Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Energy conversion”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

The phototron: A light to RF energy conversion device

The phototron, a photoelectric device that converts light to radio frequency energy, is described. It is a vacuum tube, free electron, device that is mechanically similar to a reflex klystron with the hot filament cathode replaced by a large area photocathode. The device can operate either with an external voltage source used to accelerate the photoelectrons or with zero bias voltage; in which case the photokinetic energy of the electrons sustains the R.F. oscillations in the tuned R.F. circuit. One basic design of the phototron was tested. Frequencies as high as about 1 GHz and an overall efficiency of about 1% in the biased mode were obtained. In the unbiased mode, the frequencies of operation and efficiences are considerably lower. Success with test model suggests that considerable improvements are possible through design refinements. One such design refinement is the reduction of the length of the electron flight path.

Freeman, J. W.↗
NASA NTRS1989

New energy conversion techniques in space, applicable to propulsion

The powering of aircraft with laser energy from a solar power satellite may be a promising new approach to the critical problem of the rising cost of fuel for aircraft transportation systems. The result is a nearly fuelless, pollution-free flight transportation system which is cost-competitive with the fuel-conservative airplane of the future. The major components of this flight system include a laser power satellite, relay satellites, laser-powered turbofans and a conventional airframe. The relay satellites are orbiting optical systems which intercept the beam from a power satellite and refocus and redirect the beam to its next target.

Hertzberg, A.↗
DOE OSTI2021

Dynamic Characterization and Performance Evaluation of a 10-kw Power Take-Off with Mechanical Motion Rectifier for Wave Energy Conversion

The power take-off (PTO) is a key component for wave energy converters (WECs). The dynamic properties of the PTO influence the response of the WEC and should be considered when designing the WEC and not oversimplified. In addition, the efficiency as well as the reliability can play an important role on whether the PTO can be suitable for real-world applications. In this paper, a novel compact PTO rated at 10 kW is designed and prototyped, and a comprehensive nonlinear dynamic model is established for the PTO. Through bench testing, the unknown parameters of the dynamic model are characterized and determined. Further verification shows that the model can predict the dynamic performance of the PTO well. In addition, the test results show that the mechanical motion rectifier PTO can achieve good energy transfer efficiency, especially for low-load and low-speed conditions.

bench test↗
DOE OSTI2021

Cyclic bend over sheave performance of a steel tension member belt for wave energy conversion

Rotary power take-offs (PTOs) promise many benefits for commercial wave energy converters (WECs), including longer power strokes/reduced end-stop concerns, deployment advantages, and controllability. However, these winch-type PTOs can impose millions of bending cycles on the belt or rope element every year, which may lead to a failure mode known as Cyclic Bend Over Sheave, or “CBOS”. Synthetic rope, though attractive due to its high strength, low elongation, and durability, suffers from comparatively poor CBOS performance and struggles to reach a million load cycles without failing. Using belts instead of ropes for winching elements should improve CBOS performance due to having a smaller thickness that undergoes bending. Unfortunately, belts have their own host of problems. Maintaining even tension across the width of a belt subject to twist or fleet angles is a challenge, especially for WECs which can move in all 6 degrees of freedom in the ocean. This study sought to quantify the CBOS performance of a belt constructed of steel tension members in a polyurethane matrix containing longitudinal profiles. Belt samples were tested to failure or up to two million bend-unbend cycles and subject to a range of fleet angles. This paper summarizes the utilized testing methodology and the resulting belt performance.

16 TIDAL AND WAVE POWER↗
DOE OSTI2026

Comparative Analysis of Pendulum and Flywheel Power Take-Off Mechanisms for Wave Energy Conversion

Here, this study compares three power-take-off (PTO) mechanisms for wave energy converters—a flywheel -type pitch resonator and two pendulum variants (normal and inverted)—all designed to fit within a fixed envelope. Performance is assessed via linear frequency-domain models and bi-conjugate impedance matching under a representative sea state. The inverted-pendulum PTO achieves 27.9% of the incident wave energy, versus 16.5% for the normal pendulum and 4.2% for the flywheel—that is, 6.6 × and 3.9 × improvements, respectively. These gains arise because pendulum-based systems generate higher torque for a given buoy motion and maintain impedance matching across a wider frequency band. Parametric studies of mass, pendulum arm length, spring stiffness, generator friction, and motor constant quantify the impact of key design choices on power output. By locating the pendulum pivot near the buoy's center of gravity and positioning the center of rotation below the COG, surge–pitch coupling is improved and energy transfer is further boosted.

