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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 1,261 records · Page 70
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Morphological–Electrical Property Relation in Cu(In,Ga)(S,Se) 2 Solar Cells: Significance of Crystal Grain Growth and Band Grading by Potassium Treatment

Abstract Solution‐processed Cu(In,Ga)(S,Se) 2 (CIGS) has a great potential for the production of large‐area photovoltaic devices at low cost. However, CIGS solar cells processed from solution exhibit relatively lower performance compared to vacuum‐processed devices because of a lack of proper composition distribution, which is mainly instigated by the limited Se uptake during chalcogenization. In this work, a unique potassium treatment method is utilized to improve the selenium uptake judiciously, enhancing grain sizes and forming a wider bandgap minimum region. Careful engineering of the bandgap grading structure also results in an enlarged space charge region, which is favorable for electron–hole separation and efficient charge carrier collection. Besides, this device processing approach has led to a linearly increasing electron diffusion length and carrier lifetime with increasing the grain size of the CIGS film, which is a critical achievement for enhancing photocurrent yield. Overall, 15% of power conversion efficiency is achieved in solar cells processed from environmentally benign solutions. This approach offers critical insights for precise device design and processing rules for solution‐processed CIGS solar cells.

Kim, Joo‐Hyun↗
DOE OSTI2016

Solar thermoelectric generator

Solar thermoelectric generators (STEGs) are solid state heat engines that generate electricity from concentrated sunlight. A novel detailed balance model for STEGs is provided and applied to both state-of-the-art and idealized materials. STEGs can produce electricity by using sunlight to heat one side of a thermoelectric generator. While concentrated sunlight can be used to achieve extremely high temperatures (and thus improved generator efficiency), the solar absorber also emits a significant amount of black body radiation. This emitted light is the dominant loss mechanism in these generators. In this invention, we propose a solution to this problem that eliminates virtually all of the emitted black body radiation. This enables solar thermoelectric generators to operate at higher efficiency and achieve said efficient with lower levels of optical concentration. The solution is suitable for both single and dual axis solar thermoelectric generators.

14 SOLAR ENERGY↗
DOE OSTI2017

Bi-continuous Multi-component Nanocrystal Superlattices for Solar Energy Conversion

Our SISGR program studied an emerging class of nanomaterials wherein different combinations of semiconductor or semiconductor and plasmonic nanocrystals (NCs) are self-assembled into three-dimensional multi-component superlattices. The NC assemblies were designed to form bicontinuous semiconductor NC sublattices with type-II energy offsets to drive charge separation onto electron and hole transporting sublattices for collection and introduce plasmonic NCs to increase solar absorption and charge separation. Our group is expert in synthesizing and assembling an extraordinary variety of artificial systems by tailoring the NC building blocks and the superlattice unit cell geometry. Under this DOE BES Materials Chemistry program, we introduced chemical methods to control inter-particle distance and to dope NC assemblies, which enabled our demonstration of strong electronic communication between NCs and the use of NC thin films as electronic materials. We synthesized, assembled and structurally, spectroscopically, and electrically probed NC superlattices to understand and manipulate the flow of energy and charge toward discovering the design rules and optimizing these complex architectures to create materials that efficiently convert solar radiation into electricity.

14 SOLAR ENERGY↗
NASA NTRS1980

Heat and electricity from the Sun using parabolic dish collector systems

Point focus distributed receiver solar thermal technology for the production of electric power and of industrial process heat is addressed. The thermal power systems project which emphasizes the development of cost effective systems which will accelerate the commercialization and industrialization of plants up to 10 MWe, using parabolic dish collectors is described. The projected size of the isolated load market in the 1990-2000 time period is 300 to 1000 MW/year. Although this market is small in comparison to the grid connected utility market, it is indicated that by assuming only a 20 percent market penetration, up to 10,000 power modules per year would be required to meet this need. At a production rate of 25,000 units/year and assuming no energy storage, levelized bus bar energy costs of 75 mills/kWeh are projected. These numbers are based on what is believed to be a conservative estimate regarding engine-generator conversion efficiency (40 percent) for the 1990 time period. With a more optimistic estimate of efficiency (i.e., 45 percent), the bus bar cost decreases to about 67 mills/kWeh. At very large production rates (400,000 modules/years), the costs decrease to 58 mills/kWeh. Finally, the present status of the technology development effort is discussed.

