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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 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

Mechanism of Pinhole Formation in Membrane Electrode Assemblies for PEM Fuel Cells

The pinhole formation mechanism was studied with a variety of MEAs using ex-situ and in-situ methods. The ex-situ tests included the MEA aging in oxygen and MEA heat of ignition. In-situ durability tests were performed in fuel cells at different operating conditions with hydrogen and oxygen. After the in-situ failure, MEAs were analyzed with an Olympus BX 60 optical microscope and Cambridge 120 scanning electron microscope. MEA chemical analysis was performed with an IXRF EDS microanalysis system. The MEA failure analyses showed that pinholes and tears were the MEA failure modes. The pinholes appeared in MEA areas where the membrane thickness was drastically reduced. Their location coincided with the stress concentration points, indicating that membrane creep was responsible for their formation. Some of the pinholes detected had contaminant particles precipitated within the membrane. This mechanism of pinhole formation was correlated to the polymer blistering.

Stanic, Vesna↗
NASA NTRS2004

Evaluation of a Hydrogen Fuel Cell Powered Blended-Wing-Body Aircraft Concept for Reduced Noise and Emissions

This report describes the analytical modeling and evaluation of an unconventional commercial transport aircraft concept designed to address aircraft noise and emission issues. A blended-wing-body configuration with advanced technology hydrogen fuel cell electric propulsion is considered. Predicted noise and emission characteristics are compared to a current technology conventional configuration designed for the same mission. The significant technology issues which have to be addressed to make this concept a viable alternative to current aircraft designs are discussed. This concept is one of the "Quiet Green Transport" aircraft concepts studied as part of NASA's Revolutionary Aerospace Systems Concepts (RASC) Program. The RASC Program was initiated to develop revolutionary concepts that address strategic objectives of the NASA Enterprises, such as reducing aircraft noise and emissions, and to identify advanced technology requirements for the concepts.

Guynn, Mark D.↗
NASA NTRS2007

Energy Storage: Batteries and Fuel Cells for Exploration

NASA's Vision for Exploration requires safe, human-rated, energy storage technologies with high energy density, high specific energy and the ability to perform in a variety of unique environments. The Exploration Technology Development Program is currently supporting the development of battery and fuel cell systems that address these critical technology areas. Specific technology efforts that advance these systems and optimize their operation in various space environments are addressed in this overview of the Energy Storage Technology Development Project. These technologies will support a new generation of more affordable, more reliable, and more effective space systems.

Manzo, Michelle A.↗
NASA NTRS2007

Brazing of Stainless Steel to Yttria-Stabilized Zirconia Using Gold-Based Brazes for Solid Oxide Fuel Cell Applications

Two gold-base active metal brazes (gold-ABA and gold-ABA-V) were evaluated for oxidation resistance to 850 C, and used to join yttria-stabilized zirconia (YSZ) to a corrosion-resistant ferritic stainless steel for possible use in solid oxide fuel cells. Thermogravimetric analysis and optical microscopy and scanning electron microscopy coupled with energy-dispersive spectroscopy were used to evaluate the braze oxidation behavior, and microstructure and composition of the YSZ/braze/steel joints. Both gold-ABA and gold-ABA-V exhibited nearly linear oxidation kinetics at 850 C, with gold-ABA-V showing faster oxidation than gold-ABA. Both brazes produced metallurgically sound YSZ/steel joints due to chemical interactions of Ti and V with the YSZ and steel substrates.

Singh, M.↗
NASA NTRS1981

Development status of a regenerative fuel cell system for orbital operation

Mission studies conducted by NASA for future long-term orbital operations have indicated the need for substantial increases in the power level of low-earth orbital energy storage facilities by the mid-to-late 1980's. A description is presented of the results of a comprehensive study for a state-of-the-art assessment of solid polymer electrolyte electrochemical cell technology. Questions related to the weight optimization of the dedicated system are investigated, and attention is given to the analysis of a system having reversible modules capable of operating in either the electrolysis or fuel cell mode. It was found that performance improvements and weight reduction can be realized by advancing the state of the art of solid polymer electrolyte cell technology.

Erickson, A. C.↗
NASA NTRS1979

Analysis of a fuel cell on-site integrated energy system for a residential complex

Declining supplies of domestic oil and gas and the increased cost of energy resulted in a renewed emphasis in utilizing available resources in the most efficient manner possible. This, in turn, brought about a reassessment of a number of methods for converting fossil fuels to end uses at the highest practical efficiency. One of these is the on-site integrated energy system (OS/IES). This system provides electric power from an on-site power plant and recovers heat from the power plant that would normally be rejected to the environment. An OS/IES is potentially useful in any application that requires both electricity and heat. Several OS/IES are analyzed for a residential complex. The paper is divided into two sections; the first compares three energy supply systems, the second compares various designs for fuel cell OS/IES.

