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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Power Electronics Module with Integrated Ceramic Heat Exchanger

NREL, in partnership with Synteris and Packet Digital, has developed a 3D-printable ceramic package for power electronic modules to improve their thermal management, power density, performance, and lifetime. Existing power modules contain flat ceramic substrates that serve as both the electrically insulating component and thermal conductor that transfer the large heat outputs of these devices. The team has developed an additive manufacturing process that replaces the traditional insulating metalized substrate, substrate attach, and baseplate/heat exchanger with an additively-manufactured ceramic packaging that acts as both an electrical insulator and heat exchanger for better thermal management. The design, manufacturability, and function of this power module will be discussed.

25 ENERGY STORAGE↗
DOE OSTI2023

Semiconductor Thermal and Electrical Properties Decoupled by Localized Phonon Resonances

Abstract Thermoelectric materials convert heat into electricity through thermally driven charge transport in solids or vice versa for cooling. To compete with conventional energy‐conversion technologies, a thermoelectric material must possess the properties of both an electrical conductor and a thermal insulator. However, these properties are normally mutually exclusive because of the interconnection between scattering mechanisms for charge carriers and phonons. Recent theoretical investigations on sub‐device scales have revealed that nanopillars attached to a membrane exhibit a multitude of local phonon resonances, spanning the full spectrum, that couple with the heat‐carrying phonons in the membrane and cause a reduction in the in‐plane thermal conductivity, with no expected change in the electrical properties because the nanopillars are outside the pathway of voltage generation and charge transport. Here this effect is demonstrated experimentally for the first time by investigating device‐scale suspended silicon membranes with GaN nanopillars grown on the surface. The nanopillars cause up to 21% reduction in the thermal conductivity while the power factor remains unaffected, thus demonstrating an unprecedented decoupling in the semiconductor's thermoelectric properties. The measured thermal conductivity behavior for coalesced nanopillars and corresponding lattice‐dynamics calculations provide evidence that the reductions are mechanistically tied to the phonon resonances. This finding paves the way for high‐efficiency solid‐state energy recovery and cooling.

Spann, Bryan T.↗
DOE OSTI2023

Carbon Fiber Reinforced Plastic with Substantially Improved Through-plane Thermal Conductivity

Thermal conductivity of carbon fiber support structures that also serve as cooling substrates is of increasing importance for high energy physics detectors. One of the shortcomings of current carbon fiber laminates is that they exhibit excellent thermal conductivity of order several hundred W/(m*K) along the fiber direction, whereas the through plane thermal conductivity perpendicular to the fibers is orders of magnitude lower, and at about 1 W/(m*K) more in the range of thermal insulators. This proposal aims to significantly improve the through plane thermal conductivity, by at least a factor five, changing CFRP from being a thermal insulator to a thermal conductor in the through plane direction. Between June 2021 and December 2022, a total of 36 carbon fiber laminate test samples and two carbon loaded epoxy test samples were manufactured and analyzed for thermal performance. Unfortunately, the promising results obtained with a similar sample manufactured in 2017 were not reproduced. We believe this to be mainly due the excessive age of the carbon fiber prepreg material used for this SBIR - the same material batch, produced in 2015, was used in 2017 and in 2021/2022, i.e. the material was seven years old when the final samples were produced - , and to a lesser degree to the difference in pressure attainable with the 2017 and 2021/2022 laminate curing setups. While disappointing, the results are not completely discouraging, since for the samples with the highest compression the through-plane thermal conductivities plotted as a function of per-ply thickness extrapolate well to the data point from the 2017 sample.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Final design of outer poloidal field coils for COMPASS Upgrade

The paper aims to provide an overview of the final design of the outer poloidal field coils system for COMPASS Upgrade. Due to a relatively unique combination of design features of the new device (placement in high toroidal magnetic field, copper coils sub-cooled to liquid nitrogen temperature, hot vacuum vessel operation), the poloidal field coils design faced several interesting engineering challenges. Most notably high electromagnetic stress in the coil conductor, compatibility of the insulation to thermal and mechanical stress and design of coil supports with given spatial constraints while able to accommodate coil movements and withstand considerable mechanical stress. In conclusion, the paper describes solution to these challenges together with underlying analyses and mechanical tests.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Transition between Heavy-Fermion-Strange-Metal and Quantum Spin Liquid in a $4⁢d$-Electron Trimer Lattice

