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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 1,135 records · Page 63
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

A program for the calculation of paraboloidal-dish solar thermal power plant performance

A program capable of calculating the design-point and quasi-steady-state annual performance of a paraboloidal-concentrator solar thermal power plant without energy storage was written for a programmable calculator equipped with suitable printer. The power plant may be located at any site for which a histogram of annual direct normal insolation is available. Inputs required by the program are aperture area and the design and annual efficiencies of the concentrator; the intercept factor and apparent efficiency of the power conversion subsystem and a polynomial representation of its normalized part-load efficiency; the efficiency of the electrical generator or alternator; the efficiency of the electric power conditioning and transport subsystem; and the fractional parasitic loses for the plant. Losses to auxiliaries associated with each individual module are to be deducted when the power conversion subsystem efficiencies are calculated. Outputs provided by the program are the system design efficiency, the annualized receiver efficiency, the annualized power conversion subsystem efficiency, total annual direct normal insolation received per unit area of concentrator aperture, and the system annual efficiency.

Bowyer, J. M., Jr.↗
NASA NTRS1984

Towards a 20 percent efficient silicon solar cell

A project is underway at the University of New South Wales aimed at producing a 20 percent efficient silicon solar cell. A prerequisite for obtaining such a significant increase in cell efficiency is the improvement of the open circuit voltage of these cells. Two techniques are described which have produced experimental devices with open circuit voltages of 690 mV or higher. These high voltage techniques have been combined with other high efficiency design features to produce silicon cells with independently measured energy conversion efficiencies in excess of 19 percent under standard terrestrial test conditions (direct beam AM1.5 spectrum, 100 mW/sq cm, 28 C).

Green, M. A.↗
NASA NTRS1962

Time-Dependent Structure of the Upper Atmosphere

The physical properties of the upper atmosphere are determined mainly by heat conduction, the heat sources and the barometric law. An analysis of the integro-differential equation which describes these physical processes has been carried out. It is found that heating of the thermosphere due to absorption of the solar extreme ultraviolet (EUV) radiation alone cannot explain the observed diurnal variation of density and temperature, since it would yield a maximum of these properties at about 17h local time, instead of 14h where it is observed. Secondly, if the EUV flux is adjusted to give the observed average temperature, then the diurnal variation in density would be much too large compared with the observed amplitude. Thirdly, it would require an extremely high efficiency for the conversion of EUV radiation into heat, if we compare the required flux with Hinteregger's measurements of the EUV flux. Thus, it is necessary to have another heat source in addition to the heating due to absorption of EUV radiation. If an additional beat source is used, which has a maximum at about 9h local time and a flux of 1 erg cm−1 sec−1, a time-dependent model of the upper atmosphere is obtained that is in good agreement with the observed densities. There is evidence that this additional heat source derives its energy ultimately from the solar corpuscular radiation. In this paper we present the results of calculations for a model in the equatorial and temperature zones of the earth, for those times when the average solar activity corresponds to a solar radiation flux of 200×110−22 Wm−2 (cps)−1 at 10.7-cm wavelength. The physical properties (temperature, density, pressure, scale height, mean molecular weight and the number densities of N2, O2, O, He and H) are given as a function of local time and for the altitudes between 120 km and 2050 km.

ATMOSPHERE↗
DOE OSTI2020

Carbon quantum dots interfacial modified graphene/silicon Schottky barrier solar cell

The two-dimensional thin film, as an effective interface modification layer to improve the power conversion efficiency (PCE) of graphene/silicon (Gr/Si) heterojunction solar cells has attracted extensive attention recently. However, the complicated manufacturing process and specialized equipment requirements impede its broad application. Herein, carbon quantum dots (CQDs) fabricated under the mild reaction condition was first time used to modify Gr/Si devices interface structure. The effects of CQDs size distributions and coating thickness on J-V characteristics and the energy band structure of Gr/CQDs/Si solar cells were systematically analyzed. The findings indicate that the PCE of resulting Gr/CQDs/Si solar cells could reach 9.97% when the thickness and sizes of CQDs interlayer are ~26 nm and 4–7 nm, without any chemical doping, which is 6.8-times PCE than that of virgin Gr/Si solar cells. The CQDs interlayer serves as both an electron blocking layer and hole transport layer to reduce the carrier recombination, leading to a lower reverse saturation current as well as a larger VOC then improved the device performance. The enhanced PCE shows that the CQDs species have the potential applications in a cost-effective photovoltaic device.

