Search NASA⌕ Search

SEARCH · Search NASA

Results for “Operating Mode”

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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Voltage cycling as a dynamic operation mode for high temperature electrolysis solid oxide cells

Solid Oxide Electrolysis Cells (SOECs) have emerged as a promising technology for the efficient production of H2 via high-temperature electrolysis. However, power input from dynamic energy sources remains a significant challenge for their long-term stability. It is important to analyze the tolerance of cells under dynamic operation conditions. This study focuses on evaluating the impact of voltage cycling on the performance and durability of electrode-supported SOECs. We explore the operational limits and degradation mechanisms of SOECs subjected to various voltage conditions and find that the cells have high tolerance for dynamic voltage. Voltage cycling between 1.3 V and 1.5 V for 9000 cycles does not damage the cell. Conversely, cycling to higher voltages (≥1.7 V) results in accelerated degradation. Advanced characterization is used to screen for various degradation modes post operation. Within the oxygen electrode, XRD and STEM EDS find compositional and phase evolution in all voltage cycled samples including increased decomposition of the air electrode resulting in cation migration. Microstructural analysis of the fuel electrode from nano-CT data shows minimal change throughout the sample set and no evidence of Ni migration, indicating the fuel electrode is stable and not impacted by cycling to higher voltages within the timeframe studied.

Zhu, Zhikuan↗
DOE OSTI2020

System and method to characterize and identify operating modes of electric loads

A system characterizes and identifies one of a plurality of different operating modes of a number of electric loads. The system includes a processor; a voltage sensor providing a voltage signal for one of the electric loads to the processor; a current sensor providing a current signal for the one electric load to the processor; and a routine executed by the processor and structured to characterize the different operating modes using steady state and voltage-current trajectory features determined from the voltage and current signals, and to identify a particular one of the different operating modes based on a plurality of operating mode membership functions of the steady state and voltage-current trajectory features.

Yang, Yi↗
DOE OSTI2026

Multi-facility analysis using metered power data to quantify MRI energy use and utility bill costs across scanner operating modes

This study quantifies the energy consumption of magnetic resonance imaging (MRI) scanners across discrete operating modes during routine clinical workflows, based solely on electrical power measurements. Although previous studies have investigated MRI energy consumption within single hospitals or specific clinical settings, this research provides a broader and more systematic analysis. Researchers analyzed electrical power data and applied a previously developed semi-automatic method for identifying MRI operating modes using load duration curves for 20 MRI scanners across four different U.S. healthcare facilities, encompassing outpatient, inpatient, and mixed-use clinical settings. A key innovation is the inclusion of localized hourly utility rates to estimate costs, a parameter absent in prior literature. Key findings indicate significant variability in energy and cost profiles between weekdays and weekends. Scanner characteristics, including magnet strength, manufacturer, vintage, location, and clinical setting, influenced average daily energy consumption and power thresholds for operating modes. Notably, the clinical setting of a scanner predominantly determines its energy use. For example, the scanners in outpatient facilities consumed more energy. The breakdown of energy usage and costs by operating modes showed scanners spend between 61% and 93% of their time in nonproductive modes, with one outlier spending 34%. Average daily energy use for the scanners in the study ranged from 160 to 1069 kWh, with energy costs ranging from $\$$9 to $\$$149. This study uses an existing framework to quantify MRI energy behavior, leading to insights that can enable improved performance and cost savings across different healthcare environments.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2024

Inverter Intensive Hybrid Power Plant Modeling with Small-Signal Stability Augmentation through Flexible Operation Mode Transition

