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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 919 records · Page 51
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Power converter circuitry for photovoltaic devices

Power converter circuitry includes a direct current (DC) input comprising a first DC input node and a second DC input node, an alternating current (AC) output comprising a first AC output node coupled to the first DC input node and a second AC output node, a first boost switch coupled between the second DC input node and a boost intermediate node, a second boost switch coupled between the boost intermediate node and a common node, a boost inductor coupled between the boost intermediate node and the first DC input node, a link capacitor coupled between the second DC input node and the common node, a first half-bridge switch coupled between the second DC input node and a half-bridge intermediate node, a second half-bridge switch coupled between the half-bridge intermediate node and the common node, and a half-bridge inductor coupled between the half-bridge intermediate node and the second AC output node.

Ayyanar, Rajapandian↗
DOE OSTI2022

DC compensation for power transformer through neutral DC injection

A power transmission system can include a transformer and compensator circuit(s), each coupled between a node of the transformer and a ground connection. The compensator circuit(s) can each be configured to counteract a DC signal component of an AC signal at the transformer. The compensator circuit(s) can include a converter circuit having an AC side and a DC side and configured to convert a DC voltage on the DC side to an AC signal at the AC side. The compensator circuit(s) can include a DC link coupled to the DC side of the converter circuit. The compensator circuit(s) can include a controller configured to measure a DC signal component between the load and the ground; to determine, based at least in part on the DC signal component, a compensating signal configured to counteract the DC signal component; and to inject, by the converter circuit, the compensating signal to counteract the DC signal component.

Burkes, Klaehn W.↗
DOE OSTI2022

Three-phase differential mode converter

A system for charging a battery includes three sub-modules, each receiving a respective phase of a three-phase alternating current (AC) signal. The three sub-modules cooperate to transform the respective phases of the three-phase AC signal to a direct current (DC) signal by passing the respective phases of the three-phase AC signal through a respective semiconductor device configured to discontinuously modulate the respective phase of the three-phase AC signal to convert it to a DC signal provided to the battery to charge the battery.

Mazumder, Sudip K.↗
DOE OSTI2024

Dynamic Modeling of Power Conversion Stages for an Exascale Supercomputer

In this paper a power conversion and energy consumption model for an exascale supercomputer is investigated. Power consumption, energy loss and efficiency are derived for the 27.2 MW liquid-cooled, centralized, High Performance Computing (HPC) power system, which is supplied directly from the 480 V three-phase mains. Two energy conversion stages are analyzed, measured and modeled. The model is developed in order to be adapted and implemented in a digital twin platform utilizing a Resource Allocator and Power Simulator (RAPS) module. RAPS enables estimation of potential energy savings in the direct AC power supply architecture via both conventional rectifier load sharing (commonly used in HPC systems), as well as smart rectifier load sharing. Moreover, besides the direct AC supply architecture analysis, the full direct DC supply architecture with with 1 kV DC bus were also studied. Comparison of 10 hour time frame operation of the system, with direct 480 V AC voltage supply with conventional and smart load sharing and medium dc voltage supply were done. For the direct AC supply architecture, with conventional and smart load sharing the predicted power loss was approximately 840 kW and 820 kW, respectively and the predicted total system efficiency was 92.87% and 93.05%, respectively. For the direct DC supply architecture with the 1000 V DC supply bus power loss was approximately 340 kW and the predicted total system efficiency was 97.02%.

Wojda, Rafal↗
DOE OSTI2024

Three-phase differential mode converter

A system for charging a battery includes three sub-modules, each receiving a respective phase of a three-phase alternating current (AC) signal. The three sub-modules cooperate to transform the respective phases of the three-phase AC signal to a direct current (DC) signal by passing the respective phases of the three-phase AC signal through a respective semiconductor device configured to discontinuously modulate the respective phase of the three-phase AC signal to convert it to a DC signal provided to the battery to charge the battery.