14 SOLAR ENERGY↗
NASA NTRS1974

Energetic solar proton versus terrestrially trapped proton fluxes for the active years 1977 - 1983

Ratios of solar to trapped proton fluences were computed for circular-orbit, geocentric space missions to be flown during the active phase of the next solar cycle (1977-1983). The ratios are presented as functions of orbit altitude and inclination, mission duration, proton energy threshold, and the chance the mission planner is willing to take that the actually encountered solar proton fluence will exceed the design fluence provided by the statistical solar proton model. It is shown that the ratio is most sensitively dependent on orbit altitude and inclination, with trapped protons dominant for low inclination, low and mid altitude orbits and for high inclination, mid altitude orbits. Conversely, solar protons are dominant for high inclination, low altitude orbits, and for low and high inclination, high altitude orbits.

King, J. H.↗
NASA NTRS1981

Design, fabrication, and bench testing of a solar chemical receiver

Solar thermal energy can be effectively collected, transported, stored, and utilized by means of a chemical storage and transport system employing the reversible SO2 oxidation reaction. A solar chemical receiver for SO3 thermal decomposition to SO2 and oxygen was analyzed. Bench tests of a ten foot section of a receiver module were conducted with dissociated sulfuric acid (SO3 and H2O) in an electrical furnace. Measured percent conversion of SO3 was 85% of the equilibrium value. Methods were developed to fabricate and assemble a complete receiver module. These methods included applying an aluminide coating to certain exposed surfaces, assembling concentric tubes with a wire spacer, applying a platinum catalyst to the tubing wall, and coiling the entire assembly into the desired configuration.

Summers, W. A.↗
NASA NTRS1992

Relation of the lunar power system to the SEI program and to landers

The people of Earth will need more than 20,000 billion watts (GWe) of electric power by 2050 for a high level of prosperity. Power needs in the 22nd Century could exceed 100,000 GWe. By 2100 the total quantity of thermal energy used could fully deplete the known inventory (10(exp 7) GWt-Y) of all non-renewable sources on Earth except for deuterium and hydrogen for use in proposed fusion reactors. The labor, capital, and mass of power plants required to produce 1 GWe-Y of energy from present-day power plants is summarized. Fossil and nuclear plants respectively consume 80 to 190 M$ and 12 to 48 M$ of fuel per GWe-Y. The Lunar Power System (LPS) uses solar power bases on the moon to beam electric power to Earth. The LPS in the figure supplies load-following power to rectennas on Earth. Additional solar power conversion units are located across the lunar limb from their respective Earthward transmitting stations. LPS can be augmented by mirrors in polar orbit about the moon. The construction of rectennas on Earth determines the base cost (0.001s$/kWe-H) of LPS power. A manned International Lunar Base (ILB) can accelerate the development of LPS by providing the initial transportation and habitation facilities and base operations. ILB can greatly reduce up front costs and risks by emplacing a moderate scale LPS (1-100 GWe). LPS can accelerate the development of the ILB by providing greater funding than is reasonable to expect for purely scientific research. An international ILB/LPS program can foster world trust and prosperity.

Criswell, David R.↗
DOE OSTI2022

Simultaneously Enhancing Exciton/Charge Transport in Organic Solar Cells by an Organoboron Additive

Efficient exciton diffusion and charge transport play a vital role in advancing the power conversion efficiency (PCE) of organic solar cells (OSCs). Here, a facile strategy is presented to simultaneously enhance exciton/charge transport of the widely studied PM6:Y6-based OSCs by employing highly emissive trans-bis(dimesitylboron)stilbene (BBS) as a solid additive. BBS transforms the emissive sites from a more H-type aggregate into a more J-type aggregate, which benefits the resonance energy transfer for PM6 exciton diffusion and energy transfer from PM6 to Y6. Transient gated photoluminescence spectroscopy measurements indicate that addition of BBS improves the exciton diffusion coefficient of PM6 and the dissociation of PM6 excitons in the PM6:Y6:BBS film. Transient absorption spectroscopy measurements confirm faster charge generation in PM6:Y6:BBS. Moreover, BBS helps improve Y6 crystallization, and current-sensing atomic force microscopy characterization reveals an improved charge-carrier diffusion length in PM6:Y6:BBS. Finally, owing to the enhanced exciton diffusion, exciton dissociation, charge generation, and charge transport, as well as reduced charge recombination and energy loss, a higher PCE of 17.6% with simultaneously improved open-circuit voltage, short-circuit current density, and fill factor is achieved for the PM6:Y6:BBS devices compared to the devices without BBS (16.2%).

