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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Major Drivers of Long-Term Distribution Transformer Demand

Distribution transformers, used to step-down medium voltage to service-voltage level for end-use electrical consumption, are currently experiencing major shortages. Utilities are experiencing extended lead times for transformers of up to 2 years (a 4x increase on lead times pre-2022) and prices have gone up by as much as 5-6 times in the past 2 years. Current shortages have been attributed to pent-up post-pandemic demand, workforce shortages and low retention rates, component supply chain challenges, and materials shortages (grain-oriented electrical steel, aluminum, and copper). The supply of this equipment is critical for the reliability and growth of the power system, and in meeting administration climate goals in terms of electrification of demand and the growth of renewable energy. This report details some of the initial analysis conducted by the National Renewable Energy Laboratory (NREL), supported by the Department of Energy's Office of Electricity and Office of Policy, in assessing the long-term demand trends for distribution transformers. Expected increased demand is due to a confluence of not only electrification and renewable energy growth, but also in the context of aging electric infrastructure, increased frequency and severity of extreme weather events, and utility-driven investments in reliability and resiliency of the electricity distribution system.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2021

Combined Dimensional and Topology Optimization of Interior Permanent Magnet Synchronous Machine Rotors Using a Permanent Magnet Function Interpolation Method

This paper presents a magneto-structural combined dimensional and topology optimization technique for interior permanent magnet synchronous machine (IPMSM) rotors. Dimensional changes to the permanent magnet (PM) location or size are accomplished by interpolating or projecting a smoothed Heaviside rectangular function representing the presence of PM material onto the IPMSM rotor design domain mesh. A density based Solid Isotropic with Material Penalization (SIMP) topology optimization approach is then used to vary the presence of electrical steel in mesh elements to form flux barriers around the PM. The proposed method enforces a defined shape for the PM without requiring the mesh in the design domain to be deformed. Three examples are presented to demonstrate the technique: two flat bar IPMSM and one V-shaped IPMSM.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2023

Combined Dimensional and Topology Optimization of Synchronous Machine Rotors Using a Material Density Interpolation Method

This article presents a magneto-structural combined dimensional and topology optimization technique for interior permanent magnet synchronous machine (IPMSM) and wound field synchronous machine (WFSM) rotors. Dimensional changes to the permanent magnet (PM) and rotor winding location or size are accomplished by interpolating or projecting a smoothed Heaviside rectangular function representing the presence of PM material onto the IPMSM rotor design domain mesh, whereas the presence of copper material for WFSM rotor is interpolated in the same manner. A density based Solid Isotropic Material with Penalization (SIMP) topology optimization approach is then used to vary the presence of electrical steel in mesh elements to form flux barriers around the PM. The proposed method enforces a defined shape for the PM without requiring the mesh in the design domain to be deformed. Four examples are presented to demonstrate the technique: Two flat bar IPMSM, one V-shaped IPMSM, and a WFSM. Here, a comparative study is performed on one of the flat bar IPMSMs using Metamodel of Optimal Prognosis (MOP) based method.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2024

Advanced multimaterial shape optimization methods as applied to advanced manufacturing of wind turbine generators

Abstract Currently, many utility‐scale wind turbine generator original equipment manufacturers are dependent on imported rare earth permanent magnets, which are susceptible to market risks from cost instability. To lower the production costs of these generators and stay competitive in the market, several small wind manufacturers are pursuing continuous improvements to both generator design and manufacturing. However, traditional design and manufacturing methods have yielded marginal improvements in wind power performance. This work presents novel methods to redesign a baseline 15‐kW wind turbine generator with reduced rare‐earth permanent magnets by leveraging cutting‐edge three‐dimensional (3D) printed polymer‐bonded permanent magnets and steel. Symmetric, asymmetric, and multimaterial‐magnet parametrization methods are introduced for shape optimization. We extend the symmetric and asymmetric methods to the back iron in the stator to further investigate the impact and opportunities for performance improvements with lesser active materials. We employ a design‐of‐experiments approach with parametric computer‐aided design for shape generation and evaluate different designs by magneto‐thermal modeling and finite‐element analysis. We use adaptive sampling technique to identify better performing designs with lesser magnet mass, higher efficiency, and lower cogging torque when compared with the baseline generator. Asymmetric pole designs resulted in a magnet mass in the range of 4.77–5.37 kg, which was 27%–35% lighter than the baseline generator, suggesting that a new design freedom exists that can be enabled by advanced manufacturing, such as 3D printing. Shaping the back iron in the stator resulted in material savings in electrical steel of up to 14.62 kg, which was 20% lighter than the baseline stator. We conducted a structural analysis to evaluate an optimized asymmetric rotor design from the point of view of mechanical integrity and air‐gap stiffness. The magnetically optimal shape profile was shown as having a positive impact on the radial stiffness, and an optimal solution was discovered to reduce the structural mass by nearly 30 kg, which was 29% lighter than the baseline.