Truscello, V. C.↗
DOE OSTI2022

Direct Exciton Harvesting from a Bound Triplet Pair

Abstract Singlet fission is commonly defined as the generation of two triplet excitons from a single absorbed photon. However, ambiguities within this definition arise due to the complexity of the various double triplet states that exist in SF chromophores and the corresponding interconversion processes. To clarify this process, singlet fission is frequently depicted as sequential two‐step conversion in which a singlet exciton decays into a bound triplet‐pair biexciton state that dissociates into two “free” triplet excitons. However, this model discounts the potential for direct harvesting from the coupled biexciton state. Here, it is demonstrated that individual triplet excitons can be extracted directly from a bound triplet pair. It is demonstrated that due to the requirement for geminate triplet–triplet annihilation in intramolecular singlet fission compounds, unique spectral and kinetic signatures can be used to quantify triplet‐pair harvesting yields. An internal quantum efficiency for triplet exciton transfer from the triplet pair of >50%, limited only by the solubility of the compounds is achieved. The harvesting process is not dependent on the net multiplicity of the triplet‐pair state, suggesting that an explicit, independent dissociation step is not a requirement for using triplet pairs to do chemical or electrical work.

Chemistry↗
DOE OSTI2015

Charge transport studies in donor-acceptor block copolymer PDPP-TNT and PC71BM based inverted organic photovoltaic devices processed in room conditions

Diketopyrrolopyrole-naphthalene polymer (PDPP-TNT), a donor-acceptor co-polymer, has shown versatile behavior demonstrating high performances in organic field-effect transistors (OFETs) and organic photovoltaic (OPV) devices. In this paper we report investigation of charge carrier dynamics in PDPP-TNT, and [6,6]-phenyl C{sub 71} butyric acid methyl ester (PC71BM) bulk-heterojunction based inverted OPV devices using current density-voltage (J-V) characteristics, space charge limited current (SCLC) measurements, capacitance-voltage (C-V) characteristics, and impedance spectroscopy (IS). OPV devices in inverted architecture, ITO/ZnO/PDPP-TNT:PC71BM/MoO{sub 3}/Ag, are processed and characterized at room conditions. The power conversion efficiency (PCE) of these devices are measured ∼3.8%, with reasonably good fill-factor 54.6%. The analysis of impedance spectra exhibits electron’s mobility ∼2 × 10{sup −3} cm{sup 2}V{sup −1}s{sup −1}, and lifetime in the range of 0.03-0.23 ms. SCLC measurements give hole mobility of 1.12 × 10{sup −5} cm{sup 2}V{sup −1}s{sup −1}, and electron mobility of 8.7 × 10{sup −4} cm{sup 2}V{sup −1}s{sup −1}.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Graphite Conjugation Eliminates Redox Intermediates in Molecular Electrocatalysis

The efficient interconversion of electrical and chemical energy requires the intimate coupling of electrons and small-molecule substrates at catalyst active sites. In molecular electrocatalysis, the molecule acts as a redox mediator which typically undergoes oxidation or reduction in a separate step from substrate activation. These mediated pathways introduce a high-energy intermediate, cap the driving force for substrate activation at the reduction potential of the molecule, and impede access to high rates at low overpotentials. Here we show that electronically coupling a molecular hydrogen evolution catalyst to a graphitic electrode eliminates stepwise pathways and forces concerted electron transfer and proton binding. Electrochemical and X-ray absorption spectroscopy data establish that hydrogen evolution catalysis at the graphite-conjugated Rh molecule proceeds without first reducing the metal center. These results have broad implications for the molecular-level design of energy conversion catalysts.