Simons, S. N.↗
NASA NTRS1980

Non-noble catalysts and catalyst supports for phosphoric acid fuel cells

Tungsten carbide, which is known to be active for hydrogen oxidation and CO tolerant has a hexagonal structure. Titanium carbide is inactive and has a cubic structure. Four different samples of the cubic alloys Wx-1TixC were prepared and found to be active and CO tolerant. These alloys are of interest as possible phosphoric acid fuel cell catalysts. They also are of interest as opportunities to study the activity of W in a different crystalline environment and to correlate the activities of the surface sites with surface composition.

Mcalister, A. J.↗
NASA NTRS1986

Modeling for CO poisoning of a fuel cell anode

Poisoning losses in a half-cell in the 110-190 C temperature range have been measured in 100 wt pct H3PO4 for various mixtures of H2, CO, and CO2 gases in order to investigate the polarization loss due to poisoning by CO of a porous fuel cell Pt anode. At a fixed current density, the poisoning loss was found to vary linearly with ln of the CO/H2 concentration ratio, although deviations from linearity were noted at lower temperatures and higher current densities for high CO/H2 concentration ratios. The surface coverages of CO were also found to vary linearly with ln of the CO/H2 concentration ratio. A general adsorption relationship is derived. Standard free energies for CO adsorption were found to vary from -14.5 to -12.1 kcal/mol in the 130-190 C temperature range. The standard entropy for CO adsorption was found to be -39 cal/mol per deg K.

Dhar, H. P.↗
NASA NTRS1991

Regenerative fuel cell architectures for lunar surface power

Power needs projected for the lunar and Mars exploration missions range from a few kilowatts for initial manned outposts and rovers to hundreds of kilowatts for permanent bases and in-situ resource utilization. The 354 hour lunar night presents a formidable challenge in energy storage systems for non-nuclear power systems. The Photovoltaic/Regenerative Fuel Cell (PV/RFC) power system is currently being considered as an option to meet the initial low power requirements. For lunar applications, the RFC mass can be a critical driver in the overall PV/RFC system mass. For the long duration nighttime operation missions, the hydrogen/oxygen (H2/O2) reactants and storage are the dominant components from a mass standpoint. It is important, therefore, to examine options which may reduce the reactant and storage mass and, thereby, result in mass savings for the overall PV/RFC system. Various RFC configurations for the stationary lunar missions has been examined using Rocketdyne's RFC computer model. For the stationary applications, a GaAs/Ge PV array with a 3000 psi gas storage proton exchange membrane (PEM) RFC providing 25 kWe during the day and 12.5 kWe at night was designed. PV/RFC systems utilizing super-critical H2/O2 storage and Cryogenic H2/O2 storage for the RFCs were then compared with the baseline high pressure gas storage RFC system. Preliminary results indicate that for long duration nighttime operation missions, the super-critical H2/O2 storage RFC systems offer over 20% mass advantage over the high pressure gas storage while the mass savings for the cryogenic H2/O2 storage RFC systems can be as high as 30%.

D W Harris↗
NASA NTRS2019

NASA Fuel Cell and Hydrogen Activities

This very high-level summary presentation covers 2019 NASA activities pertinent to the terrestrial hydrogen economy in general and the Department of Energy "H2@Scale" initiative in particular. The presentation introduces NASA and provides a basic review of relevant electrochemical systems before conveying basic technologies for a Lunar hydrogen economy starting with energy storage options of batteries and regenerative fuel cells before delving into locally generated and cryogenically stored propellant through in situ resource utilization (ISRU) methods.

Jakupca, Ian↗
NASA NTRS2020

Feasibility of a Solid Oxide Fuel Cell System Applied to Hybrid-Electric Regional Aircraft

NASA’s vision for the future of flight includes highly energy efficient aircraft that are environmentally friendly and have positive national economic impact. Although battery-powered electric aircraft are a viable alternative to reduce environmental impact, purely electric aircraft have drawbacks such as the low specific energy of batteries, which translates to an unfavorable weight scaling. Solid oxide fuel cell (SOFC) systems also have promise in providing environmentally friendly electrical power for new aircraft configurations at a higher efficiency than current methods, such as electrical generators. This study explores the use of the Fostering Ultra-Efficient, Low Emitting Aviation Power (FUELEAP) power system architecture for hybrid-electric regional aircraft. The FUELEAP power system utilizes a SOFC as part of a hybrid-electric power system architecture, enabling higher efficiency and specific power with a reduction in carbon and NOx emissions compared to state-of-the-art hybrid-electric SOFC architectures. The study includes comparisons of hybrid-electric power architectures and integration of the FUELEAP power system for two regional-sized passenger aircraft concepts. Results suggest that use of the FUELEAP power system as a replacement for onboard batteries may provide up to a 50% reduction in the weight of the electric d energy system for a typical regional aircraft mission.

Geuther, Steven↗
NASA NTRS1980

Study of fuel cell on-site, integrated energy systems in residential/commercial applications

Three building applications were selected for a detailed study: a low rise apartment building; a retail store, and a hospital. Building design data were then specified for each application, based on the design and construction of typical, actual buildings. Finally, a computerized building loads analysis program was used to estimate hourly end use load profiles for each building. Conventional and fuel cell based energy systems were designed and simulated for each building in each location. Based on the results of a computer simulation of each energy system, levelized annual costs and annual energy consumptions were calculated for all systems.

