Search NASA⌕ Search

SEARCH · Search NASA

Results for “Systems Modeling”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Uncertainty Quantification in Dynamic Simulations of Large-scale Power System Models using the High-Order Probabilistic Collocation Method on Sparse Grids

This paper proposes a probabilistic collocation method (PCM) to quantify the uncertainties with dynamic simulations in power systems. The appraoch was tested on a single-machine-infinite-bus system and the over 15,000 -bus Western Electricity Coordinating Council (WECC) system. Comparing to classic Monte-Carlo (MC) method, the proposed PCM applies the Smolyak algorithm to reduce the number of simulations that have to be performed. Therefore, the computational cost can be greatly reduced using PCM. The algorithm and procedures are described in the paper. Comparison was made with MC method on the single machine as well as the WECC system. The simulation results shows that using PCM only a small number of sparse grid points need to be sampled even when dealing with systems with a relatively large number of uncertain parameters. PCM is, therefore, computationally more efficient than MC method.

Uncertainty quantification, parameter estimation, ↗
DOE OSTI2012

Sub-Hour Solar Data for Power System Modeling From Static Spatial Variability Analysis: Preprint

High penetration renewable integration studies need high quality solar power data with spatial-temporal correlations that are representative of a real system. This paper will summarize the research relating sequential point-source sub-hour global horizontal irradiance (GHI) values to static, spatially distributed GHI values. This research led to the development of an algorithm for generatingcoherent sub-hour datasets that span distances ranging from 10 km to 4,000 km. The algorithm, in brief, generates synthetic GHI values at an interval of one-minute, for a specific location, using SUNY/Clean Power Research, satellite-derived, hourly irradiance values for the nearest grid cell to that location and grid cells within 40 km.

14 SOLAR ENERGY↗
DOE OSTI2023

Insights on Nuclear Energy from Long-Term System Models: Inter-Model Comparison Results

A variety of US electric power sector capacity expansion models are used by decision makers and analysts to evaluate competition among generation, transmission, and storage technologies to meeting the demands of the system. CEMs use least-cost optimization to identify optimal portfolios of investments capable of satisfying all specified requirements. While CEMs are a useful tool to inform pathways to meet future needs, projections can differ significantly between tools for apparently similar scenario assumptions. Differences in model structure, scope, and input assumption contribute to this issue. This work compares model response with harmonization between four modeling teams on issues significant to the representation and development of nuclear energy.

capacity expansion model↗
DOE OSTI2019

Development of HPWH System Model, Using All Microchannel Heat Exchangers

In this report, 24-hour energy factor (EF) and first-hour draw rating (FHR) simulations were conducted on two heat pump water heater systems (HPWHs), one using a fin-and-tube evaporator and wrapped-tank condenser coil with D-shape tubes, and the other using a micro-channel evaporator and wrapped-tank condenser coil with microchannel tubes. Alternative refrigerants as drop-in replacements of R-134a were evaluated, including R-1234yf, R-1234ze(E), propane (R-290), R-450A and R-513A. The results are summarized below: 1.Microchannel heat exchangers can decrease the system charge down to 30% relative to fin-and-tube evaporator and wrapped-tank D tubes.2.Having the same contact surface area to the water tank and evaporator frontal flow area, the system using microchannel heat exchangers (MHXs) results in 5% efficiency degradation. Due to the very small cross-sectional flow area of a microchannel tube, MHXs tend to have multiple parallel tubes to restrict the refrigerant pressure drop. The parallel pattern can’t utilize the water temperature stratification as effectively as the D-shape tubes, which are arranged in one or two circuits and counter flow to the water stratification. 3.Refrigerant drop-in system simulations were conducted for R-1234yf, R-1234ze(E), propane, R450A and R513A in comparison to R-134a. Among the alternatives, propane has the largest volumetric capacity, which results in shortest HPWH run time and highest first-hour rating. Propane leads to the smallest energy factor because its largest volumetric capacity overloads the heat exchangers. R-1234ze(E) has the smallest volumetric capacity, highest energy factor, but smallest first-hour rating. R-1234yf, R-450A and R-513A achieve similar performance indices as R-134a. 4.Propane requires the least refrigerant mass (45% relative to R-134a). If a wrapped-tank microchannel condenser and microchannel evaporator are used, the required system charge can be limited below 150 grams, which makes it feasible to use propane for domestic HPWH.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2026