17 WIND ENERGY↗
DOE OSTI2024

Wet chemistry-synthesized Fe/mixed ferrite soft magnetic composites for high-frequency power conversion

State-of-the-art soft magnetic (SM) alloy systems such as electrical steels and permalloys exhibit large eddy current losses at high-frequency (kHz range and above), limiting their application in fast switching devices. Eddy current losses can be reduced for metallic alloys through a decrease in characteristic length scale or embedding them in an insulation layer. This work proposes the development of fine-scale core materials consisting of metallic SM nano/microparticles with magnetic, inorganic insulation layers, and their synthesis using a wet chemistry-based, scalable method for high frequency and high-power applications. More specifically, a magnetic ferrite coating (Ni 0.5-x Mn x Zn 0.5 Fe 2 O 4 , x = 0.0–0.5) was applied via deposition of ferrite powder produced using a “wet chemistry-based” co-precipitation method; the ferrite was distributed through the Fe micropowder via either ball milling or ultrasonic mixing. Powder cores were prepared by compaction of the synthesized composites. Relative magnetic permeability and core loss were measured at excitation frequencies to 200 kHz. A core loss of 127 kW/m 3 was measured at excitation frequency of 100 kHz and magnetization of 0.02 T. This value improves on the 199.3 kW/m 3 reported in literature at identical excitation conditions for a compact formed from a composite comprising Fe microparticles coated with low-permeability Ni 0.5 Zn 0.5 Fe 2 O 4 . Ultrasonic mixing resulted in slightly lower core loss than ball milling, possibly because ball milling causes loss-increasing deformation of the Fe micropowder. XRD and SEM were used to observe composite composition and core cross-section microstructure.

36 MATERIALS SCIENCE↗
DOE OSTI2024

RePED 250: Manufacturing and Market Analysis of High-Temperature Alternators

The novel repetitive pulsed electric drill 250 (RePED 250) has the potential to greatly lower the costs and drilling times of geothermal projects. This tool discharges electric pulses through hard rock formations, shattering the rock in tension and allowing it to be quickly removed. One hurdle in bringing this technology to market is the RePED 250 downhole alternator. This component is essential for supplying power to the electronic drilling tool. There are currently no downhole tools on the market that meet the RePED 250 alternator's high temperature and power requirements. This report focuses on the path to commercialization for this novel alternator technology being developed as part of the RePED 250 project. One aim of this work is to identify the geothermal market size for the RePED 250 alternator, as well as other potential markets for this technology outside of geothermal. The geothermal market is very small, with only approximately 13 wells drilled in the United States each year. The worldwide market is several times this size and growing each year. The ability of the RePED 250 technology to drastically reduce the cost of geothermal projects may also lead to an increase in this market size. Technology developed for the high-temperature, high-power RePED 250 alternator can also be used to create high-temperature and high-power motors. These motors and alternators will have potential applications in oil and gas drilling, a $300 billion dollar industry in the United States alone, as well as in more distant industries such as aircraft, weapon systems, space exploration, and electric vehicles. Other aspects of the RePED 250 alternator's path to commercialization are also analyzed, including the supply chain for production materials and potential manufacturing methods. The supply chain and manufacturing practices for low-temperature motors and alternators are well established and require relatively minor changes for the high-temperature and high-power RePED 250 alternator. Sourcing for high-temperature materials has been identified, as well as potential supply chain risks. These most notably include electrical steel and high-temperature samarium cobalt (SmCo) magnets. Overall, these risks are not expected to be significant at the likely manufacturing scale required for the RePED 250.

