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Results for “energy conserving”

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 OSTI2017

Exactly energy conserving semi-implicit particle in cell formulation

We report a new particle in cell (PIC) method based on the semi-implicit approach. The novelty of the new method is that unlike any of its semi-implicit predecessors at the same time it retains the explicit computational cycle and conserves energy exactly. Recent research has presented fully implicit methods where energy conservation is obtained as part of a non-linear iteration procedure. The new method (referred to as Energy Conserving Semi-Implicit Method, ECSIM), instead, does not require any non-linear iteration and its computational cycle is similar to that of explicit PIC. The properties of the new method are: i) it conserves energy exactly to round-off for any time step or grid spacing; ii) it is unconditionally stable in time, freeing the user from the need to resolve the electron plasma frequency and allowing the user to select any desired time step; iii) it eliminates the constraint of the finite grid instability, allowing the user to select any desired resolution without being forced to resolve the Debye length; iv) the particle mover has a computational complexity identical to that of the explicit PIC, only the field solver has an increased computational cost. The new ECSIM is tested in a number of benchmarks where accuracy and computational performance are tested. - Highlights: • We present a new fully energy conserving semi-implicit particle in cell (PIC) method based on the implicit moment method (IMM). The new method is called Energy Conserving Implicit Moment Method (ECIMM). • The novelty of the new method is that unlike any of its predecessors at the same time it retains the explicit computational cycle and conserves energy exactly. • The new method is unconditionally stable in time, freeing the user from the need to resolve the electron plasma frequency. • The new method eliminates the constraint of the finite grid instability, allowing the user to select any desired resolution without being forced to resolve the Debye length. • These features are achieved at a reduced cost compared with either previous IMM or fully implicit implementation of PIC.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Yakutat Tlingit Tribe Energy Conservation Upgrades & Energy Efficiency Measures

The Yakutat Tlingit Tribe (YTT) was awarded Strategic Technical Assistance Response Team (START) assistance from the Department of Energy (DOE) Office of Indian Energy Policy and Programs (OIEPP) in 2014. The intent of the grant was to lower energy consumption at both facilities (Kwaan Plaza which houses the medical clinic and the Community Center which housed the Tribe’s 477 Social Welfare Programs) and to explore technology to provide electricity and heat to the Kwaan Plaza.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2011

Particle acceleration and energy conservation in particle in cell simulations

Particle acceleration is a process of great importance in all areas of plasma physics. In most cases, kinetic effects are dominant and require a full kinetic treatment, such as the particle in cell (PIC) method. PIC methods are widely used in all aspects of plasma physics, proving to be a precious and irreplaceable tool. Yet all methods in use and published conserve energy to a good approximation, but not exactly. A well known property of PIC methods, documented extensively in all textbooks, is that energy is not conserved exactly. In fact, the particle noise is a unphysical source of energy that, when insufficient resolution is used, can make the simulations go unstable. In the present paper, we apply a new exactly energy conserving scheme and demonstrate that indeed exact energy conservation plays a key role in determining the correct spectrum of the accelerated particles.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2019

Energy Conservation and Hydrogenase Function in Methanogenic Archaea, in Particular the Genus Methanosarcina

The biological production of methane is vital to the global carbon cycle and accounts for ca. 74% of total methane emissions. The organisms that facilitate this process, methanogenic archaea, belong to a large and phylogenetically diverse group that thrives in a wide range of anaerobic environments. Two main subgroups exist within methanogenic archaea: those with and those without cytochromes. Although a variety of metabolisms exist within this group, the reduction of growth substrates to methane using electrons from molecular hydrogen is, in a phylogenetic sense, the most widespread methanogenic pathway. Methanogens without cytochromes typically generate methane by the reduction of CO 2 with electrons derived from H 2 , formate, or secondary alcohols, generating a transmembrane ion gradient for ATP production via an Na +- translocating methyltransferase (Mtr). These organisms also conserve energy with a novel flavin-based electron bifurcation mechanism, wherein the endergonic reduction of ferredoxin is facilitated by the exergonic reduction of a disulfide terminal electron acceptor coupled to either H 2 or formate oxidation. Methanogens that utilize cytochromes have a broader substrate range, and can convert acetate and methylated compounds to methane, in addition to the ability to reduce CO 2 . Cytochrome-containing methanogens are able to supplement the ion motive force generated by Mtr with an H + -translocating electron transport system. In both groups, enzymes known as hydrogenases, which reversibly interconvert protons and electrons to molecular hydrogen, play a central role in the methanogenic process. In this review, we discuss recent insight into methanogen metabolism and energy conservation mechanisms with a particular focus on the genus Methanosarcina.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2013

ENERGY CONSERVATION AND GRAVITY WAVES IN SOUND-PROOF TREATMENTS OF STELLAR INTERIORS. II. LAGRANGIAN CONSTRAINED ANALYSIS