Hybrid power plants (HPPs) prompt the penetration of inverter-based renewable energy sources (RES) in transmission systems; however, given their low-inertia nature, HPPs are dominated by power electronic inverters, so there are inevitable challenges in system stability when increasing numbers of HPPs are integrated into the modern power grids. To boost the penetration level of HPPs without jeopardizing system stability, it is desirable to equip them with operational characteristics (i.e., grid-forming capabilities) that are comparable to those of conventional power plants dominated by synchronous generators (SGs). In this paper, a holistic model of inverter intensive HPP is derived and a bi-level hierarchical control is developed to allow HPPs to flexibly switch among the designed operation modes (i.e., P-Q, P-V, and isochronous modes). Compared to SGs, which have limited controllability, the operation mode of each HPP could vary as requested. Such flexible mode transitions could be integrated into the secondary plant-level control and be leveraged as an additional control degree to further augment system stability. Further, the system small-signal stability margin is quantified with varying HPP operation modes. More importantly, modal analysis is thereby conducted to quantify the impacts of mode transition on the system oscillatory modes. The effectiveness of the proposed HPP bi-level hierarchical control is verified using extensive case studies based on the simplified real-world island power grid, and the results validate that the system small-signal stability margin can be enhanced with the additional degree of control flexibility enabled by HPP operation mode transition. The real-time hardware-in-the-loop (HIL) results are also provided to verify the proposed method.

grid-forming control↗
DOE OSTI2020

Lifetime of Almost Strong Edge-Mode Operators in One-Dimensional, Interacting, Symmetry Protected Topological Phases

Almost strong edge-mode operators arising at the boundaries of certain interacting one-dimensional symmetry protected topological phases with Z 2 symmetry have infinite temperature lifetimes that are nonperturbatively long in the integrability breaking terms, making them promising as bits for quantum information processing. We extract the lifetime of these edge-mode operators for small system sizes as well as in the thermodynamic limit. For the latter, a Lanczos scheme is employed to map the operator dynamics to a one-dimensional tight-binding model of a single particle in Krylov space. We suggest this model to be that of a spatially inhomogeneous Su-Schrieffer-Heeger model with a hopping amplitude that increases away from the boundary, and a dimerization that decreases away from the boundary. We associate this dimerized or staggered structure with the existence of the almost strong mode. Thus, the short time dynamics of the almost strong mode is that of the edge mode of the Su-Schrieffer-Heeger model, while the long time dynamics involves decay due to tunneling out of that mode, followed by chaotic operator spreading. Furthermore, we show that competing scattering processes can lead to interference effects that can significantly enhance the lifetime.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Theoretical Understanding of Effects of Operating Modes on the Performance Durability of Solid Oxide Cells: A Comparison between Potentiostatic and Galvanostatic Operations

In solid oxide cells (SOCs), the choice between galvanostatic (constant current) and potentiostatic (constant voltage) modes does not significantly affect the performance of SOCs as long as the cell components remain unchanged and intact. However, the degradation of cell components, which leads to changes in electrochemical and physical properties of the cell, elevates the importance of the selected operating mode. This paper aims to investigate the effects of galvanostatic and potentiostatic operating modes on the evolving properties of SOCs and their subsequent influence on performance durability. Employing non-equilibrium thermodynamic analysis, a crucial approach for understanding the degradation phenomena within an active electrochemical system, this study aims to provide in-depth insights into how these operating modes affect the longevity and efficacy of SOCs. Key findings include: In cases where oxygen electrode (OE) degradation is accelerated by higher partial pressure of oxygen ( p O 2 ), operating under constant voltage electrolysis can mitigate the high p O 2 at the OE|electrolyte (OE|EL) interface. Conversely, if OE degradation occurs more rapidly under a lower p O 2 , constant current electrolysis is more effective in suppressing degradation by achieving a high p O 2 at the OE|EL interface. For degradation of the fuel electrode (FE) due to higher p O 2 , constant current electrolysis is beneficial for more stable performance, which helps maintain low p O 2 at the FE|EL interface. When FE degradation is accelerated by lower p O 2 , constant voltage electrolysis can avert low p O 2 at the FE|EL interface. In practical scenarios, more complex degradation mechanisms come into play, especially when p O 2 significantly deviates from initial conditions. Degradation in one electrode can influence p O 2 in the other electrode, a phenomenon more pronounced in potentiostatic than in galvanostatic electrolysis.