15 GEOTHERMAL ENERGY↗
DOE OSTI2026

Large Power Transformer Supply Chain Gap Analysis and Domestic Content Strategies for Hydropower Rehabilitation: Supplemental Report

Large Power Transformers (LPTs) are indispensable to U.S. hydropower operations, serving as generator step-up (GSU) units that interconnect hydro facilities to the transmission grid. Yet the LPT supply chain faces mounting stress from aging infrastructure, limited domestic production, and long lead times. Currently, more than 80% of LPT demand is met through imports, with primary suppliers including Mexico, South Korea, Brazil, Austria, and Canada. Domestic manufacturers supply only about 20% of units, constrained by bottlenecks in high-grade Grain-Oriented Electrical Steel (GOES), copper conductors, bushings, and on-load tap changers (OLTCs). Hydropower rehabilitation projects in particular face additional challenges due to custom design requirements, remote siting, and regulatory needs around domestic content. Regional cost disparities, driven by transportation logistics, labor markets, and import price volatility, further exacerbate project risks. To address these vulnerabilities, coordinated action is required: strengthening domestic capacity for GOES and secondary components, developing near-site assembly hubs, and leveraging IRS domestic content safe harbors to incentivize U.S. manufacturing. This addendum refines the 2024 NREL Hydropower Supply Chain Gap Analysis by focusing specifically on critical issues related to LPT domestic manufacturing capacity and key considerations for hydropower developers and asset owners.

13 HYDRO ENERGY↗
DOE OSTI2023

Fabrication and characterization of net-shaped iron nitride-amine-epoxy soft magnetic composites

Soft magnetic composites (SMCs) offer a promising alternative to electrical steels and soft ferrites in high performance motors and power electronics. They are ideal for incorporation into passive electronic components such as inductors and transformers, which require a non-permanent magnetic core to rapidly switch magnetization. As a result, there is a need for materials with the right combination of low coercivity, low magnetic remanence, high relative permeability, and high saturation magnetization to achieve these goals. Iron nitride is an attractive soft magnetic material for incorporation into an amine/epoxy resin matrix. This permits the synthesis of net-shaped SMCs using a “bottom-up” approach for overcoming the limitations of current state-of-the-art SMCs made via conventional powder metal processing techniques. In this work we present the fabrication of various net-shaped, iron nitride-based SMCs using two different amine/epoxy resin systems and their magnetic characterization. The maximum volume loading of iron nitride reached was ~77% via hot pressing, which produced SMCs with a saturation magnetic polarization (J s ) of ~0.9 T, roughly 2–3 times the J s of soft ferrites.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Optimization of Scrap Melting Using an Electric Arc in Steel Manufacturing

Steel industry is crucial to the national economy and security. Around 67% of crude steel in the U.S is produced in electric arc furnaces (EAF), which is energy intensive. Around 140 EAFs operate in the U.S., consuming about 8.6x10 7 MMBtu/year of electricity. One of major challenges for EAFs includes maximizing the efficiency of the electrical energy provided in the form of electric arcs to melt various scrap mixes. To address this issue, a computational fluid dynamics (CFD) methodology is chosen to analyze scrap melting using the electric arc. Due to complex furnace phenomena and the wide variety of potential scenarios, high performance computing (HPC) is essential to yield comprehensive and detailed CFD analyses and systematic parametric studies for optimized EAF operation. The objectives are to 1) simulate scrap melting using electric arc, 2) evaluate electrode/arc position for optimum scrap melting and 3) establish reduced order model for CFD data-base for fast model calculation.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2026

Hybrid Grid-Renewable Strategies for Green Steel Production under Electricity Market Uncertainty

Volatility in grid spot prices is expected to rise with climate change-driven demand pressures and the intermittency of renewable generation. This volatility poses financial risks for green hydrogen-based steel production. The Direct Reduced Iron− Electric Arc Furnace (H 2 -DRI-EAF) is a promising pathway to decarbonize steel, which accounts for ∼8% of global GHG emissions. This study assesses how increased grid spot price volatility influences the optimal sizing and operation of H2-DRIEAF plants under three operational scenarios: grid-connected, fully behind-the-meter (islanded), and mixed-mode (semi-islanded). Our analysis identifies the semi-islanded configuration as the most cost-effective solution, achieving a Levelized Cost of Steel (LCOS) 10−35% lower than sourcing energy solely from the grid. Modeling also shows hydrogen storage or selective electricity purchases at high prices (>$1000/MWh) generally outperform battery storage, except under extreme volatility. Additionally, the study explores cost reduction strategies to strengthen the economic viability and sustainability of green steel production.

