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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Determining plasmonic hot-carrier energy distributions via single-molecule transport measurements

Hot carriers in plasmonic nanostructures, generated via plasmon decay, play key roles in applications such as photocatalysis and in photodetectors that circumvent bandgap limitations. However, direct experimental quantification of steady-state energy distributions of hot carriers in nanostructures has so far been lacking. We present transport measurements from single-molecule junctions, created by trapping suitably chosen single molecules between an ultrathin gold film supporting surface plasmon polaritons and a scanning probe tip, that can provide quantification of plasmonic hot-carrier distributions. Our results show that Landau damping is the dominant physical mechanism of hot-carrier generation in nanoscale systems with strong confinement. The technique developed in this work will enable quantification of plasmonic hot-carrier distributions in nanophotonic and plasmonic devices.

Science & Technology - Other Topics↗
DOE OSTI2019

Quantifying Wavelength-Dependent Plasmonic Hot Carrier Energy Distributions at Metal/Semiconductor Interfaces

Hot carriers generated from the nonradiative decay of localized surface plasmons are capable of driving charge-transfer reactions at the surfaces of metal nanostructures. Photocatalytic devices utilizing plasmonic hot carriers are often based on metal nanoparticle/semiconductor heterostructures owing to their efficient electron–hole separation ability. The rapid thermalization of hot carriers generated at the metal nanoparticles yields a distribution of carrier energies that determines the capability of the photocatalytic device to drive redox reactions. Here in this paper, we quantify the thermalized hot carrier energy distribution generated at Au/TiO 2 nanostructures using wavelength-dependent scanning electrochemical microscopy and a series of molecular probes with different redox potentials. We determine the quantum efficiencies and oxidizing power of the hot carriers from wavelength-dependent reaction rates and photocurrent across the metal/semiconductor interface. The wavelength-dependent reaction efficiency tracks the surface plasmon resonance spectrum of the Au nanoparticles, showing that the reaction is facilitated by plasmon excitation, while the responses from molecules with different redox potentials shed light on the energy distribution of the hot holes generated at metal nanoparticle/semiconductor heterostructures. The results provide important insight into the energies of the plasmon-generated hot carriers and quantum efficiencies of plasmonic photocatalytic devices.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Alternative Energy Carriers: Unique Interfaces for Electrochemical Hydrogenic Transformations

Abstract The shift toward renewable energy generation sources, characterized by their non‐carbon emitting but variable nature, has spurred significant innovation in energy storage technologies. Advancements in foundational understanding from investments in basic science and clever engineering solutions, coupled with increasing industrial adoption, have resulted in a notable reduction in the cost of storing electricity from variable energy generation sources. These developments have paved the way for the exploration of new and innovative forms of energy storage that deviate from traditional technologies. In this perspective, it is posited that the progress made in energy storage research over recent years has opened the door to the development of energy carriers for technologies that are yet to be realized. To illustrate this concept, examples of alternative energy carriers are provided within the context of unique electrochemical interfaces for electrochemical hydrogenic transformations. The unique properties of these interfaces and electrochemical systems can be leveraged in ways not yet imagined, creating new possibilities for energy storage. A perspective on the progress and challenges for each interface as well as a general outlook for the advancement of energy carrier systems are provided.

25 ENERGY STORAGE↗
DOE OSTI2026

An Overview of Potential Future Aviation Energy Carriers

Global jet fuel demand is projected to grow to 165 billion gallons by 2050 and there is growing interest in the aviation industry to understand the capabilities of alternative energy carriers. This report considers several potential energy carriers, reviewing their production potential, operational considerations, and economic implications to inform potential next steps in aeronautics research. The following energy carriers (i.e., fuels) were evaluated in this study for future use in aviation: sustainable aviation fuel (SAF) - both biomass-based and power-to-liquids (PtL) - based SAF - cryogenic hydrogen (LH 2 ) - also known as liquid hydrogen - liquefied natural gas (LNG), liquefied ethane (LE), and Jet X. The barriers and opportunities for the evaluated energy carriers vary. SAF is a commercially available drop-in fuel compatible with existing aircraft and infrastructure. SAF is limited by both higher prices and slow commercialization of multiple pathways using different feedstocks necessary to significantly grow supply. Cryogenic fuels, in contrast, have very different thermal, physical, and chemical properties than SAF and Jet A, requiring the construction of new airport storage and dispensing infrastructure and the design of new aircraft energy systems capable of mitigating heat transfer and boil-off. Cryogenic fuels offer an opportunity to diversify aviation fuel carriers from domestic energy relevant for both energy security and resilience. This means cryogenic fuels are more of a longer-term solution for aircraft but are worth exploring for potential future cost savings and emissions benefits. Jet X refers to non-drop-in liquid hydrocarbon fuels in the early stages of investigation seeking favorable properties. There are substantial barriers to non-drop-in liquid aviation fuels that are not compatible with existing aircraft and fuel infrastructure.

