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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Control over pulsed operation modes of an erbium-doped fibre laser passively mode-locked via nonlinear polarisation rotation

We have experimentally demonstrated the possibility of controlling pulse generation modes of an erbium-doped fibre ring laser operating in the anomalous dispersion regime and passively mode-locked via nonlinear polarisation rotation. It has been shown that individual adjustment of the pump power and intracavity polarisation controllers leads to changes in pulse generation mode, without changing the cavity. We have evaluated the key spectral, temporal and energetic characteristics of the observed pulse generation modes. (control of laser radiation parameters. active media)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Operation modes of the KATRIN experiment Tritium Loop System using 83m Kr

The KArlsruhe TRItium Neutrino (KATRIN) experiment aims to search for the effective electron antineutrino mass with a sensitivity of 0.2 eV (90 % C.L.). In order to achieve this goal, KATRIN measurement phases focusing on the neutrino mass search are alternated with phases of investigations of systematic effects. During these phases, metastable 83m Kr is used as a calibration source. The monoenergetic conversion electrons emitted accompanying the decay of 83m Kr allow a direct access to the starting conditions of β-electrons produced inside the windowless gaseous tritium source (WGTS) of KATRIN. To make use of 83m Kr in the WGTS, the Tritium Loop System, which provides a stable flow of tritium to the WGTS, needs to be operated in special modes. This paper focuses on the technical implementation of these modes and their performance with regard to the achievable 83m Kr-rates, gas densities, and gas compositions inside the WGTS.

47 OTHER INSTRUMENTATION↗
DOE OSTI2021

Stability Impact of IEEE 1547 Operational Mode Changes Under High DER Penetration in the Presence of Cyber Adversary

The IEEE 1547 standard addresses the integration of Distributed Energy Resources (DER) into Area Electric Power Systems (AEPS). The updated standard, released in 2018 with revisions ongoing, specifies the need for more flexible settings, requiring the DER to remain connected during certain disturbances and provide voltage support via active and reactive power modes. With these increased capabilities comes increased risks, and our analysis of the standard has produced potential settings combinations, which, while allowable under the standard, may actually create instability. This contradicts the main purpose of the revised standard. Since the DER must support a communication interface through which the AEPS operator can change settings, adversarial mode changes are possible via a cyberattack. This concern is heightened as DER penetration increases, where under a reasonable threat model, an attacker could affect multiple DER simultaneously. We have conducted a simulation analysis of potentially adverse combinations of mode change and ridethrough parameters on a hypothetical AEPS with varying degrees of DER penetration. We conclude that certain adverse mode changes, whether through error or cyberattack, can lead to unstable conditions with DER penetrations as low as 24% of the AEPS system capacity.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2023

Optimization Formulations for Storage Devices with Disjoint Operating Modes

Optimizing State of Charge for Storage Resources Storage of generated energy has existed as a contributing resource within the power sector for more than a century in the case of pumped hydro storage. Even though most regional transmission organizations/independent system operators do not currently optimize state of charge (SOC) for storage, the SOC is an essential aspect of the operating characteristics of storage. This paper investigates the impact on computational performance of optimizing storage with explicit representation of SOC. To investigate the model, the paper considers two contexts, stand-alone and large-scale. Analysis of the stand-alone context helps to explain why the combination of features in the storage model results in a difficult problem. Numerical results for large-scale test cases verify that new tighter valid inequalities can improve the computation compared with the standard model in the literature.

