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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 NTRS1992

Improve SSME power balance model

Effort was dedicated to development and testing of a formal strategy for reconciling uncertain test data with physically limited computational prediction. Specific weaknesses in the logical structure of the current Power Balance Model (PBM) version are described with emphasis given to the main routing subroutines BAL and DATRED. Selected results from a variational analysis of PBM predictions are compared to Technology Test Bed (TTB) variational study results to assess PBM predictive capability. The motivation for systematic integration of uncertain test data with computational predictions based on limited physical models is provided. The theoretical foundation for the reconciliation strategy developed in this effort is presented, and results of a reconciliation analysis of the Space Shuttle Main Engine (SSME) high pressure fuel side turbopump subsystem are examined.

Karr, Gerald R.↗
DOE OSTI2016

A Practical Look at Assumptions and Constraints for Steady State Modeling of sCO2 Brayton Power Cycles

Modeling supercritical CO2 (sCO2) power cycles requires specification of system constraints and component performance metrics such as pressure losses and temperature limitations.? Differing assumptions made by the model designers may lead to significantly different results which are due to the assumptions and not to the underlying thermodynamics which characterize the cycle performance. As leaders in setting standards for techno-economic analyses, NETL and EPRI have collaborated to propose a set of practical modeling assumptions that can serve as a common baseline for both indirect and direct sCO2 power plant studies, allowing for more meaningful cycle comparisons. These include specifications for turbine inlet temperature (high temperature and pressure limitations), compressor inlet temperature and pressure (cooling limitations), heat exchanger effectiveness/temperature differentials and pressure drop, and full- and part-load turbine and compressor efficiencies.

Weiland, Nathan↗
DOE OSTI2016

A Practical Look at Assumptions and Constraints for Steady State Modeling of sCO2 Brayton Power Cycles

Modeling supercritical CO2 (sCO2) power cycles requires specification of system constraints and component performance metrics such as pressure losses and temperature limitations.? Differing assumptions made by the model designers may lead to significantly different results which are due to the assumptions and not to the underlying thermodynamics which characterize the cycle performance. As leaders in setting standards for techno-economic analyses, NETL and EPRI have collaborated to propose a set of practical modeling assumptions that can serve as a common baseline for both indirect and direct sCO2 power plant studies, allowing for more meaningful cycle comparisons. These include specifications for turbine inlet temperature (high temperature and pressure limitations), compressor inlet temperature and pressure (cooling limitations), heat exchanger effectiveness/temperature differentials and pressure drop, and full- and part-load turbine and compressor efficiencies.

Thimsen, David↗
DOE OSTI2013

A generalized 2D pencil beam scaling algorithm for proton dose calculation in heterogeneous slab geometries

Purpose: Pencil beam algorithms are commonly used for proton therapy dose calculations. Szymanowski and Oelfke ['Two-dimensional pencil beam scaling: An improved proton dose algorithm for heterogeneous media,' Phys. Med. Biol. 47, 3313-3330 (2002)] developed a two-dimensional (2D) scaling algorithm which accurately models the radial pencil beam width as a function of depth in heterogeneous slab geometries using a scaled expression for the radial kernel width in water as a function of depth and kinetic energy. However, an assumption made in the derivation of the technique limits its range of validity to cases where the input expression for the radial kernel width in water is derived from a local scattering power model. The goal of this work is to derive a generalized form of 2D pencil beam scaling that is independent of the scattering power model and appropriate for use with any expression for the radial kernel width in water as a function of depth. Methods: Using Fermi-Eyges transport theory, the authors derive an expression for the radial pencil beam width in heterogeneous slab geometries which is independent of the proton scattering power and related quantities. The authors then perform test calculations in homogeneous and heterogeneous slab phantoms using both the original 2D scaling model and the new model with expressions for the radial kernel width in water computed from both local and nonlocal scattering power models, as well as a nonlocal parameterization of Moliere scattering theory. In addition to kernel width calculations, dose calculations are also performed for a narrow Gaussian proton beam. Results: Pencil beam width calculations indicate that both 2D scaling formalisms perform well when the radial kernel width in water is derived from a local scattering power model. Computing the radial kernel width from a nonlocal scattering model results in the local 2D scaling formula under-predicting the pencil beam width by as much as 1.4 mm (21%) at the depth of the Bragg peak for a 220 MeV proton beam in homogeneous water. This translates into a 32% dose discrepancy for a 5 mm Gaussian proton beam. Similar trends were observed for calculations made in heterogeneous slab phantoms where it was also noted that errors tend to increase with greater beam penetration. The generalized 2D scaling model performs well in all situations, with a maximum dose error of 0.3% at the Bragg peak in a heterogeneous phantom containing 3 cm of hard bone. Conclusions: The authors have derived a generalized form of 2D pencil beam scaling which is independent of the proton scattering power model and robust to the functional form of the radial kernel width in water used for the calculations. Sample calculations made with this model show excellent agreement with expected values in both homogeneous water and heterogeneous phantoms.