We present experimental evidence that a heavy Fermi surface consisting of itinerant, charge-neutral spinons underpins both heavy-fermion-strange-metal (without f electrons) and quantum-spin-liquid states in the 4d-electron trimer lattice, Ba 4 Nb 1-x Ru 3+x O 12 (|x| < 0.20). These two exotic states both exhibit an extraordinarily large entropy, a linear heat capacity extending into the milli-Kelvin regime, a linear thermal conductivity at low temperatures, and separation of charges and spins. Furthermore, the insulating spin liquid is a much better thermal conductor than the heavy-fermion-strange-metal that separately is observed to strongly violate the Wiedemann- Franz law. Here, we propose that at the heart of this 4d system is a universal, heavy spinon Fermi surface that provides a unified framework for explaining the exotic phenomena observed throughout the entire series. The control of such exotic ground states provided by variable Nb concentration offers a new paradigm for studies of correlated quantum matter.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Insulating Nanofluids and Solids to Upgrade our Large Aging Transformer Equipment (Advanced Research Projects Agency – Energy Research Final Report)

This project developed a highly promising, minimally invasive pathway for transformers with up to double the thermal life that is achieved today. Thermal life is important because it is occasionally necessary to overload transformers in service and this overload raises the internal temperature, accelerating aging2. A seminal initial finding in the research was that a likely achievable increase in the thermal conductivity of the transformer paper could double the thermal life. Oil-impregnated paper is used to wrap the electrical conductors in a transformer to provide a good balance of electrical insulation and thermal conductivity. The novel approach to increase the thermal conductivity was to add micrometer boron nitride particles to the paper during manufacturing. This is encouraging because it provides benefits with minimal impact on the manufacturing processes of the paper or of a transformer.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2023

Heat transport with a twist

Despite the desirability of polymers for use in many products due to their flexibility, light weight, and durability, their status as thermal insulators has precluded their use in applications where thermal conductors are required. However, recent results suggest that the thermal conductance of polymers can be enhanced and that their heat transport behaviors may be highly sensitive to nanoscale control. Here we use non-equilibrium molecular dynamics simulations to study the effect of mechanical twist on the steady-state thermal conductance across multi-stranded polyethylene wires. We find that a highly twisted double-helical polyethylene wire can display a thermal conductance up to three times that of its untwisted form, an effect which can be attributed to a structural transition in the strands of the double helix. We also find that in thicker wires composed of many parallel strands, adding just one twist can increase its thermal conductance by over 30%. However, we find that unlike stretching a polymer wire, which causes a monotonic increase in thermal conductance, the effect of twist is highly non-monotonic, and certain amounts of twist can actually decrease the thermal conductance. Finally, we apply the Continuous Chirality Measure (CCM) in an attempt to explore the correlation between heat conductance and chirality. The CCM is found to correlate with twist as expected, but we attribute the observed heat transport behaviors to structural factors other than chirality.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Sensors for measuring thermal conductivity and related methods

A sensor for measuring thermal conductivity includes an insulator, a test material over the insulator, a conductor over the test material, and a gas within an open volume adjacent the test material and the conductor. An electrical source is configured to provide an alternating current through the conductor to heat the test material. Leads are connected to the conductor and configured to connect to a voltmeter. A method of measuring thermal conductivity includes disposing the sensor in a reactor core in which a nuclear fuel undergoes irradiation and radioactive decay. An alternating current is provided from the electrical source through the conductor to heat the test material. A voltage is measured as a function of time at the leads connected to the conductor. A thermal conductivity of the test material is calculated based on the voltage measured as a function of time. Methods of forming a sensor are also disclosed.