Electrochemistry↗
DOE OSTI2025

Identification of a window for quiescent H-mode operation in MHD stability diagram of DIII-D plasmas

A window for quiescent H-mode (QH-mode) operation in DIII-D plasmas in the diagram of pedestal magnetohydrodynamic (MHD) stability was identified through linear MHD stability analysis, accounting for the effects of plasma rotation and ion diamagnetic drift. The operation window lies between the stability boundaries of the kink/peeling mode (K/PM) identified with and without the inclusion of plasma rotation effects. In this region, the mode remains unstable unless rotation effects are considered alongside the ion diamagnetic drift, which is consistently included in the analysis. The stabilization of the MHD mode, facilitated by the coupled effects of plasma rotation and ion diamagnetic drift, plays a crucial role in widening the window, enabling the attainment of the QH-mode state. Furthermore, the suppression of edge localized modes (ELM) can be achieved by controlling the pedestal structure to ensure the plasma state remains within the operation window. The location of the operation window in the stability diagram depends on the K/PM stability properties. Therefore, optimizing conditions for QH-mode requires adjustments based on changes in stability characteristics. A pressure pedestal and its associated bootstrap current density near the last closed flux surface are advantageous for situating the plasma state within the window. However, excessive current density can trigger ELMs. This trend was confirmed through comparisons of MHD stability diagrams between QH-mode and ELMy H-mode plasmas.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Gasoline fuels properties for multi-mode operation – Observations in a GDI and the CFR engine

The combustion behavior of five full boiling range RON98 gasoline blends was evaluated for multi-mode operation in a GDI and the CFR octane rating engine. The GDI engine tests were conducted with stoichiometric air-fuel ratio in spark-ignition (SI), and with air-diluted homogeneous charge compression ignition (HCCI) mode. In the CFR engine, the knocking combustion was analyzed under standard RON testing conditions at both peak knocking lambda and stoichiometric air-fuel ratios, whereas compression ignited operation was characterized by utilizing the HCCI number test protocol. Disparate knock limited SI and HCCI combustion behavior was observed for the test fuels, despite four of the fuels having the same RON and octane sensitivity. It was found that knock-limited combustion phasing in the GDI engine did not align well with the RON. However, a detailed comparison of knock-limited SI operation in the GDI and CFR engine revealed that a more appropriate effective RON based on a common knock intensity metric (MAPO) and stoichiometric air-fuel ratio resulted in comparable knock characterization between the two engine platforms. Furthermore, the critical intake air temperature and the critical compression ratio were proposed to characterize knock-limited SI operation, while the minimum intake air heating and compression ratio were used to define a fuel's autoignition propensity for compression ignition operation in the GDI and CFR engine, respectively. Finally, each fuel's characteristic compression ratio needed to obtain knock-limited SI (KLSI) and HCCI operation was used to calculate an effective multi-mode octane number (MM-ON) based on the primary reference fuel blends.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2025

Extreme Enhancement-Mode Operation Accumulation Channel Hydrogen-Terminated Diamond FETs with V th < -6 V and High on-Current

In this work, a new Field Effect Transistor device concept based on hydrogen-terminated diamond (H-diamond) is demonstrated that operates in an Accumulation Channel rather than a Transfer Doping regime. The FET devices demonstrate both extreme enhancement-mode operation and high on-current with improved channel charge mobility compared to Transfer-Doped equivalents. Electron-beam evaporated Al 2 O 3 is used on H-diamond to suppress the Transfer Doping mechanism and produce an extremely high ungated channel resistance. A high-quality H-diamond surface with an unpinned Fermi level is crucially achieved, allowing for the formation of a high-density hole accumulation layer by gating the entire device channel which is encapsulated in dual-stacks of Al 2 O 3 . Completed devices with gate/channel length of 1 µm demonstrate record threshold voltage < -6 V with on-current > 80 mA mm -1 . Carrier density and mobility figures extracted by CV analysis indicate a high 2D charge density of ≈ 2 × 10 12 cm -2 and increased hole mobility of 110 cm 2 V -1 s -1 in comparison with more traditional Transfer-Doped H-diamond FETs. These results demonstrate the most negative threshold voltage yet reported for H-diamond FETs and highlight a powerful new strategy to greatly improve carrier mobility and enable enhanced high power and high frequency diamond transistor performance.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

Small-Signal Stability Constrained Optimal Power Flow of Inverter-Dominated Power Systems with Flexible Operation Mode Selection

