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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1999

Interannual Variabilities in Tropical Tropospheric Ozone

This paper presents the first detailed characterization of interannual variability in tropical tropospheric column ozone (TCO) to delineate the relative importance of biomass burning and large-scale transport. TCO time series are derived from 20 years (1979-1998) of total ozone mapping spectrometer (TOMS) data using the convective cloud differential (CCD) method. Our study identifies three regions in the tropics with distinctly different characteristics related to interannual variability. These three regions are the eastern Pacific, Atlantic, and western Pacific. The Atlantic region indicates a quasi-biennial oscillation (QBO) in TCO which is out of phase with the QBO in stratospheric ozone. This is consistent with the photochemical control of this region by ozone-producing precursors. The observed pattern however does not seem to be related to interannual variability in ozone precursors related to biomass burning. Instead it appears to be a manifestation of the UV modulation of upper tropospheric chemistry on a QBO time scale caused by stratospheric ozone. During El Nino events there is anomalously low TCO in the eastern Pacific and high values in the western Pacific, indicating the effects of convectively-driven transport. The observed increase of 10-20 DU in TCO in the Indonesian region in the western Pacific during the recent 1997-1998 El Nino was associated with large-scale fires which may have contributed 5-10 DU of the total increase.

Ziemke, Jerry R.↗
NASA NTRS2006

Tropospheric Ozone Determined from Aura OMI and MLS: Evaluation of Measurements and Comparison with the Global Modeling Initiative's Chemical Transport Model

Ozone measurements from the OMI and MLS instruments on board the Aura satellite are used for deriving global distributions of tropospheric column ozone (TCO). TCO is determined using the tropospheric ozone residual method which involves subtracting measurements of MLS stratospheric column ozone (SCO) from OMI total column ozone after adjusting for intercalibration differences of the two instruments using the convective-cloud differential method. The derived TCO field, which covers one complete year of mostly continuous daily measurements from late August 2004 through August 2005, is used for studying the regional and global pollution on a timescale of a few days to months. The seasonal and zonal characteristics of the observed TCO fields are also compared with TCO fields derived from the Global Modeling Initiative's Chemical Transport Model. The model and observations show interesting similarities with respect to zonal and seasonal variations. However, there are notable differences, particularly over the vast region of the Saharan desert.

Ziemke, J. R.↗
NASA NTRS2016

Tropospheric Column Ozone Response to ENSO in GEOS-5 Assimilation of OMI and MLS Ozone Data

We use GEOS-5 analyses of Ozone Monitoring Instrument (OMI) and Microwave Limb Sounder (MLS) ozone observations to investigate the magnitude and spatial distribution of the El Nino Southern Oscillation (ENSO) influence on tropospheric column ozone (TCO) into the middle latitudes. This study provides the first explicit spatially resolved characterization of the ENSO influence and demonstrates coherent patterns and teleconnections impacting the TCO in the extratropics. The response is evaluated and characterized by both the variance explained and sensitivity of TCO to the Nino 3.4 index. The tropospheric response in the tropics agrees well with previous studies and verifies the analyses. A two-lobed response symmetric about the Equator in the western Pacific/Indonesian region seen in some prior studies and not in others is confirmed here. This two-lobed response is consistent with the large-scale vertical transport. We also find that the large-scale transport in the tropics dominates the response compared to the small-scale convective transport. The ozone response is weaker in the middle latitudes, but a significant explained variance of the TCO is found over several small regions, including the central United States. However, the sensitivity of TCO to the Nino 3.4 index is statistically significant over a large area of the middle latitudes. The sensitivity maxima and minima coincide with anomalous anti-cyclonic and cyclonic circulations where the associated vertical transport is consistent with the sign of the sensitivity. Also, ENSO related changes to the mean tropopause height can contribute significantly to the midlatitude response. Comparisons to a 22-year chemical transport model simulation demonstrate that these results from the 9- year assimilation are representative of the longer term. This investigation brings insight to several seemingly disparate prior studies of the El Nino influence on tropospheric ozone in the middle latitudes.

