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Results for “lighting application efficiency”

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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Progress toward thin-film GaAs solar cells using a single-crystal Si substrate with a Ge interlayer

Development of a technology for fabricating light-weight, high-efficiency, radiation-resistant solar cells for space applications is reported. The approaches currently adopted are to fabricate shallow homojunction n(+)/p as well as p/n AlGaAs-heteroface GaAs solar cells by organometallic chemical vapor deposition (OM-CVD) on single-crystal Si substrates using in each case, a thin Ge epi-interlayer first grown by CVD. This approach maintains the advantages of the low specific gravity of Si as well as the high efficiency and radiation-resistant properties of the GaAs solar cell which can lead to greatly improved specific power for a solar array. The growth of single-crystal GaAs epilayers on Ge epi-interlayers on Si substrates is investigated. Related solar cell fabrication is reviewed.

Yeh, Y. C. M.↗
NASA NTRS1991

Two-Period Gratings For Surface-Emitting Lasers

Grating surfaces having two spatial periods tailored to obtain desired proportions of output coupling and inward reflection. Solid-state lasers of type emitting light perpendicularly to their broad surfaces made more efficient. Same principle also applicable to "Annular-Bragg-Grating Surface-Emitting Laser", (NPO-17912).

Lang, Robert J.↗
NASA NTRS1994

Effects of plasma hydrogenation on trapping properties of dislocations in heteroepitaxial InP/GaAs

In previous work, we have demonstrated the effectiveness of a post-growth hydrogen plasma treatment for passivating the electrical activity of dislocations in metalorganic chemical vapor deposition (MOCVD) grown InP on GaAs substrates by a more than two order of magnitude reduction in deep level concentration and an improvement in reverse bias leakage current by a factor of approximately 20. These results make plasma hydrogenation an extremely promising technique for achieving high efficiency large area and light weight heteroepitaxial InP solar cells for space applications. In this work we investigate the carrier trapping process by dislocations in heteroepitaxial InP/GaAs and the role of hydrogen passivation on this process. It is shown that the charge trapping kinetics of dislocations after hydrogen passivation are significantly altered, approaching point defect-like behavior consistent with a transformation from a high concentration of dislocation-related defect bands within the InP bandgap to a low concentration of individual dislocation related deep levels, before and after passivation. It is further shown that the 'apparent' activation energies of dislocation related deep levels, before and after passivation, reduce by approximately 70 meV as DLTS fill pulse times are increased from 1 microsecond to 1 millisecond. A model is proposed which explains these effects based on a reduction of Coulombic interaction between individual core sites along the dislocation cores by hydrogen incorporation. Knowledge of the trapping properties in these specific structures is important to develop optimum, low loss heteroepitaxial InP cells.

Ringel, S. A.↗
NASA NTRS1994

Effects of Plasma Hydrogenation on Trapping Properties of Dislocations in Heteroepitaxial InP/GaAs

In previous work, we have demonstrated the effectiveness of a post-growth hydrogen plasma treatment for passivating the electrical activity of dislocations in metalorganic chemical vapor deposition (MOCVD) grown InP on GaAs substrates by a more than two order of magnitude reduction in deep level concentration and an improvement in reverse bias leakage current by a factor of approx. 20. These results make plasma hydrogenation an extremely promising technique for achieving high efficiency large area and light weight heteroepitaxial InP solar cells for space applications. In this work we investigate the carrier trapping process by dislocations in heteroepitaxial InP/GaAs and the role of hydrogen passivation on this process. It is shown that the charge trapping kinetics of dislocations after hydrogen passivation are significantly altered, approaching point defect-like behavior consistent with a transformation from a high concentration of dislocation-related defect bands within the InP bandgap to a low concentration of individual deep levels after hydrogen passivation. It is further shown that the "apparent" activation energies of dislocation related deep levels, before and after passivation, reduce by approx. 70 meV as DLTS fill pulse times are increased from 1 usec. to 1 msec. A model is proposed which explains these effects based on a reduction of Coulombic interaction between individual core sites along the dislocation cores by hydrogen incorporation. Knowledge of the trapping properties in these specific structures is important to develop optimum, low loss heteroepitaxial InP cells.

Ringel, S. A.↗
NASA NTRS2018

Telescope Development for LISA

A laser interferometer space-based gravitational wave observatory requires an optical telescope to efficiently transfer laser light between pairs of widely-separated sciencecraft. The application is precision interferometric metrology, and therefore requires the telescope to have high optical pathlength stability, and low scattered light performance. We summarize recent activity on the development of a telescope to meet requirements for the LISA mission, including optimization of the optical design, development of a CAD and finite element model, and thinking about how to live with a high level of particulate contamination on the optics and still meet challenging scattered light requirements.