33 ADVANCED PROPULSION SYSTEMS↗
NASA NTRS1973

A hydrogen energy carrier. Volume 2: Systems analysis

A systems analysis of hydrogen as an energy carrier in the United States indicated that it is feasible to use hydrogen in all energy use areas, except some types of transportation. These use areas are industrial, residential and commercial, and electric power generation. Saturation concept and conservation concept forecasts of future total energy demands were made. Projected costs of producing hydrogen from coal or from nuclear heat combined with thermochemical decomposition of water are in the range $1.00 to $1.50 per million Btu of hydrogen produced. Other methods are estimated to be more costly. The use of hydrogen as a fuel will require the development of large-scale transmission and storage systems. A pipeline system similar to the existing natural gas pipeline system appears practical, if design factors are included to avoid hydrogen environment embrittlement of pipeline metals. Conclusions from the examination of the safety, legal, environmental, economic, political and societal aspects of hydrogen fuel are that a hydrogen energy carrier system would be compatible with American values and the existing energy system.

Savage, R. L.↗
DOE OSTI2015

Transport and capture properties of Auger-generated high-energy carriers in (AlInGa)N quantum well structures

Recent photoluminescence experiments presented by M. Binder et al. [Appl. Phys. Lett. 103, 071108 (2013)] demonstrated the visualization of high-energy carriers generated by Auger recombination in (AlInGa)N multi quantum wells. Two fundamental limitations were deduced which reduce the detection efficiency of Auger processes contributing to the reduction in internal quantum efficiency: the transfer probability of these hot electrons and holes in a detection well and the asymmetry in type of Auger recombination. We investigate the transport and capture properties of these high-energy carriers regarding polarization fields, the transfer distance to the generating well, and the number of detection wells. All three factors are shown to have a noticeable impact on the detection of these hot particles. Furthermore, the investigations support the finding that electron-electron-hole exceeds electron-hole-hole Auger recombination if the densities of both carrier types are similar. Overall, the results add to the evidence that Auger processes play an important role in the reduction of efficiency in (AlInGa)N based LEDs.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

Clean Hydrogen: Energy Carrier, Renewables Enabler, and Sector Coupler to Accelerate the Energy Transition and Meet Climate Goals

Comprehensive, concerted efforts supported by the U.S. Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy (EERE), Hydrogen and Fuel Cell Technologies Office (HFTO) are advancing research and development to demonstrate clean hydrogen production and industrial decarbonization pathways. These pathways enable an economically competitive and environmentally beneficial future energy system across sectors and can address specific applications that are difficult to decarbonize. Initiatives include the Hydrogen Energy Earthshot, H2@Scale, National Clean Hydrogen Strategy and Roadmap, H2NEW: Hydrogen from Next-generation Electrolyzers of Water Consortium, HydroGEN: Advanced Water Splitting Materials Consortium, BioH2 Consortium, HyMARC Hydrogen Materials Advanced Research Consortium, and M2FCT: Million Mile Fuel Cell Truck Consortium.

clean hydrogen↗
DOE OSTI2019

H2@Scale: Opportunities for Hydrogen as an Energy Carrier

H2@Scale is a concept where hydrogen is an energy carrier that complements electricity and the natural gas system. This presentation summarizes the motivation for developing the H2@Scale concept and provides estimates of how large the hydrogen market could be.

08 HYDROGEN↗
DOE OSTI2023

High Thermoelectric Performance in 2D Sb 2 Te 3 and Bi 2 Te 3 Nanoplate Composites Enabled by Energy Carrier Filtering and Low Thermal Conductivity