ML↗
DOE OSTI2017

Modeling and Analysis of Coupled Flow Through Packed Beds as a Diagnostic Tool for Packed Bed Reactor Health - 17172

The US Department of Energy, Office of River Protection, is building the Waste Treatment and Immobilization Plant (WTP) in Richland, Washington, to immobilize the hundreds of millions of liters of radioactive waste stored at the Hanford Site in Washington state. The offgas generated during vitrification of these wastes requires treatment to remove and/or destroy chemical and radioactive hazardous components before release to the atmosphere. In particular, volatile and semi-volatile hydrocarbon components are to be catalytically oxidized to carbon dioxide and water, whereas nitrogen oxides (NOx) are to be catalytically reduced to nitrogen and water. These tasks are accomplished in a series of packed bed reactors. Achieving the requisite Destruction/Removal Efficiency (DRE) for each of the tracked components is highly dependent on the flow characteristics of the offgas through the packed beds. The flow kinetics may be monitored and characterized during the initial warm-up of the system. The gases, initially at 76 deg. C (169 deg. F), (a) flow through one side of a countercurrent heat exchanger to recover heat from the exiting gases (which have already passed through the catalytic beds), (b) are then further heated electrically to approximately 400 deg. C (750 deg. F; the preferred operating temperature of the Thermo Catalytic Oxidizer (TCO)), (c) pass through the TCO where the reduced components of the offgas are oxidized over a supported Pt catalyst bed, (d) are partially cooled to approximately 315 deg. C (600 deg. F) by addition of approximately 25% (by weight) diluted ammonia/air mixture, (e) pass through the Selective Catalytic Reducer (SCR) where the NOx components are converted to N{sub 2} and H{sub 2}O over a supported V2O{sub 5}/TiO{sub 2} catalyst bed, and (f) exit through the hot side of the countercurrent heat exchanger. The electrical heater is not powerful enough to raise the temperature of the offgas to the desired 400 deg. C without the contribution of the heat recovered in the heat exchanger. Moreover, the thermal mass of the beds and housings of the TCO and SCR require a significant input of thermal energy to reach the desired operating temperatures; the better part of a day is required to bring the unit from ambient temperatures to operating temperatures. Therefore, the temperature of the stream during the initial warm-up of the system at each point in the system is dependent upon the thermal mass, flow dispersion, and permeability of the components, quantified as characteristic/representative volumes and residence times. By monitoring the temperature of the offgas as it enters and exits each portion of the system during this warm-up period one may model the system as a series of small Continuously Stirred Tank Reactors (CSTR)s (referred to as 'CSTRlets') to explain the flow kinetics through the catalyst beds. These component CSTRlets are adjustable in size and number, that one may model the flow profile of the gases through the catalyst beds. For example, a single large CSTR will present an effluent temperature profile with a simple exponential decay shape. Concatenating more CSTRlets generate more complex sigmoidal responses. Concatenating one CSTRlet significantly larger than the others in the train also alters the shape of the effluent temperature profile, in a fashion not replicable by a train of equal-sized CSTRlets. The ultimate goal is to accurately emulate the entire system as a representative CSTRlet train. Once accomplished, this characterization may be used in subsequent warm-ups (following shutdown for catalyst maintenance, for example) or by an intentional step change in inlet offgas temperature to detect/diagnose anomalies in flow through the beds (e.g., channeling or partial blockage.) This work presents development of this model through analytical, calculational, and empirical means. - The analytic model is accomplished by Laplace transform analysis of each component to recover component process transfer functions. - The calculational portion is performed via brute force finite element calculation. - Fitting empirical data from the warm-up of the TCO skid allows one to select the hypothetical CSTRlet trains which best fit the TCO and SCR beds for the analytical and finite element calculations. The first portion of this paper presents the development of the analytical (Laplace space) model of the coupled system. Estimated values for the initial temperature, mass, specific heat, electrical heat, and relative quantities of the offgas, catalyst beds, stainless steel housings, and ammonia dilution stream are used to generate expected temperature profiles at several selected junctures of the system. The number and size of the component hypothetical CSTRlets are calculated from the analytical model and are used to predict temperature profiles at the exit of the system and at intermediate junctions between system components (where thermocouples are present in the actual unit.) The finite element calculations employ a series of CSTRlet volumes to produce a similar suite of temperature profiles, for comparison with the analytical model results. Finally, empirical data from the Factory Acceptance Test system warm-up are used to select and compare the results from each modeling strategy to select the CSTRlet train(s) which best model the behavior of the actual system. This work presents a novel method of system component characterization, of value to the WTP plant and similar vitrification facilities as well as chemical process industries unrelated to waste management. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2021