Implementation of a Three-Dimensional Planetary Boundary Layer Parameterization in a Coupled Modeling System and Evaluation of "Gray Zone" Simulations of a Wind-Wave Event Off the US California Coast Using Observations

A three-dimensional (3D) planetary boundary layer (PBL) parameterization was added to the Coupled Ocean Atmosphere Wave Sediment Transport (COAWST) model and the first coupled atmosphere/wave "gray zone" simulations were carried out using the 3D PBL parameterization. A case study of a significant wind-wave event from 4-8 November 2020 off the US west coast was examined, with a focus on the impacts of the event within an approximate 280x280 km central California coastal region covering the Bureau of Ocean Energy Management Morro Bay wind energy lease area. Simulations with both one-dimensional (1D; Yonsei University) and 3D PBL parameterizations were examined in this nest with ..delta..x=400 m. Two-way coupling was active, with near-surface winds feeding back to the wave model and bulk wave statistics feeding back to the atmospheric model. Both simulations compared favorably with buoy observations in capturing the timing and magnitude of wind speed, temperature, dewpoint, and significant wave height, as the front associated with the maritime weather system moved southward across coastal California. However, wind speed errors over land were larger. Time series of the vertical profile of winds below z=250 m from the simulations compared favorably with observations from the US Dept. of Energy Morro Bay Doppler lidar buoy. Differences between the coupled 1D and 3D PBL simulations were minor. The most notable difference was that the simulation using the 3D PBL parameterization had approximately 10 % weaker winds at the peak of the event causing 10 % lower significant wave heights. This difference was shown to be mostly due to differences in the vertical mixing treatment between the parameterizations, in particular the nonlocal downward mixing of higher momentum air in the 1D Yonsei University parameterization in convective conditions. Overall, this work demonstrates that the 3D PBL parameterization can be used in a coupled atmosphere/wave modeling framework with similar behaviors as traditional PBL parameterizations that do not provide horizontal turbulent variances and fluxes.

16 TIDAL AND WAVE POWER↗
DOE OSTI2015

Unique natural system modeling aspects of the H-Tank Farm at the Savannah river site - 15271

The U.S. Department of Energy (DOE) is in the process of closing radioactive waste storage tanks at the Savannah River Site (SRS). One of the key technical documents supporting closure and regulatory decision documents is the Performance Assessment (PA). PAs within the DOE complex are performance-based, risk-informed analyses of the fate and transport of residual contaminants, in this case any residual material remaining following cleaning and closure of the tank systems. There are two active radioactive waste storage facilities at SRS, F-Tank Farm (FTF) and H-Tank Farm (HTF), which consist of 51 carbon steel waste tanks. To date, six tanks have been emptied and closed in FTF. Activities are currently in progress to support closure of the first tanks in HTF. A PA has been developed for HTF and includes modeling that takes into account the unique aspects of the natural system associated with HTF. These unique aspects include the water table elevation in relation to the tanks and the complex flow patterns of the groundwater beneath HTF. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Quick Urban and Industrial Complex (QUIC) CBR Plume Modeling System: Validation-Study Document

This document contains information on QUIC validation studies that have been performed to evaluate the wind, pressure, and concentration solutions produced by QUIC. Tests of QUIC's source term models and specialized transport mechanisms (e.g., buoyancy algorithms, particle settling and deposition, liquid pool growth, droplet and pool evaporation) are also provided. A brief description of the experiment, a few example validation results, and references to journal articles, reports, and/or presentations are given. Both LANL and non-LANL sources are provided.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2016

