Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “reduction”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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

At least 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Catalytic Reduction of Cyanide to Ammonia and Methane at a Mononuclear Fe Site

Nitrogenase enzymes catalyze nitrogen reduction (N 2 R) to ammonia and also the reduction of non-native substrates, including the 7H + /6e – reduction of cyanide to CH 4 and NH 3 . CN – and N 2 are isoelectronic, and it is hence fascinating to compare the mechanisms of synthetic Fe catalysts capable of both CN – and N 2 reduction. Here, we describe the catalytic reduction of CN – to NH 3 and CH 4 by a highly selective (P 3 Si )Fe(CN) catalyst (P 3 Si represents a tris(phosphine)silyl ligand). Catalysis is driven in the presence of excess acid ([Ph 2 NH 2 ]OTf) and reductant ((C 6 H 6 ) 2 Cr), with turnover as high as 73 demonstrated.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Molecular H 2 as the Reducing Agent in Low-Temperature Oxide Reduction Using Calcium Hydride

Low-temperature synthesis is crucial for advancing sustainable manufacturing and accessing novel metastable phases. Metal hydrides have shown great potential in facilitating the reduction of oxides at low temperatures, yet the underlying mechanism—whether driven by H - , H 2 , or atomic H—remains unclear. Here, in this study, we employ in situ electrical transport measurements and first- principles calculations to investigate the CaH 2 -driven reduction kinetics in epitaxial α-Fe 2 O 3 thin films. Intriguingly, samples in direct contact with or separated from CaH 2 powders exhibit similar apparent activation energies for H 2 reduction, although direct contact significantly increases the reduction rate. These findings indicate that molecular H 2 is the dominant reducing species in the low-temperature reduction of oxides using CaH 2 , with a key aspect of the hydrides' superior reducing power attributed to their ability to eliminate residual moisture. This work underscores the critical role of moisture control in enabling effective low-temperature oxide reduction for advanced material synthesis.

Wang, Jiayue [SLAC National Accelerator Laboratory↗
DOE OSTI2025

Understanding the Competition between Alcohol Formation and Dimerization during Electrochemical Reduction of Aromatic Carbonyl Compounds

The electrochemical reductive dimerization of small aromatic carbonyl compounds derived from lignocellulosic biomass is a crucial C−C coupling reaction for upgrading small molecules to longchain hydrocarbons, particularly in the synthesis of drop-in sustainable aviation fuels. Although other electrochemical reduction reactions of these reactants (i.e., hydrogenation and hydrogenolysis) have undergone extensive mechanistic investigation, the understanding of dimerization remains relatively underdeveloped. Most importantly, there is a lack of understanding of the selectivity-determining step between dimerization and monomer reduction and critical factors that can affect this step. In this study, we provide a comprehensive mechanistic model to explain the competition between dimerization and monomer reduction of benzaldehyde under various conditions. Our model proposes that the selectivity between dimerization and monomer reduction depends on the competition between desorption of a ketyl radical from the electrode, necessary for dimerization, and further reduction of the ketyl radical to an alcohol on the electrode by proton-coupled electron transfer (PCET). Computationally comparing the adsorption/desorption energy and PCET activation barrier energy is challenging because conventional DFT calculations substantially underestimate the PCET kinetic barriers. In this study, we employed constrained DFTbased configuration interaction (CDFT-CI) to obtain a reliable comparison of these energies. Our mechanistic model was tested and supported by experimental results obtained with four electrodes (Cu, Pb, Bi, graphite), three pH conditions (acidic, neutral, basic), and three potentials. Our study offers a coherent mechanistic foundation that can explain how each of these conditions impacts the desorption and PCET processes and the selectivities for dimerization and alcohol production.

