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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

An Assessment of Supercritical CO2 Power Cycles Integrated with Generic Heat Sources (Report)

Paper for the 4th sCO2 Symposium. (2014). This paper documents a detailed analysis of the supercritical CO2 (sCO2) recompression Brayton cycle to better understand at a fundamental level the dependence of the cycle performance on operating conditions. The focus of this study is on cycle performance, particularly efficiency. No cost estimates were performed. However, a number of indirect measures of cycle cost were examined to provide an indication of whether the operating conditions were in a region of great cost sensitivity. In this study, a sCO2 recompression cycle is described and a set of baseline operating conditions proposed. The heat source for the study was considered generic or agnostic. No temperature value, temperature range, or heat flux was assumed to limit cycle design.

Generic heat source↗
DOE OSTI2014

SnS{sub 2} nanoflakes decorated multiwalled carbon nanotubes as high performance anode materials for lithium-ion batteries

Graphical abstract: The synthesized SnS{sub 2} nanoflakes decorated multiwalled carbon nanotubes hybrid structures exhibit large reversible capacity, superior cycling performance, and good rate capability as compared to pure SnS{sub 2} nanoflakes. - Highlights: • Synthesis of SnS{sub 2} nanoflakes decorated multiwalled carbon nanotubes hybrid structures. • Simple solution-phase approach. • Morphology feature of SnS{sub 2}. • Enhanced performance as Li-ion batteries. - Abstract: SnS{sub 2} nanoflakes decorated multiwalled carbon nanotubes (MWCNTs) hybrid structures are directly synthesized via a simple solution-phase approach. The as-prepared SnS{sub 2}/MWCNTs structures are investigated as anode materials for Li-ion batteries as compared with SnS{sub 2} nanoflakes. It has been found that the composite structure exhibit excellent lithium storage performance with a large reversible capacity, superior cycling performance, and good rate capability as compared to pure SnS{sub 2} nanoflakes. The first discharge and charge capacities have been found to be 1416 and 518 mA h g{sup −1} for SnS{sub 2}/MWCNTs composite electrodes at a current density of 100 mA g{sup −1} between 5 mV and 1.15 V versus Li/Li{sup +}. A stable reversible capacity of ∼510 mA h g{sup −1} is obtained for 50 cycles. The improved electrochemical performance may be attributed to the flake-morphology feature of SnS{sub 2} and the addition of MWCNTs that can hinder the agglomeration of the active materials and improve the conductivity of the composite electrode simultaneously.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Ultra-Stretchable, Ionic Conducting, Pressure-Sensitive Adhesive with Dual Role for Stable Li-Metal Batteries

The practical application of lithium (Li) metal battery is impeded by the Li dendrite growth and unstable solid electrolyte interphase (SEI) layer. Herein, an ultra-stretchable and ionic conducting chemically crosslinked pressure-sensitive adhesive (cPSA) synthesized via the copolymerization of 2-ethylhexyl acrylate and acrylic acid with poly(ethyleneglycol)dimethacrylate as crosslinker (short for 70cPSA), is developed as both artificial SEI layer and solid polymer electrolyte (SPE) for stable Li-metal electrode, enabling all-solid-state Li metal batteries with excellent cycling performance. As an artificial SEI layer, the 70cPSA-modified electrodes exhibit excellent electrochemical performance in Li|70cPSA@Cu half cells and 70cPSA@Li|70cPSA@Li symmetric cells. In full cells with LiFePO 4 (LFP) as cathode, the 70cPSA@Li|LFP cell exhibits stable cycling performance over 250 cycles. Utilized as SPE, the all-solid-state Li|SPE|LFP cell delivers excellent cycling stability with a capacity retention of 86% over 500 cycles. With high-voltage LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) as cathode, the Li|SPE|NMC811 cell exhibits a discharge capacity of 124.3 mAh g -1 with a capacity retention of 71% after 200 cycles. Furthermore, the rational design of PSAs and investigation of their dual role for stable and safe Li-metal batteries may shed a light on adhesive polymers for battery applications.