Daw, Joshua↗
DOE OSTI2023

Hierarchical thermal-conductive polymer nanocomposites for thermal management

Managing heat in electrical conductors is a major challenge to meet the demands for sustainable energy use and electrical reliability, most notably power electronics and energy-critical electrical machines. Achieving such disparate functionalities, such as high temperature thermal and electrical reliability, require rational design and manufacturing of thermal conductor material and its hierarchical structures. Here we present hierarchical thermal-conductive nanocomposites, consisting of nanostructured ceramic conformal coating and aligned ultrahigh molecular weight polyethylene fiber, to tailor heat dissipation in electric conductors. The hybrid aligned thermal interface exhibits a highly desirable temperature dependent anisotropic high thermal conductivity with 0.98W m –1 K –1 and dielectric strength with 3.4. In addition, electrically insulating thermal interfaces demonstrate high-performing and reliable electrical systems under the dynamic load conditions. The surface temperature of heterogeneous ceramic-polymer encapsulated conductor is 17.8 °C lower than that of polymer-encapsulated conductor at the same electrical load. Consequently, the findings shown here hold great promises for directing heat extraction in electrical machine systems, advancing thermal management for emerging electronic applications.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Frequency Domain Reflectometry (FDR) Simulation Techniques for Digital Twin Representation of an Electrical Cable

Simulation of cable system response to frequency domain reflectometry (FDR) tests can be instrumental to understanding these tests and the nature and influence of various cable anomalies on test signatures. Reflectometry simulations are based upon a finite element representation of cable conductors and insulation to produce an S-parameter at each evaluated frequency. The aggregate collection of cable model S-parameters can simulate the influence on a test signal injected into a physical cable. Such an approach was undertaken in this work to produce a digital twin simulation of a low-voltage electrical cable. The electrical cable digital twin examined the influence of test simulation parameters and the relative influence of cable anomalies, including thermal aging, water or moisture exposure, water or moisture ingress, and other anomalies. The digital twin in this work included modeling of the conductors, insulation, jacket, and surrounding environment (air, water, etc.). The digital twin could be expanded to include cable bends, junctions and splices, branch or T systems, and termination impedances of motors or instruments. Observations and conclusions of this work include: 1. Fully 3D digital twin simulation of an electrical cable using an FDR approach is possible. However, there are tradeoffs between simulation fidelity and solution time, which must be balanced to ensure the simulation solves in an adequate amount of time (e.g., less than 20 minutes). Simulation parameters to balance include frequency bandwidth, number of frequencies, mesh density, connection impedance, and permittivity tolerance. 2. The digital twin simulation can explain FDR sensitivity to various cable anomalies, including entry and exit from an oven or water bath. 3. The digital twin simulation FDR response attenuates with distance along the cable and is further affected by the frequency bandwidth, which is similar to that observed with physical measurements. 4. The resolution of the digital twin FDR peaks increased with increasing bandwidth and with increasing number of frequencies, again similar to physical measurements. 5. The presence of multiple anomalies in the digital twin does not substantially attenuate the FDR response to anomalies located beyond the first encountered anomaly and impedance mismatch. 6. Spectral variation of the permittivity did not have a significant effect on the FDR response compared to a fixed nominal value. 7. Extension of the digital twin to 1000 ft still allowed for detection of distal anomalies near the far end of the electrical cable from the instrument connection point. 8. The ARENA test bed facilitates efficient NDE evaluations of well understood cable anomalies with various NDE methods without risking actual plant damage.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2023

High Power Density Cost-Effective MVDC Aircraft Cable

To make the power density of electric aircraft closer to conventional aircraft, an electric power system (EPS) with high power delivery and low system mass is necessary. As an essential component of aircraft EPS, cables are necessary to transmit power from one node to another. Virginia Tech will design high-power density, cost-effective ±5 kV cables for twin-aisle all-electric aircraft. Innovations include conductors with increased current-carrying capacity and a multilayer, multifunctional insulation system made of exceptionally high thermal conductivity materials. Designed for DC voltage, the new insulator will allow fewer partial discharge events and provide improved electromagnetic interference protection.