Business & Economics↗
DOE OSTI2024

Evaluation of SPARC divertor conditions in H-mode operation using SOLPS-ITER

The predicted divertor conditions for the SPARC tokamak are calculated using SOLPS-ITER for a range of scrape-off-layer (SOL) heat flux widths λ q , input powers, and particle fueling locations. Under H-mode scenario conditions with an upstream separatrix density of 1 x 10 20 m -3 , the most conservative range of λ q extrapolations ( 0.15 mm) results in extremely high unmitigated particle and energy fluxes to the divertor, both under full field (12.2 T) and power (P SOL = 29 MW) conditions, and 2/3 field with P SOL = 10 MW. Increasing the cross-field SOL diffusivities by 2–10× reduces the magnitude of the mitigation challenge, however strategies such as impurity seeding or strike-point-sweeping will likely still be required. A combination of steady-state and time-dependent SOLPS-ITER simulations are used to map out phase space diagrams of upstream and divertor conditions. The simulations include parallel currents but neglect cross-field drifts. At low upstream density the inner and outer divertor conditions are highly asymmetric, with a large temperature difference and significant heat fluxes driven by parallel currents. The solution has sharp bifurcations with a region of hysteresis, depending on whether the initial state is at a low or high density. This behavior is observed even when the fueling location, cross-field diffusivity, and impurity level is changed, although the density window with asymmetry is reduced with increasing diffusivity. The addition of neon impurity seeding reduces the divertor heat fluxes, but also causes a drop in the upstream electron density with fixed particle throughput. This drop can be counteracted by increased main ion throughput, however too much neon results in a back transition into the asymmetric divertor regimes suggesting a need for control of both main ion and impurity seeding levels to achieve a desired divertor state.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Operational Modes of a 2.0 MWth Chloride Molten-Salt Pilot-Scale System

The limit of traditional solar-salt thermal stability is around 600 °C with ambient air as the cover gas. Nitrate molten salt concentrating solar power (CSP) systems are currently deployed globally and are considered to be state-of the art heat transfer fluids (HTFs) for present day high-temperature operation. However, decomposition challenges occur with these salts for operation beyond 600 C. Although slightly higher limits may be possible with solar salt, to fully realize SunShot efficiency goals of $15/kWhth HTFs and an LCOE of 6¢/kWh, molten-salt technologies working at higher temperatures (e.g., 650 °C to 750 °C) will require an alternative salt chemistry composition, such as chlorides. In this investigation a 2.0MWth Pilot-scale CSP plant design is developed to assess thermodynamic performance potential for operation up to 720 C. Here, an Engineering Equation Solver (EES) model is developed with respect to 14 state-points from the base of a solar tower at the Sandia National Laboratories, National Solar Thermal Test Facility (NSTTF), to solar receiver mounted 120 ft. above the ground. The system design considers a ternary chloride ternary chloride (20%NaCl/40%MgCl/40%KCl by mol%) salt as the HTF, with 6 hrs. of storage and a 1 MWth primary salt to sCO2 heat exchanger. Preliminary system modelling results indicate a minimum non-dimensional Cv of 60 required for both cold and hot-side throttle recirculation valves for the operational pump operating between speeds of 1800 and 2400 RPM. Further receiver comparison study results suggest that the ternary salt requires an average 15.2% higher receiver flux with a slightly lower calculated receiver efficiency when compared to a binary carnelite salt to achieve a 2.0 MWth desired input power design.

associated liquids↗
DOE OSTI2023

Cooling performance of an active-passive hybrid composite phase change material (HcPCM) finned heat sink: Constant operating mode

Here, the present study explores a hybrid thermal management technology based on air cooling and hybrid composite phase change material (HcPCM) filled finned heat sink for cooling performance of lower to medium heat flux dissipating electronic devices. Two-dimensional numerical simulations are conducted to study the conjugate heat transfer effects of three types of finned heat sink: air-cooled finned heat sink, HcPCM-cooled finned heat sink, and hybrid (air-HcPCM) cooled finned heat sink. A heat sink with a constant volume faction of plate-fins is designed in all cases and simultaneous effects of hybrid nanoparticles and air are investigated to keep the heat sink temperature at safe operating conditions between 40–60°C. The effect of air is incorporated into the heat sink by applying the convective heat transfer coefficient of h c = 10–100W /m 2 .K which tends to create the natural convection and forced convection heat transfer characteristics. The heat flux is varied from 25–40kW /m 2 in the current study. The hybrid nanoparticles of carbon additives (GO and MWCNTs) are dispersed into the RT-35HC, used as a PCM, with a volume fraction of 0% to 6%. Transient simulations are carried out using COMSOL Multiphysics to solve the governing equations for PCM based conjugate heat transfer model. The results showed that forced convection heat transfer improved the cooling performance of the hybrid heat sink compared to natural convection heat transfer. The addition of nanoparticles further enhanced thermal enhancement and uniform melting distribution of PCM inside the finned heat sink. The h c between 30 to 50W/m 2 .K shows optimized values for forced convection heat transfer operating conditions. The volume fraction of 2% of GO+MWCNTs nanoparticles in recommended or optimum concentration for uniform melting of PCM inside the finned heat sink.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Protection schemes used in North American microgrids

