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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 55 records · Page 3

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NASA NTRS1974

Electrically rechargeable redox flow cells

Considering the topographical and sizing requirements for a typical pumped water storage installation and the immergence of energy conversion schemes that are time dependent as to their generating capability, a closer look is being given to nonpumped water storage schemes for storing electricity. An electrochemical bulk power storage concept, which was named a rechargeable redox flow cell is described. This scheme, based on pumping a redox couple through a power conversion section, appears to offer high overall efficiency, no cycle life limitations for the electrodes, and deep discharger capability.

Thaller, L. H.↗

NASA NTRS1974

Electrically rechargeable redox flow cells

Considering the topographical and sizing requirements for a typical pumped water storage installation and the immergence of energy conversion schemes that are time-dependent as to their generating capability, a closer look is being given to nonpumped water storage schemes for storing electricity. An electrochemical bulk power storage concept, called a rechargeable redox flow cell, is described. This scheme, based on pumping a redox couple through a power conversion section, appears to offer high overall efficiency, no cycle life limitations for the electrodes, and deep discharge capability.

Thaller, L. H.↗

NASA NTRS1979

Efficiency optimization of a thermionic converter array

Intensive study of the outer planets of the solar system requires the use of nuclear power for electric propulsion of spacecraft. Among the power conversion devices being considered for this application are thermionic converters. This paper presents the results of computer modeling of thermionic converters to identify the major design variables and select an optimum size for each of the thermionic converters for the power conversion system under consideration. Among the variables investigated were electrical and thermal losses in electrodes, leads and heat chokes. Those elements which minimized the electrical losses tended to increase thermal losses and system weight. Overall mechanical design and relative positioning of components also had impacts on converter efficiency and the power subsystem weight. Numerical calculations were made using the computer heat transfer code SINDA coupled with electrical loss parameters. The results of the computations are presented in this paper.

Kuo, Y. S.↗

NASA NTRS1983

Six-Axis Electrical-Discharge Machine

Electrical discharge machine (EDM) of unusual versitility made by conversion of radial drill. Drilling head is replaced by ram that holds and positions electrode. Tank and recirculation system for coolant are added. EDM has six independent motions and drastically reduced cost of manufacturing. New applications are constantly being found.

Werner, A. R.↗

NASA NTRS1976

Photoassisted electrolysis of water - Conversion of optical to chemical energy

A description is given of devices, termed photoelectrochemical cells, which can, in principle, be used to directly convert light to fuels and/or electricity. The fundamental principles on which the photoelectrochemical cell is based are related to the observation that irradiation of a semiconductor electrode in an electrochemical cell can result in the flow of an electric current in the external circuit. Attention is given to the basic mechanisms involved, the energy conversion efficiency, the advantages of photoelectrochemical cells, and the results of investigations related to the study of energy conversion via photoelectrochemical cells.

Wrighton, M. S.↗

NASA NTRS2003

A miniaturized neuroprosthesis suitable for implantation into the brain

This paper presents current research on a miniaturized neuroprosthesis suitable for implantation into the brain. The prosthesis is a heterogeneous integration of a 100-element microelectromechanical system (MEMS) electrode array, front-end complementary metal-oxide-semiconductor (CMOS) integrated circuit for neural signal preamplification, filtering, multiplexing and analog-to-digital conversion, and a second CMOS integrated circuit for wireless transmission of neural data and conditioning of wireless power. The prosthesis is intended for applications where neural signals are processed and decoded to permit the control of artificial or paralyzed limbs. This research, if successful, will allow implantation of the electronics into the brain, or subcutaneously on the skull, and eliminate all external signal and power wiring. The neuroprosthetic system design has strict size and power constraints with each of the front-end preamplifier channels fitting within the 400 x 400-microm pitch of the 100-element MEMS electrode array and power dissipation resulting in less than a 1 degree C temperature rise for the surrounding brain tissue. We describe the measured performance of initial micropower low-noise CMOS preamplifiers for the neuroprosthetic.