Super Flexible Transparent Conducting Oxide-Free Organic–Inorganic Hybrid Perovskite Solar Cells with 19.01% Efficiency (Active Area=1 cm 2 )

Highly efficient organic-inorganic hybrid perovskite solar cells (OIHP-SCs) are often fabricated on a transparent conducting oxide (TCO) substrate such as indium tin oxide (ITO). However, the presence of TCOs is disadvantageous to the development of flexible OIHP-SCs due to the brittle nature of ITO which is easily breakable during bending. Herein, a flexible TCO-free OIHP-SC is demonstrated by using lithium bis(trifluoromethane)sulfonimide (Li-TFSI) as a codopant for the single-layer graphene transparent conducting electrode and poly(triarylamine) hole-transporting material (HTM) on a flexible polydimethylsiloxane substrate. The optical and electrical properties of the Li-TFSI-doped graphene substrate are measured by controlling the doping amount and the best conditions for charge extraction are established at a doping concentration of 20 mm Li-TFSI, thus optimizing the device photovoltaic performance. As a result, a highest power conversion efficiency of 19.01% is demonstrated by the flexible TCO-free OIHP-SC devices with an active area of 1 cm 2 . In addition, the flexible TCO-free OIHP-SCs exhibit good bending stability after 5000 bending cycles at radii of 6, 4, and 2 mm and excellent light soaking stability under 1 Sun light intensity over 1000 h as opposed to the poor stability when using poly(3,4-ethylenedioxythiophene) polystyrene sulfonate as the HTM.

14 SOLAR ENERGY↗
DOE OSTI2022

Pressure Engineering Promising Transparent Oxides with Large Conductivity Enhancement and Strong Thermal Stability

Abstract Transparent conducting oxides (TCO) with high electrical conductivity and high visible light transparency are desired for a wide range of high‐impact engineering. Yet, usually, a compromise must be made between conductivity and transparency, limiting the practical application of a TCO to the next level. Furthermore, TCO performance is highly sensitive to composition, so conventional synthesis methods, such as chemical doping, cannot unravel the mysteries of the quantitative structure–performance relationship. Thus, improving the fundamental understanding or creating materials‐by‐design has limited success. Here, a strategy is proposed to modulate the lattice and electronic and optical properties precisely by applying pressure on a TCO. Strikingly, after compression–decompression treatment on the indium titanium oxides (ITiO), a highly transparent and metastable phase with two orders of magnitude enhancement in conductivity is synthesized from an irreversible phase transition. Moreover, this phase possesses previously unattainable filter efficiency on hazardous blue light up to 600 °C, providing potential for healthcare‐related applications with strong thermal stability up to 200 °C. These results demonstrate that pressure engineering is a clean and effective tool for tailoring functional materials that are not achievable by other means, providing an exciting alternative property‐tuning dimension in materials science.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Strategies for the Photoreduction of Tc-99 Pertechnetate to Low-Valent Tc by Keggin Polyoxometalates