Given the intermittence and low inertia nature of inverter-based resources (IBRs), modern power systems with high penetration of IBRs challenge the conventional optimal power flow (OPF) analysis and the system may experience unexpected failures if stability constraints are not incorporated. This study proposes a small-signal stability-constrained OPF (SSSC-OPF) with flexible operation mode selection between grid-forming (GFM) and grid-following (GFL) modes for IBRs to address these challenges. The approach aims to maintain system stability with a sufficient stability margin while minimizing operation costs. The effectiveness of the proposed method is validated through extensive case studies on the IEEE 14-bus system. The results demonstrate that the proposed method is able to support system-level power flow analysis, reduce generation costs, and ensure stability under various disturbances.

grid-following↗
DOE OSTI2020

HTS Quadrupole Magnet for the Persistent Current Mode Operation

In this work, a new high-temperature superconducting (HTS) quadrupole magnet with circular coils was designed and built at Fermilab. Several HTS coils were also investigated at the temperature of liquid nitrogen. The main goal of this activity was to investigate the coils and magnet operation in a persistent current mode to reduce accelerator magnets’ capital and operational expenses. To accomplish this, HTS short-circuit coils were used. In the paper, HTS coils and magnet design, fabrication, and tests were discussed. The magnetic field in the magnet aperture and the field decay when the magnet operated in the “frozen flux” mode were measured. The test and simulation results were compared, confirming the advantages of the proposed approach.

43 PARTICLE ACCELERATORS↗
DOE OSTI2020

FOFB-compatible AC Local Bump as a Potential New Operations Mode for NSLS-II

AC local bumps of the beam orbit developed at NSLS-II are successfully used for accelerator physics studies. Recently, AC bumps localized at light-generating insertion devices (ID) are considered by NSLS-II beamline scientists as a possible user operation mode. The AC perturbation of the X-ray beam in a controllable way will provide a possibility to investigate the effects of the source size and temporal evolution on the coherence of the photon beam. It also can be used to average out the spatial non-uniformity of the beam intensity caused by the beamline optics. Before the implementation of the AC orbit bumps into user operations, we must investigate if the electron beam perturbation affects the other beamlines. A proof-of-principle experiment was carried out: an AC bump was created and well localized in the CSX and/or FXI beamline. Transparency of this AC bump to other beamlines has been studied, the results are discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Cation Migration and LSCF/SDC Decomposition Related to Long-Term Operation Mode as Revealed by Electron Microscopy

This study utilized energy dispersive spectroscopy (EDS) in a scanning electron microscope (SEM) and a scanning transmission electron microscope (STEM) in order to track cation migration and related particle decomposition for air electrode components of solid oxide cells. The influence of a Sm-doped ceria (SDC) barrier layers was assessed for three operation modes (fuel cell, electrolysis, reversible) over long time periods (1000-1500 hours). Composition profiles across air electrode/electrolyte interfaces indicated negligible accumulation of La/Sr cations to the yttria-stabilized zirconia (YSZ) electrolyte during operation. Instead, air electrode particles composed of SDC and/or La-Sr-Co-Fe-oxides (LSCF) exhibited decomposition by Sr evaporation and Sm migration to LSCF particle edges.

Picard, Yoosuf↗
DOE OSTI2023

Thermal Energy Distribution System (TEDS) Operating Modes and Control Strategies

A Thermal Energy Delivery System was constructed at the Idaho National Laboratory for demonstrating distribution of thermal energy to and from co-located systems sited in the INL Dynamic Energy Transport and Integration Laboratory (DETAIL). DETAIL includes a flow loop simulating a pressurized water reactor, a high-temperature steam electrolysis unit and a thermal energy storage system. This report discusses the various operating modes and control strategies for enabling simultaneous, flexible and efficient transfer of heat from thermal energy sources to end users.