Livas, Jeff↗
DOE OSTI2026

Prototype Development, Testing, and Modeling for a Solar Light-Trapping Planar-Cavity Particle Receiver

Many applications for concentrating solar thermal power (CSP) technologies of high efficiency power cycles or thermochemical processes require higher operating temperatures and alternative heat transfer media. Inert solid particles for next-generation CSP and reactive gas and/or solid media for solar thermochemical processes are common options; however, these have significantly lower heat transfer capabilities than thermal oil, molten salt, or molten metal media. Conventional solar receivers operating temperatures >700 degrees Celsius face challenges including thermal performance and thermal-mechanical issues. To overcome these limitations, we have developed a novel light-trapping, planar-cavity receiver (LTPCR) that can heat solid-phase media within an enclosed receiver while maintaining a high aperture solar flux concentration for high efficiency. This paper presents progress on design, fabrication, and testing of a 100 kWt prototype receiver to demonstrate the LTPCR operability and its commercial feasibility.

14 SOLAR ENERGY↗
NASA NTRS1983

Screw expander for light duty diesel engines

Preliminary selection and sizing of a positive displacement screw compressor-expander subsystem for a light-duty adiabatic diesel engine; development of a mathematical model to describe overall efficiencies for the screw compressor and expander; simulation of operation to establish overall efficiency for a range of design parameters and at given engine operating points; simulation to establish potential net power output at light-duty diesel operating points; analytical determination of mass moments of inertia for the rotors and inertia of the compressor-expander subsystem; and preparation of engineering layout drawings of the compressor and expander are discussed. As a result of this work, it was concluded that the screw compressor and expander designed for light-duty diesel engine applications are viable alternatives to turbo-compound systems, with acceptable efficiencies for both units, and only a moderate effect on the transient response.

Source record↗
NASA NTRS1984

Hybrid integrated optic modules for real-time signal processing

The most recent progress on four relatively new hybrid integrated optic device modules in LiNbO3 waveguides and one in YIG/GGG waveguide that are currently being studied are discussed. The five hybrid modules include a time-integrating acoustooptic correlator, a channel waveguide acoustooptic frequency shifter/modulator, an electrooptic channel waveguide total internal reflection moculator/switch, an electrooptic analog-to-digital converter using a Fabry-Perot modulator array, and a noncollinear magnetooptic modulator using magnetostatic surface waves. All of these devices possess the desirable characteristics of very large bandwidth (GHz or higher), very small substrate size along the optical path (typically 1.5 cm or less), single-mode optical propagation, and low drive power requirement. The devices utilize either acoustooptic, electrooptic or magnetooptic effects in planar or channel waveguides and, therefore, act as efficient interface devices between a light wave and temporal signals. Major areas of application lie in wideband multichannel optical real-time signal processing and communications. Some of the specific applications include spectral analysis and correlation of radio frequency (RF) signals, fiber-optic sensing, optical computing and multiport switching/routing, and analog-to-digital conversion of wide RF signals.

Tsai, C. S.↗
NASA NTRS1989

Efficient Cavity-Dumped, Frequency-Doubled Nd:YAG Laser

New design expected to increase efficiency of cavity-dumped, frequency-doubled Nd:YAG laser. Frequency doubled outside primary laser resonator, and portion of fundamental-frequency light not used by doubler returned to primary laser cavity to increase efficiency. Applications of laser foreseen in data communictions, laser ranging, studies of atmosphere, remote sensing, and laboratory studies.

Robinson, D. L.↗
NASA NTRS1993

Planetary Instrument Definition and Development Program (PIDDP). Instrument for future planetary flight missions: A visible-infrared imaging spectrometer for planetary missions

The objective of this project is to develop and prove a small, light-weight, efficient imaging spectrometer design to cover the VIS/NIR spectral range for applications particularly but not exclusively to NASA inner solar system space missions. A design and a brassboard prototype will be developed and tested. Progress over the first year of this project includes design specification, optical design layout, grating specifications, infrared detector selection, and mechanical design. Mechanical and grating manufacturing drawings were begun. We developed an agreement in principle to cooperate with the German space group, DLR, to apply some of their electronics microminiaturization technology to this imaging spectrometer project, mostly or entirely at their expense. Funds from NASA for the second year of this effort have been received and the effort is on track. Release of funds for the third year of this award will be requested later this year in order to accelerate this work and bring it to a conclusion in time for new NASA missions considerations as well as to make effective use of the DLR contributions.