Batteries↗
DOE OSTI2021

The effect of electrical current on premature failures and microstructural degradation in bearing steel

Premature failures associated with microstructural degradation, i.e. white etching cracks (WECS), are becoming commonplace as applications are requiring tribological components to operate under extreme conditions. Although the specific drivers of WECs are still debated, the failures are often found in applications where cyclic loading is combined with added energy from stressors such as slip, impacts, or stray current. The aim of the current work is to elucidate effect that variable current has on premature failure. Numerous commercially available lubricants were tested, and both lubricant base oil type and additive package were found to have an effect on WEC failure time.

Bearing failure↗
DOE OSTI2020

Cost Effective 6.5% Silicon Steel Laminate for Electric Machines

Iowa State University teamed with United Technologies Research Center and the University of Delaware and demonstrated a high switching frequency non-rare earth permanent magnet motor. A prototype motor with 400 Hz switching frequency, dummy MnBi permanent magnet with 8 MGOe energy density, and 6.5%Si steel as the laminate materials was designed, built, and tested. The performance of the prototype met the expectations showing a higher frequency motor enabled by 6.5%Si steel is a viable approach to meet DOE 2022 cost and performance targets for electric vehicle drive. Adoption of 6.5%Si steel will result in 3% improvement in energy conversion efficiency of the soft magnetic materials. In addition, the ability to use non-rare earth magnet for high power density application effectively mitigate the risk of EV traction motor from the rising rare earth price.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2021

A Mechanism for Carbon Depletion at Bondline of High-Frequency Electric-Resistance-Welded X70 Pipeline Steel

The bondline of electric-resistance-welded (ERW) linepipe steel, often etched white (i.e., ferrite) in optical microscopy, is generally believed to be carbon depleted. The mechanism for the carbon depletion, however, is not fully understood by researchers. To this end, here we used atom probe tomography (APT) to measure elemental segregation of the as-welded and post-weld heat-treated bondline regions of X70 linepipe welds. The thin vertical features at the bondline in the as-welded condition were identified as carbon-rich martensite-austenite (M-A) constituents, and the majority ferrite phase in the bondline was identified as carbon-depleted ferrite. Following the post-weld normalization, all alloying elements, except Nb and Mo, are homogenized across the bondline and heat-affected zone. The carbon depletion in the ERW bondline was accurately measured. A new mechanism for carbon depletion has been proposed using Scheil calculations of elemental partitioning during weld formation. Segregation of elements in the heat-affected zone was shown to follow the negligible partitioning local equilibrium (NPLE) kinetics for bainite transformation.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Electric current-induced precipitation hardening in advanced high-strength steel

Effect of electric current on precipitation hardening for advanced high-strength steel is investigated based on mechanical testing and microscopic observation. Complex-phase steel containing nano-sized Nb-bearing carbides was used. By comparing the flow stress between uniaxial tension with applied electric current (pulsed tension) and without electric current (nonpulsed tension) at various elevated temperatures, the influence of electric current on precipitation hardening was confirmed. A higher values of Vickers hardness and full-width-at-half-maximum were obtained in the pulsed tensile specimen compared to the identically heat treated specimen after the same deformation. Small angle neutron scattering analysis showed that the volume fraction and mean diameter of newly formed precipitates in the pulsed tensile specimen were higher and larger than those in the induction heat treated specimen, respectively. In conclusion, it clearly shows that additional precipitation hardening could be induced by the athermal effect of electric current, which is distinct from the thermal effect of Joule heating.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Postweld Heat Treatment on Toughness of Electric- Resistance Welded X70 Steel

In this report the effect of postweld heat treatment (PWHT) on Charpy V-notch impact toughness of a highfrequency electric-resistance welded (HF-ERW) grade X70 pipeline steel is investigated. PWHT thermal cycles are simulated using the Gleeble on the as-welded specimens. Microstructure, along with crystallographic texture and microhardness, is characterized in specimens that are impact tested at –5°C (23°F), –30°C (–22°F), and –45°C (–49°F). The impact toughness values show a wide scatter band and decrease with the increasing peak temperature of the PWHT. For higher peak temperatures, the microstructure of the heat-affected zone (HAZ) gradually changed from equiaxed ferrite to bainitic ferrite. Furthermore, the prior austenite grain size (PAGS) increases with the increasing peak temperature. The density of high-angle grain boundaries decreases, and the fraction of cleavage planes {100} parallel to the impact fracture plane increases for higher peak temperatures of the PWHT