61 RADIATION PROTECTION AND DOSIMETRY↗
NASA NTRS1947

Correlation of the Trim Limits of Stability Obtained for a PB2Y-3 Flying Boat and a 1/8-Size Powered Dynamic Model

Tests of a PB2Y-3 flying boat were made at the U.S> Naval Air Station, Patuxent River, Md., to determine its hydrodynamic trim limits of stability. Corresponding tests were also made of a 1/8-size powered dynamic model of the same flying boat in Langley tank no. 1. During the tank tests, the full-size testing procedure was reproduced as closely as possible in order to obtain data for a direct correlation of the results. As a nominal gross load of 66,000 pounds, the lower trim limits of the full-size and model were in good agreement above a speed of 80 feet per second. As the speed decreased below 80 feet per second, the difference between the model trim limits and full-scale trim limits gradually became larger. The upper trim limit of the model with flaps deflected 0 deg was higher than that of the full-size, but the difference was small over the speed range compared. At flap deflections greater than 0 deg, it was not possible to trim either the model of the airplane to the upper limit with the center of gravity at 28 percent of the mean aerodynamic chord. The decrease in the lower trim limits with increase in flap deflection showed good agreement for the airplane and model. The lower trim limits obtained at different gross loads for the full-size airplane were reduced to approximately a single curve by plotting trim against the square root of C(sub delta (sub o)) divided by C(sub V).

Garrison, Charlie C.↗
DOE OSTI2017

Measurement-based Power System Dynamic Model Reductions

Interconnected power systems have experienced a significant increase in its size and complexity, due to continuous topology and operating condition changes. It is computationally burdensome to represent entire system models in detail to conduct power system analysis. In the large-scale power system dynamic simulations, the models in the study area need to be retained in detail while the external area can be reduced without compromising accuracy, which can preserve the full system dynamic properties. This paper develops measurement-based continuous-time dynamic equivalents for power systems in order to both improve the model accuracy of the reduced system and increase the speed of dynamic simulation. Our method is based on a set of measurements at the boundary nodes between the study area and external area. Case studies demonstrate that the measurement-based model can capture the full system behavior sufficiently, and improve computational efficiency.Interconnected power systems experienced a significant increase in size and complexity. It is computationally burdensome to represent the entire system in detail to conduct power system analysis. Therefore, the model of the study system must be retained in detail while the external system can be reduced using system reduction techniques. This paper proposes a measurement-based dynamic equivalent in order to increase both model accuracy and simulation speed. The proposed method uses a set of measurements at the boundary nodes between the study area and external area for model parameter identification. Case studies demonstrate that the measurement-based technique can capture the main system behaviors accurately and improve computational efficiency.

Xue, Yaosuo↗
NASA NTRSDate not supplied

Brayton Cycle Power Conversion Model for MW-Class Nuclear Electric Propulsion Mars Missions

A Brayton cycle based power conversion system for a nuclear electric propulsion application was modeled in Simulink as part of NASA’s space nuclear program in order to explore the impact of technology assumptions on the power conversion system performance and capabilities. The thermodynamic processes and algorithms within the model are documented, including a higher fidelity reactor model. Assumptions are chosen based on literature and subject matter expert review, and example results and capabilities of the model are shown. The effects of the turbine inlet and compressor inlet temperature on radiator area and thermal efficiency are discussed. For a He-Xe closed Brayton cycle, radiator areas as low as 650 m2/MWe are shown, with corresponding thermal efficiences at roughly 20% for the minimal radiator area solutions.