Mccord, Thomas B.↗
NASA NTRSDate not supplied

Advances in PSP Testing in LaRC High Reynolds Number Facilities

The use of luminescent coatings for the global measurement of surface aerodynamic properties at full-flight Reynolds numbers has been ongoing at the NASA Langley Research Center since the late 1990s, beginning with Temperature Sensitive Paint (TSP) for boundary layer analysis at the 0.3-m Transonic Cryogenics Tunnel. Since then, significant work has been made to extend these measurements to pressure using Pressure Sensitive Paint (PSP) as well as develop systems for application in larger scale, full-flight Reynolds number facilities, such as the National Transonic Facility (NTF). Recently, a system for the measurement of time-resolved pressure using recently developed unsteady PSP (uPSP) formulations has been designed and implemented in the Transonic Dynamics Tunnel (TDT). The use of PSP (or uPSP) in either of these large scale, full-fight Reynolds number wind tunnels is complicated by the fact that both facilities operate best in oxygen deficient environments; however, the PSP technique relies on the presence of oxygen to work. The NTF is typically operated in cryogenic conditions, which is achieved using liquid nitrogen. In this facility, temperatures can reach as low as 116 K (-250 °F) with nominal oxygen concentrations of less than 50 ppm. This has resulted in the development of specialized PSP formulations that can operate in the cryogenic environment with the introduction of low amounts of oxygen (typically less than 2000 ppm) for PSP response. Likewise, to achieve full-flight Reynolds number conditions in the TDT, the atmosphere in the tunnel is replaced with a “heavy gas” of R-134A (1,1,1,2-tetrafluoroethane), which also has minimal oxygen native in the flow. The use of uPSP in this case will also depend on the introduction of trace amounts of oxygen, with the precise concentrations to be determined in an upcoming test. This presentation will describe some recent advancements that have been made for PSP measurements in both facilities. For the NTF system, there has been significant development of enhanced lighting for use at cryogenic conditions, as well as improvements in the application efficiency of the PSP. Furthermore, there are efforts underway to incorporate advanced data analysis techniques to acquire additional surface aerodynamic properties using the PSP technique that can yield not only improved experimental efficiency, but also provide data needed for next generation vehicle design and development. For the uPSP system in TDT, significant efforts to improve the data transfer rates to a high-performance computing environment for analysis are underway and performance and initial results from the system in the heavy-gas environment will be presented.

Pressure Sensitive Paint↗
DOE OSTI2025

Solar Spectrum Conversion for an Algae Bioreactor (CRADA Final Report)

This project focused on developing advanced optical coatings to improve solar energy utilization. The research aimed to create lanthanide-doped upconversion nanoparticles (UCNPs) capable of capturing unused near-infrared (NIR) light from the sun and converting it into visible light (blue and red photons) that can be used for photosynthesis. The primary goal was to identify, synthesize, and integrate highly efficient UCNPs into a transparent thin-film device. Through a comprehensive workflow involving computer simulations, high-throughput robotic synthesis, and detailed optical characterization, the project successfully developed a high-performance material. The key technical achievement was the creation of a core-shell UCNP (NaYF₄:20%Yb³⁺, 2%Er³⁺ coated with a 10 nm NaYF₄ shell) that demonstrated a quantum yield of 3.2% for converting 980 nm NIR light into visible light. Transparent thin films fabricated from these nanoparticles showed excellent optical properties, confirming their potential for practical applications. This research adds to the scientific understanding of energy transfer in lanthanide materials and demonstrates a technically effective method for creating efficient light-converting coatings. The primary benefit to the public lies in the potential for these coatings to enhance the efficiency of solar-driven processes, such as boosting the growth of algae in photobioreactors for biofuel production.

14 SOLAR ENERGY↗
DOE OSTI2026

Prototype Development, Testing, and Modeling for a Solar Light-Trapping Planar-Cavity Particle Receiver (LTPCR)

Many applications for concentrating solar thermal power (CSP) technologies of high efficiency power cycles or thermochemical processes require higher operating temperatures and alternative heat transfer media. Inert solid particles for next-generation CSP and reactive gas and/or solid media for solar thermochemical processes are common options; however, these have significantly lower heat transfer capabilities than thermal oil, molten salt, or molten metal media. Conventional solar receivers operating temperatures >700 degrees Celsius face challenges including thermal performance and thermal-mechanical issues. To overcome these limitations, we have developed a novel light-trapping, planar-cavity receiver (LTPCR) that can heat solid-phase media within an enclosed receiver while maintaining a high aperture solar flux concentration for high efficiency. This paper presents progress on design, fabrication, and testing of a 100 kWt prototype receiver to demonstrate the LTPCR operability and its commercial feasibility.