14 SOLAR ENERGY↗
DOE OSTI2023

Characterization of high-temperature figure of merit for solar-thermal absorbers

The figure of merit (FOM) is a widely used metric to characterize the solar-thermal conversion performance of solar absorber layers. Many of previous works have reported FOMs estimated from the radiative properties measured at room temperature. However, advanced concentrated solar power (CSP) plants operate at very high temperatures (~750°C), which can strongly affect the absorber’s radiative properties. Here, the present work proposes using a 1-D conduction-based reference bar technique to directly measure the converted thermal energy to determine the FOM at high absorber temperatures (≳ 750°C) while operating under a large solar concentration (~ 1200 x suns). Using the finite difference method, we carefully analyze several key parameters influencing the design of the experimental setup, such as temperature distribution, material properties, heat loss, and sensor accuracy. In addition, a rigorous uncertainty analysis is incorporated into the FOM to ascertain the confidence level of the result. We validate this new technique on a custom-built tungsten reference bar with an oxidized Inconel 625 solar-thermal absorber. A good agreement between the model and the experiment shows the reliability of the FOM measurement with a well-defined uncertainty. The same method can be implemented to measure the high-temperature FOM of most surface or volumetric solar absorbers for CSP.

14 SOLAR ENERGY↗
NASA NTRS1975

NASA Office of Aeronautics and Space Technology Summer Workshop. Volume 4: Power technology panel

Technology requirements in the areas of energy sources and conversion, power processing, distribution, conversion, and transmission, and energy storage are identified for space shuttle payloads. It is concluded that the power system technology currently available is adequate to accomplish all missions in the 1973 Mission Model, but that further development is needed to support space opportunities of the future as identified by users. Space experiments are proposed in the following areas: power generation in space, advanced photovoltaic energy converters, solar and nuclear thermoelectric technology, nickel-cadmium batteries, flywheels (mechanical storage), satellite-to-ground transmission and reconversion systems, and regenerative fuel cells.

Source record↗
NASA NTRS1986

Advanced solar thermal technologies for the 21st century

The paper considers the present status of solar thermal dynamic space power technologies and projects the various attributes of these systems into the future, to the years 2000 and 2010. By the year 2000, collector weights should decrease from 1.25 kg/sq m (1985 value) to about 1.0 kg/sq m. The specific weight is also expected to decrease from 6.0 kg/kw. By the year 2010, slight improvements in the free piston Stirling energy conversion system are postulated with efficiencies reaching 32 percent. In addition, advanced concentrator concepts should be operational.

Kohout, L. L.↗
NASA NTRS1989

Soliton and strong Langmuir turbulence in solar flare processes

The occurrence of modulational instability in the current sheet of a solar flare is investigated. Special attention is given to the plasma microinstability in this sheet and its relation to the flare process. It is found that solitons or strong Langmuir turbulence are likely to occur in the diffusion region under solar flare conditions in which the electric resistivity could be enhanced by several orders of magnitude in the region, resulting in significant heating and stochastic acceleration of particles. A numerical example is used to demonstrate the transition of the magnetic field velocity and plasma density from the outer MHD region into the diffusive region and then back out again with the completion of the energy conversion process. This is all made possible by an increase in resistivity of four to five orders of magnitude over the classical value.