25 ENERGY STORAGE↗
DOE OSTI2022

Constructing a multi-functional polymer network for ultra-stable and safe Li-metal batteries

We report the practical application of lithium (Li) metal electrodes is impeded by Li dendrite growth and unstable solid electrolyte interphase (SEI). Herein, a multi-grafting polymer network, poly(dimethyl siloxane)-g-[poly(poly(ethylene glycol) methyl ether methacrylate)-r-sodium poly(p-styrene sulfonate)] (PPS), is chemically synthesized from reversible addition-fragmentation chain transfer (RAFT) polymerization. With integrated stretchability, ionic conductivity, and mechanical robustness, it serves a dual role to stabilize the Li electrode. As artificial SEI layer, the PPS enables superior electrochemical performance in half cells, symmetric cells, and full cells (PPS@Li/LiFePO 4 , capacity retention of >70% after 600 cycles). Utilized as solid polymer electrolyte (SPE), the all-solid-state Li/SPE/LiFePO 4 full cell delivers excellent cycling performance with an unprecedented capacity retention of 90% over 1,700 cycles at 0.5 C and 81% over 1,000 cycles at 1.0 C. With high-voltage LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) as cathode, the Li/SPE/NMC811 cell exhibits an initial discharge capacity of 162.2 mAh g -1 with a capacity retention of 72% after 200 cycles. The assembled solid-state Li/SPE/LiFePO4 pouch cell with SPE exhibits stable cycling performance over 200 cycles with a capacity retention of 75% and still operates well even after curling, folding, and cutting, demonstrating great potential for achieving ultra-safe and high energy density batteries.

25 ENERGY STORAGE↗
DOE OSTI2023

Defining a compact dry cooler design to reduce LCOE contribution in a CSP facility

Concentrating solar power (CSP), when coupled with a supercritical carbon dioxide (sCO 2 ) power cycle and sensible heat storage, presents a renewable and clean alternative for utility-scale power generation. However, in order to be competitive in the current and future markets, CSP facilities must limit their levelized cost of electricity (LCOE) by minimizing capital costs and reducing operating costs over the lifetime of the plant. Targeting this goal, this study investigates the LCOE impact of the power cycle pre-cooler. This study considers a compact dry cooler with micro-channel technology on the CO 2 side and formed fin geometry on the air side, using directly-coupled centrifugal fans and a transition duct to improve air distribution across the fins as well as protect the fins from contaminants which may cause blockage, soiling, fouling, and damage. In an effort to better understand the dry cooler impact on LCOE, a sensitivity study was conducted using various combinations of end-to-end approach temperatures, air-side pressure drop values, CO 2 -side pressure drop values, fan types, cooler turndown control schemes, cooler module sizes, and design-point ambient temperatures. Furthemore, off-design cycle performance data was calculated for each dry cooler design using NPSS simulation software; cycle performance data were then input to System Advisor Model (SAM) along with the associated capital costs for LCOE prediction of a 100 MW system over a 30 year plant lifetime. Results of this study show the LCOE is most sensitive to air-side performance, followed by heat transfer effectiveness and capital cost. It was found that a power cycle with a mid- to high-performance dry cooler will produce the most competitive power-production costs. Designing at the extreme ends for approach temperature (or effectiveness), design-point ambient temperature, and compactness (footprint) produce higher LCOE values; mid-range values for these parameters balance performance, operating costs, and associated capital cost to optimize LCOE.

14 SOLAR ENERGY↗
DOE OSTI2014

Impact of Charge Degradation on the Life Cycle Climate Performance of a Residential Air-Conditioning System

Vapor compression systems continuously leak a small fraction of their refrigerant charge to the environment, whether during operation or servicing. As a result of the slow leak rate occurring during operation, the refrigerant charge decreases until the system is serviced and recharged. This charge degradation, after a certain limit, begins to have a detrimental effect on system capacity, energy consumption, and coefficient of performance (COP). This paper presents a literature review and a summary of previous experimental work on the effect of undercharging or charge degradation of different vapor compression systems, especially those without a receiver. These systems include residential air conditioning and heat pump systems utilizing different components and refrigerants, and water chiller systems. Most of these studies show similar trends for the effect of charge degradation on system performance. However, it is found that although much experimental work exists on the effect of charge degradation on system performance, no correlation or comparison between charge degradation and system performance yet exists. Thus, based on the literature review, three different correlations that characterize the effect of charge on system capacity and energy consumption are developed for different systems as follows: one for air-conditioning systems, one for vapor compression water-to-water chiller systems, and one for heat pumps. These correlations can be implemented in vapor compression cycle simulation tools to obtain a better prediction of the system performance throughout its lifetime. In this paper, these correlations are implemented in an open source tool for life cycle climate performance (LCCP) based design of vapor compression systems. The LCCP of a residential air-source heat pump is evaluated using the tool and the effect of charge degradation on the results is studied. The heat pump is simulated using a validated component-based vapor compression system model and the LCCP results obtained using the three charge degradation correlations are compared.