Wakefield, R. A.↗
NASA NTRS1996

Modeling of Thermal Performance of Multiphase Nuclear Fuel Cell Under Variable Gravity Conditions

A unique numerical method has been developed to model the dynamic processes of bulk evaporation and condensation processes, associated with internal heat generation and natural convection under different gravity levels. The internal energy formulation, for the bulk liquid-vapor phase change problems in an encapsulated container, was employed. The equations, governing the conservation of mass, momentum and energy for both phases involved in phase change, were solved. The thermal performance of a multiphase uranium tetra-fluoride fuel element under zero gravity, micro-gravity and normal gravity conditions has been investigated. The modeling yielded results including the evolution of the bulk liquid-vapor phase change process, the evolution of the liquid-vapor interface, the formation and development of the liquid film covering the side wall surface, the temperature distribution and the convection flow field in the fuel element. The strong dependence of the thermal performance of such multiphase nuclear fuel cell on the gravity condition has been revealed. Under all three gravity conditions, 0-g, 10(exp -3)-g, and 1-g, the liquid film is formed and covers the entire side wall. The liquid film covering the side wall is more isothermalized at the wall surface, which can prevent the side wall from being over-heated. As the gravity increases, the liquid film is thinner, the temperature gradient is larger across the liquid film and smaller across the vapor phase. This investigation provides valuable information about the thermal performance of multi-phase nuclear fuel element for the potential space and ground applications.

Ding, Z.↗
NASA NTRS1975

Lightweight fuel cell powerplant for Tug

The design and characteristics of a lightweight powerplant based on advanced cell technology to meet the requirements of the Space Tug are described. The powerplant can be operated off low-pressure hydrogen and oxygen rocket propellant tanks and avoid the need for a dedicated reactant supply. Product water can be condensed or not, depending on vehicle or payload requirements. The heart of the unit, the fuel cell power section, consist of lightweight, series-connected, alkaline cells, while the power section contains accessory components for reactant conditioning, distribution, and venting, coolant circulation, passive product water removal and electric control. The proposed design offers at least a 50 per cent saving in powerplant weight, so that the total estimated powerplant dry weight including structure, tubing, wiring, interface connectors, and interface heat exchanger is 48 lb.

Handley, L. M.↗
NASA NTRS1998

Systems Analysis in Support of the NASA Fuel Cell Upgrade Program for the Space Shuttle Orbiter

In early 1996 as part of NASA's overall efforts to improve space shuttle operations, NASA undertook an internal assessment of the shuttle to identify subsystems in the greatest need of upgrading. The criteria used to rank the candidate subsystems were safety improvement, reduction in acquisition and operational costs, improvement in fleet supportability, improvement in mission effectiveness, implementation risk, and commonality with future NASA missions. On the basis of the preliminary results of the NASA assessment, the Fuel Cell Power Plant (FCP) for the shuttle orbiter was among those subsystems selected for further consideration.

Hoberecht, Mark A.↗
NASA NTRS1981

Non-noble catalysts and catalyst supports for phosphoric acid fuel cells

Tungsten carbide, which is active for hydrogen oxidation, is CO tolerant and has a hexagonal structure is discussed. Titanium carbide is inactive and has a cubic structure. Four different samples of the cubic alloys W sub x-1Ti sub XC sub 1-y were found to be active and CO tolerant. When the activities of these cubic alloys are weighted by the reciprocal of the square to those of highly forms of WC. They offer important insight into the nature of the active sites on W-C anode catalysts for use in phosphoric acid fuel cells.

Mcalister, A. J.↗
NASA NTRS1981

Non-noble catalysts and catalyst supports for phosphoric acid fuel cells

Four different samples of the cubic alloys W sub x-1 Ti sub x C sub 1-y were prepared and found to be active and CO tolerant. When the activities of these cubic alloys were weighted by the reciprocal of the square of the W exchange, they displayed magnitudes and dependence on bulk C deficiency comparable to those of highly active forms of WC. It is concluded that they may offer important insight into the nature of the active sites on, and means for improving the performance of, W-C anode catalysts for use in phosphoric acid fuel cells.

Mcalister, A. J.↗
NASA NTRS2004

Electrochemical Characterization of Carbon Nanotubes for Fuel Cell MEA's

Single-walled and multi-walled carbon nanotubes from different sources have been evaluated before and after sonication to identify structural differences and evaluate electrochemical performance. Raman spectral analysis and cyclic voltammetry in situ with QCM were the principle means of evaluating the tubes. The raman data indicates that sonication in toluene modifies the structural properties of the nanotubes. Sonication also affects the electrochemical performance of single-walled nanotubes and the multi-walled tubes differently. The characterization of different types of carbon nanotubes leads up to identifying a potential candidate for incorporating carbon nanotubes for fuel cell MEA structures.

Panagaris, Jael↗