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

Engineering new limits to magnetostriction through metastability in iron-gallium alloys

Magnetostrictive materials transduce magnetic and mechanical energies and when combined with piezoelectric elements, evoke magnetoelectric transduction for high-sensitivity magnetic field sensors and energy-efficient beyond-CMOS technologies. The dearth of ductile, rare-earth-free materials with high magnetostrictive coefficients motivates the discovery of superior materials. Fe 1- x Ga x alloys are amongst the highest performing rare-earth-free magnetostrictive materials; however, magnetostriction becomes sharply suppressed beyond x = 19% due to the formation of a parasitic ordered intermetallic phase. Here, we harness epitaxy to extend the stability of the BCC Fe 1- x Ga x alloy to gallium compositions as high as x = 30% and in so doing dramatically boost the magnetostriction by as much as 10x relative to the bulk and 2x larger than canonical rare-earth based magnetostrictors. A Fe 1- x Ga x - [Pb(Mg 1/3 Nb 2/3 )O 3 ] 0.7 -[PbTiO 3 ] 0.3 (PMN-PT) composite magnetoelectric shows robust 90° electrical switching of magnetic anisotropy and a converse magnetoelectric coefficient of 2.0 × 10 -5 s m -1 . When optimally scaled, this high coefficient implies stable switching at ~80 aJ per bit.

36 MATERIALS SCIENCE↗
DOE OSTI2020

15.9% organic tandem solar cell with extended near-infrared absorption

Stacking single-junction organic solar cells is effective in increasing the power conversion efficiency (PCE) by reducing the thermalization loss and increasing the open circuit voltage. Current developments of non-fullerene acceptors (NFAs) offer a range of materials whose energy gaps are suited for absorbing relatively narrow slices of the solar spectrum, thus easing requirements for current balance between sub-elements in the multijunction stacks. In this report, we demonstrate a solution-processed tandem organic solar cell comprising a binary, visible-absorbing sub-cell and a ternary near-infrared (NIR) absorbing sub-cell. The ternary NIR sub-cell utilizes a narrow energy gap NFA acceptor that enables a broadened and increased absorption compared to a binary NIR sub-cell. An isopropanol surface treatment is developed to connect the hydrophilichydrophobic surfaces in the charge recombination zone (CRZ) located between the sub-cells. The nearly optically and electrically lossless CRZ combined with an anti-reflection coating results in a tandem OPV with PCE = 15.9 ± 0.2 % under AM 1.5G simulated illumination.

14 SOLAR ENERGY↗
DOE OSTI2025

Feed the fish: A review of aquaculture feeders and their strategic implementation

Automatic feeders are revolutionizing aquaculture by enabling precise and controlled feeding regimens that optimize growth, reduce feed waste, and enhance the overall efficiency of farming operations. Demand feeders provide some similar benefits but with feeding tailored to fish appetites and, in some cases, feed dispersal without electricity. This review explores the evolution, technological advancements, and applications of these feeders with a survey of recent research. It looks at common feeder designs and compares the pros and cons of five automatic feeder configurations in commercial use today. The article contrasts feeders and feed sizes for farmed species in different life stages and facilities, from hatcheries to ponds and offshore cages. It discusses the importance of species-tailored feeding strategies as well as impacts on fish behavior and health, nutrient delivery, and environmental sustainability. Incorporating sensors and on-site computing enables optimization in feeding algorithms that feeders then implement precisely and reliably. The review compiles results from multiple studies comparing growth rate, weight, and feed conversion ratio (FCR) outcomes from automatic feeders and demand feeders versus traditional hand-feeding regimens. The integration of feeders with real-time monitoring and data analytics is also discussed, highlighting future directions for research and adoption across the industry.