09 BIOMASS FUELS↗
DOE OSTI2016

Reductive Elimination of H 2 Activates Nitrogenase to Reduce the N≡N Triple Bond: Characterization of the E 4 (4H) Janus Intermediate in Wild-Type Enzyme

Here, we have proposed a reductive elimination/oxidative addition ( re/oa ) mechanism for reduction of N 2 to 2NH 3 by nitrogenase, based on identification of a freeze-trapped intermediate of the α-70 Val→Ile substituted MoFe protein as the Janus intermediate that stores four reducing equivalents on FeMo-co as two [Fe-H-Fe] bridging hydrides (denoted E 4 (4H)). The mechanism postulates that obligatory re of the hydrides as H 2 drives reduction of N 2 to a state (denoted E 4 (2N2H)) with a moiety at the diazene (HN=NH) reduction level bound to the catalytic FeMo-cofactor. In the present work, EPR/ENDOR and photophysical measurements show that a state freeze-trapped during N 2 reduction by wild type (WT) MoFe protein is the same Janus intermediate, thereby establishing the α-70 Val→Ile intermediate as a reliable guide to mechanism, and enabling new experimental tests of the re/oa mechanism with WT enzyme. These allow us to show that the re/oa mechanism accounts for the longstanding Key Constraints on mechanism. Monitoring the S = ½ FeMo-co EPR signal of Janus in WT MoFe during N 2 reduction under mixed-isotope condition, H 2 O buffer/D 2 , and the converse, establishes that the bridging hydrides/deuterides do not exchange with solvent during enzymatic turnover, thereby explaining earlier observations and verifying the re/oa mechanism. Relaxation of E 4 (2N2H) to the WT resting-state is shown to occur via oa of H 2 and release of N 2 to form Janus, followed by sequential release of two H 2 , demonstrating the kinetic reversibility of the re/oa equilibrium.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Lattice-Hydride Mechanism in Electrocatalytic CO 2 Reduction by Structurally Precise Copper-Hydride Nanoclusters

Copper electrocatalysts can reduce CO2 to hydrocarbons at high overpotentials. However, a mechanistic understanding of CO2 reduction on nanostructured Cu catalysts has been lacking. Herein we show that the structurally precise ligand-protected Cu-hydride nanoclusters, such as Cu32H20L12 (L is a dithiophosphate ligand), offer unique selectivity for electrocatalytic CO2 reduction at low overpotentials. Our density functional theory (DFT) calculations predict that the presence of the negatively charged hydrides in the copper cluster plays a critical role in determining the selectivity of the reduction product, yielding HCOOH over CO with a lower overpotential. The HCOOH formation proceeds via the lattice-hydride mechanism: first, surface hydrides reduce CO2 to HCOOH product, and then the hydride vacancies are readily regenerated by the electrochemical proton reduction. DFT calculations further predict that hydrogen evolution is less competitive than HCOOH formation at the low overpotential. Confirming the predictions, electrochemical tests of CO2 reduction on the Cu32H20L12 cluster demonstrate that HCOOH is indeed the main product at low overpotential, while H2 production dominates at higher overpotential. The unique selectivity afforded by the lattice-hydride mechanism opens the door for further fundamental and applied studies of electrocatalytic CO2 reduction by copper-hydride nanoclusters and other metal nanoclusters that contain hydrides.

Tang, Qing↗
DOE OSTI2017

Molecular Cobalt Catalysts for O 2 Reduction: Low-Overpotential Production of H 2 O 2 and Comparison with Iron-Based Catalysts

A series of mononuclear pseudo-macrocyclic cobalt complexes have been investigated as catalysts for O2 reduction. Each of these complexes, with CoIII/II reduction potentials that span nearly 400 mV, mediate highly selective two- electron reduction of O2 to H2O2 (93–99%) using decamethylferrocene (Fc*) as the reductant and acetic acid as the proton source. Kinetic studies reveal that the rate exhibits a first- order dependence on [Co] and [AcOH], but no dependence on [O2] or [Fc*]. A linear correlation is observed between log(TOF) vs. E1/2(CoIII/II) for the different cobalt complexes (TOF = turnover frequency). The thermodynamic potential for+ O2 reduction to H2O2 was estimated by measuring the H /H2 open-circuit potential under the reaction conditions. This value provides the basis for direct assessment of the thermodynamic efficiency of the different catalysts and shows that H2O2 is formed with overpotentials as low as 90 mV. These results are compared with a recently reported series of Fe-porphyrin complexes, which catalyze four-electron reduction of O2 to H2O. The data show that the TOFs of the Co complexes exhibit a shallower dependence on E1/2(MIII/II) than the Fe complexes. This behavior, which underlies the low overpotential, is rationalized on the basis of the catalytic rate law.

