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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 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Damping optimization for wave energy converters with compressible volumes.

The addition of a compressible degree of freedom (CDOF) to a wave energy converter (WEC)-which results in a compressible WEC-has been shown to significantly increase power absorption compared to a rigid WEC of the same shape and mass for a variety of architectures. This study demonstrates that a compressible point absorber, with a passive power-take-off (PTO) and optimized damping, can also achieve equal or better performance levels than an optimally controlled rigid point absorber (with the same shape and mass) using reactive power from the PTO. Wave energy is converted to mechanical energy in both cases using a linear damper PTO, with the PTO coefficient optimized for each resonance frequency and compressible volume. The large compressible volume required to tune the compressible point absorber to the desired frequency is a practical limitation that needs to be addressed with further research, especially for low frequencies. While realistic, these auxiliary units would increase the CapEx and OpEx costs, potentially reducing the aforementioned benefits gained by CDOF. However, alternative approaches can be developed to implement CDOF without the large compressible volume requirements, including the development of flexible surface panels tuned with mechanical springs.

16 TIDAL AND WAVE POWER↗
DOE OSTI2018

Converter topologies and control

An inverter includes a transformer that includes a first winding, a second winding, and a third winding, a DC-AC inverter electrically coupled to the first winding of the transformer, a cycloconverter electrically coupled to the second winding of the transformer, an active filter electrically coupled to the third winding of the transformer. The DC-AC inverter is adapted to convert the input DC waveform to an AC waveform delivered to the transformer at the first winding. The cycloconverter is adapted to convert an AC waveform received at the second winding of the transformer to the output AC waveform having a grid frequency of the AC grid. The active filter is adapted to sink and source power with one or more energy storage devices based on a mismatch in power between the DC source and the AC grid.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2018

Phosphor-converted white light emitting diodes having narrow-band green phosphors

In one aspect, a phosphor converted white light LED comprising a narrow green phosphor rather than a conventional broad green phosphor may simultaneously exhibit high R9, and high Luminance Efficacy of Radiation, optionally without use of a deep red phosphor to maintain desired red color rendering. In another aspect, a phosphor converted white light LED comprising a narrow green phosphor rather than a conventional broad green phosphor may provide an emission spectrum exhibiting a significant dip in the yellow region of the spectrum and thereby provide high red-green contrast without use of a filter. The yellow dip may be shallower than in conventional devices, and the device may therefore be brighter, while maintaining desired CRI and R9.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Rotating switching strategy for power converters

Systems and methods for operating a power converter with a plurality of inverter blocks with silicon carbide MOSFETs are provided. A DC to AC converter can include a plurality of inverter blocks. Each inverter block can include a plurality of switching devices. A control method can include identifying one of a plurality of switching patterns for operation of the inverter block for each inverter block. Each switching pattern can include a plurality of switching commands. The control method can further include controlling each inverter block based on the identified switching pattern for the inverter block. The control method can further include rotating the switching patterns among the plurality of inverter blocks.

Dong, Dong↗
DOE OSTI2019

Optimal control of wave energy converters

A wave energy converter and method for extracting energy from water waves maximizes the energy extraction per cycle by estimating an excitation force of heave wave motion on the buoy, computing a control force from the estimated excitation force using a dynamic model, and applying the computed control force to the buoy to extract energy from the heave wave motion. Analysis and numerical simulations demonstrate that the optimal control of a heave wave energy converter is, in general, in the form of a bang-singular-bang control; in which the optimal control at a given time can be either in the singular arc mode or in the bang-bang mode. The excitation force and its derivatives at the current time can be obtained through an estimator, for example, using measurements of pressures on the surface of the buoy in addition to measurements of the buoy position. A main advantage of this approximation method is the ease of obtaining accurate measurements for pressure on the buoy surface and for buoy position, compared to wave elevation measurements.

16 TIDAL AND WAVE POWER↗
DOE OSTI2019

Model predictive control of parametric excited pitch-surge modes in wave energy converters

A parametric excitation dynamic model is used for a three degrees-of-freedom (3-DOF) wave energy converter. Since the heave motion is uncoupled from the pitch and surge modes, the pitch-surge equations of motion can be treated as a linear time varying system, or a linear system with parametric excitation. In such case the parametric exciting frequency can be tuned to twice the natural frequency of the system for higher energy harvesting. A parametric excited 3-DOF wave energy converter can harvest more power, for both regular and irregular waves, compared to the linear 3-DOF. For example, in a Bretschneider wave, the harvested energy in the three modes is about 3.8 times the energy harvested in the heave mode alone; while the same device produces about 3.1 times the heave mode energy when using a linear 3-DOF model.

