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At least 433 records · Page 24

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NASA NTRS2006

Data Converters Performance at Extreme Temperatures

Space missions often require radiation and extreme-temperature hardened electronics to survive the harsh environments beyond earth's atmosphere. Traditional approaches to preserve electronics incorporate shielding, insulation and redundancy at the expense of power and weight. However, a novel way of bypassing these problems is the concept of evolutionary hardware. A reconfgurable device, consisting of several switches interconnected with analog/digital parts, is controlled by an evolutionary processor (EP). When the EP detects degradation in the circuit it sends signals to reconfgure the switches, thus forming a new circuit with the desired output. This concept has been developed since the mid-90s, but one problem remains - the EP cannot degrade substantially. For this reason, extensive testing at extreme temperatures (-180' to 120(deg)C) has been done on devices found on FPGA boards (taking the role of the EP) such as the Analog to Digital and the Digital to Analog Converter. Analysis of the results has shown that FPGA boards implementing EP with some compensation may be a practical solution to evolving circuits. This paper describes results on the tests of data converters at extreme temperatures.

evolvable hardware↗

NASA NTRS2019

Modeling and Mitigation of Multi-Loops Related Device Overvoltage in Three Level Active Neutral Point Clamped Converter

This paper establishes an analytical model for the device drain-source overvoltage related to the two loops in three level active neutral point clamped (3L-ANPC) converters. Taking into account the non-linear device output capacitance, two commonly used modulations are investigated in detail. The result shows that the line switching frequency device usually has higher overvoltage, and the switching speed of the high switching frequency device is not strongly influenced by the multiple loops. By keeping the non-active clamping switch off, the effect of the non-linear device output capacitance can be significantly mitigated, which helps reduce the overvoltage. Moreover, the loop inductance can be reduced with vertical loop layout and magnetic cancellation in PCB and busbar design. A 500 kVA 3L-ANPC converter using SiC MOSFETs is built and tested. The experimental results validate the overvoltage model of the two modulations as well as the busbar design. With the non-active clamping switch off, the overvoltage of both the high and line switching frequency devices is significantly reduced, which helps achieve higher switching speed.

Model↗

NASA NTRSDate not supplied

Investigation into High Power Converter Topologies

The NESC commissioned NASA Glenn Research Center (GRC) to perform a study of high-power DC-DC converter topologies Why perform the study? • Several past contractor-led converter development programs have been plagued with development delays and cost overruns due to: • Poor initial design decisions • Complex requirements driving designs • Better inform government engineers about strengths and weaknesses of various topologies, learn about new topologies/design strategies. • Allow NASA to be better prepared for upcoming high power/high voltage power conversion systems work, such as Lunar and Martian surface missions, high power electric propulsion, as well as terrestrial systems, such as electrified aircraft. • Contractors often do not have the option to restart poor decisions – allows NASA to be better informed at the start of programs.

Power Converter↗

NASA NTRSDate not supplied

Design and Development of a Fluid Immersion Cooled, SiC MOSFET, 37.5 kW, Bi-Directional Motor Converter

NASA's SUb-sonic Single Aft eNgine (SUSAN) aircraft is a concept aircraft whose architecture is that of a subsonic regional jet transport aircraft. SUSAN contains a single turbofan engine coupled to an electrified aircraft propulsion (EAP) system. To provide a path towards this goal, a 25% scale version of the SUSAN aircraft is being researched. A main component of the 25% power train is the Motor And Generator Intelligent Converter (MAGIC). This paper presents the design, development, and initial test results from MAGIC, a 37.5 kW, fluid immersion cooled, silicon carbide (SiC) MOSFET-based, bi-directional converter and controller.

PAO↗

NASA NTRSDate not supplied

Design and Development of a Fluid Immersion Cooled, SiC MOSFET, 37.5 kW, Bi-Directional Motor Converter

Immersion↗

DOE OSTI2020

Revisiting Theoretical Limits for One-Degree-of-Freedom Wave Energy Converters: Preprint