Technetium-99 (half-life of 2.1 × 10 5 yrs, β max = 0.29 MeV) is a hazardous radiological contaminant, which, in its predominant form of pertechnetate (TcO 4 – ), is highly mobile in the environment. Most strategies for the removal of pertechnetate from the environment involve uptake and/or absorption of pertechnetate using resins, clays, cationic metal-organic frameworks and even thorium borate ceramic like materials. Alternative approaches have involved the reduction and subsequent sequestration of lower valent technetium species using iron, sulfides, or iron sulfides. Here, our lab has explored this strategy using the lacunary alpha-2 Wells–Dawson polyoxometalate (α 2 -[P 2 W 17 O 61 ] 10– ) to both reduce and sequester lower valent technetium, and we have reported on the ligand features that stabilize the reduced species. In this work we investigate the potential of “plenary” Keggin POMs (XW 12 O 40 n – ) (X = P, Si, Al, n = 3, 4, 5, respectively) to both reduce TcO 4 – and stabilize the reduced Tc species. Specifically, we report on the mechanism by which the reduction of technetium occurs and find that PW 12 , SiW 12 , and AlW 12 promote the reduction of TcO 4 – to lower valent states. X-ray absorption spectroscopy was used to confirm a combination of Tc IV {in the form of TcO 2 · 2H 2 O and Tc 2 (µ-O) 2 4+ } and Tc V , which is subsequently complexed into a POM defect as a Tc V =O species.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Reduction of Pertechnetate by Chemical and Photochemical Approaches and Incorporation of Tc(IV) into Titanium Dioxide

Technetium-99 is a prevalent fission product from nuclear waste. The long half-life (211,000 yr) and environmental mobility of pertechnetate (TcO 4 - ) render Tc particularly challenging to isolate and stabilize. Here, in this study, we present two approaches for development of potential wasteforms using titanium dioxide, TiO 2 . Approach 1 is a low temperature chemical synthesis of TiO 2 doped with Tc(IV) from TcO 4 - intended to mimic the Tc waste stream from the UREX family of separations and removes 98.5 % of the Tc, mainly present as edge-shared Tc(IV) pairs. Approach 2 utilizes TiO 2 to photocatalytically reduce TcO 4 - to Tc(IV) stabilized on the surface of or within the TiO 2 lattice. The %Tc removed from solution and adsorbed to TiO 2 is pH dependent, with the maximum Tc(IV) adsorbed at pH 3–4 as either TcO 2 or edge-sharing Tc(IV) octahedra. The Tc(IV)-TiO 2 composites materials formed by both approaches are suitable for consolidation into a dense wasteform by Hot Isostatic Pressing (HIPing).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Part I: Predicting performance of Purolite A532E resins for remediation of comingled contaminants in groundwater

Ion exchange (IX) resins are used in pump-and-treat (P&T) facilities to remove soluble groundwater contaminants. However, natural anions present at concentrations orders of magnitude higher than contaminants can compete for IX sites and impact resin lifecycles. Here, the Hanford Site’s 200 West Area P&T facility (Washington State, USA) was selected as a case study because it currently uses two IX resins: Purolite® A532E (A532E) to remove pertechnetate (TcO 4 - ) and DOWEX 21K (DOWEX) to remove uranium from groundwater. Nitrate (NO 3 - ), sulfate (SO 4 2- ), chloride (Cl - ), and carbonate (CO 3 2- ) anions have been identified to potentially compete for A532E and DOWEX IX sites. Hanford-relevant anion groundwater concentrations were used to design a series of laboratory-scale batch experiments to evaluate the impact of competing anions on resin performance and potential kinetic effects. These data are then modeled to obtain Cl--normalized equilibrium exchange coefficients (K) needed to predict IX resin performance. The work is presented in two parts, with IX performance evaluated for A532E in Part I and DOWEX in Part II. Part I results demonstrate that TcO 4 - uptake is not impacted by NO 3 - , SO 4 2- , Cl - , CO 3 2- (as HCO 3 - ) and U(VI) carbonate anions, with K TcO4-/Cl- > 4,000, likely due to the high selectivity of A532E trihexylammonium sites for the large, weakly hydrated TcO 4 - anion. Other anion K values were K NO3-/Cl- = 20, K SO4--/Cl- = 0.2, K HCO3-/Cl- = 0.09, K U/Cl- = 370–1000. These K values provide conservative parameters for predicting A532E performance, and demonstrate that, under these test conditions, A532E will remove TcO 4 - from current and future influent streams to meet groundwater treatment objectives.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2025

