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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Design concepts of high power bipolar rechargeable lithium battery

The present study shows that current bipolar Li/TiS2 batteries using a 0.38 mm thick TiS2 bipolar plate can yield moderate specific power and also high specific energy battery. The computer design studies project that a 100 V, 10 A h bipolar Li/TiS2 battery can achieve 150 W h/kg, 210 W h/l, and 150 W/kg. The unoptimized experimental bipolar Li/TiS2 batteries (3 cells, 90 mA h) exhibited 47 W h/kg, 90 W h/l, and 140 W/kg. Preliminary results on the cycleability of the bipolar batteries are demonstrated. The results also show that enhanced rate capability can be achieved by using pulse discharge and longer rest period between pulses.

Shen, David H.↗
DOE OSTI2022

Power Converter Circuit Design Automation using Parallel Monte Carlo Tree Search

The tidal waves of modern electronic/electrical devices have led to increasing demands for ubiquitous application-specific power converters. A conventional manual design procedure of such power converters is computation- and labor-intensive, which involves selecting and connecting component devices, tuning component-wise parameters and control schemes, and iteratively evaluating and optimizing the design. To automate and speed up this design process, we propose an automatic framework that designs custom power converters from design specifications using Monte Carlo Tree Search. Specifically, the framework embraces the upper-confidence-bound-tree (UCT), a variant of Monte Carlo Tree Search, to automate topology space exploration with circuit design specification-encoded reward signals. Moreover, our UCT-based approach can exploit small offline data via the specially designed default policy and can run in parallel to accelerate topology space exploration. Further, it utilizes a hybrid circuit evaluation strategy to substantially reduce design evaluation costs. Empirically, we demonstrated that our framework could generate energy-efficient circuit topologies for various target voltage conversion ratios. Compared to existing automatic topology optimization strategies, the proposed method is much more computationally efficient --- the sequential version can generate topologies with the same quality while being up to 67% faster. Here, the parallelization schemes can further achieve high speedups compared to the sequential version.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2012

Control of the UV flux of a XeCl dielectric barrier discharge excilamp through its current variation

The efficiency of the electrical power transfer to the gas mixture of a XeCl dielectric barrier discharge (DBD) exciplex lamp is analysed. An equivalent circuit model of the DBD is considered. It is shown that the excilamp power can be controlled by applying current to the lamp. This highly desired property is ensured by means of a specific power supply topology, whose concepts and design are discussed. The experimental prototype of a current-mode converter operating in the pulsed regime at pulse repetition rate of 50 kHz is presented and its capability to control the amount of energy transferred during each current pulse is demonstrated. The capability of this power supply to maintain specific operating conditions for the DBD lamp, with a very stable behaviour (even at a very low current, in the regime of a single discharge channel), is illustrated. The experimental results of a combined use of this converter and a XeCl excilamp are presented. The influence of the supply parameters on the 308-nm XeCl excilamp is analysed. The shape of the UV pulse of the lamp is experimentally shown to be similar to that of the current, which actually flows into the gas mixture. The UV radiation power is demonstrated to be tightly correlated to the current injected into the gas and controlled by the available degrees of freedom offered by the power supply. The measured UV output characteristics and performance of the system are discussed. Time resolved UV imaging of a XeCl DBD excilamp is used to analyse the mechanisms involved in the production of exciplexes at various power supply regimes. It is shown that a pulsed voltage source leads to formation of short high intensity UV peaks, while current pulses lead to formation of sustained discharge filaments. Based on the results of modelling of the above-mentioned operation conditions, the two power supply regimes are compared and analysed from the point of view of the UV power and radiative control.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

5-minute Wind Power Data based on WFIP2 WRF Simulation

The second Wind Forecast Improvement Project (WFIP2) was a public-private partnership funded by the U.S. Department of Energy and NOAA, aimed at enhancing the forecast skill of numerical weather prediction models for turbine-height winds in regions with complex terrain. An 18-month Weather Research and Forecasting (WRF) model simulation was conducted over the Pacific Northwest, with model outputs validated against observational data collected during WFIP2. Simulated wind speeds were used to estimate wind power generation using reV (the Renewable Energy Potential Model developed by NREL) at ten wind project sites. Two sets of results were produced: one using wind speeds extracted from the model grid cell at the project centroid, and another using wind speeds from the actual turbine locations. For each dataset, power output was calculated using both actual turbine-specific power curves and nine generic power curves to convert wind speed into power.