42 ENGINEERING↗
NASA NTRS1981

Parametric analysis of closed cycle magnetohydrodynamic (MHD) power plants

A parametric analysis of closed cycle MHD power plants was performed which studied the technical feasibility, associated capital cost, and cost of electricity for the direct combustion of coal or coal derived fuel. Three reference plants, differing primarily in the method of coal conversion utilized, were defined. Reference Plant 1 used direct coal fired combustion while Reference Plants 2 and 3 employed on site integrated gasifiers. Reference Plant 2 used a pressurized gasifier while Reference Plant 3 used a ""state of the art' atmospheric gasifier. Thirty plant configurations were considered by using parametric variations from the Reference Plants. Parametric variations include the type of coal (Montana Rosebud or Illinois No. 6), clean up systems (hot or cold gas clean up), on or two stage atmospheric or pressurized direct fired coal combustors, and six different gasifier systems. Plant sizes ranged from 100 to 1000 MWe. Overall plant performance was calculated using two methodologies. In one task, the channel performance was assumed and the MHD topping cycle efficiencies were based on the assumed values. A second task involved rigorous calculations of channel performance (enthalpy extraction, isentropic efficiency and generator output) that verified the original (task one) assumptions. Closed cycle MHD capital costs were estimated for the task one plants; task two cost estimates were made for the channel and magnet only.

Owens, W.↗
DOE OSTI2025

EV Charging Infrastructure Energization An Overview of Approaches for Simplifying and Accelerating Timelines to Processing EV Charging Load Service Requests

The United States has seen significant growth in electric vehicle (EV) adoption, leading to increased demand for EV charging infrastructure. Over the past decade, EV charging infrastructure site developers, site hosts, and electric distribution utilities have navigated the process to integrate chargers onto the electric grid. Site developers and site hosts have raised the alarm that the integration process for high-powered EV charging projects does not meet the needs of the EV market for timeliness or cost. High-powered charging stations typically require a load service request or an agreement with the local utility to connect to the grid. The process of energizing a new high-powered charging site can be complex and time-consuming, often taking up to 2 years. This timeline is the result of current utility energization processes having been designed for construction projects that take longer to build (i.e., buildings). The specific challenges stem from various factors, including compartmentalization in application processes, the integration of EV charging process approvals with other distributed energy resources (DERs), and the need to ensure grid reliability. The energization process needs to evolve to meet the growing demand for high-powered EV charging. This white paper compiles information gathered through various conversations with key stakeholders, including utilities, utility regulators, EV charging operators, site developers, and authorities having jurisdiction (AHJ) as well as through an extensive literature review. This document identifies the challenges and provides potential solutions to streamline the process of connecting EV charging infrastructure to the power grid in the United States, serving as a starting point for future conversations around these solutions. The solutions noted in this white paper require collaborative efforts among utilities, regulators, and EV charging infrastructure developers to streamline the grid connection process for EV charging infrastructure. They are broadly organized into four areas: 1. Increase data access and transparency: Develop automated load service request tools, integrate hosting capacity and load service request analyses, incorporate EV adoption forecasts, and provide transparency on the processing queue. 2. Improve energization processes and timing: Create fast-track options based on prescreening criteria, provide flexibility or phased approvals in the load service request/interconnection process, build internal knowledge within utilities about EV charging technologies, and provide standardized workforce training. 3. Promote economic efficiency: Right size distribution components to accurately reflect the load requirements of EV charging infrastructure, make proactive investments in grid infrastructure based on EV adoption forecasts and growth projections, and consider energy equity and environmental justice factors such as equitable access to EV charging when planning infrastructure. 4. Improve grid reliability and resilience: Use load management/power control systems (PCS) at EV charging stations, adopt and implement harmonized standards for communication protocols and information models between the EV charging and grid control infrastructure, and address cybersecurity considerations by implementing robust security measures and standards for EV charging infrastructure—with particular emphasis on clarifying the security requirements for the interface to the grid. The objective of the solutions proposed in this white paper is to accelerate the timeline and decrease costs associated with connecting EV charging infrastructure to the grid. Electric utilities, utility regulators, EV charging infrastructure developers, and site hosts will first need to understand which solutions are available in their service territory, and if warranted, which combination of solutions would support their specific needs. Through the successful implementations of solutions at scale detailed here, industry will demonstrate a new and innovative ecosystem where timely deployment and energization of EV charging infrastructure with greater grid resiliency and reliability is a reality.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2019