This study reviewed existing conventional and nonconventional protection schemes for grid-connected and islanded mode operations in North American microgrid projects. The microgrid projects investigated in this study used different types of distributed energy resources (DERs) and integrated hydropower/diesel generators, gas/steam/wind turbines, and photovoltaic systems with energy storage. In this work, conventional protection schemes were defined as those within the IEEE Standard C37.2-2008, whereas nonconventional schemes were those not defined within this standard. The pros and cons of conventional and nonconventional protection schemes were discussed in detail. The overvoltage, undervoltage, and frequency elements were the most common conventional protection schemes applied in microgrid projects in North America. These protection elements were used to detect the islanded conditions and faults that could not be sensed by overcurrent relays because of small fault currents contributed by low-inertia DERs and power-electronic sources. Directional overcurrent elements were used to distinguish between external (grid) and internal (microgrid) faults. Adaptive protection was the most popular nonconventional protection scheme applied to the microgrid projects. In conclusion, different types of DERs and operational modes must be considered in order to address the protection and control challenges of each microgrid and to obtain the best technical and economical solution.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2021

Development of a Power Electronics-based Testbed for a Flexible Combined Heat and Power System

A flexible combined heat and power (F-CHP) concept, enabled by a power electronics-based power conditioning system (PCS), has been recently proposed as a cost-effective way for supporting the grid with high penetration of renewable energy sources. To verify the design, control, and performance of the overall system, a laboratory-scale testbed is essential. This paper focuses on the development of a power electronics-based testbed for such a F-CHP system. The developed testbed can test the control, grid-connected mode operation, islanded mode operation, and mode transitions, including planned/unplanned islanding and reconnection, of the F-CHP system. In the grid-connected mode, both the steady state and transients of the ac grid can be emulated, and various grid support functions can be tested with the help of the developed PCS converter. In the islanded mode, the external ac loads can also be supported by the F-CHP system. Also, the central controller, which is implemented in a NI CompactRIO, can be tested. Experimental test results for the grid-connected mode, islanded mode, and mode transitions are provided to validate the testbed design.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2020

Assessment of operational availability for the PIP-II Superconducting Radio Frequency linear accelerator facility

Operational availability is a critical performance measure for an accelerator facility in modern time. A high availability enables the facility to serve a wide range of users simultaneously. Consequently, besides pure accelerator physics considerations, newly proposed accelerator facilities account for the availability and reliability aspects in the design phases. It allows incorporation of appropriate mitigation strategies for the most vulnerable systems in the machine and therefore, minimizes unscheduled interruptions during the operation. This report lays out a methodology for the availability assessment of the complete particle accelerator facility and presents an initial assessment of the availability of the newly proposed Proton Improvement Plan-II (PIP-II) accelerator facility at Fermilab. The paper describes a comprehensive reliability model of the PIP-II facility that comprises not only 800 MeV linear accelerator (linac) system but also essential utility systems in the form of cryogenic, water, power and air systems. The paper details estimations of the availability of the PIP-II facility for two operational modes i.e. the nominal operational mode featuring 800 MeV beam and critical operational mode involving operation with the lowest objective beam energy of 600 MeV.

43 PARTICLE ACCELERATORS↗