Air Conditioning↗
DOE OSTI2020

Controlling Ion Coordination Structure and Diffusion Kinetics for Optimized Electrode-Electrolyte Interphases and High Performance Si Anodes

The cycling performance of batteries is largely determined by electrode-electrolyte interphase associated with the chemical and electrochemical properties of electrolyte salts and solvents. In this work, we used a localized high concentration electrolyte (LHCE) that enables high performance of Si anodes as a model system and investigated the scientific mechanism behind the optimization of electrolyte. The correlation between electrode (cathode/anode)-electrolyte interphase and ion coordination structure and diffusion kinetics were elucidated systematically. Among all the LHCEs tested, the one with 1.8M LiFSI concentration and 1:2 molar ratio of carbonate solvents and fluorinated diluents has the highest proportion of solvent-separated ion pairs and contact ion pairs and fastest ion diffusion. It enables the most stable electrode-electrolyte interphase and hence the best Si anode performance. These results reveal the fundamental mechanism behind the stability of LHCEs and provide guidance on the new electrolyte design for Si anodes and other battery systems.

Jia, Haiping↗
NASA NTRS1977

ENGINEL: A single rotor turbojet engine cycle match performance program

ENGINEL is a computer program which was developed to generate the design and off-design performance of a single rotor turbojet engine with or without afterburning using a cycle match procedure. It is capable of producing engine performance over a wide range of altitudes and Mach numbers. The flexibility, of operating with a variable geometry turbine, for improved off-design fuel consumption or with a fixed geometry turbine as in conventional turbojets, has been incorporated. In addition, the option of generation engine performance with JP4, liquid hydrogen or methane as fuel is provided.

Lovell, W. A.↗
DOE OSTI2018

Effect of Binder Architecture on the Performance of Silicon/Graphite Composite Anodes for Lithium Ion Batteries

Although significant progress has been made in improving cycling performance of silicon-based electrodes, few studies have been performed on the architecture effect on polymer binder performance for lithium-ion batteries. A systematic study on the relationship between polymer architectures and binder performance is especially useful in designing synthetic polymer binders. In this paper, a graft block copolymer with readily tunable architecture parameters is synthesized and tested as the polymer binder for the high-mass loading silicon (15 wt %)/graphite (73 wt %) composite electrode (active materials >2.5 mg/cm 2 ). With the same chemical composition and functional group ratio, the graft block copolymer reveals improved cycling performance in both capacity retention (495 mAh/g vs 356 mAh/g at 100th cycle) and Coulombic efficiency (90.3% vs 88.1% at first cycle) than the physical mixing of glycol chitosan (GC) and lithium polyacrylate (LiPAA). Galvanostatic results also demonstrate the significant impacts of different architecture parameters of graft copolymers, including grafting density and side chain length, on their ultimate binder performance. Finally, by simply changing the side chain length of GC-g-LiPAA, the retaining delithiation capacity after 100 cycles varies from 347 mAh/g to 495 mAh/g.

25 ENERGY STORAGE↗
NASA NTRS1987

Two-watt, 4-Kelvin closed cycle refrigerator performance

A 2-watt, 4-K helium refrigerator using the Gifford-McMahon/Joule Thomson cycle is described. The unit features a removable displacer cylinder and high-efficiency, low-pressure drop heat exchangers. These improvements result in a 100 percent increase in cooling power over the existing Deep Space Network system. The effects of the heat exchanger efficiency and Gifford-McMahon expander performance on refrigerator capacity are also discussed.

Britcliffe, M.↗
DOE OSTI2019

Influence of Y-Rich Compounds on High-Cycle Fatigue Performance of Y-Doped M951 Superalloy

The performance of Y-doped M951 superalloy under high-cycle fatigue was investigated experimentally to determine the effect of Y-rich compounds on this behavior. The selected testing temperatures were 700 and 900 °C, and the stress ratio was R = 0.1. The fatigue life was shown to decrease as the stress amplitude increased, according to a typical Whöler S-N diagram. Two types of crack initiation sites were observed on the fractured surfaces: microshrinkage clusters and Y-rich compounds. Analysis by TEM indicated that the Y-rich compounds consisted of Al{sub 2}Ni{sub 6}Y{sub 3} particles with BCC structure and Ni{sub 5}Y particles with hexagonal structure. Cracks had initiated and propagated along the interface between Al{sub 2}Ni{sub 6}Y{sub 3} phase and the matrix. These Y-rich compounds varied considerably in size, from 1 to 769 μm, and the large-size Y-rich compounds were shown to be the preferred site for fatigue crack origin. The ability of Y in the removal of sulfur was considered. And the small-size Y-S product from the reaction between Y and S was shown to exhibit no deleterious effect on the fatigue property of the M951 Ni-based superalloy.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Method for controlling start-up and steady state performance of a closed split flow recompression brayton cycle

A method of resolving a balanced condition that generates control parameters for start-up and steady state operating points and various component and cycle performances for a closed split flow recompression cycle system. The method provides for improved control of a Brayton cycle thermal to electrical power conversion system. The method may also be used for system design, operational simulation and/or parameter prediction.