Mazumder, Sudip K.↗
DOE OSTI2020

Alternating Current Photovoltaic Effect

It is well known that the photovoltaic effect produces a direct current (DC) under solar illumination owing to the directional separation of light-excited charge carriers at the p–n junction, with holes flowing to the p-side and electrons flowing to the n-side. In this study, we found that apart from the DC generated by the conventional p–n photovoltaic effect, there is another new type of photovoltaic effect that generates alternating current (AC) in the nonequilibrium states when the illumination light periodically shines at the junction/interface of materials. The peak current of AC at high switching frequency can be much higher than that from DC. The AC cannot be explained by the established mechanisms for conventional photovoltaics; instead, it is suggested to be a result of the relative shift and realignment between the quasi-Fermi levels of the semiconductors adjacent to the junction/interface under the nonequilibrium conditions, which results in electron flow in the external circuit back and forth to balance the potential difference between two electrodes. By virtue of this effect, the device can work as a high-performance broadband photodetector with extremely high sensitivity under zero bias; it can also work as a remote power source providing extra power output in addition to the conventional photovoltaic effect.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Robust cycloid crossover driven by anisotropy in the skyrmion host GaV 4 S 8

We report on the anomalous magnetization dynamics of the cycloidally modulated spin textures under the influence of uniaxial anisotropy in multiferroic GaV 4 S 8 . The temperature and field dependence of the linear ac susceptibility [$χ'_{1ω}$ (T, H)], AC magnetic loss [$χ''_{1ω}$ (T, H)], and nonlinear AC magnetic response [$M_{3ω}$ (T, H)] are examined across the magnetic phase diagram in the frequency range f = 10 - 10 000 Hz. According to recent theory, skyrmion vortices under axial crystal symmetry are confined along specific orientations, resulting in enhanced robustness against oblique magnetic fields and altered spin dynamics. We characterize the magnetic response of each spin texture and find that the dynamic rigidity of the Néel skyrmion lattice appears enhanced compared to Bloch-type skyrmions in cubic systems, even in the multidomain state. Anomalous M 3 ω and strong dissipation emerge over the same phase regime where strong variations in the cycloid pitch were observed on lowering temperature in recent small-angle neutron-scattering experiments [White et al., Phys. Rev. B 97, 020401(R) (2018)]. Here, we show that strong anisotropy also drives an extended crossover of the zero-field cycloid texture in GaV 4 S 8 . The frequency dependence of these dynamic signatures is consistent with that of a robust anharmonic spin texture exhibiting a correlated domain arrangement. The results underpin the essential role of magnetic anisotropy in enhancing the rigidity of topological spin textures for diverse applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Materials Data on AcH2 by Materials Project

AcH2 is Fluorite structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Ac is bonded in a body-centered cubic geometry to eight equivalent H atoms. All Ac–H bond lengths are 2.56 Å. H is bonded to four equivalent Ac atoms to form a mixture of edge and corner-sharing HAc4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ac2S3 by Materials Project

Ac2S3 crystallizes in the tetragonal I-42d space group. The structure is three-dimensional. there are three inequivalent Ac3+ sites. In the first Ac3+ site, Ac3+ is bonded in a 8-coordinate geometry to eight S2- atoms. There are a spread of Ac–S bond distances ranging from 2.99–3.46 Å. In the second Ac3+ site, Ac3+ is bonded to eight S2- atoms to form a mixture of distorted corner, edge, and face-sharing AcS8 hexagonal bipyramids. There are a spread of Ac–S bond distances ranging from 3.01–3.23 Å. In the third Ac3+ site, Ac3+ is bonded to eight S2- atoms to form a mixture of distorted corner, edge, and face-sharing AcS8 hexagonal bipyramids. There are a spread of Ac–S bond distances ranging from 3.03–3.28 Å. There are three inequivalent S2- sites. In the first S2- site, S2- is bonded in a 6-coordinate geometry to six Ac3+ atoms. In the second S2- site, S2- is bonded to five Ac3+ atoms to form a mixture of distorted corner, edge, and face-sharing SAc5 trigonal bipyramids. In the third S2- site, S2- is bonded to five Ac3+ atoms to form a mixture of distorted corner, edge, and face-sharing SAc5 square pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CaAcIn2 by Materials Project