Brayton↗
DOE OSTI2024

Open Source Modeling for Power Systems Dynamics

Time-domain simulations for power systems (both phasor and electromagnetic transients) are mostly dominated by commercial tools, such as PSS/E or PSCAD. However, with the increasing penetration of inverter-based resources and changes in model paradigm, new open-source tools are looking into become a possible alternative for a range of stakeholders. In this presentation we will focus on how to improve communication with industry and other stakeholders to properly showcase the value of open source simulators. Participants will identify current barriers facing the adoption of open-source time-domain tools, and will discuss how to improve the bench-marking processes across different tools, while maintaining software modularity to include new features and models as new challenges continue to happen in energy systems.

ENERGY PLANNING, POLICY, AND ECONOMY,MATHEMATICS A↗
DOE OSTI2015

Improving Power System Modeling. A Tool to Link Capacity Expansion and Production Cost Models

Capacity expansion models (CEM) provide a high-level long-term view at the prospects of the evolving power system. In simulating the possibilities of long-term capacity expansion, it is important to maintain the viability of power system operation in the short-term (daily, hourly and sub-hourly) scales. Production-cost models (PCM) simulate routine power system operation on these shorter time scales using detailed load, transmission and generation fleet data by minimizing production costs and following reliability requirements. When based on CEM 'predictions' about generating unit retirements and buildup, PCM provide more detailed simulation for the short-term system operation and, consequently, may confirm the validity of capacity expansion predictions. Further, production cost model simulations of a system that is based on capacity expansion model solution are 'evolutionary' sound: the generator mix is the result of logical sequence of unit retirement and buildup resulting from policy and incentives. The above has motivated us to bridge CEM with PCM by building a capacity expansion - to - production cost model Linking Tool (CEPCoLT). The Linking Tool is built to onset capacity expansion model prescriptions onto production cost model inputs. NREL's ReEDS and Energy Examplar's PLEXOS are the capacity expansion and the production cost models, respectively. Via the Linking Tool, PLEXOS provides details of operation for the regionally-defined ReEDS scenarios.

24 POWER TRANSMISSION AND DISTRIBUTION↗
NASA NTRS1947

Tank Investigation of a Powered Dynamic Model of a Large Long-Range Flying Boat

Principles for designing the optimum hull for a large long-range flying boat to meet the requirements of seaworthiness, minimum drag, and ability to take off and land at all operational gross loads were incorporated in a 1/12-size powered dynamic model of a four-engine transport flying boat having a design gross load of 165,000 pounds. These design principles included the selection of a moderate beam loading, ample forebody length, sufficient depth of step, and close adherence to the form of a streamline body. The aerodynamic and hydrodynamic characteristics of the model were investigated in Langley tank no. 1. Tests were made to determine the minimum allowable depth of step for adequate landing stability, the suitability of the fore-and-aft location of the step, the take-off performance, the spray characteristics, and the effects of simple spray-control devices. The application of the design criterions used and test results should be useful in the preliminary design of similar large flying boats.

Parkinson, John B↗
DOE OSTI2023

Power Flow Models of Grid-Forming Inverters in Unbalanced Distribution Grids

Load unbalance in electric distribution systems is unavoidable. Unbalanced load currents will lead to negative sequence (NS) voltages that may damage electric equipment. Unbalanced power flow analysis is a common tool to detect and mitigate NS voltage issues and requires accurate models of grid components. While traditional source models are available, grid-forming (GFM) inverter models are not well developed. GFM inverters implement various control strategies, which affect their power flow models. Here, in this paper, a novel GFM inverter model considering control effects is proposed. We show that for some control methods, unbalanced system loading will lead to unbalanced terminal voltages of the GFM inverters, which are modeled through an equivalent negative sequence impedance. The proposed models are initially validated using a simple test circuit. Then, they are applied in the power flow analysis on the IEEE 13-bus and 34-bus systems to demonstrate the accuracy improvement over the state-of-the-art. Using time-domain simulations as benchmarks, we show that the proposed models reduce the calculation error of negative sequence voltages by at least 25% in unbalanced distribution systems.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2017

Modeling Electric Power and Natural Gas Systems Interdependencies: Application to Natural Hazards