36 MATERIALS SCIENCE↗
DOE OSTI2024

Circular Economy Contributions to Decarbonizing the US Steel Sector

The potential benefits of the circular economy (CE) for decarbonization have recently attracted much attention in the academic and grey literature. The department of energy (DOE) industrial decarbonization roadmap highlight that in addition to the four pillars (energy efficiency, electrification, low-carbon fuels, feedstocks, and energy sources, and carbon capture, utilization, and storage (CCUS)) identified in the roadmap, "scenarios [...] will need to be developed that incorporate materials efficiency and circular economy strategies". Moreover, the roadmap identifies hard-to-abate CO2 emissions across the five industrial subsectors included in the analysis (iron & steel, chemical, food & beverage, refining, and cement manufacturing). Thus, additional options to decarbonize the industrial sector, like the CE, could prove beneficial to address those hard-to-abate emissions. Moreover, they may be less costly, require less R&D or incentives, and be more readily adopted than other strategies such as energy efficiency and CCUS. While the Industrial Decarbonization Roadmap includes some CE strategies (e.g., the increasing market share of steel from electric arc furnaces - which incorporate steel scrap), a deeper dive into what role the CE could play in the United States (US) industrial decarbonization is needed. In this work, we present several industrial decarbonization scenarios that incorporate materials efficiency and circular economy strategies for the iron & steel subsector. The scenarios identify barriers (including technical limits and constraints), opportunities, and R&D needs.Moreover, we estimate the contribution of those scenarios to reducing the industrial sector's CO2 emissions and their potential synergies with the Industrial Decarbonization Roadmap's four pillars. Iron & steel manufacturing was responsible for 90 million tons of industrial CO2 emissions in 2020 - 7% of the industrial sector's total process- related emissions. Besides recycling - which presents technical limitations due to trace contaminants - CE strategies on the demand side could lower iron & steel manufacturing emissions (e.g., the development of lighter products or business models that encourage a more intensive use). This study reviews barriers, opportunities, and trade-offs for 5 material efficiency strategies. Many topics explored in the review call for further research.

barriers↗
DOE OSTI2025

Porous Interlayers that Getter Surface-Segregating Species for Improved Silver Wetting, Adhesion, and Electrical Contact on Stainless Steel SOFC Components

Here, porous nickel interlayers or porous platinum interlayers were shown to promote the wetting, spreading, and adhesion of silver on alumina-forming ferritic stainless steel (AFFSS) and chromia-forming ferritic stainless steel (CFFSS). These interlayers resulted in dense, crack-free AFFSS|Ag-Ni|CFFSS and AFFSS|Ag-Pt|CFFSS braze joints that, after 300 h in 650 °C air, displayed shear strengths up to 70 MPa similar to, or larger than, those of AFFSS|Ag-CuO|CFFSS or AFFSS|Ag|CFFSS joints subjected to identical treatment. Similarly, after exposure to 25 cycles of (50 switches between) 12 h of 650 °C air and 12 h of 650 °C 4%H 2 –96%N 2 , AFFSS|Ag-Ni|CFFSS and AFFSS|Ag-Pt|CFFSS braze joints displayed shear strengths significantly larger than those of AFFSS|Ag-CuO|CFFSS or AFFSS|Ag|CFFSS joints subjected to identical treatment. In addition, nickel and platinum were found to chemically getter surface-segregating steel constituents, particularly Al from the AFFSS. As a result, Ag-Ni and Ag-Pt electrical contact resistances on AFFSS and CFFSS substrates were several orders of magnitude lower than those of conventional Ag-CuO reactive air brazes or Heraeus C8710 Ag contact pastes. Together, these results suggest that Ag-Pt and especially Ag-Ni may be useful for the fabrication of durable joints, seals, and/or electrical contacts in electrical/electrochemical devices exposed to high temperatures and/or variable oxygen partial pressure environments.

36 MATERIALS SCIENCE↗