This work revisits the theoretical limits of one-degree of freedom wave energy converters (WECs). This paper considers the floating sphere used in the Ocean Energy Systems (OES) Task 10 Wave Energy Converter modeling and verification effort for analysis. Analytical equations are derived to determine bounds on the motion amplitude, time-averaged power, and power take-off (PTO) force. A unique result was found that shows the time-averaged power absorbed by a WEC can be defined solely by the inertial properties and the radiation hydrodynamic coefficients. In addition, a unique expression for the PTO force amplitude was derived which has provided upper and lower bounds when resistive control is used to maximize power generation. For complex conjugate control, this same expression can only provide a lower bound as there is theoretically no upper bound. These bounds are used to compare the performance of a floating sphere if it were to extract energy using surge or heave motion. The analysis shows that because of the differences in hydrodynamic coefficients of each oscillating mode there will be different frequency ranges that provide better power capture efficiency. The influence of a motion constraint on power absorption while also utilizing a nonideal power take-off is examined and found to reduce the losses associated with bidirectional energy flow. The expression to calculate the time-averaged power with a nonideal PTO is modified by the mechanical-to-electrical efficiency and the ratio of the PTO spring and damping coefficients. These were separated in the expression which allows for limits to be set on the possible values of PTO coefficients to ensure a net flow of power to the grid.

50 EE - Wind and Water Power Program - Water (EE-4↗

DOE OSTI2022

Influence on Structural Loading of a Wave Energy Converter by Controlling Variable-Geometry Components and the Power Take-Off: Preprint

Oceans are a harsh environment and can impose significant loads on deployed structures. Deployment of wave energy converters (WECs) faces a design challenge with apparently contradictory goals. A WEC should be designed to maximize the energy absorbed while ensuring the operating wave condition does not exceed the failure limits of the device itself. Therefore, the loads endured by the support structure are a design constraint for the system. Adaptability to different sea states is, therefore, highly desirable. This work uses a WEC-Sim model of a Variable Geometry Oscillating Wave Energy Converter (VGOSWEC) mounted on a support structure simulated under different wave scenarios. A VGOSWEC resembles a paddle pitching about a fixed hinge perpendicular to the incoming waves-fronts. Therefore, the hinge experiences loads perpendicular to its axis as it maintains its position. The geometry of the VGOSWEC was varied by opening a series of controllable flaps on the pitching paddle when the structure experiences threshold loads. Since opening the flaps lets the waves transmit through the paddle, it is hypothesized that opening the flaps should result in load shedding at the base of the support structure. This load shedding is achieved by reducing the moments about the hinge axis. This work compares the hydrodynamic coefficients, natural periods, and Response Amplitude Operators (RAOs) from completely closed to completely open configurations of the controllable flaps. These comparisons quantify the effects of letting the waves transmit through the VGOSWEC. This work shows that the completely open configuration can reduce the pitch and surge loads on the base of the support structure by as much as 80%. It was observed that at the paddle's resonance frequency, the loads on the structure increased substantially. This increase in loads can be mitigated by a rotational Power Take-off (PTO) damping about the hinge axis. Changing the rotational PTO damping was identified as an additional design parameter that can be used to control the loads experienced by the WEC's support structure.

fixed and floating structures↗

DOE OSTI2022

2.1.1.1.401 - Wave Energy Converter Modeling

The Wave Energy Converter (WEC) Modeling Project began in 2013 with the aim of driving innovation and advancing the state of the wave energy industry by developing publicly available, easy to use software that's customizable to meet end user needs. This project is primarily focused on development of open source software for numerical design and analysis of wave energy converters (WEC), and it also supports international collaboration on standards (IEC TC 114), code verification and validation (IEA OES Task 10) and a competition (WECCCOMP).

MATHEMATICS AND COMPUTING,TIDAL AND WAVE POWER↗

DOE OSTI2023

Hexagonal Distributed Embedded Energy Converter (HexDEEC)

Hexagonal Distributed Embedded Energy Converters are relatively small, centimeter scale, energy transducers that leverage variable capacitance to generate electricity when their hyperelastic structure is dynamically deformed. A multitude of HexDEECs can be woven to form construction materials that can be used to build complete energy conversion structures, such as ocean wave energy converters.

BFSF↗

DOE OSTI2023

An Efficient Three-Dimensional CFD-Based Numerical Wave Tank for a Wave Energy Converter in Extreme Irregular Waves: Preprint