Increasing Revenue of Nuclear Power Plants With Thermal Storage

Introducing large amounts of electricity produced from variable renewable energy sources such as wind and solar decreases wholesale electricity price while increasing the volatility of the market. These conditions drive the need for peak-load power generation, while regulation requirements fuel the push for flexible power generation. The increase of variable renewable energy in the market share, along with falling natural gas prices, makes nuclear power plants less competitive. Thermal storage is being considered to increase the nuclear power plant revenue. Thermal storage increases the flexibility of the nuclear plant system without sacrificing its efficiency. There are multiple opportunities to increase the nuclear power plant revenue, including increased capacity payments, arbitrage, and ancillary services. An economic analysis was performed to investigate the revenue increase of the system with thermal storage. The investment cost was assessed, and net present value was evaluated for the considered scenarios. Two system designs were considered in the analysis: a thermal storage system using the existing power conversion infrastructure and an integrated design with thermal storage fully incorporated into the reactor system design. The preliminary analysis showed that introducing a thermal storage system is profitable for some scenarios considered. Profitability depends significantly on the storage size, output flexibility, share of variable renewable energy, and market characteristics.

25 ENERGY STORAGE↗
DOE OSTI2017

Intelligent Facades for High Performance Green Buildings

Progress Towards Net-Zero and Net-Positive-Energy Commercial Buildings and Urban Districts Through Intelligent Building Envelope Strategies Previous research and development of intelligent facades systems has been limited in their contribution towards national goals for achieving on-site net zero buildings, because this R&D has failed to couple the many qualitative requirements of building envelopes such as the provision of daylighting, access to exterior views, satisfying aesthetic and cultural characteristics, with the quantitative metrics of energy harvesting, storage and redistribution. To achieve energy self-sufficiency from on-site solar resources, building envelopes can and must address this gamut of concerns simultaneously. With this project, we have undertaken a high-performance building integrated combined-heat and power concentrating photovoltaic system with high temperature thermal capture, storage and transport towards multiple applications (BICPV/T). The critical contribution we are offering with the Integrated Concentrating Solar Façade (ICSF) is conceived to improve daylighting quality for improved health of occupants and mitigate solar heat gain while maximally capturing and transferring onsite solar energy. The ICSF accomplishes this multi-functionality by intercepting only the direct-normal component of solar energy (which is responsible for elevated cooling loads) thereby transforming a previously problematic source of energy into a high quality resource that can be applied to building demands such as heating, cooling, dehumidification, domestic hot water, and possible further augmentation of electrical generation through organic Rankine cycles. With the ICSF technology, our team is addressing the global challenge in transitioning commercial and residential building stock towards on-site clean energy self-sufficiency, by fully integrating innovative environmental control systems strategies within an intelligent and responsively dynamic building envelope. The advantage of being able to use the entire solar spectrum for active and passive benefits, along with the potential savings of avoiding transmission losses through direct current (DC) transfer to all buildings systems directly from the site of solar conversion, gives the system a compounded economic viability within the commercial and institutional building markets. With a team that spans multiple stakeholders across disparate industries, from CPV to A&E partners that are responsible for the design and development of District and Regional Scale Urban Development, this project demonstrates that integrating utility-scale high efficiency CPV installations with urban and suburban environments is both viable and desirable within the marketplace. The historical schism between utility scale CPV and BIPV has been one of differing scale and cultures. There is no technical reason why utility-scale CPV cannot be located within urban embedded district scale sites of energy harvesting. New models for leasing large areas of district scale roofs and facades are emerging, such that the model for utility scale energy harvesting can be reconciled to commercial and public scale building sites and campuses. This consortium is designed to unite utility scale solar harvesting into building applications for smart grid development.

14 SOLAR ENERGY↗
DOE OSTI2018

Solar Water Oxidation by an InGaN Nanowire Photoanode with a Bandgap of 1.7 eV

The performance of overall solar water splitting has been largely limited by the half-reaction of water oxidation. Here, we report a 1.7 eV bandgap InGaN nanowire photoanode for efficient solar water oxidation. It produces a low onset potential of 0.1 V versus a reversible hydrogen electrode (RHE) and a high photocurrent density of 5.2 mA/cm 2 at a potential as low as 0.6 V versus RHE. The photoanode yields a half-cell solar energy conversion efficiency up to 3.6%, a record for a single-photon photoanode to our knowledge. Furthermore, in the presence of hole scavengers, the photocurrent density of the InGaN photoanode reaches 21.2 mA/cm 2 at 1.23 V versus RHE, which approaches the theoretical limit for a 1.7 eV InGaN absorber. Furthermore, the InGaN nanowire photoanode may serve as an ideal top cell in a photoelectrochemical tandem device when stacked with a 0.9–1.2 eV bandgap bottom cell, which can potentially deliver solar-to-hydrogen efficiency over 25%.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Power Electronics Thermal Management

