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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

A potential-energy surface study of the 2A1 and low-lying dissociative states of the methoxy radical

Accurate, ab initio quantum chemical techniques are applied in the present study of low lying bound and dissociative states of the methoxy radical at C3nu conformations, using a double zeta quality basis set that is augmented with polarization and diffuse functions. Excitation energy estimates are obtained for vertical excitation, vertical deexcitation, and system origin. The rate of methoxy photolysis is estimated to be too small to warrant its inclusion in atmospheric models.

Jackels, C. F.↗
NASA NTRS1987

Potential energy surfaces for atomic oxygen reactions: Formation of singlet and triplet biradicals as primary reaction products with unsaturated organic molecules

The experimental study of the interaction of atomic oxygen with organic polymer films under LEO conditions has been hampered by the inability to conduct detailed experiments in situ. As a result, studies of the mechanism of oxygen atom reactions have relied on laboratory O-atom sources that do not fully reproduce the orbital environment. For example, it is well established that only ground electronic state O atoms are present at LEO, yet most ground-based sources are known to produce singlet O atoms and molecules and ions in addition to O(3P). Engineers should not rely on such facilities unless it can be demonstrated either that these different O species are inert or that they react in the same fashion as ground state atoms. Ab initio quantum chemical calculations have been aimed at elucidating the biradical intermediates formed during the electrophilic addition of ground and excited-state O atoms to carbon-carbon double bonds in small olefins and aromatic molecules. These biradicals are critical intermediates in any possible insertion, addition and elimination reaction mechanisms. Through these calculations, we will be able to comment on the relative importance of these pathways for O(3P) and O(1D) reactions. The reactions of O atoms with ethylene and benzene are used to illustrate the important features of the mechanisms of atomic oxygen reaction with unsaturated organic compounds and polymeric materials.

Jaffe, Richard L.↗
NASA NTRS1992

Computed potential energy surfaces for chemical reactions

The work on the NH + NO system which was described in the last progress report was written up and a draft of the manuscript is included in the appendix. The appendix also contains a draft of a manuscript on an Ar + H + H surface. New work which was completed in the last six months includes the following: (1) calculations on the (1)CH2 + H2O, H2 + HCOH, and H2 + H2CO product channels in the CH3 + OH reaction; (2) calculations for the NH2 + O reaction; (3) calculations for the CH3 + O2 reaction; and (4) calculations for CH3O and the two decomposition channels--CH2OH and H + H2CO. Detailed descriptions of this work will be given in manuscripts; however, brief descriptions of the CH3 + OH and CH3 + O2 projects are given.

Heinemann, K.↗
NASA NTRS1993

Computed Potential Energy Surfaces for Chemical Reactions

A manuscript describing the calculations on the (1)CH2 + H2O, H2 + HCOH, and H2 + H2CO product channels in the CH3 + OH reaction, which were described in the last progress report, has been accepted for publication in J. Chem. Phys., and a copy of the manuscript is included in the appendix. The production of (1)CH2 in this reaction is important in hydrocarbon combustion since (1)CH2 is highly reactive and would be expected to insert into N2, possibly leading to a new source for prompt NO(x) (vide infra). During the last six months new calculations have been carried out for the NH2 + NO system, which is important in the thermal de-NO(x) process.

Heinemann, K.↗
NASA NTRS2001

Effective Potential Energies and Transport Properties for Nitrogen and Oxygen

The results of recent theoretical studies for N--N2, O--O2, N2--N2 interactions are applied to the transport properties of nitrogen and oxygen gases. The theoretical results are used to select suitable oxygen interaction energies from previous work for determining the diffusion and viscosity coefficients at high temperatures. A universal formulation is applied to determine the collision integrals for O2--O2 interactions at high temperatures and to calculate certain ratios for determining higher-order collision integrals.

Stallcop, James R.↗
NASA NTRS2005

Reliable Spectroscopic Constants for CCH-, NH2- and Their Isotopomers from an Accurate Potential Energy Function

Accurate quartic force fields have been determined for the CCH- and NH2- molecular anions using the singles and doubles coupled-cluster method that includes a perturbational estimate of the effects of connected triple excitations, CCSD(T). Very large one-particle basis sets have been used including diffuse functions and up through g-type functions. Correlation of the nitrogen and carbon core electrons has been included, as well as other "small" effects, such as the diagonal Born-Oppenheimer correction, and basis set extrapolation, and corrections for higher-order correlation effects and scalar relativistic effects. Fundamental vibrational frequencies have been computed using standard second-order perturbation theory as well as variational methods. Comparison with the available experimental data is presented and discussed. The implications of our research for the astronomical observation of molecular anions will be discussed.

Lee, Timothy J.↗
DOE OSTI2023

Demand reduction and energy saving potential of thermal energy storage integrated heat pumps [Réduction de la demande et potentiel d'économie d'énergie des pompes à chaleur avec stockage d'énergie thermique intégré]

A heat pump (HP) moves heat from a low-temperature source to a high-temperature sink with an input of energy. Often, one temperature body fluctuates with time (e.g., diurnal ambient temperature), causing the HP efficiency to vary. Integrating thermal energy storage (TES) into a HP system adds a third temperature body, enabling the HP to be advantageously coupled to any two: the application, the ambient, or the TES at strategic times. Although TES integration with HPs is an important emerging technology to lower energy consumption and decrease energy demand during critical times, the favorable circumstances for TES integration are poorly understood. Here, this paper establishes the energy reduction and demand reduction potential of TES-integrated HPs with both analytical and numerical HP models. All possible temperature arrangements are considered for HP-TES systems with two fixed temperature bodies (application and TES) and one variable temperature (ambient). Results show that overall energy savings are most attainable when the TES temperature is near the application temperature, whereas a large temperature difference between the TES and the application leads to the most peak demand reduction. The potential for overall energy savings increases as the magnitude of ambient temperature fluctuations increases.