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

Push or Pull? Proton Responsive Ligand Effects in Rhenium Tricarbonyl CO 2 Reduction Catalysts

Proton responsive ligands offer control of catalytic reactions through modulation of pH-dependent properties, second coordination sphere stabilization of transition states, or by providing a local proton source for multi-proton, multi-electron reactions. Two fac -[ReI(α-diimine)(CO)₃Cl] complexes with α-diimine = 4,4'- (or 6,6'-) dihydroxy-2,2'-bipyridine (4DHBP and 6DHBP) have been prepared and analyzed as electrocatalysts for reduction of carbon dioxide. Consecutive electrochemical reduction of these complexes yields species identical to those obtained by chemical deprotonation. An energetically feasible mechanism for reductive deprotonation is proposed in which the bpy anion is protonated followed by loss of H₂ and 2H⁺. Cyclic voltammetry reveals a two-electron, three-wave system owing to competing EEC and ECE pathways. The chemical step of the ECE pathway might be attributed to the reductive deprotonation. but cannot be distinguished from chloride dissociation. The rate obtained by digital simulation is approximately 8 s⁻¹. Under CO₂, these competing reactions generate a two-slope catalytic waveform with onset potential of –1.65 V vs Ag/AgCl. Reduction of CO₂ to CO by the [ReI (4DHBP–2H⁺)(CO)₃]⁻ suggests the interaction of CO₂ with the deprotonated species or a third reduction followed by catalysis. Conversely, the reduced form of [Re(6DHBP)(CO)₃Cl] converts CO₂ to CO with a single turnover.

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

The corrinoid cofactor of reductive dehalogenases affects dechlorination rates and extents in organohalide-respiring Dehalococcoides mccartyi

Corrinoid auxotrophic organohalide-respiring Dehalococcoides mccartyi (Dhc) strains are keystone bacteria for reductive dechlorination of toxic and carcinogenic chloroorganic contaminants. We demonstrate that the lower base attached to the essential corrinoid cofactor of reductive dehalogenase (RDase) enzyme systems modulates dechlorination activity and affects the vinyl chloride (VC) RDases BvcA and VcrA differently. Amendment of 5,6-dimethylbenzimidazolyl-cobamide (DMB-Cba) to Dhc strain BAV1 and strain GT cultures supported cis-1,2-dichloroethene-to-ethene reductive dechlorination at rates of 107.0 (±12.0) μM and 67.4 (±1.4) μM Cl - released per day, respectively. Strain BAV1, expressing the BvcA RDase, reductively dechlorinated VC to ethene, although at up to fivefold lower rates in cultures amended with cobamides carrying 5-methylbenzimidazole (5-MeBza), 5-methoxybenzimidazole (5-OMeBza) or benzimidazole (Bza) as the lower base. In contrast, strain GT harboring the VcrA RDase failed to grow and dechlorinate VC to ethene in medium amended with 5-OMeBza-Cba or Bza-Cba. The amendment with DMB to inactive strain GT cultures restored the VC-to-ethene-dechlorinating phenotype and intracellular DMB-Cba was produced, demonstrating cobamide uptake and remodeling. The distinct responses of Dhc strains with BvcA versus VcrA RDases to different cobamides implicate that the lower base exerts control over Dhc reductive dechlorination rates and extents (that is, detoxification), and therefore the dynamics of Dhc strains with discrete reductive dechlorination capabilities. Furthermore, these findings emphasize that the role of the corrinoid/lower base synthesizing community must be understood to predict strain-specific Dhc activity and achieve efficacious contaminated site cleanup.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Manipulating the oxygen reduction reaction pathway on Pt-coordinated motifs