17 WIND ENERGY↗
NASA NTRS1971

Measurements of plasma parameters in a simulated thermionic converter

Cesium-filled thermionic energy converters are examined as candidate electrical energy sources in spacecraft requiring tens to hundreds of kilowatts of electric power. The high operating temperatures necessary for a large specific power and high efficiency inevitably impose stringent constraints on the converter fabrication to achieve the desired reliability of the power system. The converter physics for reducing operating temperatures and cesium plasma losses are studied to achieve high reliability without sacrificing the power performance of the converters. Various cesium parameters which affect the converter performance are: (1) electron temperatures, (2) plasma ion densities, and (3) electric potential profiles. These were investigated using a Langmuir probe in a simulated converter. The parameters were measured in different cesium discharge modes.

Shimada, K.↗
NASA NTRS1972

Probe measurements of a cesium plasma in a simulated thermionic energy converter

Cesium-filled thermionic energy converters are considered as electrical energy sources in future spacecraft requiring tens to hundreds of kilowatts of electric power. The high operating temperatures necessary for a large specific power and high efficiency impose stringent constraints on the converter fabrication. The converter physics for reducing operating temperatures and cesium plasma losses are being studied to achieve high reliability without sacrificing the power performance of the converters. Various cesium parameters which affect the converter performance are: (1) electron temperatures, (2) plasma ion densities, and (3) electric potential profiles. These were investigated using a Langmuir probe in a simulated converter. The parameters were measured in different cesium discharge modes.

Shimada, K.↗
NASA NTRS1982

Assessment of steam-injected gas turbine systems and their potential application

Results were arrived at by utilizing and expanding on information presented in the literature. The results were analyzed and compared with those for simple gas turbine and combined cycles for both utility power generation and industrial cogeneration applications. The efficiency and specific power of simple gas turbine cycles can be increased as much as 30 and 50 percent, respectively, by the injection of steam into the combustor. Steam-injected gas turbines appear to be economically competitive with both simple gas turbine and combined cycles for small, clean-fuel-fired utility power generation and industrial cogeneration applications. For large powerplants with integrated coal gasifiers, the economic advantages appear to be marginal.

Stochl, R. J.↗
NASA NTRS1981

Photovoltaic outlook from the NASA viewpoint

The NASA photovoltaic outlook for space applications focuses on the needs for increasing the specific power (W/kg), establishing radiation damage control, and reducing the specific cost ($/W). In each of these areas the technology requirements and potential impediments are presented. Technology trends and forecasts are also discussed.

Randolph, L. P.↗
NASA NTRS1989

Deployable aerospace PV array based on amorphous silicon alloys

The development of the first commercial, ultralight, flexible, deployable, PV array for aerospace applications is discussed. It is based on thin-film, amorphous silicon alloy, multijunction, solar cells deposited on a thin metal or polymer by a proprietary, roll-to-roll process. The array generates over 200 W at AM0 and is made of 20 giant cells, each 54 cm x 29 cm (1566 sq cm in area). Each cell is protected with bypass diodes. Fully encapsulated array blanket and the deployment mechanism weigh about 800 and 500 g, respectively. These data yield power per area ratio of over 60 W/sq m specific power of over 250 W/kg (4 kg/kW) for the blanket and 154 W/kg (6.5 kg/kW) for the power system. When stowed, the array is rolled up to a diameter of 7 cm and a length of 1.11 m. It is deployed quickly to its full area of 2.92 m x 1.11 m, for instant power. Potential applications include power for lightweight space vehicles, high altitude balloons, remotely piloted and tethered vehicles. These developments signal the dawning of a new age of lightweight, deployable, low-cost space arrays in the range from tens to tens of thousands of watts for near-term applications and the feasibility of multi-100 kW to MW arrays for future needs.

Hanak, Joseph J.↗
NASA NTRS1995

Wave rotor-enhanced gas turbine engines

The benefits of wave rotor-topping in small (400 to 600 hp-class) and intermediate (3000 to 4000 hp-class) turboshaft engines, and large (80,000 to 100,000 lb(sub f)-class) high bypass ratio turbofan engines are evaluated. Wave rotor performance levels are calculated using a one-dimensional design/analysis code. Baseline and wave rotor-enhanced engine performance levels are obtained from a cycle deck in which the wave rotor is represented as a burner with pressure gain. Wave rotor-toppings is shown to significantly enhance the specific fuel consumption and specific power of small and intermediate size turboshaft engines. The specific fuel consumption of the wave rotor-enhanced large turbofan engine can be reduced while operating at significantly reduced turbine inlet temperature. The wave rotor-enhanced engine is shown to behave off-design like a conventional engine. Discussion concerning the impact of the wave rotor/gas turbine engine integration identifies tenable technical challenges.