CaAcIn2 is Heusler structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Ca is bonded in a body-centered cubic geometry to eight equivalent In atoms. All Ca–In bond lengths are 3.47 Å. Ac is bonded in a body-centered cubic geometry to eight equivalent In atoms. All Ac–In bond lengths are 3.47 Å. In is bonded in a body-centered cubic geometry to four equivalent Ca and four equivalent Ac atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on AcTlHg2 by Materials Project

AcHg2Tl is Heusler structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Ac is bonded in a body-centered cubic geometry to eight equivalent Hg atoms. All Ac–Hg bond lengths are 3.36 Å. Hg is bonded in a body-centered cubic geometry to four equivalent Ac and four equivalent Tl atoms. All Hg–Tl bond lengths are 3.36 Å. Tl is bonded in a distorted body-centered cubic geometry to eight equivalent Hg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on AcZnAu2 by Materials Project

AcAu2Zn is Heusler structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Ac is bonded in a body-centered cubic geometry to eight equivalent Au atoms. All Ac–Au bond lengths are 3.17 Å. Au is bonded in a body-centered cubic geometry to four equivalent Ac and four equivalent Zn atoms. All Au–Zn bond lengths are 3.17 Å. Zn is bonded in a body-centered cubic geometry to eight equivalent Au atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on AcMgTl2 by Materials Project

MgAcTl2 is Heusler structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Mg is bonded in a body-centered cubic geometry to eight equivalent Tl atoms. All Mg–Tl bond lengths are 3.40 Å. Ac is bonded in a body-centered cubic geometry to eight equivalent Tl atoms. All Ac–Tl bond lengths are 3.40 Å. Tl is bonded in a body-centered cubic geometry to four equivalent Mg and four equivalent Ac atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on AcCdRh2 by Materials Project

AcRh2Cd is Heusler structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Ac is bonded in a body-centered cubic geometry to eight equivalent Rh atoms. All Ac–Rh bond lengths are 3.01 Å. Rh is bonded in a body-centered cubic geometry to four equivalent Ac and four equivalent Cd atoms. All Rh–Cd bond lengths are 3.01 Å. Cd is bonded in a distorted body-centered cubic geometry to eight equivalent Rh atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on AcGaTe2 by Materials Project

AcTe2Ga is Heusler structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional and consists of four gallium molecules and one AcTe2 framework. In the AcTe2 framework, Ac is bonded in a body-centered cubic geometry to eight equivalent Te atoms. All Ac–Te bond lengths are 3.46 Å. Te is bonded to four equivalent Ac atoms to form a mixture of corner and edge-sharing TeAc4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ac3Sn by Materials Project

Ac3Sn is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Ac is bonded in a distorted square co-planar geometry to four equivalent Sn atoms. All Ac–Sn bond lengths are 3.77 Å. Sn is bonded to twelve equivalent Ac atoms to form a mixture of face and corner-sharing SnAc12 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on AcHgAu2 by Materials Project

AcAu2Hg is Heusler structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Ac is bonded in a body-centered cubic geometry to eight equivalent Au atoms. All Ac–Au bond lengths are 3.22 Å. Au is bonded in a body-centered cubic geometry to four equivalent Ac and four equivalent Hg atoms. All Au–Hg bond lengths are 3.22 Å. Hg is bonded in a distorted body-centered cubic geometry to eight equivalent Au atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on AcHg3 by Materials Project

AcHg3 crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Ac is bonded to twelve equivalent Hg atoms to form a mixture of corner and face-sharing AcHg12 cuboctahedra. There are six shorter (3.39 Å) and six longer (3.57 Å) Ac–Hg bond lengths. Hg is bonded in a 4-coordinate geometry to four equivalent Ac atoms.

36 MATERIALS SCIENCE↗