Keow, Alicia Li Jen [Sandia National Laboratories ↗
NASA NTRS1974

Advanced thermionic energy conversion

Basic analytical and experimental exploration was conducted on several types of advanced thermionic energy converters, and preliminary analysis was performed on systems utilizing advanced converter performance. The Pt--Nb cylindrical diode which exhibited a suppressed arc drop, as described in the preceding report, was reassembled and the existence of the postulated hydrid mode of operation was tentatively confirmed. Initial data obtained on ignited and unignited triode operation in the demountable cesium vapor system essentially confirmed the design principles developed in earlier work, with a few exceptions. Three specific advanced converter concepts were selected as candidates for concentrated basic study and for practical evaluation in fixed-configuration converters. Test vehicles and test stands for these converters and a unique controlled-atmosphere station for converter assembly and processing were designed, and procurement was initiated.

Britt, E. J.↗
NASA NTRS2009

Offshore Hydrokinetic Energy Conversion for Onshore Power Generation

Design comparisons have been performed for a number of different tidal energy systems, including a fully submerged, horizontal-axis electro-turbine system, similar to Verdant Tidal Turbines in New York's East River, a platform-based Marine Current Turbine, now operating in Northern Ireland's Strangford Narrows, and the Rotech Lunar Energy system, to be installed off the South Korean Coast. A fourth type of tidal energy system studied is a novel JPL/Caltech hydraulic energy transfer system that uses submerged turbine blades which are mechanically attached to adjacent high-pressure pumps, instead of to adjacent electrical turbines. The generated highpressure water streams are combined and transferred to an onshore hydroelectric plant by means of a closed-cycle pipeline. The hydraulic energy transfer system was found to be cost competitive, and it allows all electronics to be placed onshore, thus greatly reducing maintenance costs and corrosion problems. It also eliminates the expenses of conditioning and transferring multiple offshore power lines and of building offshore platforms embedded in the sea floor.

hydraulic↗
NASA NTRS1976

Laser plasmadynamic energy conversion

The generation of electrons ions by interacting an intense laser beam with cesium vapor is considered. Theoretical calculation shows that the conversion efficiency is as high as 40 percent if the entire photon energy is utilized in ionizing the cesium vapor that is generated initially by the incoming laser beam. An output voltage is expected to be generated across two electrodes, one of which is the liquid cesium, by keeping the other electrode at a different work function. Evaluation of the laser plasmadynamic (LPD) converter was performed using pulsed ruby and Nd-glass lasers. Although the results obtained to date indicate an efficiency smaller than that of theoretical predictions, an unoptimized LPD converter did demonstrate the capability of converting laser energy at large power levels. The limitations in the performance may by due to converter geometry, the types of lasers used, and other limitations inherent to the cesium plasma.

Shimada, K.↗
DOE OSTI2025

Electrocatalytic Oxidation of Ammonia for Energy Conversion and Storage (Final Report)

Ammonia is one of the most promising candidates to be a major renewable fuel. Ammonia is synthesized from H 2 and N 2 , which is the most abundant gas in the Earth’s atmosphere, using the Haber-Bosch (HB) process in the largest scale production of a chemical commodity. Using H 2 generated from renewable resources would result in a scalable, carbon-free, high energy density liquid fuel. The HB reaction is almost thermoneutral, which means hydrogen’s intrinsic energy is largely retained in the ammonia product, making NH 3 possibly the best candidate for storing and transporting H 2 . The conversion of NH 3 to energy has received very little attention, however. As part of this project we demonstrated the first example of a well-defined complex capable of driving electrocatalytic ammonia oxidation to N 2 , protons and electrons. We further thoroughly investigated the mechanistic underpinnings of the electrocatalytic reactions. We have also developed new chemistry to synthesize transition metal complexes aimed at increasing the efficiency and activity of electrocatalysts for the conversion of NH 3 to H 2 and N 2 at ambient temperatures.

08 HYDROGEN↗
DOE OSTI2019

Adaptive harnessing damping in hydrokinetic energy conversion by two rough tandem-cylinders using flow-induced vibrations