Song, M. T.↗
DOE OSTI2025

Investigation of Solid Particle Reactors for Nonoxidative Dehydrogenation of Ethane: Toward Solar Thermal Ethylene Production

Concentrating solar power plants can generate renewable heat at temperatures well above those of most industrial processes. Ceramic particles irradiated with concentrated sunlight can store high-quality sensible heat and transfer this to power generation systems. These concepts and materials hold great potential to also enable thermal processes in the chemical industry, but effective strategies for transferring heat from thermal energy storage media into chemical reactors are still under development. This present work evaluated the thermal and chemical compatibility of various solid particle media (including quartz, bauxite, and alumina particles) integrated directly into tube reactors and the subsequent effects on reactor performance for the nonoxidative dehydrogenation of ethane reaction. Empty tube reactors without loaded particles (representing conventional ethane cracking coils) showed significant heat transfer limitations as the tube diameter was scaled. The incorporation of media into the reactor significantly aided heat transfer to the gaseous ethane reactant and increased its conversion by as much as 10% at similar space velocities. Despite direct contact with hydrocarbon gases, alumina and quartz media showed negligible coke formation. Even during reaction in 100% ethane feed gas at 825 °C, the average selectivity of the coke product was only 0.57% when using the quartz media. These materials further demonstrated excellent thermal stability during subsequent reoxidation in air at 800 °C, which simulated the reheating of particles in a circulating particle solar receiver. Conversely, high rates of coke formation, with a product selectivity of 27.5%, were observed on sintered bauxite particles during the reaction, likely promoted by transition metal constituents. These particles fractured upon reoxidation due to exotherms generated from coke combustion. In conclusion, while the use of cofed steam could mitigate attrition of redox-active particles, the ability of inert metal oxide particles to efficiently transfer heat to concentrated ethane reactant gas while suppressing side reactions or degradation suggests that these media could effectively couple solar thermal plants to reactors for next-generation production of ethylene and other critical chemicals.

Hydrocarbons↗
DOE OSTI2019

Developing Efficient Perovskite/Silicon Tandem Devices

This project aims at developing highly efficient perovskite/silicon tandem solar cells by developing efficient perovskite top cells, silicon bottom cells, and monolithically integrating the subcells for highly efficient tandem solar cells. The project focused on increasing the efficiency of perovskite solar cells to 20% and understanding related materials science and device physics, as well as developing a compatible bottom high-efficiency c-Si solar cell. The perovskite cells with a wide bandgap of 1.61 eV and 1.84 eV are fabricated by a low-cost, low-temperature, scalable solution process on lower bandgap silicon bottom cells. The bandgaps of perovskite top cells have been tuned between 1.61 eV and 1.84 eV by composition engineering mainly through controlling the halide mixing ratio in perovskite materials. The efficiencies of the wide bandgap perovskite solar cells have been improved to an excellent efficiency of 21.0% for perovskites with a bandgap of 1.63 eV with increased grain size, reduced energy disorder at cathode contact, and defect passivation. We invented a solvent annealing approach with solvent vapor during thermal annealing to enlarge grain size of perovskite film which reduces the charge trap density and improves the device efficiency. Moreover, we discovered that the non-wetting surface could further increase the grain size for perovskite films, because non-wetting surface could prevent the formation of too dense nuclei from heterogeneous nucleation process. We proposed to reduce the energy disorder of organic charge extraction layer to reduce the power loss in perovskite cells. We pioneered defect passivation concept and techniques to suppress the charge non-radiative recombination in perovskite solar cells to boost the efficiency. For the silicon bottom cell development, different from the conventional silicon cell work under full illumination, the light available for the silicon bottom cell in tandem structure is mainly NIR region. We developed a NIR enhanced silicon cell with efficiency of 21.2% by applying a double-layer antireflection coating at the front side and a MgF2 back reflector layer at the rear side. For the perovskite/silicon tandem device, we achieved a highest reported power conversion efficiency of 25.4% in 2018, and further increased the efficiency up to 26.0% in 2019. The research on tandem solar cells focused on reducing reflection loss to <5% at spectrum of 300-1100 nm by antireflection layer, tuning the bandgap of perovskite film for matched current density between sub-cells, and utilizing a ITO layer between perovskite top cell and silicon bottom cell as interconnect layer without Voc loss. Finally, we developed a blading technique to fabricate perovskite films which produces perovskite solar cells with comparable or even superior efficiency to those made by non-scalable spin coating method. This paves the way for scaling up perovskite/silicon tandem solar cells using solution approach.