Exact thermal density functional theory for a model system: Correlation components and accuracy of the zero-temperature exchange-correlation approximation

Thermal density functional theory calculations often use the Mermin-Kohn-Sham scheme, but employ ground-state approximations to the exchange-correlation (XC) free energy. In the simplest solvable nontrivial model, an asymmetric Hubbard dimer, we calculate the exact many-body energies and the exact Mermin-Kohn-Sham functionals for this system and extract the exact XC free energy. For moderate temperatures and weak correlation, we find this approximation to be excellent. Here we extract various exact free-energy correlation components and the exact adiabatic connection formula.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2013

System Modeling and Design Optimization for a Next-Generation Unattended Sensor

We are developing a next-generation unattendedsensor that can detect and identify radiation sources while operating on battery power for several weeks. The system achieves smaller size and weight over systems that use NaI:Tl and 3He detectors by using a relatively new scintillator, Cs2LiYCl6:Ce:Ce (CLYC). This material can detect both gamma rays and thermal neutrons, has energy resolution of ~4% full width at half maximum at 662 keV, and allows for particle discrimination by pulse amplitude as well as pulse shape. The overall design features an array of sixteen CLYC detectors, each read out by a photomultiplier tube and custom pulse processing electronics. A field-programmable gate array analyzes the energy spectra using computationally efficient algorithms for anomaly detection.

McDonald, Benjamin S.↗
DOE OSTI2017

System Modeling and Simulation of In-Stream Hydrokinetic Turbines for Power Management and Control

Electricity generation from moving currents without using dams (i.e., in-stream hydrokinetic electricity) has the potential to introduce multiple GW of renewable power to U.S. grids. Here this study evaluates a control system designed to regulate the generator rotor rate (rpm) to improve power production from in-stream hydrokinetic turbines. The control algorithm is evaluated using numerical models of both a rigidly mounted tidal turbine (TT) and a moored ocean current turbine (OCT) coupled to an induction electric machine model. The moored simulation utilizes an innovative approach for coupling a multiple degrees-of-freedom (DOF) nonlinear hydrodynamic/mechanical turbine model with a nonlinear electromechanical generator model. Based on the turbine torque-speed characteristic, as well as the asynchronous machine features, a proportional–integral (PI) controller is used to generate a correction term for the frequency of the three-phase sinusoidal voltages that are supplied to the asynchronous generator. The speed control of the induction generator through the supply frequency is accomplished by a simplified voltage source inverter (VSI). The simplified VSI consists of control voltage sources (CVSs), while the comparison with a real VSI using diodes and transistors, which are controlled by pulse width modulation (PWM) technique, is also presented. Simulations are used to evaluate the developed algorithms showing that rpm fluctuations are around 0.02 for a tidal turbine operating in a wave field with a 6 m significant wave height and around 0.005 for a moored ocean current turbine operating in a wave field with a 2 m significant wave height.

16 TIDAL AND WAVE POWER↗
DOE OSTI2012

A Test Bed for Self-regulating Distribution Systems: Modeling Intergrated Renewable Energy and Demand Response in the GridLAB-D/MATLAB Environment

This paper discusses the development of a simulation test bed permitting the study of integrated renewable energy generators and controlled distributed heat pumps operating within distribution systems. The test bed is demonstrated in this paper by addressing the important issue of the self-regulating effect of consumer-owned air-source heat pumps on the variability induced by wind power integration, particularly when coupled with increased access to demand response realized through a centralized load control strategy.