42 ENGINEERING↗
DOE OSTI2023

Ultrasonic waveguide reflectometry for quench detection (CRADA Final Report)

Early detection of thermal runaway (quench) is critical for safely operating high-temperature superconductor (HTS) magnets. Voltage-based techniques provide late detection of quenching in HTS, which can lead to magnet burnout and system damage. Various non-voltage quench-detection approaches are therefore investigated nowadays that are based on magnetic, acoustic, and optical sensing. LBNL has been actively developing the quench detection principle based on diffuse ultrasonic wave propagation since 2017 and has demonstrated the approach's viability with several peer-reviewed publications and a patent application. Over the last decade, Etegent, LBNL partner for this proposal and effort, has been developing a sensing technology that utilizes the propagation of stress waves through the solid metallic and nonmetallic waveguides (WG). The method is based on the dependence of materials' elastic properties and the speed of sound on temperature. Compared with optical analog, acoustic WG operates at much lower frequencies, eliminating the need for expensive, complex, highly sensitive receivers and data processing. Etegent proved this technology in many harsh environments, mainly concentrated high-temperature measurements. The initial contact between LBNL and Etegent started in 2020, aiming at combining our knowledge and effort toward developing a viable ultrasound-based quench detection technique for use with HTS magnets. A preliminary study conducted jointly in 2022 found no principle restrictions for expanding the WG technology toward cryogenic temperature operation. The present CRADA work aimed at designing, building, and testing ultrasonic waveguide temperature sensors at relevant cryogenic conditions, and demonstrating this technology's applicability to detecting heating and quenching in High Temperature Superconductor (HTS)-based cables and magnets. The technical objectives of the project included: (1) Design and fabricate ultrasonic WG sensors suitable for cryogenic operation, (2) Test ultrasonic WGs under cryogenic conditions, (3) Determining a suitable way of insulating WGs to prevent ultrasonic leakage while maintaining good thermal contact with the surrounding medium, (4) WG integration and cryogenic test with HTS conductors and HTS magnets, and (5) Design and basic prototyping of a standalone WG-based quench detection system. This project adds value to the present LBNL magnet diagnostics portfolio and enables a breakthrough in addressing the HTS magnet quench detection challenge.

47 OTHER INSTRUMENTATION↗
DOE OSTI2022

On the mechanism of radiation and thermal-induced degradation of the insulation cables in nuclear power plants-the presence of long-lived polyenyl C-centered radicals

Radiolytically and thermally produced long-lived polyenyl C-centered radicals in the nuclear power plants’ insulation cables are detected and measured after more than 45 months of aging since the irradiation and the thermal treatment. Electron Paramagnetic Resonance (EPR) results of the irradiated Cross-linked Polyethylene (XLPE) and Ethylene Propylene Rubber (EthProRu), used as primary insulation materials at Nuclear Power Plants (NPP), clearly demonstrate the presence of polyenyl radicals along with allyl and peroxyl radicals. The yields of these free radicals are dose-rate dependent. EPR results also show the presence of the long-lived polyenyl along with allyl and peroxyl free radicals in the thermally treated XLPE, and EthProRu. These free radicals can cause a major failure in the performance of these cables in NPPs. Besides, the results showed the enhancement in the oxidation reactions due to the migration of copper ions from the conductor to the bulk of the insulation. Further, this study also shows that the oxidation index (OI) and Elongation at Break (EAB) increases and decreases respectively at higher doses and temperatures.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Experimental Investigation of Steel-Borne Acoustic Pulses for Fault Pinpointing in Pipe-Type Cable Systems: A Scaled-Down Model Approach