Thermoelectrics are an important class of materials with great potential in alternative energy applications. In this study, two-dimensional (2D) nanoplates of the layered chalcogenides, Sb 2 Te 3 and Bi 2 Te 3 , are synthesized and composites of the two are investigated for their thermoelectric properties. The two materials, Sb 2 Te 3 and Bi 2 Te 3 , were synthesized as hexagonal, 2D nanoplates via a colloidal polyol route. The as-synthesized Sb 2 Te 3 and Bi 2 Te 3 vary drastically from one another in their lateral and vertical dimensions as revealed by scanning electron microscopy and atomic force microscopy. The single crystalline nanoplate nature is deduced by high-resolution transmission electron microscopy and selected area electron diffraction. Nanoplates have well-defined hexagonal facets as seen in the scanning and transmission electron microscopy images. The nanoplates were consolidated as an anisotropic nanostructured pellet via spark plasma sintering. Preferred orientation observed in the powder X-ray diffraction pattern and scanning electron microscopy images of the fractured pellets confirm the anisotropic structure of the nanoplates. Thermoelectric properties in the parallel and perpendicular directions were measured, revealing strong anisotropy with a significant reduction to thermal conductivity in the perpendicular direction due to increased phonon scattering at nanoplate interfaces. All compositions, except that of the 25% Bi 2 Te 3 nanoplate composite, behave as degenerate semiconductors with increasing electrical resistivity as the temperature increases. The Seebeck coefficient is also increased dramatically in the nanocomposites, the highest reaching 210 μV/K for 15% Bi 2 Te 3 . The increase in Seebeck is attributed to energy carrier filtering at the nanoplate interfaces. Overall, these enhanced thermoelectric properties lead to a drastic increase in the thermoelectric performance in the perpendicular direction, with zT ~ 1.26, for the 15% Bi 2 Te 3 nanoplate composite at 450 K.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Hydrogen energy carriers

The versatility of hydrogen will provide opportunities in large scale, long duration energy storage, and the decarbonization of industry. Further, hydrogen energy carriers are molecules and materials that store hydrogen at higher volumetric density than possible using gas phase hydrogen.

08 HYDROGEN↗
NASA NTRS1976

Thermodynamic analysis of alternate energy carriers, hydrogen and chemical heat pipes

The paper discusses the production concept and efficiency of two new energy transmission and storage media intended to overcome the disadvantages of electricity as an overall energy carrier. These media are hydrogen produced by water-splitting and the chemical heat pipe. Hydrogen can be transported or stored, and burned as energy is needed, forming only water and thus obviating pollution problems. The chemical heat pipe envisions a system in which heat is stored as the heat of reaction in chemical species. The thermodynamic analysis of these two methods is discussed in terms of first-law and second-law efficiency. It is concluded that chemical heat pipes offer large advantages over thermochemical hydrogen generation schemes on a first-law efficiency basis except for the degradation of thermal energy in temperature thus providing a source of low-temperature (800 K) heat for process heat applications. On a second-law efficiency basis, hydrogen schemes are superior in that the amount of available work is greater as compared to chemical heat pipes.

Cox, K. E.↗
DOE OSTI2024

The role of hydrogen as long-duration energy storage and as an international energy carrier for electricity sector decarbonization

With countries and economies around the globe increasingly relying on non-dispatchable variable renewable energy (VRE), the need for effective energy storage and international carriers of low-carbon energy has intensified. This study delves into hydrogen's prospective, multifaceted contribution to decarbonizing the electricity sector, with emphasis on its utilization as a scalable technology for long-duration energy storage and as an international energy carrier. Using Japan as a case study, based on its ambitious national hydrogen strategy and plans to import liquefied hydrogen as a low-carbon fuel source, we employ advanced models encompassing capacity expansion and hourly dispatch. We explore diverse policy scenarios to unravel the timing, quantity, and operational intricacies of hydrogen deployment within a power system. Our findings highlight the essential role of hydrogen in providing a reliable power supply by balancing mismatches in VRE generation and load over several weeks and months and reducing the costs of achieving a zero-emission power system. The study recommends prioritizing domestically produced hydrogen, leveraging renewables for cost reduction, and strategically employing imported hydrogen as a risk hedge against potential spikes in battery storage and renewable energy costs. Furthermore, the strategic incorporation of hydrogen mitigates system costs and enhances energy self-sufficiency, informing policy design and investment strategies aligned with the dynamic global energy landscape.