Wang, Dan↗
DOE OSTI2025

Thermal Systems Modeling for Integration of Industrial Processes with Advanced Nuclear

Applying combined heat and power concepts to advanced nuclear reactors can enable increased nuclear utilization in the future clean economy, as well as provide safe and reliable clean energy to industrial systems. Analyses have been performed to evaluate the integration of nuclear energy with industrial processes for both clean electricity production and providing process heat for direct use to reduce emissions in the production of chemical commodities. The key research question that needs to be answered is: "What are the prospective approaches for integrating nuclear-generated heat energy into non-electric applications that can facilitate combined heat and power operations by advanced nuclear reactor systems?" This presentation will highlight several case studies showing conceptual designs for thermal delivery systems to integrate small modular reactor (SMR) process steam and electricity with industrial processes including oil refining, hydrogen production, and methanol production.

hydrogen↗
DOE OSTI2026

A Comprehensive Comparison of Methods for Evaluating Dispatch of Long-Duration Energy Storage in Power Systems Models

Long-duration energy storage (LDES) could play a pivotal role in the transformation of electricity grids with high shares of variable renewable energy (VRE) such as solar and wind. However, the weather-dependent nature of VRE introduces challenges for grid balancing and stability, which LDES - along with short-duration energy storage (SDES) - can help address. However, modeling LDES in production cost models (PCMs) is particularly challenging due to the need for high temporal resolution over extended optimization windows while preserving chronology, which ensures the alignment of energy storage operations with VRE generation over multi-day periods. This report compares traditional dispatch methods with advanced LDES dispatch strategies, such as the extended horizon approach, across different PCM platforms and examines tradeoffs and scalability. The comparison reveals that the traditional 1-day optimization horizon within the PCM leads to inefficient utilization of LDES. In contrast, extending the optimization horizon as much as possible significantly reduces curtailment and improves storage dispatch, especially in renewable-dense systems. There is also promise in using state-of-charge or end volume targets set by an external model, however this requires an additional modeling set and generally increases computational burden. This paper presents a comparison of these various methods in a number of power systems, showing algorithms initially in small test systems and scaling up to large, country-wide simulations. Overall, the research presents the trade-offs of various computational methods and illustrates how LDES may play an essential role in power systems of the future.

14 SOLAR ENERGY↗
DOE OSTI2011

RF system models for the CERN Large Hadron Collider with application to longitudinal dynamics

The LHC RF station-beam interaction strongly influences the longitudinal beam dynamics, both single bunch and collective effects. Non-linearities and noise generated within the Radio Frequency (RF) accelerating system interact with the beam and contribute to beam motion and longitudinal emittance blowup. Thus, the noise power spectrum of the RF accelerating voltage strongly affects the longitudinal beam distribution. Furthermore, the coupled-bunch instabilities are also directly affected by the RF components and the configuration of the Low Level RF (LLRF) feedback loops. In this work we present a formalism relating the longitudinal beam dynamics with the RF system configurations, an estimation of collective effects stability margins, and an evaluation of longitudinal sensitivity to various LLRF parameters and configurations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

The role of high-order electron correlation effects in a model system for non-valence correlation-bound anions

The diffusion Monte Carlo (DMC), auxiliary field quantum Monte Carlo (AFQMC), and equation-of-motion coupled cluster (EOM-CC) methods are used to calculate the electron binding energy (EBE) of the non-valence anion state of a model (H2O)4 cluster. Two geometries are considered, one at which the anion is unbound and the other at which it is bound in the Hartree–Fock (HF) approximation. It is demonstrated that DMC calculations can recover from the use of a HF trial wave function that has collapsed onto a discretized continuum solution, although larger EBEs are obtained when using a trial wave function for the anion that provides a more realistic description of the charge distribution and, hence, of the nodal surface. For the geometry at which the cluster has a non-valence correlation-bound anion, both the inclusion of triples in the EOM-CC method and the inclusion of supplemental diffuse d functions in the basis set are important. DMC calculations with suitable trial wave functions give EBE values in good agreement with our best estimate EOM-CC result. AFQMC using a trial wave function for the anion with a realistic electron density gives a value of the EBE nearly identical to the EOM-CC result when using the same basis set. For the geometry at which the anion is bound in the HF approximation, the inclusion of triple excitations in the EOM-CC calculations is much less important. The best estimate EOM-CC EBE value is in good agreement with the results of DMC calculations with appropriate trial wave functions.

Upadhyay, Shiv (ORCID:0000000285010501)↗