16 TIDAL AND WAVE POWER↗
DOE OSTI2018

Brazings for Metal-Ceramic Joining in Sodium Thermal Electrochemical Converter (Na-TEC) Devices

Sodium thermal electrochemical converters (Na-TECs) offer a high efficiency advancement for converting thermal energy into electrical energy without moving parts. Since the cell operates using a Na pressure difference between the high temperature evaporator and the lower temperature condenser, a hermetic seal capable of maintaining that pressure difference is essential. This study looked at brazing of the ceramic electrolyte used in these cells, which is a β”-alumina solid-electrolyte referred to as BASE. Since a literature search found no papers pertaining to brazing of BASE, knowledge from ceramic to metal brazing called widegap brazing was used. Specifically, the widegap brazing of α-alumina to nickel-based alloys. Initial brazing trials used a traditional inert atmospheric brazing technique with an Ar-H2 gas mixture. However, the very low pO2 atmosphere resulted in the destruction of the BASE layers due to the diffusion of carbon to the outer surface of the electrolyte during brazing. A new and radically different brazing technique called air brazing was then attempted. This brazing technique proved successful using the brazing alloy Ag-8CuO. Both Ag and Cu are not deleteriously affected by Na corrosion; thus, Ag-8CuO were a good choice for the braze alloy. Leak tests were performed on these cells to establish their hermeticity. This cell structure and brazing technique proved to be successful. Air brazing is an exciting joining operation for these types of cells.

14 SOLAR ENERGY↗
DOE OSTI2020

Model, Design, and Control for Power Conversion in Wave Energy Converter System

Wave energy, if all been harvested along the U.S. coastline, can power around 65% of the energy consumption in U.S.. Comparing to other renewable energy sources like solar or wind, ocean wave can provide up to 90% of steady uptime. With the high energy density (2-3 kW/m 2 ), it can produce more energy with the same amount of installation area comparing to the energy density of wind turbine (0.6 kW/m 2 ) and solar panel(0.2 kW/m 2 ). The predictability of wave provides advantages like planning installation, power dispatching, and maintenance activities. Although with all these advantages, wave energy converter system is still in the research stage due to its high system cost per electricity production. One of the challenges that need to be solved is the irregularity from the wave motion that leads to high instantaneous peak power into the wave energy converter, which usually reaches up to 10 - 20 times of the average power. The high peak power will not only bring high mechanical/electrical stress but also result in an overrating design of the components in the system. Another obstacle that prevents the wave energy system from moving forward is the high testing cost from the validations in wave-energy-test sites or tank-test sites. A high-fidelity multi-disciplinary system model, including hydrodynamics, mechanical dynamics, electromagnetics, and power electronics, is needed to predict the behavior of the system and reduce the cost of design validation.

16 TIDAL AND WAVE POWER↗
DOE OSTI2020

Integrated circuits with programmable gate timing signal generation for power converters and apparatus comprising the same

An apparatus is disclosed that includes a semiconductor device to control a power converter having two or more power FETs. The semiconductor device includes a gate signal generator configured to produce two or more gate signals able to drive the two or more FETs. The gate signal generator has programmable timing configuration parameters to control operation of the two or more gate signals, wherein the timing configuration parameters are digitally programmed via a memory in the semiconductor device. The memory may be implemented with fuses, other non-volatile memory or volatile memory. The parameters may be fixed or updated during a lifetime of the apparatus. A serial-to-parallel conversion may be used to input the parameters. Optimization methods may be performed to determine parameters considered to be optimal. The apparatus may also include the power converter.

42 ENGINEERING↗
DOE OSTI2020

Fault-tolerant controller for modular multi-level converters

Various examples are provided related to fault-tolerant controller architectures for multi-level converters. In one example, a multi-level converter includes an array of power modules. The power modules can include a controller communicatively coupled to controllers of adjacent power modules in the array of power modules. Circuitry of the controllers can receive operational data from the adjacent power modules; identify a fault condition in an adjacent power module using the operational data; and initiate reconfiguration of the array of power modules in response to an indication of the fault condition, where the reconfiguration bypasses the adjacent power module. In another example, a method includes identifying a fault condition in an adjacent power module in an array of power modules based upon operational data from one or more adjacent power modules of the array; and initiating reconfiguration of the array of power modules in response to an indication of the fault condition.