To assist the evaluation of infrastructure assets from an all-hazards perspective, this paper describes the 16 progress of continuing infrastructure modeling and integration efforts underway by researchers at 17 Argonne National Laboratory under its Resilient Infrastructure Initiative. A unique approach is adopted 18 that integrates existing and proven electric power and natural gas infrastructure models used for impact 19 assessment analyses to aid and enhance the design of resilient energy systems. Significant benefits of the 20 combined electric power-natural gas model (EP-NG Model) are that the generalized framework permits 21 the integration and automation of the entire process, including threat and hazard identification and data 22 acquisition, impact zone estimation and projection, simulation of the initial effects on the initiating 23 infrastructure, evaluation of propagating effects within each infrastructure, and simulation of the influence 24 of cascading effects of the disruption on interdependent infrastructure. Two state-level case studies 25 demonstrate the approach’s effectiveness in simulating the propagation of disruptions between the natural gas and electric power systems, and the usefulness for designing resilient energy systems considering 27 hazards related to climate change and other natural hazards.

all-hazards↗
DOE OSTI2017

Pulsational Pair-instability Model for Superluminous Supernova PTF12dam:Interaction and Radioactive Decay

Being a superluminous supernova, PTF12dam can be explained by a {sup 56}Ni-powered model, a magnetar-powered model, or an interaction model. We propose that PTF12dam is a pulsational pair-instability supernova, where the outer envelope of a progenitor is ejected during the pulsations. Thus, it is powered by a double energy source: radioactive decay of {sup 56}Ni and a radiative shock in a dense circumstellar medium. To describe multicolor light curves and spectra, we use radiation-hydrodynamics calculations of the STELLA code. We found that light curves are well described in the model with 40 M {sub ⊙} ejecta and 20–40 M {sub ⊙} circumstellar medium. The ejected {sup 56}Ni mass is about 6 M {sub ⊙}, which results from explosive nucleosynthesis with large explosion energy (2–3)×10{sup 52} erg. In comparison with alternative scenarios of pair-instability supernova and magnetar-powered supernova, in the interaction model, all the observed main photometric characteristics are well reproduced: multicolor light curves, color temperatures, and photospheric velocities.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

USAID Haiti Training Session #4: Resilience and Power Sector Modeling Part I [Slides]

Welcome to Engage! Engage is a capacity expansion modeling tool supported by the National Renewable Energy Laboratory and based on the Calliope open-source capacity expansion model developed by the ETH Zurich University, maintained at the TU Delft University. Engage is an accessible (free, open-access, web-hosted) and flexible web-based energy system planning application for rapid multiple-energy-form energy system scenario exploration. Its cloud-based, collaborator-sharable data model, intuitive interface and visualization capabilities facilitate collaboration and communication among teams, with experts, and among diverse stakeholder groups exploring energy system implications at from district to national-scale models. This training series was developed under USAID to empower Haitian stakeholders to explore modeling scenarios in Engage to develop a Haiti Energy Master Plan. This training series includes a general overview of how Engage works along with tailored exercises that target Haiti's specific energy needs, such as modeling the capacity expansion of the bulk power system, fuel scarcity challenges, the development of microgrids, and the economic viability of transmission strategies. See NREL/PR-7A40-89408 for the French translation of this document.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2024

USAID Haiti Training Session #4: Resilience and Power Sector Modeling Part II [Slides]

Welcome to Engage! Engage is a capacity expansion modeling tool supported by the National Renewable Energy Laboratory and based on the Calliope open-source capacity expansion model developed by the ETH Zurich University, maintained at the TU Delft University. Engage is an accessible (free, open-access, web-hosted) and flexible web-based energy system planning application for rapid multiple-energy-form energy system scenario exploration. Its cloud-based, collaborator-sharable data model, intuitive interface and visualization capabilities facilitate collaboration and communication among teams, with experts, and among diverse stakeholder groups exploring energy system implications from district to national-scale models. This training series was developed under USAID to empower Haitian stakeholders to explore modeling scenarios in Engage to develop a Haiti Energy Master Plan. This training series includes a general overview of how Engage works along with tailored exercises that target Haiti's specific energy needs, such as modeling the capacity expansion of the bulk power system, fuel scarcity challenges, the development of microgrids, and the economic viability of transmission strategies. See NREL/PR-7A40-89412 for the French translation of this document.

24 POWER TRANSMISSION AND DISTRIBUTION↗