Electrochemical oxygen reduction could proceed via either 4e - -pathway toward maximum chemical-to-electric energy conversion or 2e - -pathway toward onsite H 2 O 2 production. Bulk Pt catalysts are known as the best monometallic materials catalyzing O 2 -to-H 2 O conversion, however, controversies on the reduction product selectivity are noted for atomic dispersed Pt catalysts. Here, we prepare a series of carbon supported Pt single atom catalyst with varied neighboring dopants and Pt site densities to investigate the local coordination environment effect on branching oxygen reduction pathway. Manipulation of 2e - or 4e - reduction pathways is demonstrated through modification of the Pt coordination environment from Pt-C to Pt-N-C and Pt-S-C, giving rise to a controlled H 2 O 2 selectivity from 23.3% to 81.4% and a turnover frequency ratio of H 2 O 2 /H 2 O from 0.30 to 2.67 at 0.4 V versus reversible hydrogen electrode. Energetic analysis suggests both 2e - and 4e - pathways share a common intermediate of *OOH, Pt-C motif favors its dissociative reduction while Pt-S and Pt-N motifs prefer its direct protonation into H 2 O 2 . By taking the Pt-N-C catalyst as a stereotype, we further demonstrate that the maximum H 2 O 2 selectivity can be manipulated from 70 to 20% with increasing Pt site density, providing hints for regulating the stepwise oxygen reduction in different application scenarios.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Efficient Sn Recovery from SnO 2 by Alkane (C x H y=2x+2 , 0 ≤ x ≤ 4) Reduction

We study the mechanism of alkane reduction of SnO 2 for efficient low-temperature recovery of Sn from SnO 2 . Based on thermodynamic simulation results, we comparatively analyze the reduction behavior and the efficiency of SnO 2 reduction by H 2 and alkanes (C x H y=2x+2 , 0 ≤ x ≤ 4). We found that alkanes (n·C x H y ) with the higher nx generally complete the reduction of SnO 2 (T 100 ) at the lower temperature. Moreover, the T 100 of the SnO 2 reduction by alkanes (n·C x H y ) was decreased from the T 100 of pure hydrogen with the same amount of hydrogen atoms (n·H y ). We found that the concentration of a gas phase product mixture, the amount of the produced solid carbon, and the T 100 complementary vary as a function of the nx and ny, the total amount of carbon and hydrogen atoms in the reducing gas phase molecules. Our results demonstrate a viability of the low temperature reduction method of SnO 2 by alkanes for efficient recovery of Sn from SnO 2 , which can be applied for Sn recovery from Sn containing industrial wastes or Sn ores with economic value added that is held by the co-produced H 2 .

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

Operational constraints and strategies for systems to effect the sustainable, solar-driven reduction of atmospheric CO 2