Action Potentials/physiology↗

NASA NTRS2015

Martian Superoxide and Peroxide O2 Release (OR) Assay: A New Technology for Terrestrial and Planetary Applications

This study presents an assay for the detection and quantification of soil metal superoxides and peroxides in regolith and soil. The O2 release (OR) assay is based on the enzymatic conversion of the hydrolysis products of metal oxides to O2, and their quantification by an O2 electrode based on the stoichiometry of the involved reactions: The intermediate product O2 from the hydrolysis of metal superoxides is converted by cytochrome c to O2, and also by superoxide dismutase (SOD) to 1/2 mol O2 and 1/2 mol H2O2, which is then converted by catalase (CAT) to 1/2 mol O2. The product H2O2 from the hydrolysis of metal peroxides and hydroperoxides is converted to 1/2 mol O2 by CAT. The assay-method was validated in a sealed sample chamber using a liquid-phase Clark-type O2 electrode with known concentrations of O2 and H2O2, and with commercial metal superoxide and peroxide mixed with Mars analogue Mojave and Atacama Desert soils. Carbonates and perchlorates, both present on Mars, do not interfere with the assay. The assay lower limit of detection, using luminescence quenching/optical sensing O2-electrodes, is 1 nmol O2 cm(exp. -3) or better. The activity of the assay enzymes SOD and cytochrome c was unaffected up to 6 Gy exposure by gamma-radiation, while CAT retained 100% and 40% of its activity at 3 and 6 Gy, respectively, demonstrating the suitability of these enzymes for planetary missions, e.g., in Mars or Europa.

soil metal superoxides and peroxides↗

NASA NTRS1976

Conversion of laser energy to chemical energy by the photoassisted electrolysis of water

Ultraviolet irradiation of the n-type semiconductor TiO2 crystal electrode of an aqueous electrochemical cell evolves O2 at the TiO2 electrode and H2 at the Pt electrode. The gases are typically evolved in a 2:1 (H2:O2) volume ratio. The photoassisted reaction seems to require applied voltages, but values as low as 0.25 V do allow the photoassisted electrolysis to proceed. Prolonged irradiation in either acid or base evolves the gaseous products in amounts which clearly demonstrate that the reaction is catalytic with respect to the TiO2. The wavelength response of the TiO2 and the correlation of product yield and current are reported. The results support the claim that TiO2 is a true photoassistance agent for the electrolysis of water. Minimum optical storage efficiencies of the order of 1 percent can be achieved by the production of H2.

Wrighton, M. S.↗

NASA NTRS1978

Preliminary results on the conversion of laser energy into electricity

A preliminary experiment was performed to investigate conversion of 10.6 micron laser energy to electrical energy via a laser-sustained argon plasma. Short-circuit currents of 0.7 A were measured between a thoriated-tungsten emitter and collector electrodes immersed in the laser-sustained argon plasma. Open-circuit voltages of about 1.5 V were inferred from the current-voltage load characteristics. The dominant mechanism of laser energy conversion is uncertain at this time. Much higher output powers appear possible.

Thompson, R. W.↗

NASA NTRS1977

High efficiency thermionic converter studies

Research in thermionic energy conversion technology is reported. The objectives were to produce converters suitable for use in out of core space reactors, radioisotope generators, and solar satellites. The development of emitter electrodes that operate at low cesium pressure, stable low work function collector electrodes, and more efficient means of space charge neutralization were investigated to improve thermionic converter performance. Potential improvements in collector properties were noted with evaporated thin film barium oxide coatings. Experiments with cesium carbonate suggest this substance may provide optimum combinations of cesium and oxygen for thermionic conversion.

Huffman, F. N.↗

NASA NTRS2014

Novel Materials, Processing and Device Technologies for Space Exploration with Potential Dual-Use Applications

We highlight results of a broad spectrum of efforts on lower-temperature processing of nanomaterials, novel approaches to energy conversion, and environmentally rugged devices. Solution-processed quantum dots of copper indium chalcogenide semiconductors and multiwalled carbon nanotubes from lower-temperature spray pyrolysis are enabled by novel (precursor) chemistry. Metal-doped zinc oxide (ZnO) nanostructured components of photovoltaic cells have been grown in solution at low temperature on a conductive indium tin oxide substrate. Arrays of ZnO nanorods can be templated and decorated with various semiconductor and metallic nanoparticles. Utilizing ZnO in a more broadly defined energy conversion sense as photocatalysts, unwanted organic waste materials can potentially be repurposed. Current efforts on charge carrier dynamics in nanoscale electrode architectures used in photoelectrochemical cells for generating solar electricity and fuels are described. The objective is to develop oxide nanowire-based electrode architectures that exhibit improved charge separation, charge collection and allow for efficient light absorption. Investigation of the charge carrier transport and recombination properties of the electrodes will aid in the understanding of how nanowire architectures improve performance of electrodes for dye-sensitized solar cells. Nanomaterials can be incorporated in a number of advanced higher-performance (i.e. mass specific power) photovoltaic arrays. Advanced technologies for the deposition of 4H-silicon carbide are described. The use of novel precursors, advanced processing, and process studies, including modeling are discussed from the perspective of enhancing the performance of this promising material for enabling technologies such as solar electric propulsion. Potential impact(s) of these technologies for a variety of aerospace applications are highlighted throughout. Finally, examples are given of technologies with potential spin-offs for dual-use or terrestrial applications.