Welch, Gerard E.↗
NASA NTRS2007

New 5 Kilowatt Free-piston Stirling Space Convertor Developments

The NASA Vision for Exploration of the moon may someday require a nuclear reactor coupled with a free-piston Stirling convertor at a power level of 30-40 kW. In the 1990s, Mechanical Technology Inc. s Stirling Engine Systems Division (some of whose Stirling personnel are now at Foster-Miller, Inc.) developed a 25 kW free piston Stirling Space Power Demonstrator Engine under the SP-100 program. This system consisted of two 12.5 kW engines connected at their hot ends and mounted in tandem to cancel vibration. Recently, NASA and DoE have been developing dual 55 W and 80 W Stirling convertor systems for potential use with radioisotope heat sources. Total test times of all convertors in this effort exceed 120,000 hours. Recently, NASA began a new project with Auburn University to develop a 5 kW, single convertor for potential use in a lunar surface reactor power system. Goals of this development program include a specific power in excess of 140 W/kg at the convertor level, lifetime in excess of five years and a control system that will safely manage the convertors in case of an emergency. Auburn University awarded a subcontract to Foster-Miller, Inc. to undertake development of the 5 kW Stirling Convertor Assembly. The characteristics of the design along with progress in developing the system will be described.

Brandhorst, Henry W., Jr.↗
NASA NTRS2008

Progress in High Power Free-Piston Stirling Convertor Development

The U.S. Space Exploration Policy has established a vision for human exploration of the moon and Mars. One option for power for future outposts on the lunar and Martian surfaces is a nuclear reactor coupled with a free-piston Stirling convertor at a power level of 30-40 kWe. A 25 kW convertor was developed in the 1990s under the SP-100 program. This system consisted of two 12.5 kWe engines connected at their hot ends and mounted in tandem to cancel vibration. Recently, NASA began a new project with Auburn University to develop a 5 kWe, single convertor for use in such a possible lunar power system. Goals of this development program include a specific power in excess of 140 We/kg at the convertor level, lifetime in excess of five years and a control system that will safely manage the convertors in case of an emergency. Foster-Miller, Inc. is developing the 5 kWe Stirling Convertor Assembly. The characteristics of the design along with progress in developing the system will be described.

Brandhorst, Henry W., Jr.↗
NASA NTRS2007

Stretched Lens Array Squarerigger (SLASR) Technology Maturation

Since April 2005, our team has been underway on a competitively awarded program sponsored by NASA s Exploration Systems Mission Directorate to develop, refine, and mature the unique solar array technology known as Stretched Lens Array SquareRigger (SLASR). SLASR offers an unprecedented portfolio of performance metrics, SLASR offers an unprecedented portfolio of performance metrics, including the following: Areal Power Density = 300 W/m2 (2005) - 400 W/m2 (2008 Target) Specific Power = 300 W/kg (2005) - 500 W/kg (2008 Target) for a Full 100 kW Solar Array Stowed Power = 80 kW/cu m (2005) - 120 kW/m3 (2008 Target) for a Full 100 kW Solar Array Scalable Array Capacity = 100 s of W s to 100 s of kW s Super-Insulated Small Cell Circuit = High-Voltage (300-600 V) Operation at Low Mass Penalty Super-Shielded Small Cell Circuit = Excellent Radiation Hardness at Low Mass Penalty 85% Cell Area Savings = 75% Lower Array Cost per Watt than One-Sun Array Modular, Scalable, & Mass-Producible at MW s per Year Using Existing Processes and Capacities

O'Neill, Mark↗
NASA NTRS2017

Risk Management for Dynamic Radioisotope Power Systems

The implementation of dynamic power conversion technology in Radioisotope Power Systems (RPS) for spaceflight has potential for improved specific power and efficiency, compared with existing Radioisotope Thermoelectric Generators (RTGs). This proposed expansion of current RPS technology necessitates a full exploration of the requirements, goals, and concerns related to risks in developing and deploying such systems. The nature of dynamic systems also presents a new set of challenges related to the presence of moving machinery not intrinsic to traditional RTG units. A general RPS risk management methodology is outlined, which is used to identify and assess the variables and operational scenarios introducing risk throughout the design, fabrication, and system integration processes. This paper will demonstrate how mission requirements for Dynamic RPS concepts (DRPS) drive decisions throughout the development process. This work will define the standard practices for decision making within the scope of the risks associated with DRPS hardware development and deployment in sensitive spacecraft near sensitive payloads. Examples of potential risk areas are analyzed for the proposed dynamic systems, and compared to those associated with traditional RTG technologies. This analysis shows the promise for DRPS systems to elevate and extend the capabilities for power systems used in future NASA missions.

