November 22, and 1979 March 1. For the first two events, the event-integrated spectra of protons possess double power-law profiles with break energies in a range of several MeV to tens of MeV, while the spectra integrated in the decay (reservoir) phase yield single power laws. Moreover, a general trend from a double power law at the rising phase to a single power law at the decay phase is observed. For the third event, both the event-integrated and the reservoir spectra show double power-law features. However, the difference between the low- and high-energy power-law indices is smaller for the reservoir spectrum than the event-integrated spectrum. These features were reproduced by solving the 1D diffusion equation analytically and we suggest that the transport process, especially the diffusion process, plays an important role in breaking the energy spectra.

79 ASTRONOMY AND ASTROPHYSICS↗