The speed of sound greatly exceeds typical flow velocities in many stellar and planetary interiors. To follow the slow evolution of subsonic motions, various sound-proof models attempt to remove fast acoustic waves while retaining stratified convection and buoyancy dynamics. In astrophysics, anelastic models typically receive the most attention in the class of sound-filtered stratified models. Generally, anelastic models remain valid in nearly adiabatically stratified regions like stellar convection zones, but may break down in strongly sub-adiabatic, stably stratified layers common in stellar radiative zones. However, studying stellar rotation, circulation, and dynamos requires understanding the complex coupling between convection and radiative zones, and this requires robust equations valid in both regimes. Here we extend the analysis of equation sets begun in Brown et al., which studied anelastic models, to two types of pseudo-incompressible models. This class of models has received attention in atmospheric applications, and more recently in studies of white-dwarf supernova progenitors. We demonstrate that one model conserves energy but the other does not. We use Lagrangian variational methods to extend the energy conserving model to a general equation of state, and dub the resulting equation set the generalized pseudo-incompressible (GPI) model. We show that the GPI equations suitably capture low-frequency phenomena in both convection and radiative zones in stars and other stratified systems, and we provide recommendations for converting low-Mach number codes to this equation set.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

ENERGY CONSERVATION AND GRAVITY WAVES IN SOUND-PROOF TREATMENTS OF STELLAR INTERIORS. PART I. ANELASTIC APPROXIMATIONS

Typical flows in stellar interiors are much slower than the speed of sound. To follow the slow evolution of subsonic motions, various sound-proof equations are in wide use, particularly in stellar astrophysical fluid dynamics. These low-Mach number equations include the anelastic equations. Generally, these equations are valid in nearly adiabatically stratified regions like stellar convection zones, but may not be valid in the sub-adiabatic, stably stratified stellar radiative interiors. Understanding the coupling between the convection zone and the radiative interior is a problem of crucial interest and may have strong implications for solar and stellar dynamo theories as the interface between the two, called the tachocline in the Sun, plays a crucial role in many solar dynamo theories. Here, we study the properties of gravity waves in stably stratified atmospheres. In particular, we explore how gravity waves are handled in various sound-proof equations. We find that some anelastic treatments fail to conserve energy in stably stratified atmospheres, instead conserving pseudo-energies that depend on the stratification, and we demonstrate this numerically. One anelastic equation set does conserve energy in all atmospheres and we provide recommendations for converting low-Mach number anelastic codes to this set of equations.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

Final Report: Weatherization and Energy Conservation Education and Home Energy and Safety Review in the Aleutian Islands

Aleutian/Pribilof Islands Association, Inc. (APIA) hired three part-time local community members that desire to be Energy Technicians. The energy technicians were trained in methods of weatherization assistance, energy conservation and home safety. They developed a listing of homes in the region that required weatherization, and conducted on-site weatherization and energy conservation education and a home energy and safety reviews in the communities of Akutan, False Pass, King Cove and Nelson Lagoon. Priority was given to these smaller communities as they tend to have the residences most in need of weatherization and energy conservation measures. Local residents were trained to provide all three aspects of the project: weatherization, energy conservation education and a home energy and safety review. If the total energy saved by installing these products is a 25% reduction (electrical and heating, both of which are usually produced by combustion of diesel fuel), and the average Alaska home produces 32,000 pounds of CO2 each year, so we have saved about: 66 homes x 16 tons of CO2 each year x .25 = 264 tons of CO2 each year.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2018

Adaptive QM/MM for Molecular Dynamics Simulations: 5. On the Energy-Conserved Permuted Adaptive-Partitioning Schemes

In combined quantum-mechanical/molecular-mechanical (QM/MM) dynamics simulations, the adaptive-partitioning (AP) schemes reclassify atoms on-the-fly as QM or MM in a smooth manner. This yields a mobile QM subsystem with contents that are continuously updated as needed. Here, we tailor the Hamiltonian adaptive many-body correction (HAMBC) proposed by Boreboom et al. [J. Chem. Theory Comput. 2016, 12, 3441] to the permuted AP (PAP) scheme. The treatments lead to the HAMBC-PAP method (HPAP), which both conserves energy and produces accurate solvation structures in the test of “water-in-water” model system.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Charge-and-energy conserving moment-based accelerator for a multi-species Vlasov–Fokker–Planck–Ampère system, part II: Collisional aspects

In this study, we extend the moment-based acceleration algorithm for the charge, momentum, and energy conserving Vlasov–Ampère discretization developed in Ref. [1] by including a reduced Fokker–Planck operator. We propose an energy conserving discretization for the Fokker–Planck collision operator. We show by numerical experiment that the new algorithm 1) efficiently converges the nonlinearly coupled Vlasov–Fokker–Planck–Ampère system, and 2) accurately steps over stiff time-scales such as the inverse electron plasma frequency, and the electron–electron collision time-scale. We demonstrate that discrete energy conservation is critical to eliminate numerical heating issues when strong density gradients exist.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Charge-and-energy conserving moment-based accelerator for a multi-species Vlasov–Fokker–Planck–Ampère system, part I: Collisionless aspects