42 ENGINEERING↗
DOE OSTI2021

Semiconductor topologies and devices for soft starting and active fault protection of power converters

Various examples are provided related to semiconductor topologies and devices that can be used for soft starting and active fault protection of power converters. In one example, an active switch device includes an active switch having a gating control input; and a thyristor having a gating control input. The thyristor is coupled in parallel with the active switch. The active switch can be an IGBT, MOSFET, or other appropriate device. In another example, a power converter can include the active switch devices and switching control circuitry coupled to gating control inputs of the active switch devices.

Beddingfield, Richard B.↗
DOE OSTI2016

CHERENKOV CONVERTER FOR LARGE DYNAMIC RANGE, HIGH SENSITIVITY DETECTORS FOR USE ON WIRE-SCANNERS

We are developing a wire-scanner with a dynamic range of 1e+6 or larger. In addition to the large dynamic range (LDR), high sensitivity is very desirable so that measurements can be made with a small amount of beam or small duty cycle beam. This high sensitivity requirement makes photo multiplier tubes (PMT) with low background levels, the preferred detector. Low dark current PMTs have maximum quantum efficiency in the visible wavelength range. We describe a converter where Cherenkov radiation (CR) is used to generate visible photons from electrons and positrons that are present due to wire-beam interaction. An optical system used to collect and couple the CR into an optical fiber is also described. The high directivity of the CR is used in such a way that, when CR in the radiating medium is generated by particles not directed from the wire-beam interaction point to the converter, the CR is not coupled into the optical fiber and therefore does not create background for the wire-scanner measurements. It is envisioned that the optical fiber will be used to deliver the visible photons to the PMT located outside of the accelerator tunnel to further reduce the background level. Sensitivities to the refractive index of the radiating medium, alignment and mechanical fabrication tolerances are also presented. *Work supported by US DOE office of Basic Energy Sciences under the early career program; DOE award number FWP#JLAB-BES11-05

Gubeli, Joseph↗
DOE OSTI2022

Multi-channel high-speed converter clock synchronization with autonomous coherent deterministic latency

A system and corresponding method that achieves coherency and deterministic latency (CDL) autonomously upon power on is disclosed. The system, for example, a multi-channel RF system, may require CDL with respect to the digital-to-analog converters (DACs) and analog-to-digital converters (ADCs) assigned to the channels in the system. CDL is achieved through a timed combination of external reference and synchronization signals, resetting and disabling of various clock dividers, and enabling clock generation. In addition to synchronizing all of the clocks, the data acquisition sequence must be synchronized across all of the channels, whether they are on chips, cards, or chassis. Data acquisition synchronization may be implemented using an initiator/target or a wired OR mode configuration.

Brady, Charles E.↗
DOE OSTI2023

A Comprehensive Assessment Tool for Low-TRL Current Energy Converters: Preprint

Along with a market-competitive levelized cost of energy, a current energy converter technology strongly benefits from an extensive consideration of socioeconomic, environmental, and regulatory factors early in the design process. As part of a technology performance level assessment, a series of assessment questions and guidance are developed and presented to evaluate an early-stage current energy technology on holistic criteria considering the entire device lifecycle. The assessment represents an accumulation of industry and research experience to date and relies on regular updates to ensure alignment with industry best-practices, regulatory requirements, and up-to-date technical understanding. A cradle-to-grave (materials, manufacturing, installation and deployment, operations and maintenance, and end-of-life) assessment of capabilities and functional requirements for tidal, river, and ocean current technologies has been completed. This work presents the evaluation questions and qualitative performance criteria for current energy converters deployed in tidal, ocean current, and/or river applications. Key considerations related to manufacturing and installation include supply chain robustness, manufacturability and related job creation in the end-user and/or adjacent communities, and the time-to-repayment of the embodied energy debt. During deployment and maintenance operations, the safety of the device and subsystems during disconnect or grid failure, the difficulty and frequency of offshore heavy-lift activities, the avoidance or mitigation of area use conflicts, the sea-states and weather conditions that permit maintenance access, and the availability of contingency plans (should conditions change unexpectedly) are a portion of the considered assessment criteria. Results include the potential impact of early-stage design decisions on the socioeconomic, environmental, and regulatory performance of a technology that allows developers to increase the product value and probability of success, and minimize costly late-stage design iterations through early and broad consideration of factors affecting overall performance and acceptability.