Pipe-type cable systems, including high-pressure fluid-filled (HPFF) and high-pressure gas-filled cables, are widely used for underground high-voltage transmission. These systems consist of insulated conductor cables within steel pipes, filled with pressurized fluids or gases for insulation and cooling. Despite their reliability, faults can occur due to insulation degradation, thermal expansion, and environmental factors. As many circuits exceed their 40-year design life, efficient fault localization becomes crucial. Fault location involves prelocation and pinpointing. Therefore, a novel pinpointing approach for pipe-type cable systems is proposed, utilizing accelerometers mounted on a steel pipe to capture fault-induced acoustic signals and employing the time difference of arrival method to accurately pinpoint the location of the fault. The experimental investigations utilized a scaled-down HPFF pipe-type cable system setup, featuring a carbon steel pipe, high-frequency accelerometers, and both mechanical and capacitive discharge methods for generating acoustic pulses. The tests evaluated the propagation velocity, attenuation, and pinpointing accuracy with the pipe in various embedment conditions. The experimental results demonstrated accurate fault pinpointing in the centimeter range, even when the pipe was fully embedded, with the acoustic pulse velocities aligning closely with the theoretical values. These experimental investigation findings highlight the potential of this novel acoustic pinpointing technique to improve fault localization in underground systems, enhance grid reliability, and reduce outage duration. Further research is recommended to validate this approach in full-scale systems.

Moutassem, Zaki↗
DOE OSTI2022

Analysis of Defect Irrelevancy in a Non-Insulated REBCO Pancake Coil Using an Electric Network Model

High-temperature superconducting REBCO coated conductor is one of the main candidates for next-generation high field magnets in fusion reactors and particle accelerators owing to their high current-carrying capability. Although these materials can operate at higher temperatures and generate higher magnetic fields than their counterparts with lower critical temperatures, protecting the REBCO magnet against quench is challenging. A variety of candidate technologies that may be able to enable self-protection, including no-insulation technology and insulative coatings with temperature-dependent resistance, are in development. Here, in order to understand current sharing and thermal processes during a quench, we model a REBCO pancake coil as an electrical circuit, considering power generation and heat transfer along conductor turns, and study the current distribution around a local defect with lower critical current. The magnetic field and coil terminal voltage predicted by the simulation was compared to published experimental results. Our results provide useful insights into how current sharing occurs around defects.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Study of the Heater-Coil Electrical Insulation for the HL-LHC Low Beta Quadrupoles

In the framework of the HL-LHC project, the present LHC low-β superconducting quadrupoles will be substituted with higher performance Nb 3 Sn magnets (MQXF) with 11.4 T coil peak field. MQXF coils are impregnated with epoxy resin to reduce risk of stress concentration on the brittle conductor. The magnet quench protection is provided by CLIQ and quench heaters to ensure a redundant system. Quench heaters are impregnated with the coils in order to have suitable thermal contact with them, and to prevent the hot spot temperature from exceeding 350K during normal operation in case of a quench. Quench heaters are insulated from the coil by S-2 Glass and polyimide. Here, the test of the first MQXF prototype (4 m long) MQXFAP1 was stopped by a coil-to-ground short circuit triggered by a heater-to-coil short. This issue triggered a root analysis of the causes of this short. Here we prove that the use of a non-conforming cloth in coil impregnation, further weakened by non-conforming high voltage test, has triggered the shorts. Moreover, we present an analysis of the heater-to-coil insulation strength, showing the role of blistering phenomena and how they are triggered by a combination of magnet powering and heater firing.

43 PARTICLE ACCELERATORS↗
DOE OSTI2025

The Quench Protection of Direct Wind Magnets

The direct wind magnets have several unique features. The conductor layout is characterized by thin single conductors wound over long lengths and separated from the other turns with thick layer of insulation. Moreover, there are several layers of winding. The strong non-uniformity in the magnetic field distribution results in different current and thermal margins for quenching in different regions. The quench protection modeling involves multi-physics coupling between electrical, thermal and magnetic transient. The material properties vary over time and location. This coupled with the complexity in the geometry adds to long computation times. The objective of this study is to understand the quench propagation in an EIC high inductance direct wind magnet which enables one to design appropriate quench protection strategies to protect the magnet. An advanced modeling program has been developed to simulate direct wind magnet quench. In conclusion, we validate theoretical simulations with experimental data.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