25 ENERGY STORAGE↗
DOE OSTI2025

Wind and solar energy droughts: Potential impacts on energy system dynamics and research needs

This Perspective article provides a brief overview of the topic of wind and solar energy droughts (henceforth WSDs). It does not attempt to provide a complete literature review of the subject but rather highlights some of the main concepts associated with WSDs. These include wind and solar energy drought definitions and metrics; meteorological conditions producing WSDs; a comparison of their characteristics with hydrologic droughts and hydropower droughts; model-based and observational datasets useful for WSD analyses; the linkage of WSDs to transmission, storage, and demand response; the potential impacts of WSDs vs energy demand variations; wind and solar flood events; WSD predictability; WSD dependency on climate modes of variability; climate change impacts on WSDs; and the special challenge of evaluating the characteristics of WSDs in developing countries that have limited historical data available. Finally, the manuscript identifies research areas that the authors believe would provide immediate benefit to energy system planners.

14 SOLAR ENERGY↗
DOE OSTI2021

Miscellaneous Electric Loads: Characterization and Energy Savings Potential

Over time, miscellaneous electric loads (MELs) are expected to increase both in magnitude and share of residential and commercial building energy consumption. This trend is most apparent in North America, but it is also occurring in Japan and Europe. However, the contribution of MELs to building energy use is not currently well understood, both because the products in this category are transforming rapidly and the definition and classification of MELs is ambiguous. This study estimated the national energy consumption of 36 MELs using best-available data and found them to comprise 12% of delivered electricity to the U.S. residential and commercial building sectors. If 26 of these MELs were replaced with the most energy-efficient product models available on the market, their energy consumption could be halved to 6% of delivered electricity. National energy models will better account for building energy consumption by incorporating the MELs data collected and analyzed for this study, leading to improved policy decisions.

Miscellaneous electric loads, Plug loads, Taxonomy↗
DOE OSTI2023

Shadow energy functionals and potentials in Born–Oppenheimer molecular dynamics

In Born–Oppenheimer molecular dynamics (BOMD) simulations based on the density functional theory (DFT), the potential energy and the interatomic forces are calculated from an electronic ground state density that is determined by an iterative self-consistent field optimization procedure, which, in practice, never is fully converged. The calculated energies and forces are, therefore, only approximate, which may lead to an unphysical energy drift and instabilities. Here, we discuss an alternative shadow BOMD approach that is based on backward error analysis. Instead of calculating approximate solutions for an underlying exact regular Born–Oppenheimer potential, we do the opposite. Instead, we calculate the exact electron density, energies, and forces, but for an underlying approximate shadow Born–Oppenheimer potential energy surface. In this way, the calculated forces are conservative with respect to the approximate shadow potential and generate accurate molecular trajectories with long-term energy stabilities. We show how such shadow Born–Oppenheimer potentials can be constructed at different levels of accuracy as a function of the integration time step, δt, from the constrained minimization of a sequence of systematically improvable, but approximate, shadow energy density functionals. For each energy functional, there is a corresponding ground state Born–Oppenheimer potential. These pairs of shadow energy functionals and potentials are higher-level generalizations of the original “zeroth-level” shadow energy functionals and potentials used in extended Lagrangian BOMD. The proposed shadow energy functionals and potentials are useful only within this extended dynamical framework, where also the electronic degrees of freedom are propagated as dynamical field variables together with the atomic positions and velocities. The theory is quite general and can be applied to MD simulations using approximate DFT, Hartree–Fock, or semi-empirical methods, as well as to coarse-grained flexible charge models.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2009

Investigation of Condensing Ice Heat Exchangers for MTSA Technology Development

Metabolic heat regenerated Temperature Swing Adsorption (MTSA) technology is being developed for thermal, carbon dioxide (CO2) and humidity control for a Portable Life Support Subsystem (PLSS). Metabolically-produced CO2 present in the ventilation gas of a PLSS is collected using a CO2-selective adsorbent via temperature swing adsorption. The temperature swing is initiated through cooling to well below metabolic temperatures. Cooling is achieved with a sublimation heat exchanger using water or liquid carbon dioxide (L CO2) expanded below sublimation temperature when exposed to low pressure or vacuum. Subsequent super heated vapor, as well as additional coolant, is used to further cool the astronaut. The temperature swing on the adsorbent is then completed by warming the adsorbent with a separate condensing ice heat exchanger (CIHX) using metabolic heat from moist ventilation gas. The condensed humidity in the ventilation gas is recycled at the habitat. The water condensation from the ventilation gas represents a significant source of potential energy for the warming of the adsorbent bed as it represents as much as half of the energy potential in the moist ventilation gas. Designing a heat exchanger to efficiently transfer this energy to the adsorbent bed and allow the collection of the water is a challenge since the CIHX will operate in a temperature range from 210K to 280K. The ventilation gas moisture will first freeze and then thaw, sometimes existing in three phases simultaneously.

Padilla, Sebastian↗