14 SOLAR ENERGY↗
NASA NTRS1982

Losses in chopper-controlled DC series motors

Motors for electric vehicle (EV) applications must have different features than dc motors designed for industrial applications. The EV motor application is characterized by the following requirements: (1) the need for highest possible efficiency from light load to overload, for maximum EV range, (2) large short time overload capability (The ratio of peak to average power varies from 5/1 in heavy city traffic to 3/1 in suburban driving situations) and (3) operation from power supply voltage levels of 84 to 144 volts (probably 120 volts maximum). A test facility utilizing a dc generator as a substitute for a battery pack was designed and utilized. Criteria for the design of such a facility are presented. Two motors, differing in design detail, commercially available for EV use were tested. Losses measured are discussed, as are waves forms and their harmonic content, the measurements of resistance and inductance, EV motor/chopper application criteria, and motor design considerations.

Hamilton, H. B.↗
DOE OSTI2025

Operando Contactless EFISH Study of the Rate-Determining Step of Light-Driven Water Oxidation on TiO 2 Photoanodes

For many slow solar-fuel-forming reactions, the accumulation of photogenerated minority carriers on the photoelectrode surface leads to light-induced band edge unpinning, affecting the junction properties by decreasing band bending in the semiconductor space charge layer and increasing the driving force of surface reactions in the electric double layer. In this study, we demonstrate a contactless operando electric field-induced second harmonic generation (EFISH) method for measuring the band bending change (δΔΦ SCR L ) on photoelectrodes upon photoexcitation. For ndoped rutile TiO 2 water oxidation photoanodes at pH 7, δΔΦ SCR L increases at more positive potentials or higher illumination power density until it reaches saturation values. We show that under fast mass transport conditions, δΔΦ SCR L is exclusively attributed to the accumulated charged rate-determining species that can be regarded as temporary surface states, and the relationship between the photocurrent and δΔΦ SCR L can be well modeled by assuming that hole trap states function as the reaction center. Kinetic isotope experiments identify proton-coupled electron transfer as the rate-determining step and suggest a possible chemical nature of the key intermediate. We demonstrate that light-induced band edge unpinning is a beneficial feature under high illumination conditions for oxygen evolution reaction on TiO 2 because it maintains the photon-to-current conversion efficiency by enhancing the surface reaction driving force, shedding light on the actual device application.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRSDate not supplied

The Application of Photonic Lanterns in Free Space Optical Communications

Photonic lanterns offer an efficient solution to transition distorted light from free space into small aperture or single-mode waveguide devices. As a result, photonic lanterns can be useful for free space optical communications, where light is transmitted across a channel with varying atmospheric conditions. This paper will give an overview of studies using photonic lanterns in photon counting optical communication receivers where the detectors are small in aperture and fiber coupled. This paper will also survey other potential uses of photonic lanterns in coherent optical communication receivers or as wavefront sensors in adaptive optical systems.

Optical communications↗
NASA NTRSDate not supplied

The Application of Photonic Lanterns in Free Space Optical Communications

Photonic lanterns offer an efficient solution to transition distorted light from free space into small aperture or single-mode waveguide devices. As a result, photonic lanterns can be useful for free space optical communications, where light is transmitted across a channel with varying atmospheric conditions. This paper will give an overview of studies using photonic lanterns in photon counting optical communication receivers where the detectors are small in aperture and fiber coupled. This paper will also survey other potential uses of photonic lanterns in coherent optical communication receivers or as wavefront sensors in adaptive optical systems.

Optical communicatons↗
NASA NTRS2019

Airfoil Selection for Mars Rotor Applications

This short white paper is aimed at providing an overview of design considerations for airfoil choices for rotor applications in the Martian atmosphere, at very low chord-based Reynolds number flows, around Rec = O (103 -104). The low Reynolds number typical of rotorcraft operation in the Martian atmosphere reduces the rotor lifting force and efficiency, which is only partially compensated for by a lower gravity on Mars. Additionally, the low temperature and largely CO2 based atmosphere of Mars compound the overall aerodynamic problem by resulting in a lower speed of sound, further constraining rotor operation in the Martian atmosphere by limiting the maximum rotor tip speed possible so as not to exceed an acceptable tip Mach number. In light of the expected reduced rotor efficiency, evaluating airfoils for compressible, low-Reynolds number Mars rotor applications is key. Prior research on airfoil optimization and performance evaluation at low Reynolds numbers, especially in the compressible regime, is scarce and deserves further understanding. Specifically, the proposed goal stemming from this overview is to develop airfoils tailored to the unique demands of the second generation of Mars rotorcraft, i.e. the Mars Science Helicopter (MSH). This research focuses on the airfoil performance at low Reynolds numbers and hopes to add to the work performed by, amongst others, Kroo et al., Kunz and Kroo, Oyama and Fujii, Anyoji et al.

Koning, Witold J. F.↗