42 ENGINEERING↗
DOE OSTI2013

Preparation and characterization of MnFe{sub 2}O{sub 4} in the solvothermal process: Their magnetism and electrochemical properties

Graphical abstract: - Highlights: • Effect of CTAB on the morphology and crystallization of MnFe{sub 2}O{sub 4}. • The lowest coercivity of MnFe{sub 2}O{sub 4} polyhedron is 11.9 Oe. • MnFe{sub 2}O{sub 4} as anode for LIB shows good reversible capacity and cycle performances. - Abstract: The uniform different morphologies MnFe{sub 2}O{sub 4}, including cube, truncated cube, polyhedron and octahedron, were successfully synthesized via a solvothermal route using cetyltrimethylammonium bromide. The results of control experiments revealed that the concentration of cetyltrimethylammonium bromide was an important factor, which affected the morphology and crystallization of MnFe{sub 2}O{sub 4} submicro-crystals. All the prepared samples exhibited soft-magnetic behavior at room temperature. Especially, the coercivity of MnFe{sub 2}O{sub 4} polyhedron with 200 nm diameter was 11.9 Oe, which was among the lowest values reported so far. Moreover, MnFe{sub 2}O{sub 4} submicro-crystals with special morphologies demonstrated higher reversible capacity (about 1000 mAh g{sup −1}) and different cycle performances. After 50 cycles, polyhedron structure remained 428 mAh/g. The MnFe{sub 2}O{sub 4} would have a potential application as anode material for lithium ion batteries.

36 MATERIALS SCIENCE↗
DOE OSTI2018

All-solid-state interpenetrating network polymer electrolytes for long cycle life of lithium metal batteries

A star-shape polymer of 3-armed poly(ethylene glycol) methyl ether methacrylate-co-glycidyl methacrylate copolymer (3PPEGM-co-GMA) was synthesized using an atom transfer radical polymerization (ATRP) technique. All-solid-state interpenetrating network polymer electrolytes (INSPEs) were fabricated by simultaneous reaction of 3PPEGM-co-GMA and bisphenol A diglycidyl ether (BPDE) with polyetherdiamine (ED2003) in the presence of lithium bis(trifluoromethane) sulfonamide (LiTFSI). The INSPEs exhibited ionic conductivities higher than 10 -5 S cm -1 at room temperature, a high oxidation stability of 4.5 vs. Li/Li + and remarkable stability towards lithium metal. Li metal batteries with LiFePO 4 as the cathode and INSPEs as the electrolyte cycled at a current rate of 0.1C at 60 °C showed a high initial discharge capacity of 156.2 mA h g -1 and a stable cycling performance over 200 cycles with a high coulombic efficiency of 99%. In conclusion, the results demonstrate that the interpenetrating network polymer electrolytes are promising electrolytes for next generation lithium-based batteries with high ionic conductivity, improved safety, and stable electrochemical performance.

25 ENERGY STORAGE↗
NASA NTRS1992

Tracking performance and cycle slipping in the all-digital symbol synchronizer loop of the block 5 receiver

Computer simulated noise performance of the symbol synchronizer loop (SSL) in the Block 5 receiver is compared with the theoretical noise performance. Good agreement is seen at the higher loop SNR's (SNR(sub L)'s), with gradual degradation as the SNR(sub L) is decreased. For the different cases simulated, cycle slipping is observed (within the simulation time of 10(exp 4) seconds) at SNR(sub L)'s below different thresholds, ranging from 6 to 8.5 dB, comparable to that of a classical phase-locked loop. An important point, however, is that to achieve the desired loop SNR above the seemingly low threshold to avoid cycle slipping, a large data-to-loop-noise power ratio, P(sub D)/(N(sub 0)B(sub L)), is necessary (at least 13 dB larger than the desired SNR(sub L) in the optimum case and larger otherwise). This is due to the large squaring loss (greater than or equal to 13 dB) inherent in the SSL. For the special case of symbol rates approximately equaling the loop update rate, a more accurate equivalent model accounting for an extra loop update period delay (characteristic of the SSL phase detector design) is derived. This model results in a more accurate estimation of the noise-equivalent bandwidth of the loop.