A numerical wave tank approach for computational fluid dynamics (CFD) modelling of an extreme irregular seastate is presented. The technique couples a potential flow solution with a CFD solver for more efficient numerical predictions. This method has recently become attractive both for the research community and the industry working with offshore structures. The model is used to determine the response of a submerged pressure differential wave energy converter (WEC) in a fully nonlinear irregular wave condition using the high fidelity CFD code, STAR-CCM+. Potential flow based numerical models are commonly used to predict motions and performance of wave energy converters. Wave kinematics can deviate from potential flow predictions for extreme wave conditions; the excitation loads on an absorber can also be increasingly influenced by viscous effects, not captured in engineering level models. In these extreme conditions, a Reynolds-averaged Navier-Stokes CFD model can better predict motions and loads for a WEC. Long time series with varying random seed numbers can be used to identify singular extreme wave events from a stochastic irregular sea state. This approach simulates a more realistic wave series for a given sea state than a regular wave or a focused wave. However, it is computationally infeasible to run these long time series for three-dimensional (3D) CFD simulations. In this work, two-dimensional (2D) CFD simulations with a long domain allow the full development of an extreme nonlinear wave condition. The results are used to identify extreme events from a 50-year storm condition for the PacWave site off the coast of Oregon. A relatively short time window including this extreme event is then mapped to a 3D simulation using a user defined wave methodology. Convergence studies for domain length, wave forcing lengths, and time before the extreme event were conducted.

cfd↗

DOE OSTI2023

A Comprehensive Assessment Tool for Low-TRL Current Energy Converters

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.

converter↗

DOE OSTI2024

Interleaved Cuk Converter Wave Energy System With Advanced Control and Grid Support Functions for Seamless Integration: Preprint

This paper presents an innovative wave energy conversion system employing an interleaved Cuk converter and advanced nonlinear control for seamless integration with the grid. The proposed system utilizes the interleaved Cuk converter for efficient power extraction on the DC side, while an inverter facilitates power transfer to the grid or load on the AC side. A sophisticated nonlinear control architecture based on Lyapunov energy functions ensures stable and optimal operation under varying wave conditions. Case study results demonstrate the effectiveness of the proposed system, highlighting its ability to efficiently harness wave energy and seamlessly integrate with the grid, thus paving the way for sustainable and reliable renewable energy generation. The overall system is verified via computer simulations based on MATLAB/Simulink and various case study results are presented.

HYDRO ENERGY,TIDAL AND WAVE POWER↗

DOE OSTI2024

Performance of a Drifting Acoustic Instrumentation SYstem (DAISY) for characterizing radiated noise from marine energy converters

Marine energy converters can generate electricity from energetic ocean waves and water currents. Because sound is extensively used by marine animals, the radiated noise from these systems is of regulatory interest. However, the energetic nature of these locations poses challenges for performing accurate passive acoustic measurements, particularly with stationary platforms. The Drifting Acoustic Instrumentation SYstem (DAISY) is a modular hydrophone recording system purpose-built for marine energy environments. Using a flow shield in currents and mass–spring–damper suspension system in waves, we demonstrate that DAISYs can effectively minimize the masking effect of flow noise at frequencies down to 10 Hz. In addition, we show that groups of DAISYs can utilize time-delay-of-arrival post-processing to attribute radiated noise to a specific source. Consequently, DAISYs can rapidly measure radiated noise at all frequencies of interest for prototype marine energy converters. Furthermore, the resulting information from future operational deployments should support regulatory decision-making and allow technology developers to make design adjustments that minimize the potential for acoustic impacts as their systems are scaled up for utility-scale power generation.

16 TIDAL AND WAVE POWER↗

DOE OSTI2020

A compact mechanical power take-off for wave energy converters: Design, analysis, and test verification

Power Take-off (PTO) is one of the most critical components in the ocean wave conversion. This paper introduces an innovative compact mechanical PTO using a ball screw mechanism and a Mechanical Motion Rectifier (MMR) to improve the energy conversion performance. The proposed MMR PTO converts bidirectional oscillatory motion of the ocean waves into unidirectional rotation. The detailed design and working principle of the MMR PTO are explicitly explained. Dynamic analysis is presented for the three most important factors that influence the performance, including the equivalent mass, the equivalent damping, and the excitation frequency. The analytical relationship between these factors and the disengaged freewheeling motion caused by the MMR mechanism is derived, and the analytical solution is verified through dry lab testing. Experimental results in bench tests show that compared with the traditional linear PTO which use the ball screw to drive the generator directly, the MMR PTO is more efficient because of the unique freewheeling motion, achieving a maximum 81.2% energy transfer efficiency. After integrating the prototype PTO with a single-body point absorber type of wave energy converter, testing in a water tank yields total PTO efficiency up to 62.4%, showing a very promising potential for real applications.