Matthes, Christopher S. R.↗
NASA NTRS2000

Chemical Fabrication Used to Produce Thin-Film Materials for High Power-to- Weight-Ratio Space Photovoltaic Arrays

The key to achieving high specific power (watts per kilogram) space solar arrays is the development of a high-efficiency, thin-film solar cell that can be fabricated directly on a flexible, lightweight, space-qualified durable substrate such as Kapton (DuPont) or other polyimide or suitable polymer film. Cell efficiencies approaching 20 percent at AM0 (air mass zero) are required. Current thin-film cell fabrication approaches are limited by either (1) the ultimate efficiency that can be achieved with the device material and structure or (2) the requirement for high-temperature deposition processes that are incompatible with all presently known flexible polyimide or other polymer substrate materials. Cell fabrication processes must be developed that will produce high-efficiency cells at temperatures below 400 degrees Celsius, and preferably below 300 degress Celsius to minimize the problems associated with the difference between the coefficients of thermal expansion of the substrate and thin-film solar cell and/or the decomposition of the substrate.

Hepp, Aloysius F.↗
NASA NTRS2001

Atmospheric-Pressure-Spray, Chemical- Vapor-Deposited Thin-Film Materials Being Developed for High Power-to- Weight-Ratio Space Photovoltaic Applications

The key to achieving high specific power (watts per kilogram) space photovoltaic arrays is the development of high-efficiency thin-film solar cells that are fabricated on lightweight, space-qualified substrates such as Kapton (DuPont) or another polymer film. Cell efficiencies of 20 percent air mass zero (AM0) are required. One of the major obstacles to developing lightweight, flexible, thin-film solar cells is the unavailability of lightweight substrate or superstrate materials that are compatible with current deposition techniques. There are two solutions for working around this problem: (1) develop new substrate or superstrate materials that are compatible with current deposition techniques, or (2) develop new deposition techniques that are compatible with existing materials. The NASA Glenn Research Center has been focusing on the latter approach and has been developing a deposition technique for depositing thin-film absorbers at temperatures below 400 C.

Hepp, Aloysius F.↗
DOE OSTI2017

Impacts of Variable Renewable Energy on Bulk Power System Assets, Pricing, and Costs

We synthesize available literature, data, and analysis on the degree to which growth in variable renewable energy (VRE) has impacted to date or might in the future impact bulk power system assets, pricing, and costs. We do not analyze impacts on specific power plants, instead focusing on national and regional system-level trends. The issues addressed are highly context dependent—affected by the underlying generation mix of the system, the amount of wind and solar penetration, and the design and structure of the bulk power system in each region. Moreover, analyzing the impacts of VRE on the bulk power system is a complex area of research and there is much more to be done to increase understanding of how VRE impacts the dynamics of current and future electricity markets. While more analysis is warranted, including additional location-specific assessments, several high-level findings emerge from this synthesis: -VRE Is Already Impacting the Bulk Power Market -VRE Impacts on Average Wholesale Prices Have Been Modest -VRE Impacts on Power Plant Retirements Have So Far Been Limited -VRE Impacts on the Bulk Power Market will Grow with Penetration -The ’System Value’ of VRE will Decline with Penetration -Power System Flexibility Can Reduce the Rate of VRE Value Decline All generation types are unique in some respect—bringing benefits and challenges to the power system—and wholesale markets, industry investments, and operational procedures have evolved over time to manage the characteristics of a changing generation fleet. With increased VRE penetrations, power system planners, operators, regulators, and policymakers will continue to be challenged to develop methods to smoothly and cost-effectively manage the reliable integration of these new and growing sources of electricity supply.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2024

Field Emission Current Transfer for Homopolar Machines

With the increasing electrification of transportation, the need for high power density electric machines is higher than ever. The required specific power for the more demanding applications, such as airplane propulsion, is over 20 kW/kg for multi-megawatt range power levels. Fully superconducting synchronous machines could reach the required performance, but significant challenges remain to be addressed such as AC losses management and rotating cryogenics implementation. Homopolar machines constitute the simplest electro-mechanical conversion systems possible, however the difficulty of establishing reliable and efficient low voltage, high DC current transfer from a stationary to a rotating system has prevented homopolar machines from competing with AC electrical machines. While sliding contacts or liquid metal contacts are feasible, they lead to high losses, high maintenance requirements and the use of environmentally unfriendly materials. We investigated field emission current transfer as an alternative to sliding contacts. We have demonstrated field emission current transfer in vacuum between a copper electrode and carbon nanotubes and diamond pyramids to evaluate the feasibility of contact-free current transfer for homopolar machines. The initial field emission testing was successfully demonstrated with current densities in the 10 mA/cm 2 range. The initial experiments validated the concept and supported the development of a roadmap for the development of contactless current transfer for homopolar machines, helped understand the limitations of the current test system and identify the key parameters that will lead to better performance.

99 GENERAL AND MISCELLANEOUS↗