Recovering high-purity uranyl nitrate from simulated used nuclear fuel dissolver solutions by crystallization: rejecting technetium

The separation of U from Tc and other problematic fission product elements like Mo and Ru, along with Sr, Zr, Cs, and Nd, has been achieved via the crystallization of uranyl nitrate hexahydrate (UNH). Rejection of technetium as pertechnetate anion ( 99 TcO 4 – ) is an especially important feature of this system, as it otherwise tends to follow U (VI) in extractive separations. It also raises the salient question regarding why this oxoanion cannot replace nitrate within the crystalline lattice of UNH. Results showed high-yield (>90 %), high-purity (>99 %) recovery of U as UNH from solutions containing 99 TcO 4 – by simple reduction of temperature from 60°C to 20°C. There was no observable interaction of 99 TcO 4 – with UO 2 2+ . The addition of other cations like, Sr 2+ , Zr 4+ , Cs + , and Nd 3+ , also did not form secondary, contaminant solid phases, leaving the > 99 % of the fission product elements in the mother liquor, while the U was recovered at > 90 %. Similarly, Mo and Ru, when added to the mixture, were shown to behave as the other fission-product elements, remaining in the mother liquor during crystallization. As a result, DFT calculations showed that, despite the higher binding strength of TcO 4 – , HMoO 4 – , and BiO 3 – with the UO 2 2+ cation compared to NO 3 – , the hydrogen-bonding network of the two coordinated ions and four waters of hydration in the UNH crystal structure is the driving force for the high specificity of this separation.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2016

Structure and Thermochemistry of Perrhenate Sodalite and Mixed Guest Perrhenate/Pertechnetate Sodalite

Treatment and immobilization of technetium-99 ( 99 Tc) contained in reprocessed nuclear waste and present in contaminated subsurface systems represents a major environmental challenge. One potential approach to managing this highly mobile and long-lived radionuclide is immobilization into micro- and meso-porous crystalline solids, specifically sodalite. We synthesized and characterized the structure of perrhenate sodalite, Na 8 [AlSiO 4 ]6(ReO 4 ) 2 , and the structure of a mixed guest perrhenate/pertechnetate sodalite, Na 8 [AlSiO 4 ] 6 (ReO 4 ) 2-x (TcO 4 ) x . Perrhenate was used as a chemical analogue for pertechnetate. Bulk analyses of each solid confirm a cubic sodalite-type structure (P$\overline{43}$n, No. 218 space group) with rhenium and technetium in the 7+ oxidation state. High-resolution nanometer scale characterization measurements provide first-of-a-kind evidence that the ReO 4 – anions are distributed in a periodic array in the sample, nanoscale clustering is not observed, and the ReO 4 – anion occupies the center of the sodalite β-cage in Na 8 [AlSiO 4 ] 6 (ReO 4 ) 2 . We also demonstrate, for the first time, that the TcO 4 – anion can be incorporated into the sodalite structure. Lastly, thermochemistry measurements for the perrhenate sodalite were used to estimate the thermochemistry of pertechnetate sodalite based on a relationship between ionic potential and the enthalpy and Gibbs free energy of formation for previously measured oxyanion-bearing feldspathoid phases. The results collected in this study suggest that micro- and mesoporous crystalline solids maybe viable candidates for the treatment and immobilization of 99 Tc present in reprocessed nuclear waste streams and contaminated subsurface environments.