Alternating lift technology (ALT) harnesses hydrokinetic energy from currents and tides and is different from conventional steady lift technologies (turbines). ALT is still under development with an important research issue being the mitigation of wake effect on downstream cylinders in Flow Induced Oscillations (FIO) of multi-cylinder Current Energy Converters (CEC). Rather than adjust the configuration/parameters of the converter, a more direct and effective way is to actively adjust the harnessed power. In this paper, a hydrokinetic energy converter using FIO of two cylinders in tandem in one-degree-of-freedom oscillators, with nonlinear adaptive damping and linear spring stiffness, is tested experimentally. FIO include Vortex Induced Vibrations (VIV), galloping, and their coexistence. Introducing adaptive damping into the tandem cylinders overcomes the shielding effect, which previous research on two tandem cylinders has shown to reduce power output by the downstream cylinder. Shielding along with fixed damping result either in ceasing motion due to excessive damping, or in low harnessed energy due to insufficient damping. In this experimental study, damping-to-velocity rate, linear spring-stiffness, cylinder spacing, and flow-velocity are the parameters with Reynolds number 30,000 ≤ Re ≤ 120,000. Comparison to linear-oscillators in FIO shows that this nonlinear converter, with velocity-proportional damping coefficient, is more effective over the entire FIO range but especially in galloping, where both flow and cylinder speeds are higher. Experimental results for energy harvesting, efficiency and instantaneous energy of the converter are presented and discussed supported by amplitude and frequency response data. Here the results show that the nonlinear, adaptive, velocity-proportional damping coefficient is an effective way to increase the overall harnessed power and the power of downstream cylinder. The harnessed power in the VIV to galloping transition increases by up to 94%. The most significant improvement is in the galloping region, where the increase in harnessed power and efficiency is around 33%.

13 HYDRO ENERGY↗
DOE OSTI2022

Bioinspired and biomolecular catalysts for energy conversion and storage

Metalloenzymes are remarkable for facilitating challenging redox transformations with high efficiency and selectivity. In the area of alternative energy, scientists aim to capture these properties in bioinspired and engineered biomolecular catalysts for the efficient and fast production of fuels from low-energy feedstocks such as water and carbon dioxide. In this short review, efforts to mimic biological catalysts for proton reduction and carbon dioxide reduction are highlighted. Two important recurring themes are the importance of the microenvironment of the catalyst active site and the key role of proton delivery to the active site in achieving desired reactivity. As a result, perspectives on ongoing and future challenges are also provided.

14 SOLAR ENERGY↗
DOE OSTI2026

Deep Learning enabled spectral energy conversion for in situ exposure measurements

A detector-specific deep learning (DL) approach is presented for spectra-to-exposure conversion using large-format sodium iodide (NaI(Tl)) detectors deployed for in situ environmental radiation measurements in emergency response scenarios. Accurate determination of exposure from NaI spectra is challenging due to poor energy resolution, partial energy absorption, and the strong sensitivity of traditionally deployed analytical conversion methods to calibrated source geometry and pre-deployment assumptions. Here, to address these limitations, a multi-layer perceptron model was trained on a hybrid in situ /Monte Carlo dataset constructed to span a broad range of photon energies, spatial extents, and realistic deployment variability, representative of general in situ emergency response conditions. The DL model was evaluated against commonly fielded analytical approaches under matched simulation conditions, including a single-factor method, a G-function method, and a modeled pressurized ion chamber (PIC) baseline. This study was intentionally computational in scope to enable controlled, like-for-like comparisons between conversion techniques while minimizing confounding real-world variability. Comparison to the modeled PIC provides contextual benchmarking and is not intended as a field inter-comparison with deployed instruments. Across the evaluated 20 keV to 3 MeV energy range, the DL approach consistently exhibited higher accuracy and reduced variance relative to the analytical methods against a deterministically calculated exposure. This may indicate improved robustness to spectral complexity without reliance on source-, geometric-, or spectral region-specific optimization. While results do not represent real-world validation, the presented work demonstrates that deep learning may effectively learn the nonlinear detector response-to-exposure relationship for asymmetric NaI(Tl) detectors and offers a promising pathway for improving in situ exposure estimation using spectroscopic systems already integrated into initial real-time emergency response operations.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2019

Molecular Engineering of Hydroxide Conducting Polymers for Anion Exchange Membranes in Electrochemical Energy Conversion Technology