16 TIDAL AND WAVE POWER↗

DOE OSTI2020

A Bioinspired Multicomponent Catalytic System for Converting Carbon Dioxide into Methanol Autocatalytically

Nature utilizes multicomponent catalyst systems to convert simple, abundant starting materials to complex molecules that are essential for life. In contrast, synthetic chemical transformations rarely adopt this strategy because the sophisticated supramolecular assemblies used by biology for active site separation and substrate trafficking are difficult to replicate. Herein, a method is described for multicomponent catalyst separation that involves encapsulating transition metal complexes in nanoporous materials called metal-organic frameworks. The multicomponent catalyst system was highly active for converting hydrogen and carbon dioxide to methanol, and it could be formulated so that it is readily recyclable. Moreover, an autocatalytic feature was uncovered that was only made possible by utilizing the multicomponent catalyst strategy employed. Furthermore, these results open avenues for obtaining fuel from abundant and renewable resources.

08 HYDROGEN↗

DOE OSTI2024

Power capture and power take-off load of a self-balanced dual-flap oscillating surge wave energy converter

Wave energy converters are an important part of future renewable energy infrastructure. Predicting their power matrix, capture width ratio, and power take-off loads at a targeted site is required for performance assessment before deployment. Because their testing is very expensive, numerical modeling and simulations play a significant role in those assessments. Linear potential flow theory has limited accuracy under large amplitude wave forcing. More accurate predictions can be obtained by using higher-fidelity models, which are computationally expensive. We present a framework for multi-fidelity numerical simulations to determine the hydrodynamic response, wave capture capability, and power take-off load of a full-scale dual-flap oscillating surge wave energy converter. This design exploits out-of-phase motion by setting the distance between the flaps to half the wavelength of the most occurring wave. The simulations are validated using a 1:10 model experiments in a wave tank. Based on these validations, it was determined that Euler simulations provide an acceptable prediction with 90% reduction in computational time with only 11% error. Utilizing Euler simulations at full-scale, the results demonstrate that the annual electrical energy output is 1.79 GWh under regular wave conditions. Here, one significant improvement over single-flap designs is the capture width ratio which exceeds unity.

16 TIDAL AND WAVE POWER↗

DOE OSTI2025

Innovative use of CaO in combination with amino acid salt to convert CO 2 as CaCO 3 nanoparticles under mild pH and low temperature

The increasing demand for sustainable CO 2 management has driven the development of innovative methods that can convert point source CO 2 into value-added products. In this study, CaO in combination with amino acid salt was used to convert CO 2 into CaCO 3 nanoparticles. Different from the conventional method where CO 2 diffusion presents a major challenge in reacting with CaO to form CaCO 3 , amino acid salt solvent was applied to absorb CO 2 first and then rapidly reacted with CaO to form CaCO 3 nanoparticles (∼50 nm) at a low temperature (e.g., 60 °C). Our experiments showed that at a glycine (Gly)/NaOH ratio of 2:1 or 3:1, the solution pH values during the CO 2 absorption and conversion were about 8–9 at 60 °C, while at a ratio of 1:1, the solution pH values were about 9–11; without Gly, the solution pH values were about 12. Gly-optimized solvent substantially reduced corrosion risk to reactors. In addition, the use of amino acid (i.e., Gly) led to much smaller CaCO 3 particles, distinctly different chemical phases, and fundamentally different chemical reactions. Moreover, in the presence of Gly, the solution pH was completely reversed and the solution was regenerated for cyclic use when CaO was added. The solvent was recyclable and reusable, highlighting the cost-effectiveness and sustainability of this approach. The Gly-modulated CaCO 3 nanoparticles may have significant potential for industrial applications in the biomedicine, construction, plastics, and rubber industries.

36 MATERIALS SCIENCE↗

DOE OSTI2026

Analysis of synergies in converting underground storage sites: Natural gas to hydrogen with co-located CO2 storage

This study examines the untapped potential of synergistically converting underground natural gas storage (UGS) into underground hydrogen storage (UHS) with co-located CO2 storage. Current approaches to subsurface storage technology (SST) development often prioritise single-use scenarios, overlooking the benefits of integrating multiple technologies. We investigate converting UGS assets into UHS through gradual cushion-gas injection over multiple years, rather than injecting all cushion gas in the first year, and include on-site CO2 storage to offset site emissions. Mechanistic modelling shows this gradual transition reduces the Levelised Cost of Storage (LCOS) of H2 by 1.2-13.1% while retaining energy output within 3% of the current status quo. We also show that combined UHS and CO2 storage hubs can reduce the LCOS of CO2 by 45-77% for only a 3-10% increase in hydrogen LCOS relative to the status quo. This analysis framework may help future-proof SST sites and support a resilient, economically beneficial energy transition.

Mouli-Castillo, Julien↗