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

Reducing sputter induced stress and damage for efficient perovskite/silicon tandem solar cells

Reducing damages caused by sputtering of transparent conductive oxide (TCO) electrodes is critical in achieving highly efficient and stable perovskite/silicon tandem solar cells. Here we study the sputter caused damage to bathocuproine (BCP), which is widely used in highly efficient p-i-n structure single junction perovskite solar cells. While BCP buffer layer protects the underneath layers from damage, itself can be damaged by sputtering of TCOs at a wide range of target-substrate distances, supported by molecular dynamic simulation. More intriguingly, it is observed that TCO easily peeled off after sputtering when the sputtering target is close to substrate. This is ascribed to formation of stress during cooling down process after sputtering due to different thermal expansion coefficients of the layers. Our studies explain why tin oxide (SnO2) made by atomic layer deposition can replace BCP for a much better tandem device performance. SnO2 has high affinity with sputtered TCO electrode to suppress peeling-off issue and has higher bond energy to resist sputter induced damage, thus it allows a wider window of target-substrate distances than BCP during TCO sputtering. Ultimately, we demonstrate an efficient perovskite/silicon monolithic tandem solar cell with efficiency of 26.0% to illustrate the beneficial effects of reduced stress and damage.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Tuning optical properties of transparent conducting barium stannate by dimensional reduction

We report calculations of the electronic structure and optical properties of doped n-type perovskite BaSnO 3 and layered perovskites. While doped BaSnO 3 retains its transparency for energies below the valence to conduction band onset, the doped layered compounds exhibit below band edge optical conductivity due to transitions from the lowest conduction band. This gives absorption in the visible for Ba 2 SnO 4 . It is important to minimize this phase in transparent conducting oxide (TCO) films. Ba 3 Sn 2 O 7 and Ba 4 Sn 3 O 10 have strong transitions only in the red and infrared, respectively. Thus, there may be opportunities for using these as wavelength filtering TCO.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Uniaxial stress study of spin and charge stripes in La1.875Ba0.125CuO4 by 139La NMR and 63Cu NQR

We study the response of spin and charge order in single crystals of La1.875Ba0.125CuO4 to uniaxial stress, through 139La nuclear magnetic resonance (NMR) and 63Cu nuclear quadrupole resonance (NQR), respectively. In unstressed La1.875Ba0.125CuO4, the low-temperature tetragonal structure onsets below TLTT = 57 K, while the charge order and the spin order transition temperatures are TCO = 54 K and TSO = 37 K, respectively. We find that uniaxial stress along the [110] lattice direction strongly suppresses TCO and TSO, but has little effect on TLTT. In other words, under stress along [110] a large splitting (≈ 21 K) opens between TCO and TLTT, showing that these transitions are not tightly linked. On the other hand, stress along [100] causes a slight suppression of TLTT but has essentially no effect on TCO and TSO. Magnetic field H along [110] stabilizes the spin order: the suppression of TSO under stress along [110] is slower under H ∥ [110] than H ∥ [001]. We develop a Landau free energy model and interpret our findings as an interplay of symmetry breaking terms driven by the orientation of spins.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Tuning the structure and superconductivity of SrNi 2⁢ P 2 by Rh substitution