This project develops thermal management strategies to enable efficient and high-temperature wide-bandgap (WBG)-based power electronic systems (e.g., emerging inverter and DC-DC converter designs). The use of WBG-based devices in automotive power electronics will improve efficiency and increase driving range in electric-drive vehicles; however, the implementation of this technology is limited, in part, due to thermal issues. This project will develop system-level thermal models to determine the thermal limitations of current automotive power modules under elevated device temperature conditions. Additionally, novel cooling concepts and material selection will be evaluated to enable high-temperature silicon and WBG devices in power electronics components. WBG devices (silicon carbide [SiC], gallium nitride [GaN]) promise to increase efficiency, but will be driven as hard as possible. This creates challenges for thermal management and reliability. This project is a Vehicle Technologies Office, U.S. Department of Energy Office of Energy Efficiency and Renewable Energy funded project.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2019

Computational study of full-scale VHTR lower plenum for turbulent mixing assessment

Next-generation nuclear reactors are poised to efficiently provide reliable power at enhanced safety levels for many years to come. Among the fundamental designs for these reactors is the very-hightemperature reactor (VHTR), which employs helium as the primary coolant and has the potential of reaching elevated temperatures such that chemical processing (e.g., electrolysis for hydrogen production) is viable alongside traditional electricity generation. This and other next-generation reactors also represent a strategic bridge for ultimately transitioning from fossil fuel-dominated energy portfolios to one where renewable options abound. For the VHTR, the ultimate goal of constructing a new plant will be preceded by additional fundamental research aimed at generating trusted models for behavior prediction under normal and accident scenarios. This paper presents a detailed computational fluid dynamics simulation of the lower plenum, where hot coolant from the core mixes together in a turbulent fashion before traveling to power conversion equipment. Because the flow is expected to enter the lower plenum across a wide range of temperatures and velocities, concerns exist when the mixing is incomplete. The potential hot spots on cylindrical support pedestals and the uniformity of the main outlet are the primary metrics of interest in this study, along with flow velocities and temperatures at different locations within the lower plenum. Three locations are probed in detail and suggest a large range exists for approach velocities and temperatures. A large degree of stratification is also seen on the surfaces of the support pedestals, suggesting a facility should accommodate testing for such behavior. The characterizations presented provide the valuable data needed in order to design appropriate experimental testbeds, where scaled modeling can be carried out in a manner meaningful in predicting the full-scale behavior.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Current status and grand challenges for small wind turbine technology

While modern wind turbines have become by far the largest rotating machines on Earth with further upscaling planned for the future, a renewed interest in small wind turbines (SWTs) is fostering energy transition and smart grid development. Small machines have traditionally not received the same level of aerodynamic refinement as their larger counterparts, resulting in lower efficiency, lower capacity factors, and therefore a higher cost of energy. In an effort to reduce this gap, research programs are developing worldwide. With this background, the scope of the present study is 2-fold. In the first part of this paper, an overview of the current status of the technology is presented in terms of technical maturity, diffusion, and cost. The second part of the study proposes five grand challenges that are thought to be key to fostering the development of small wind turbine technology in the near future, i.e. (1) improving energy conversion of modern SWTs through better design and control, especially in the case of turbulent wind; (2) better predicting long-term turbine performance with limited resource measurements and proving reliability; (3) improving the economic viability of small wind energy; (4) facilitating the contribution of SWTs to the energy demand and electrical system integration; (5) fostering engagement, social acceptance, and deployment for global distributed wind markets. To tackle these challenges, a series of unknowns and gaps are first identified and discussed. Based on them, improvement areas are suggested, for which 10 key enabling actions are finally proposed.

17 WIND ENERGY↗