Aung, M.↗
DOE OSTI2019

Incorporating Solvate and Solid Electrolytes for All‐Solid‐State Li 2 S Batteries with High Capacity and Long Cycle Life

Abstract The development of all‐solid‐state lithium–sulfur batteries is hindered by the poor interfacial properties at solid electrolyte (SE)/electrode interfaces. The interface is modified by employing the highly concentrated solvate electrolyte, (MeCN) 2 −LiTFSI:TTE, as an interlayer material at the electrolyte/electrode interfaces. The incorporation of an interlayer significantly improves the cycling performance of solid‐state Li 2 S batteries compared to the bare counterpart, exhibiting a specific capacity of 760 mAh g −1 at cycle 100 (330 mAh g −1 for the bare cell). Electrochemical impedance spectroscopy shows that the interfacial resistance of the interlayer‐modified cell gradually decreases as a function of cycle number, while the impedance of the bare cell remains almost constant. Cross‐section scanning electron microscopy (SEM)/ energy dispersive X‐ray spectroscopy (EDS) measurements on the interlayer‐modified cell confirm the permeation of solvate into the cathode and the SE with electrochemical cycling, which is related to the decrease in cell impedance. In order to mimic the full permeation of the solvate across the entire cell, the solvate is directly mixed with the SE to form a “solvSEM” electrolyte. The hybrid Li 2 S cell using a solvSEM electrolyte exhibits superior cycling performance compared to the solid‐state cells, in terms of Li 2 S loading, Li 2 S utilization, and cycling stability. The improved performance is due to the favorable ionic contact at the battery interfaces.

Shin, Minjeong↗
DOE OSTI2016

Modification of Ni-Rich FCG NMC and NCA Cathodes by Atomic Layer Deposition: Preventing Surface Phase Transitions for High-Voltage Lithium-Ion Batteries

The energy density of current lithium-ion batteries (LIBs) based on layered LiMO 2 cathodes (M=Ni, Mn, Co: NMC; M=Ni, Co, Al: NCA) needs to be improved significantly in order to compete with internal combustion engines and allow for widespread implementation of electric vehicles (EVs). In this report, we show that atomic layer deposition (ALD) of titania (TiO 2 ) and alumina (Al 2 O 3 ) on Ni-rich FCG NMC and NCA active material particles could substantially improve LIB performance and allow for increased upper cutoff voltage (UCV) during charging, which delivers significantly increased specific energy utilization. Our results show that Al2O3 coating improved the NMC cycling performance by 40% and the NCA cycling performance by 34% at 1C/₋1C with respectively 4.35V and 4.4V UCV in 2Ah pouch cells. High resolution TEM/SAED structural characterization revealed that Al 2 O 3 coatings prevented surface-initiated layered-to-spinel phase transitions in coated materials which were prevalent in uncoated materials. Lastly, EIS confirmed that Al 2 O 3 -coated materials had significantly lower increase in the charge transfer component of impedance during cycling. In conclusion, the ability to mitigate degradation mechanisms for Ni-rich NMC and NCA illustrated in this report provides insight into a method to enable the performance of high-voltage LIBs.

25 ENERGY STORAGE↗
DOE OSTI2018

Hybrid Lithium-Sulfur Batteries with an Advanced Gel Cathode and Stabilized Lithium-Metal Anode

The insulating nature of sulfur, polysulfide shuttle effect, and lithium metal deterioration cause a decrease in practical energy density and fast capacity fade in lithium-sulfur batteries. Here, we present an integrated strategy for the development of hybrid Li-S batteries based on a gel sulfur cathode, a solid electrolyte, and a protective anolyte composed of highly-concentrated salt electrolyte containing mixed additives. The dense solid electrolyte completely blocks polysulfide diffusion, and also makes it possible to investigate the cathode and anode independently. This gel cathode effectively traps the polysulfide active material while maintaining a low electrolyte to sulfur ratio (E/S) of 5.2 mL/g. The anolyte effectively protects the Li metal and suppresses the consumption of liquid electrolyte, enabling stable long-term cycling for over 700 hours in Li symmetric cells. This advanced design can simultaneously suppress the polysulfide shuttle, protect Li metal, and reduce the liquid electrolyte usage. The assembled hybrid batteries exhibit remarkably stable cycling performance over 300 cycles with high capacity. Finally, surface-sensitive techniques were carried out to directly visualize and to probe the interphase formed on the surface of the LAGP pellet, which may help stabilize the solid-liquid interface.

25 ENERGY STORAGE↗