industry support↗
DOE OSTI2023

Modified Virtual Oscillator-Based Operation of Grid-Forming Converters with Single Voltage Sensor: Preprint

This paper proposes a virtual oscillator-based control architecture for a grid-forming converter with an inner current control loop. In general, the virtual oscillator is based on a Lienard type of oscillator equation with a cubic nonlinearity. A virtual oscillator alone cannot accommodate unbalanced or harmonic mitigation while operating converters in grid-forming mode. Therefore, to accomplish better tracking performance, incorporating the provision for nonlinear and/or unbalanced loads, an inner current control loop is utilized that is based on the Lyapunov energy function type control architecture. To reduce the overall cost of implementation and ensure proper phase difference in the generated voltages, the implemented virtual oscillator operates with only one voltage feedback from the point of common coupling. To verify the effectiveness of the proposed approach, the overall system has been modeled in MATTLAB/Simulink and PLECS domain. This paper also presents case studies showing the successful production of low harmonic load voltages under nonideal loading conditions, along with other important results.

dual second order generalized integrator↗
DOE OSTI2016

Disposition of Chicago Pile 5 (CP-5) Converter Tubes in the 10-160B Cask - 16632

This paper will focus on the unique characterization, packaging, and transportation issues associated with the disposition of the two CP-5 Converter Tube assemblies from Argonne National Laboratory. The converter tubes were constructed of combinations of HEU and alloys of zirconium, and were part of the original research facilities attached to the CP-5 reactor during operating evolutions. These assemblies were heavily irradiated during their operational lifetime, and were segregated from the balance of irradiated test specimens when the reactor was deactivated and slated for Decontamination and Demolition (D and D). In addition, the substantial contribution of fissile material to the assemblies' inventory made the potential disposition pathways extremely challenging. As a result, these items became part of Argonne's legacy 'nuclear footprint', and were added to the Nuclear Footprint Reduction Project scope for disposition. The Project was responsible for the size reduction and characterization of these items, as well as the ultimate disposition. After negotiating a disposal pathway for these tubes, there were significant transportation issues that required a small team to overcome, in order to successfully ship these items to the Nevada National Security Site (NNSS). The Project team at Argonne, technical support from transportation specialists, licensing support from the 10-160B license owner, the Savannah River National Lab (SRNL) Packaging Certification Team (PCT, and the DOE EM-33 staff contributed to license and safety analysis report amendments that eventually authorized the shipment of the material. The paper will identify the organizations, and the specific actions, required to successfully make three 'one of a kind' shipments of irradiated test specimen material. This will include the unique packaging configurations, contents modification for the cask license (via the Amendment process), criticality evaluations, and associated review and approval processes. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2023

Power converter with co-packaged secondary field effect transistors (FETs)

A power converter with co-packaged secondary field effect transistors (FETs) are described. The power converter can include a first circuit, a transformer connected to an output of the first circuit, and a second circuit connected to an output of the transformer. The second circuit can include an inductor, a first FET coupled between the transformer and the inductor, and a second FET coupled between the first FET and ground. The first FET and the second FET can be co-packaged as a single package.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2024

GIS Supported Optimal Site Selection for Coastal Structure Integrated Wave Energy Converters: Preprint

There is an urgent need for adaptative engineering towards more resilient coastal communities, and Coastal Structure Integrated Wave Energy Converters (CSI-WECs) are a promising solution. CSI-WECs are wave energy converters (WECs) that are built into coastal protection structures, such as breakwaters. These devices provide the dual benefits of coastal protection and local energy production, and unlike other WECs, maximizing energy production is not always the main objective. CSI-WECs are located near the shore, where the wave resource is lower, thus site selection for these devices differs from the typical offshore WECs. Other attributes of a site that may be more important than wave power include existing coastal structures, port proximity, electric transmission line proximity, and location of disadvantaged communities. Geospatial information systems (GIS) interfaces can be used to easily visualize geospatial data that represents these difference kinds of criteria important for the determination of optimal marine energy sites. Multi-Criteria Decision Analysis (MCDA) is a geospatial analysis method that allows for the evaluation of multiple, usually overlapping, criteria. This project applies GIS-based MCDA methods to two distinct case studies in Puerto Rico and California for CSI-WEC site selection. The two study sites contrast in terms of wave resource, coastal hazards, and local energy needs. This research demonstrates the utility of applying an MCDA framework within GIS to facilitate efficient site selection for devices with unique characteristics in different use cases.

coastal protection↗