25 ENERGY STORAGE↗
DOE OSTI2023

Model Predictive Control-Based Dual-Mode Operation of an Energy-Stored Quasi-Z-Source Photovoltaic Power System

The energy-stored quasi-Z-source inverter (ES-qZSI) has attracted much attention for photovoltaic (PV) power generations, due to its capability to stabilize the PV power fluctuations with simple structure and other advantages of Z-source inverter. The improved dual-mode (DM) ES-qZSI is able to support all-weather operation even at night or cloudy days when PV power is extremely low. However, the traditional proportional–integral (PI) based control suffers from complicated controller design and poor dynamic response during mode transition, due to two sets of PI control required for the daytime and night operation modes. In order to overcome that, here in this article, we propose a model predictive control strategy for the DM-ES-qZSI PV power system. The system predictive models in both day and night operating modes are derived. The control strategy is disclosed to ensure high performance of the system, through calling the predictive models and defined cost functions of the two modes within a single control loop. Simulation and experiment are carried out to verify the effectiveness of the proposed control strategy.

14 SOLAR ENERGY↗
DOE OSTI2023

Reversible solid oxide cells: Early performance and microstructural evolution during electrolysis and switched mode operation

Incorporating more renewables into our energy mix will require a diversity of technological solutions. Reversible solid oxide cell systems (RSOCs) operating reversibly between fuel cell and electrolysis modes with high round-trip efficiencies offer one such solution. However, questions remain about the stability of the oxygen and fuel electrodes under reversible operation. Here, in this study, single cells with the configuration Ni-YSZ|YSZ|GDC10|NNO-NDC50|NNO are operated by reversible cycling under potentiostatic conditions. Test conditions are chosen to be representative of average stack conditions that are likely to be encountered during operation of a stack constructed of such cells. The results of reversible cycling over 500 h (21 cycles) are compared with operating the cells under potentiostatic conditions in the electrolysis-only mode (i.e., without cycling). Voltage-current density (DC), AC complex impedance spectroscopy, distribution of relaxation times (DRT) analysis, and scanning electron microscopy (SEM) indicate excellent reversibility and stability of the neodymium nickelate-based oxygen electrodes in both electrolysis and reversible cycling modes. Degradation behavior is attributed to the loss and coarsening of connected Ni particles in the fuel electrode, particularly in the active layer. However, reversible operation mitigates this degradation compared to operation in the electrolysis-only (SOEC-only) mode.

25 ENERGY STORAGE↗
DOE OSTI2022

Radiative pulsed L-mode operation in ARC-class reactors

Abstract A new ARC-class, highly-radiative, pulsed, L-mode, burning plasma scenario is developed and evaluated as a candidate for future tokamak reactors. Pulsed inductive operation alleviates the stringent current drive requirements of steady-state reactors, and operation in L-mode affords ELM-free access to ∼ 90 % core radiation fractions, significantly reducing the divertor power handling requirements. In this configuration the fusion power density can be maximized despite L-mode confinement by utilizing high-field to increase plasma densities and current. This allows us to obtain high gain in robust scenarios in compact devices with P fus > 1000 MW despite low confinement. We demonstrate the feasibility of such scenarios here; first by showing that they avoid violating 0D tokamak limits, and then by performing self-consistent integrated simulations of flattop operation including neoclassical and turbulent transport, magnetic equilibrium, and radiofrequency current drive models. Finally we examine the potential effect of introducing negative triangularity with a 0D model. Our results show high-field radiative pulsed L-mode scenarios are a promising alternative to the typical steady state advanced tokamak scenarios which have dominated tokamak reactor development.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Characterization of groove density variation of VLS gratings with ALS XROL LTP-II in different operation modes

The long trace profiler, LTP-II, available at the Advanced Light Source (ALS) X-ray Optics Laboratory (XROL), was recently upgraded by replacing a multimode diode laser light source with a single-mode, wavelength-stabilized, fibercoupled diode laser system. The upgrade enables us to reliably characterize the lateral variation of groove density of variable-line-spacing (VLS) x-ray diffraction gratings. Here, we discuss the LTP-II performance with an example of measurements with a VLS grating with the groove density at the grating center of 300 lines/mm. For the measurements, we use the LTP-II in two different operation arrangements, the single Gaussian beam and the pencil beam interferometer arrangements. For each operation arrangement, we apply two data processing algorithms: with calculating the centroid position and with determining the position of a characteristic features of the detected beam intensity distributions. Additionally, we discuss the observed strong correlation between the LTP-II modes of operation and the resulted (extracted) groove density variations. We also speculate on possible origin of the correlation.

42 ENGINEERING↗