The operational constraints for a 6-electron/6-proton CO 2 reduction system that operates at the concentration of CO 2 in the current atmosphere (p CO 2 = 400 ppm) have been evaluated on a variety of scale lengths that span from laboratory scale to global scale. Due to the low concentration of CO 2 in the atmosphere, limitations due to mass transport of CO 2 from the tropopause have been evaluated through five different regions, each with different characteristic length scales: the troposphere; the atmospheric boundary layer (ABL); the canopy layer; a membrane layer; and an aqueous electrolyte layer. The resulting CO 2 conductances, and associated physical transport limitations, will set the ultimate limit on the efficiency and areal requirements of a sustainable solar-driven CO 2 reduction system regardless of the activity or selectivity of catalysts for reduction of CO 2 at the molecular level. At the electrolyte/electrode interface, the steady-state limiting current density and the concomitant voltage loss associated with the CO 2 concentration overpotential in a one-dimensional solar-driven CO 2 reduction cell have been assessed quantitatively using a mathematical model that accounts for diffusion, migration and convective transport, as well as for bulk electrochemical reactions in the electrolyte. At p CO 2 = 400 ppm, the low diffusion coefficient combined with the low solubility of CO 2 in aqueous solutions constrains the steady-state limiting current density to <0.1 mA cm -2 in a typical electrochemical cell with natural convection and employing electrolytes with a range of pH values. Hence, in such a system, the CO 2 capture area must be 100- to 1000-fold larger than the solar photon collection area to enable a >10% efficient solar-driven CO 2 reduction system (based on the solar collection area). This flux limitation is consistent with estimates of oceanic CO 2 uptake fluxes that have been developed in conjunction with carbon-cycle analyses for use in coupled atmosphere/ocean general circulation models. Two strategies to improve the feasibility of obtaining efficient and sustainable CO 2 transport to a cathode surface at p CO 2 = 400 ppm are described and modeled quantitatively. The first strategy employs yet unknown catalysts, analogous to carbonic anhydrases, that dramatically accelerate the chemically enhanced CO 2 transport in the aqueous electrolyte layer by enhancing the acid–base reactions in a bicarbonate buffer system. The rapid interconversion from bicarbonate to CO 2 in the presence of such catalysts near the cathode surface would in principle yield significant increases in the steady-state limiting current density and allow for >10% solar-fuel operation at the cell level. The second strategy employs a thin-layer cell architecture to improve the diffusive transport of CO 2 by use of an ultrathin polymeric membrane electrolyte. Rapid equilibration of CO 2 at the gas/electrolyte interface, and significantly enhanced diffusive fluxes of CO 2 in electrolytes, are required to increase the steady-state limiting current density of such a system. This latter approach however only is feasible for gaseous products, because liquid products would coat the electrode and therefore thicken the hydrodynamic boundary layer and accordingly reduce the diffusive CO 2 flux to the electrode surface. Regardless of whether the limitations due to mass transport to the electrode surface are overcome on the laboratory scale, at global scales the ultimate CO 2 flux limitations will be dictated by mass transport considerations related to transport of atmospheric CO 2 to the boundary plane of the solar-driven reactor system. The transport of CO 2 across the troposphere/ABL interface, the ABL/canopy layer interface, and the canopy layer/electrolyte interface have therefore been assessed in this work, to provide upper bounds on the ultimate limits for the solar-to-fuel (STF) conversion efficiency for systems that are intended to effect the reduction of atmospheric CO 2 in a sustainable fashion at global scale.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2015

Uranium isotopes fingerprint biotic reduction

Knowledge of paleo-redox conditions in the Earth’s history provides a window into events that shaped the evolution of life on our planet. The role of microbial activity in paleo-redox processes remains unexplored due to the inability to discriminate biotic from abiotic redox transformations in the rock record. The ability to deconvolute these two processes would provide a means to identify environmental niches in which microbial activity was prevalent at a specific time in paleo-history and to correlate specific biogeochemical events with the corresponding microbial metabolism. Here, we demonstrate that the isotopic signature associated with microbial reduction of hexavalent uranium (U), i.e., the accumulation of the heavy isotope in the U(IV) phase, is readily distinguishable from that generated by abiotic uranium reduction in laboratory experiments. Thus, isotope signatures preserved in the geologic record through the reductive precipitation of uranium may provide the sought-after tool to probe for biotic processes. Because uranium is a common element in the Earth’s crust and a wide variety of metabolic groups of microorganisms catalyze the biological reduction of U(VI), this tool is applicable to a multiplicity of geological epochs and terrestrial environments. The findings of this study indicate that biological activity contributed to the formation of many authigenic U deposits, including sandstone U deposits of various ages, as well as modern, Cretaceous, and Archean black shales. In addition, engineered bioremediation activities also exhibit a biotic signature, suggesting that, although multiple pathways may be involved in the reduction, direct enzymatic reduction contributes substantially to the immobilization of uranium.