In this study, we propose a charge, momentum, and energy conserving discretization for the 1D–1V Vlasov–Ampère system of equations on an Eulerian grid. The new conservative discretization is nonlinear in nature, but can be efficiently converged with a moment-based nonlinear accelerator algorithm. We demonstrate the conservation and convergence properties of the scheme with various numerical examples, including a multi-scale ion–acoustic shockwave problem.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Performance Assurance Planning: Continuous Design-Level Performance of Each Energy Conservation Measure in a Utility Energy Service Contract is Fundamental to Achieving Projected Results

An energy savings performance contract energy sales agreement (ESPC ESA) is a project structure, similar to a power purchase agreement, that uses the multiyear ESPC authority to implement renewable energy projects (referred to as ESA energy conservation measures [ECMs]) on federal buildings or land. The ESA ECM is initially privately owned for tax-incentive purposes, and the federal agency purchases the electricity it produces. An ESPC ESA is one of the most cost-effective methods for implementing on-site distributed energy projects at civilian federal agency sites.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2019

Performance Assurance Planning: Continuous Design-Level Performance of Each Energy Conservation Measure in a Utility Energy Service Contract is Fundamental to Achieving Projected Results

Design-level performance of each energy conservation measure (ECM) in an awarded utility energy service contract (UESC) is fundamental to achieving the projected results through the term of the contract and over the life of the measure. Because the authority for a UESC does not require contractual guarantees of energy, water, or cost savings, FEMP developed a protocol for emphasizing sustained performance to help ensure projected savings are realized. The information and templates offered within this paper reflect responsible project management and oversight, align with UESC best practices, and satisfy the conditions for annual scoring provided by the Office of Management and Budget (OMB). OMB memorandum M-12-21 requires, 'energy savings performance assurances,' 'measurement and verification (M&V) of savings through commissioning and retrocommissioing,' and 'competition or an alternatives analysis as part of the selection process.'

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2012

Using Qualified Energy Conservation Bonds for Public Building Upgrades. Reducing Energy Bills in the City of Philadelphia

Qualified Energy Conservation Bonds (QECBs) are federally-subsidized bonds that enable state, tribal, and local government issuers to borrow money to fund a range of energy conservation projects, including public building upgrades that reduce energy use by at least 20 percent, at very attractive borrowing rates and long terms. As part of the American Recovery and Reinvestment Act (ARRA), the City of Philadelphia received a $\$$15 million QECB award from the U.S. Department of the Treasury (Treasury). The city leveraged $\$$6.25 million of its QECB allocation to finance half of a $\$$12.6 million initiative to upgrade the energy efficiency of City buildings. The upgrades to four city facilities are expected to deliver over $10 million of net savings, and are a major step towards achieving the city’s goal of reducing government energy consumption by 30 percent by 2015.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2014

On energy conservation in extended magnetohydrodynamics

A systematic study of energy conservation for extended magnetohydrodynamic models that include Hall terms and electron inertia is performed. It is observed that commonly used models do not conserve energy in the ideal limit, i.e., when viscosity and resistivity are neglected. In particular, a term in the momentum equation that is often neglected is seen to be needed for conservation of energy.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2017

A framework for quantifying the impact of occupant behavior on energy savings of energy conservation measures

To improve energy efficiency—during new buildings design or during a building retrofit—evaluating the energy savings potential of energy conservation measures (ECMs) is a critical task. In building retrofits, occupant behavior significantly impacts building energy use and is a leading factor in uncertainty when determining the effectiveness of retrofit ECMs. Current simulation-based assessment methods simplify the representation of occupant behavior by using a standard or representative set of static and homogeneous assumptions ignoring the dynamics, stochastics, and diversity of occupant's energy-related behavior in buildings. The simplification contributes to significant gaps between the simulated and measured actual energy performance of buildings. This paper presents a framework for quantifying the impact of occupant behaviors on ECM energy savings using building performance simulation. During the first step of the study, three occupant behavior styles (austerity, normal, and wasteful) were defined to represent different levels of energy consciousness of occupants regarding their interactions with building energy systems (HVAC, windows, lights and plug-in equipment). Next, a simulation workflow was introduced to determine a range of the ECM energy savings. Then, guidance was provided to interpret the range of ECM savings to support ECM decision making. Finally, a pilot study was performed in a real building to demonstrate the application of the framework. Simulation results show that the impact of occupant behaviors on ECM savings vary with the type of ECM. Occupant behavior minimally affects energy savings for ECMs that are technology-driven (the relative savings differ by less than 2%) and have little interaction with the occupants; for ECMs with strong occupant interaction, such as the use of zonal control variable refrigerant flow system and natural ventilation, energy savings are significantly affected by occupant behavior (the relative savings differ by up to 20%). Finally, the study framework provides a novel, holistic approach to assessing the uncertainty of ECM energy savings related to occupant behavior, enabling stakeholders to understand and assess the risk of adopting energy efficiency technologies for new and existing buildings.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