solid state devices↗

NASA NTRSDate not supplied

Molten Salt Electrolytes: Computational Analysis of Transport, Electrochemical Properties and Designing New Mixtures

Electric aircraft propulsion has gained a traction over the last decade due to possible high-energy density electrochemistries with reasonable cycle life and identification of non-flammable chemistries that can guarantee much better safety. Commercial Li-ion batteries cannot reach such high capacities because of weight limitations that arise from the widely used intercalation electrodes. Also, use of organic electrolytes make them highly susceptible to fire on exposure to air and humidity. Currently, use of Lithium metal anode along with conversion electrochemistries such as Li-O2 and Li-S are being pursued to achieve such high energy densities. Safer inorganic solid-state electrolytes, recently discovered Water-in-Salt electrolytes, molten salt electrolytes are some of the alternatives being pursued for a safer/non-flammable battery. Of these safer alternatives, molten-salt electrolytes offer some attractive properties: liquid at operating temperatures resulting in better electrode-wetting, stable interface with Li-metal anodes and good ionic conductivity; their only drawback being high operating temperatures. In this talk, we will discuss some of the computational studies, driven via atomistic simulations, of the properties of molten-salt electrolytes including transport mechanism and interface stability. We will also discuss predicting electrochemical properties of these high-temperature electrolytes. Further, we will discuss a thermodynamic approach to predicting new molten-salt eutectics with lower melting points.

Molten Salt Electrolytes↗

NASA NTRS1972

The development of a non-cryogenic nitrogen/oxygen supply system

Development of the hydrazine/water electrolysis process in a manned spacecraft to provide metabolic oxygen and both oxygen and nitrogen for cabin leakage makeup was studied. Electrode development efforts were directed to stability, achieved with catalyst additives and improved processing techniques, and a higher hydrazine conversion efficiency, achieved by reducing catalyst loading on the cathodes. Extensive testing of the one-man breadboard N2/02 system provided complete characterization of cabin atmosphere control aspects. A detailed design of a prototype modular N2/02 unit was conducted. The contact heat exchanger which is an integral component of this design was fabricated and sucessfully design-verification tested.

Greenough, B. M.↗

NASA NTRS1974

Energy-conversion research and development with diminiodes

Diminiodes are variable-gap cesium diodes with plane emitters and guarded collectors a few millimeters in diameter. This miniaturization allows the electrodes to be made of little pieces of rare materials like single crystals of unusual metals or metallides. In addition to smallness, diminiode advantages include simplicity, precision, fabrication ease, parts interchangeability, cleanliness, full instrumentation, ruggedness, and economy. The diminiode design also stresses effective, economical use with computers that control, collect, and correlate thermionic current and voltage data. Such diminiode tests completed recently for ultrapure metal electrodes produced relatively low, sharply defined ultimate power outputs.

Morris, J. F.↗

NASA NTRS2015

Novel Materials, Processing, and Device Technologies for Space Exploration with Potential Dual-Use Applications

We highlight results of a broad spectrum of efforts on lower-temperature processing of nanomaterials, novel approaches to energy conversion, and environmentally rugged devices. Solution-processed quantum dots of copper indium chalcogenide semiconductors and multi-walled carbon nanotubes from lower-temperature spray pyrolysis are enabled by novel (precursor) chemistry. Metal-doped zinc oxide (ZnO) nanostructured components of photovoltaic cells have been grown in solution at low temperature on a conductive indium tin oxide substrate. Arrays of ZnO nanorods can be templated and decorated with various semiconductor and metallic nanoparticles. Utilizing ZnO in a more broadly defined energy conversion sense as photocatalysts, unwanted organic waste materials can potentially be re-purposed. Current efforts on charge carrier dynamics in nanoscale electrode architectures used in photoelectrochemical cells for generating solar electricity and fuels are described. The objective is to develop oxide nanowire-based electrode architectures that exhibit improved charge separation, charge collection and allow for efficient light absorption. Investigation of the charge carrier transport and recombination properties of the electrodes will aid in the understanding of how nanowire architectures improve performance of electrodes for dye-sensitized solar cells. Nanomaterials can be incorporated in a number of advanced higher-performance (i.e. mass specific power) photovoltaic arrays. Advanced technologies for the deposition of 4H-silicon carbide are described. The use of novel precursors, advanced processing, and process studies, including modeling are discussed from the perspective of enhancing the performance of this promising material for enabling technologies such as solar electric propulsion. Potential impact(s) of these technologies for a variety of aerospace applications are highlighted throughout. Finally, examples are given of technologies with potential spin-offs for dual-use or terrestrial applications.