Anion exchange membranes (AEMs) based on hydroxide-conducting polymers (HCPs) are a key component for anion-based electrochemical energy technology such as fuel cells, electrolyzers, and advanced batteries. Although these alkaline electrochemical applications offer a promising alternative to acidic proton exchange membrane electrochemical devices, access to alkaline-stable and high-performing polymer electrolyte materials has remained elusive until now. Despite vigorous research of AEM polymer design, literature examples of high-performance polymers with good alkaline stability at an elevated temperature are uncommon. Traditional aromatic polymers used in AEM applications contain a heteroatomic backbone linkage, such as an aryl ether bond, which is prone to degradation via nucleophilic attack by hydroxide ion. In this Account, we highlight some of the progress our group has made in the development of advanced HCPs for applications in AEMs and electrode ionomers. Here, we propose that a synthetic polymer design with an all C−C bond backbone and a flexible chain-tethered quaternary ammonium group provides an effective solution to the problem of alkaline stability. Because of the critical demand for such a polymer system, we have established new synthetic strategies for polymer functionalization and polycondensation using an acid catalyst. The first approach is to graft a cationic tethered alkyl group to pre-existing, commercially available styrene-based block copolymers. The second approach is to synthesize high-molecular-weight aromatic backbone polymers using acid-catalyzed polycondensation of arene monomers and a functionalized trifluoromethyl ketone substrate. Both strategies involve a simple two-step reaction process and avoid the use of expensive metal-based catalysts and toxic chemicals, thereby making the synthetic processes easily scalable to large industrial quantities. Both polymer systems were found to have excellent alkaline stability, confirmed by the preservation of ion exchange capacity and ion conductivity of the membrane after an alkaline test under conditions of 1 M NaOH at 80−95 °C. In addition, the advantage of good solvent processability and convenient scalability of the reaction process generates considerable interest in these polymers as commercial standard AEM candidates. AEM fuel cell and electrolyzer tests of some of the developed polymer membranes showed excellent performance, suggesting that this new class of HCPs opens a new avenue to electrochemical devices with real-world applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Hydrokinetic Energy Conversion by Flow-Induced Oscillation of Two Tandem Cylinders of Different Stiffness

Abstract The vortex-induced vibration for aquatic clean energy (VIVACE) converter harnesses hydrokinetic energy by enhancing flow-induced oscillations (FIOs) of elastically supported rigid cylinders in a river, tide, or ocean current. The harnessing power depends on the intensity of the oscillation, which is a consequence of the flow–structure interaction. The inflow condition for the downstream (second) cylinder is slowed down and perturbed by the upstream (first) cylinder, due to the shielding effect. Therefore, the optimal structural parameters, i.e., stiffness and damping ratio, for the second cylinder may be different from the first cylinder, in terms of energy harnessing. To improve the performance of the VIVACE converter, a series of experiments are conducted in a recirculating water channel, with various stiffness combinations of two cylinders in tandem. Results show that the stiffness of the second cylinder, K2, does not affect the energy harnessing power in vortex-induced vibration (VIV) occurring at low speeds, because the oscillation of the downstream cylinder in this velocity range is completely dominated by the wake of the upstream cylinder. K2 has a great influence on the harnessing power at higher velocities in the transition region from VIV to galloping and in galloping. Changing K2 onsets and enhances galloping at lower flow velocity and harnesses up to 110% more energy than the case of K1 = K2.

Engineering↗
NASA NTRS2011

Thermoelectric Energy Conversion Technology for High-Altitude Airships

The High Altitude Airship (HAA) has various application potential and mission scenarios that require onboard energy harvesting and power distribution systems. The power technology for HAA maneuverability and mission-oriented applications must come from its surroundings, e.g. solar power. The energy harvesting system considered for HAA is based on the advanced thermoelectric (ATE) materials being developed at NASA Langley Research Center. The materials selected for ATE are silicon germanium (SiGe) and bismuth telluride (Bi2Te3), in multiple layers. The layered structure of the advanced TE materials is specifically engineered to provide maximum efficiency for the corresponding range of operational temperatures. For three layers of the advanced TE materials that operate at high, medium, and low temperatures, correspondingly in a tandem mode, the cascaded efficiency is estimated to be greater than 60 percent.

Choi, Sang H.↗
DOE OSTI2023

IC Project: The Role of Compressibility in Regulating Magnetic Energy Conversion in Reconnection Processes with Turbulence and Implications for Particle Transport and Energization

Diagnostics for the contribution of different regions in low-energy injection: a) Distribution function for the time duration of E > B particles within E > B regions. The estimated time limits for achieving injection are labeled; b) Distribution of energy gain during injection (for E > B particles) for E > B regions (blue), before E > B crossing (red), and outside E > B regions after the first crossing (black); c) Spectra for self-consistent particles (blue), test-particles that do not see electric fields in E > B regions (red) and test-particles with a resetting energy approach (green).

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1976

Experimental and theoretical studies on solar energy for energy conversion

This paper presents the results of investigations made experimentally and theoretically to evaluate the various parameters that affect the amount of solar energy received on a collector surface. Measurements were made over a long period of time using both pyranometer and pyrheliometer. Computation of spectral and total irradiance at ground level have been made for a large variety of combinations of atmospheric parameters for ozone density, precipitable water vapor, turbidity-coefficients and air mass. A study of the air mass as a function of irradiance measured at GSFC, and comparison of the data with the computed values of total direct solar irradiance for various parameters indicate that turbidity changes with time of the day; atmospheric opacity is less in the afternoon than in the morning.

Thomas, A. P.↗