58 GEOSCIENCES↗
DOE OSTI2023

Fast Response of East Asian Precipitation in June 2020 to Local and Remote Aerosol Emission Reductions during COVID-19

Here, in this study, the fast response of East Asian summer precipitation to COVID-19–induced aerosol emission reductions is examined using the Community Earth System Model, version 2.2 (CESM2.2). The emission reductions decreased aerosol optical depth and cloud cover over northern China in June 2020. The troposphere became warmer, strengthening the land–sea thermal contrast and anomalous southerly winds. The subtropical westerly jet accelerated and shifted southward, favoring low-level convergence, upward air motions, and subsequent condensational heating over the Yangtze River basin (YRB). The feedback of condensational heating in return strengthened the convergence and ascent. The western North Pacific subtropical high was intensified, which further enhanced the moisture advection and convergence over the YRB. Both the enhanced moisture convergence and ascent increased precipitation over the YRB during June 2020. Furthermore, local and remote emission reductions show different impacts on convection and moisture transport over the YRB. The emission reductions over China caused stronger convective precipitation (1.15 vs 0.63 mm day −1 ) but weaker larger-scale precipitation (1.17 vs 2.24 mm day −1 ) than the emission reductions outside China. In addition to the emission reductions, the sea surface temperature (SST) anomalies in 2020 also play an important role in increasing precipitation over the YRB, contributing about 42.8%. The relative contribution of SST anomalies also increases under the COVID-19–induced emission scenario.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Electrolytic Oxide Reduction of Plutonium Oxide Surrogates

Our research team has investigated electrolytic oxide reduction (EOR) as an improved metal production process versus the currently employed multiple cycle direct oxide reduction (MCDOR) process for the conversion of plutonium oxide to plutonium metal. Inherent advantages in safety, waste generation, efficiency, and operational ease make EOR an attractive alternative to traditional metal production practices. Phase I of the project consisted of the construction of a prototype electrochemical cell, and proof of concept experiments towards the reduction of SnO 2 and CeO 2 compounds. Phase II of the project was focused on the optimization of the cerium system in preparation for future plutonium EOR experiments. We observed the electrolytic reduction of cerium oxide resulting in mixed degrees of success, and discovered this was a result of parasitic side reactions and partial reduction. We employed cyclic voltammetry (CV) to identify the products of these side reactions and characterize partially reduced species. We also observed that, when metal was successfully produced by EOR, a large amount of passed charge was required. We concluded that this observation was due to several inefficiencies of the process relating to the reduction mechanism (e.g. inefficient use of cathodically produced calcium). We used our CV results to guide our optimization of the EOR of CeO 2 by refining our electrochemical method, cell geometry, and materials of construction. Finally, we developed a next generation cell, worked to establish a new molten salt electrochemical capability in the Plutonium Facility, and completed a strategy for plutonium experiments. Our electrochemical method to produce plutonium metal clearly supports the core mission of the laboratory. Furthermore, this project has allowed for the development of capabilities that will provide valuable data to programs interested in characterization and detection, as well as science of signatures. Additionally, establishing this capability in the plutonium facility will facilitate future safeguard studies that can assist with safeguard development in molten salt reprocessing flowsheets, and molten salt reactor designs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Adoption of Plug-in Electric Vehicles: Local Fuel Use and Greenhouse Gas Emissions Reductions Across the U.S.

The dependence on gasoline-powered light-duty automobiles has made U.S. households vulnerable to the burden of fuel costs. Tailpipe emissions from these vehicles constitute 58% of greenhouse gas (GHG) emissions in the U.S., which are damaging to the environment (EPA, 2023). The adoption of plug-in electric vehicles (PEVs) has been shown to effectively reduce fuel costs and GHG emissions. However, local effects on these benefits are not well understood by American consumers, potentially limiting adoption and therefore the realization of PEV benefits at scale (MacInnis & Krosnick, 2020; EY Americas, 2023). To fill this research gap, this study estimates the fuel cost savings and GHG emission reductions at the state and ZIP code levels by considering local fuel prices, vehicle class preference, average vehicle model year, fuel efficiencies, and driving intensities. The study's findings reveal that the adoption of PEVs can yield substantial benefits in terms of fuel cost savings and GHG emission reductions nationwide. Specifically, driving a battery electric vehicle (BEV) is estimated to result in annual savings of up to $\$2,200$, while driving a plug-in hybrid electric vehicle (PHEV) can lead to savings up to $\$1,500$, when compared to an internal combustion engine vehicle (ICEV) of equivalent size. Moreover, using population-weighted averages by ZIP code, BEVs and PHEVs show the potential to save 400 and 200 grams of carbon dioxide equivalent per mile, respectively, compared to a representative ICEV of the same class. The magnitude of fuel cost savings and emissions reduction vary by region due to various factors. Generally, regions with high gasoline prices, low electricity prices, preferences for larger vehicles, and high driving intensities tend to see relatively large fuel savings. The emissions reductions are more pronounced in areas with clean grids where consumer preferences lie with large vehicles. This regional variability underscores the importance of considering local contextual factors when assessing the potential benefits of PEV adoption. In more than 99% of U.S. ZIP codes, PEVs result in overall savings in fuel use (and subsequent costs) and GHG emissions. While not a central focus of this analysis, reductions in GHG tailpipe emissions from PEV adoption would also come with reductions in criteria pollutant emissions, contributing to improved local air quality depending on the PEV penetration, population density, and electricity generation infrastructure in the locality.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2022