The compound SrNi 2⁢ P 2 is unique among the ThCr 2 ⁢Si 2 class since it exhibits a temperature-induced transition upon cooling from an uncollapsed tetragonal (ucT) state to a one-third-collapsed orthorhombic (tcO) state where one out of every three P-rows bond across the Sr layers. This compound is also known for exhibiting bulk superconductivity below 1.4 K at ambient pressure. Here, in this paper, we report on the effects of Rh substitution in Sr⁢(Ni 1-x ⁢Rh x ) 2 ⁢P 2 on the structural and superconducting properties. We studied the variation of the nearest P-P distances as a function of the Rh fraction at room temperature, as well as its temperature dependence for selected compositions. We find that increasing the Rh fraction leads to a decrease in the transition temperature between the ucT and tcO states, until a full suppression of the tcO state for x ≥ 0.166. The superconducting transition first remains nearly insensitive to the Rh fraction, and then it increases to 2.3 K after the tcO state is fully suppressed. These results are summarized in a phase diagram, built upon the characterization by energy dispersive x-ray spectroscopy, x-ray diffraction, resistance, magnetization, and specific heat measurements done on crystalline samples with varying Rh content. The relationship between band structure, crystal structure, and superconductivity is discussed based on previously reported band structure calculations on SrRh 2 ⁢P 2 . Moreover, the effect of Rh fraction on the stress-induced structural transitions is also addressed by means of strain-stress studies done by uniaxial compression of single-crystalline micropillars of Sr⁢(Ni 1-x ⁢Rh x ) 2 ⁢P 2 .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Robust Large-Scale Dynamic Windows using Reversible Metal Electrodeposition

This project funded the study and development of dynamic windows based on reversible metal electrodeposition (RME). Dynamic windows allow user control over light and heat flow into and out of buildings, which offer both advantages in building aesthetics (with worker productivity improvement of 2%) and energy efficiency (up to 20% savings) compared to static controls such as low emissivity coatings and blinds/shades. Despite these advantages, dynamic windows, which traditionally rely on electrochromic metal oxides or conductive organic molecules for light modulation have failed to significantly impact the market due to issues related to cost, color, and optical dynamic range. Dynamic windows based on reversible metal electrodeposition (RME) are an exciting alternative approach and have the potential to overcome the issues associated with traditional technologies. A RME dynamic window is an electrochemical cell that modulates light using the reversible electrodeposition of metal on and off a transparent conducting oxide (TCO), which serves as the working electrode. The electrolyte has nearly colorless metal salts dissolved, and application of a cathodic potential on the TCO reduces the metal cations across the TCO surface to their metallic form, making a thin film that is efficient at blocking out light. A reverse in polarity oxidizes the metal, where it dissolves into solution, returning the window back to transparent. The counter electrode typically employed is a metal mesh, which is used to balance the electrochemical reactions happening on the TCO working electrode. These RME dynamic windows have the largest dynamic range (capable of reaching <<0.1% transmission) with color neutral tinting of any existing technology using solution processed techniques, which positions the technology as a promising candidate to penetrate the residential market. We have successfully scaled up the windows from 25 cm2 to 929 cm 2 , and we have demonstrated significant improvements to both the cycle life (10,000 cycles in a 3-electrode half-cell) and shelf life (>1 month) of our windows. We have published our work in high impact journals (6 published and 2 manuscripts in prep), filed 5 patents, and have incorporated TYNT Technologies to commercialize the technology.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2025

Assessment of Heavy-Duty Fueling Methods and Components-Modeling and Analysis

The goal of the Assessment of Heavy-Duty Fueling Methods and Components project was to comprehensively assess heavy-duty (HD) fuel cell electric vehicle fueling protocols and their effects on techno-economic assessments (TEA) and total cost of ownership (TCO). The project leveraged and built upon ongoing international HD fueling protocols and fueling component development activities to deliver component performance assessments, modeling tools and methods evaluations, TEA of industry-selected protocol structures, and experimental validations of the strategies at the station scale. The effects of the protocols on the fueling times, station costs, and TCO were explored. Fueling time, which was influenced by temperature and protocol selection, had a large impact on the station cost due to component sizing and satisfying hourly demand. As the fleet size increased, the station cost was shown to exponentially decrease by achieving economies of scale. Technology year and fuel economy were the largest contributors to the TCO; however, the choice of fueling protocol had a minor impact on the TCO.

33 ADVANCED PROPULSION SYSTEMS↗