08 HYDROGEN↗
DOE OSTI2026

Mechanistic Tuning of Chemical Transformations for Coupling the Geo-mimicry of Acid Gas Storage with Design Strategies to Produce Clean Energy Carriers in Multi-Phase Reaction Environments (MATTER) (Final Report)

The need to diversify approaches to produce essential energy carriers such as H 2 motivate advances in thermodynamically downhill geo-inspired pathways. Currently, more than 80% of hydrogen is produced via steam methane reforming (SMR) followed by water gas shift reaction (WGSR) pathway with the co-production of CO 2 . As an alternative to introducing CO 2 separation strategies downstream such as the use of membranes, solvents, or sorbents, geo-inspired carbon mineralization is harnessed as an alternative crystallization pathway. The thermodynamically downhill carbon mineralization pathways are hypothesized to accelerate H2 conversion while separating CO 2 . The work conducted through this project discusses the mechanisms associated with coupling the water gas shift reaction (WGSR) with carbon mineralization. In addition to harnessing Ca- and Mg-bearing oxides or hydroxides that are known to be reactive for CO 2 capture, the use of earth abundant silicate minerals such as Ca- and Mg-bearing silicates, is also investigated. Key outcomes include approaches to architect Mg-silicate with well-controlled pore size distributions, probing the enhancement in H 2 yield with inherent CO 2 suppression using Ca- and Mg-bearing oxides, hydroxides, and silicates, elucidating the changes in silicate chemistry during carbon mineralization, and exploring direct integration of carbon mineralization with WGSR and the development of separate low temperature pathway for reactive CO 2 capture and mineralization are developed.

08 HYDROGEN↗
DOE OSTI2019

Dopant-Dependent Increase in Seebeck Coefficient and Electrical Conductivity in Blended Polymers with Offset Carrier Energies

The strong and counterproductive interrelationship of thermoelectric parameters remains a bottleneck to improving thermoelectric performance, especially in polymer-based materials. In this paper, we decouple the electrical conductivity and Seebeck coefficient, achieving increases in at least one of these two parameters while the other is maintained or slightly increased as well. This is done using an alkylthio-substituted polythiophene (PQTS12) as additive in poly(bisdodecylquaterthiophene) (PQT12) with tetrafluorotetracyanoquinodimethane (F4TCNQ) and nitrosyl tetrafluoroborate (NOBF4) as dopants. The power factor increased two orders of magnitude with the PQTS12 additive at constant doping level. Using a second pair of polymers, poly(2,5-bis(3-dodecylthiophen-2-yl)thieno[3,2-b]thiophene (PBTTTC12) and poly(2,5-bis(3-dodecylthiothiophen-2-yl)thieno[3,2-b]thiophene, (PBTTTSC12), with higher mobilities, we also observed the decoupling of the Seebeck coefficient and electrical conductivity, and achieved higher power factor. Distinguished from recently reported works, these two sets of polymers possess very closely offset carrier energy levels (0.05 ~ 0.07 eV), and the microstructure, assessed using grazing incidence X-ray scattering, and mobility evaluated in field-effect transistors, was not adversely affected by the blending. Experiments, calculations and simulations are consistent with the idea that blending and doping polymers with closely-spaced energy levels and compatible morphologies to promote carrier mobility favors increased power factors.

42 ENGINEERING↗
DOE OSTI2017

Renewable energy carriers derived from concentrating solar power and nonstoichiometric oxides

In this study, we offer a perspective on the current state of material research in a part of the solar fuels community that exploits process heat derived from concentrated solar energy to power simple thermochemical gas-splitting cycles. The working fluid in this process is a nonstoichiometric oxide subject to extreme conditions that repeatedly distorts the lattice by forcing oxygen atoms to move in and out of the crystal. This technology is currently challenged by a need to discover optimal materials and derive robust processes to increase cycle efficiency. In the realm of emerging technologies for converting solar insulation to portable and storable energy carriers, this approach has already proven to be scalable with demonstrations that approach 100 kW. Innovations in materials and methods are required to increase solar utilization and process efficiency in order to achieve commercial viability.

14 SOLAR ENERGY↗
NASA NTRS1973

A hydrogen energy carrier. Volume 1: Summary

The production, technology, transportation, and implementation of hydrogen into the energy system are discussed along with the fossil fuel cycle, hydrogen fuel cycle, and the demands for energy. The cost of hydrogen production by coal gasification; electrolysis by nuclear energy, and solar energy are presented. The legal aspects of a hydrogen economy are also discussed.

Savage, R. L.↗
NASA NTRS1976

Thermodynamic analysis of alternate energy carriers, hydrogen and chemical heat pipes

Hydrogen and chemical heat pipes were proposed as methods of transporting energy from a primary energy source (nuclear, solar) to the user. In the chemical heat pipe system, primary energy is transformed into the energy of a reversible chemical reaction; the chemical species are then transmitted or stored until the energy is required. Analysis of thermochemical hydrogen schemes and chemical heat pipe systems on a second law efficiency or available work basis show that hydrogen is superior especially if the end use of the chemical heat pipe is electrical power.

Cox, K. E.↗