Realistic Estimation of CO2 Emission Reductions Due to Building Retrofit

Constant CO2 emission factors of electricity are often used to study the emissions of buildings. However, in the era of increased renewable energy for power generation, emission factors of electricity are dynamically changing. This study is to investigate the impact of dynamic CO2 emission factors, which are more realistic than constant ones, on the emission reductions due to building retrofits. The results reveal that if dynamic CO2 emission factors are used for U.S. medium office buildings, improving the efficiency of lighting or electric equipment will lead to more emission reductions in locations with high wind power penetration (e.g., 12% more reductions in Rochester) and fewer reductions in locations with high solar power penetration (e.g., 8% fewer reductions in San Diego). As for improving envelope insulation, dynamic CO2 emission factors have more impact on the emission reductions in hot climates than in cold climates.

Lou, Yingli↗
DOE OSTI2022

Diesel-Range Fuel Property Effects on Medium-Duty Advanced Compression Ignition for Low-Load NO X Reduction

A diesel premixed-charge compression ignition (PCCI) technique was used at low loads at which exhaust temperature makes urea-selective catalytic reduction (SCR) use for nitrogen oxides (NOx) reduction challenging. A fuels matrix to examine the effects of increasing fuel volatility, bio-blendstocks, and cetane number on PCCI was formulated using a near-constant 15% aromatic content. The results showed that PCCI could provide greater than 67% NOx emissions reductions at 1,200 RPM, 3.1 bar indicated mean effective pressure (IMEP), and 2.0 bar IMEP. The filter smoke number (FSN) could also be reduced relative to a conventional diesel combustion (CDC) baseline. The reductions in FSN were more moderate in the order of 40-50%, depending upon the fuel used, IMEP, and combustion phasing (CA50) timing. Hydrocarbon (HC) emissions could be held to a marginally lower level than CDC emissions at some CA50 conditions by using higher-volatility and higher cetane number fuels and could potentially be traded for further NOx reductions. This outcome is important as it points to the possibility of achieving significant NOx reduction while doing no harm in terms of HC emissions. Carbon monoxide (CO) emissions increased in PCCI, but increasing the fuel volatility and cetane number could be helpful in keeping these emissions at a manageable level.

02 PETROLEUM↗
NASA NTRS1978

The cost of applying current helicopter external noise reduction methods while maintaining realistic vehicle performance

Analytical methods were developed and/or adopted for calculating helicopter component noise, and these methods were incorporated into a unified total vehicle noise calculation model. Analytical methods were also developed for calculating the effects of noise reduction methodology on helicopter design, performance, and cost. These methods were used to calculate changes in noise, design, performance, and cost due to the incorporation of engine and main rotor noise reduction methods. All noise reduction techniques were evaluated in the context of an established mission performance criterion which included consideration of hovering ceiling, forward flight range/speed/payload, and rotor stall margin. The results indicate that small, but meaningful, reductions in helicopter noise can be obtained by treating the turbine engine exhaust duct. Furthermore, these reductions do not result in excessive life cycle cost penalties. Currently available main rotor noise reduction methodology, however, is shown to be inadequate and excessively costly.

Bowes, M. A.↗