14 SOLAR ENERGY↗
DOE OSTI2022

Mechanochemistry of Phosphorus and Arsenic Alloys for Visible and Infrared Photonics

Incorporating few‐layer 2D phosphorus–arsenic alloys (PAs) into optoelectronic devices requires a synthesis technique that allows control of the alloy composition while producing volumes of material suitable for application development such as photodetectors, solar cells, and lasers. With that goal in mind, high‐energy ball milling allows production of both orthorhombic (o‐PAs) and trigonal (t‐PAs) alloys by reacting red phosphorus and metallic arsenic powders. The synthesis follows a two‐step process in which arsenic rapidly reacts with red phosphorus to first produce t‐PAs followed by a slower phase transformation into o‐PAs; synthesis time and overall conversion rate are slightly enhanced by the presence of arsenic. Optical measurements on exfoliated alloys at the few‐layer atomic limit of the 2D PAs reveal emission spanning from the visible (≈1.9 eV) into the near‐infrared region, covering a broad application space. Rapid powder synthesis within a closed system for stochiometric control of the solid‐solution PAs alloys combined with solution‐based exfoliation opens up opportunities for a whole new class of optoelectronic devices based on PA nanomaterials.

Pedersen, Samuel V.↗
DOE OSTI2020

CsI-Antisolvent Adduct Formation in All-Inorganic Metal Halide Perovskites

The excellent optoelectronic properties shown by hybrid organic/inorganic metal halide perovskites are all predicated on precisely controlling the exact nucleation and crystallization dynamics that occur during film formation. In general, high-performance thin films are obtained by a method commonly called solvent engineering (or antisolvent quench) processing. The solvent engineering method removes excess solvent, but importantly leaves behind solvent that forms chemical adducts with the lead-halide precursor salts. These adduct-based precursor phases control nucleation and the growth of the polycrystalline domains. There has not yet been a comprehensive study comparing the various antisolvents used in different perovskite compositions containing cesium. In addition, there have been no reports of solvent engineering for high efficiency in all-inorganic perovskites such as CsPbI 3 . In this work, inorganic perovskite composition CsPbI 3 is specifically targeted and unique adducts formed between CsI and precursor solvents and antisolvents are found that have not been observed for other A-site cation salts. These CsI adducts control nucleation more so than the PbI 2 -dimethyl sulfoxide (DMSO) adduct and demonstrate how the A-site plays a significant role in crystallization. The use of methyl acetate (MeOAc) in this solvent engineering approach dictates crystallization through the formation of a CsI-MeOAc adduct and results in solar cells with a power conversion efficiency of 14.4%.

14 SOLAR ENERGY↗
DOE OSTI2022

Device Performance of Emerging Photovoltaic Materials (Version 3)

Abstract Following the 2nd release of the “Emerging PV reports,” the best achievements in the performance of emerging photovoltaic devices in diverse emerging photovoltaic research subjects are summarized, as reported in peer‐reviewed articles in academic journals since August 2021. Updated graphs, tables, and analyses are provided with several performance parameters, e.g., power conversion efficiency, open‐circuit voltage, short‐circuit current density, fill factor, light utilization efficiency, and stability test energy yield. These parameters are presented as a function of the photovoltaic bandgap energy and the average visible transmittance for each technology and application, and are put into perspective using, e.g., the detailed balance efficiency limit. The 3rd installment of the “Emerging PV reports” extends the scope toward triple junction solar cells.

14 SOLAR ENERGY↗
DOE OSTI2021

Effect of heterostructure engineering on electronic structure and transport properties of two-dimensional halide perovskites

Organic-inorganic halide perovskite solar cells have attracted much attention due to their low-cost fabrication, flexibility, and high-power conversion efficiency. More recent efforts show that the reduction from three- to two-dimensions (2D) of organic–inorganic halide perovskites promises an exciting opportunity to tune their electronic properties. Here, we explore the effect of reduced dimensionality and heterostructure engineering on the intrinsic material properties, such as energy stability, bandgap and transport properties of 2D hybrid organic–inorganic halide perovskites using first-principles density functional theory. We show that the energy stability of engineered perovskite heterostructures is significantly enhanced. The heterostructures with improved stability also show excellent transport properties similar to their bulk counterparts. Furthermore, these layered chemistries demonstrate the advantage of a broad range of tunable bandgaps and high-absorption coefficient in the visible spectrum. The proposed 2D heterostructured material holds potential for nano-optoelectronic devices as well as for effective photovoltaics.

36 MATERIALS SCIENCE↗