thin films↗

NASA NTRS1982

The alkali metal thermoelectric converter /AMTEC/ - A new direct energy conversion technology for aerospace power

A thermally regenerative electrochemical device for the direct conversion of heat to electrical energy, the alkali metal thermoelectric converter (AMTEC), is characterized by potential efficiencies on the order of 15-40% and possesses no moving parts, making it a candidate for space power system applications. Device conversion efficiency is projected on the basis of experimental voltage vs current curves exhibiting power densities of 0.7 W/sq cm and measured electrode efficiencies of up to 40%. Preliminary radiative heat transfer measurements presented may be used in an investigation of methods for the reduction of AMTEC parasitic radiation losses. AMTEC assumes heat input and rejection temperatures of 900-1300 K and 400-800 K, respectively. The working fluid is liquid sodium, and the porous electrode employed is of molybdenum.

Bankston, C. P.↗

NASA NTRS2006

Alpha-Voltaic Sources Using Liquid Ga as Conversion Medium

A family of proposed miniature sources of power would exploit the direct conversion of the kinetic energy of alpha particles into electricity. In addition to having long operational lives, these sources are expected to operate with energy-conversion efficiencies from 70 to 90 percent. A power source as proposed (see figure) would be an electrolytic cell in which liquid gallium would serve as both an electrolyte and an energy-conversion medium. The cell would contain an iridium cathode and a zirconium anode. The alpha particles, each with a kinetic energy approx.5.8 MeV, would be emitted by radioactive decay of Cm-244, which has a half-life of 18 years. The Cm-244 source would be positioned so that the a particles would enter the liquid gallium, where their kinetic energy would be dissipated mostly through ionization of Ga atoms, creating Ga(+) ions and free electrons. The electrons would be collected by iridium cathode, and the Ga(+) ions would be neutralized at the zirconium cathode by electrons returning after flowing through an external circuit. Gallium is a candidate for use as the electrolyte and the energy-conversion medium because in the liquid state it is a semimetal: its electrical conductivity is greater than that of a typical semiconductor but small in comparison with the conductivities of metals. Consequently, in liquid gallium, electrons and Ga(+) can exist without immediate recombination and can be moved by electric fields. It is expected that electric fields, resulting at least partly from the difference between the work functions of the electrode metals, would move the electrons and ions to their respective electrodes. The open-circuit potential of the cell is expected to be 1.62 V - equal to the difference between the work functions of iridium and zirconium. Unlike in a solid-state energy conversion medium, the impingement of energetic a particles would not give rise to displacement damage in the liquid gallium. Hence, the cell should have a long life, limited only by the half-life of Cm-244. A cell having a volume less than 25 cu mm, containing 1 curie of Cm-244 (the curie is a unit of radioactivity equal to 3.7 10(exp 10) disintegrations per second) is expected to deliver a current between 7 and 12 mA, which, at the expected open-circuit potential, would provide a power in the approximate range of 11 to 20 mW.

Patel, Jagdish U.↗

NASA NTRS1987

Negative-Electrode Catalysts for Fe/Cr Redox Cells

Electrodes perform more consistently and less expensive. Surfaces catalyzed by bismuth and bismuth/lead developed for application on chromium electrode in iron/chromium redox electrochemical energy storage system. NASA Fe/Cr storage system incorporates two soluble electrodes consisting of acidified solutions of iron chloride (FeC13 and FeC12) and chromium chloride (CrC13 and CrC12) oxidized and reduced in power-conversion unit to store and produce electricity. Electrolytes circulated with pumps and stored in external tanks.

Gahn, R. F.↗