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NASA NTRS2006

Modeling of Transient Flow Mixing of Streams Injected into a Mixing Chamber

Ignition is recognized as one the critical drivers in the reliability of multiple-start rocket engines. Residual combustion products from previous engine operation can condense on valves and related structures thereby creating difficulties for subsequent starting procedures. Alternative ignition methods that require fewer valves can mitigate the valve reliability problem, but require improved understanding of the spatial and temporal propellant distribution in the pre-ignition chamber. Current design tools based mainly on one-dimensional analysis and empirical models cannot predict local details of the injection and ignition processes. The goal of this work is to evaluate the capability of the modern computational fluid dynamics (CFD) tools in predicting the transient flow mixing in pre-ignition environment by comparing the results with the experimental data. This study is a part of a program to improve analytical methods and methodologies to analyze reliability and durability of combustion devices. In the present paper we describe a series of detailed computational simulations of the unsteady mixing events as the cold propellants are first introduced into the chamber as a first step in providing this necessary environmental description. The present computational modeling represents a complement to parallel experimental simulations' and includes comparisons with experimental results from that effort. A large number of rocket engine ignition studies has been previously reported. Here we limit our discussion to the work discussed in Refs. 2, 3 and 4 which is both similar to and different from the present approach. The similarities arise from the fact that both efforts involve detailed experimental/computational simulations of the ignition problem. The differences arise from the underlying philosophy of the two endeavors. The approach in Refs. 2 to 4 is a classical ignition study in which the focus is on the response of a propellant mixture to an ignition source, with emphasis on the level of energy needed for ignition and the ensuing flame propagation issues. Our focus in the present paper is on identifying the unsteady mixing processes that provide the propellant mixture in which the ignition source is to be placed. In particular, we wish to characterize the spatial and temporal mixture distribution with a view toward identifying preferred spatial and temporal locations for the ignition source. As such, the present work is limited to cold flow (pre-ignition) conditions

Voytovych, Dmytro M.↗

NASA NTRS2010

Modified Universal Design Survey: Enhancing Operability of Launch Vehicle Ground Crew Worksites

Operability is a driving requirement for next generation space launch vehicles. Launch site ground operations include numerous operator tasks to prepare the vehicle for launch or to perform preflight maintenance. Ensuring that components requiring operator interaction at the launch site are designed for optimal human use is a high priority for operability. To promote operability, a Design Quality Evaluation Survey based on Universal Design framework was developed to support Human Factors Engineering (HFE) evaluation for NASA s launch vehicles. Universal Design per se is not a priority for launch vehicle processing however; applying principles of Universal Design will increase the probability of an error free and efficient design which promotes operability. The Design Quality Evaluation Survey incorporates and tailors the seven Universal Design Principles and adds new measures for Safety and Efficiency. Adapting an approach proven to measure Universal Design Performance in Product, each principle is associated with multiple performance measures which are rated with the degree to which the statement is true. The Design Quality Evaluation Survey was employed for several launch vehicle ground processing worksite analyses. The tool was found to be most useful for comparative judgments as opposed to an assessment of a single design option. It provided a useful piece of additional data when assessing possible operator interfaces or worksites for operability.

Blume, Jennifer L.↗

NASA NTRS2010

Evaluation of Dual Pressurized Rover Operations During Simulated Planetary Surface Exploration

Introduction: A pair of small pressurized rovers (Space Exploration Vehicles, or SEVs) is at the center of the Global Point-of-Departure architecture for future human planetary exploration. Simultaneous operation of multiple crewed surface assets should maximize productive crew time, minimize overhead, and preserve contingency return paths. Methods: A 14-day mission simulation was conducted in the Arizona desert as part of NASA?s 2010 Desert Research and Technology Studies (DRATS). The simulation involved two SEV concept vehicles performing geological exploration under varied operational modes affecting both the extent to which the SEVs must maintain real-time communications with mission control ("Continuous" vs. "Twice-a-Day") and their proximity to each other ("Lead-and-Follow" vs. "Divide-and-Conquer"). As part of a minimalist lunar architecture, no communications relay satellites were assumed. Two-person crews consisting of an astronaut and a field geologist operated each SEV, day and night, throughout the entire 14-day mission, only leaving via the suit ports to perform simulated extravehicular activities. Standard metrics enabled quantification of the habitability and usability of all aspects of the SEV concept vehicles throughout the mission, as well as comparison of the extent to which the operating modes affected crew productivity and performance. Practically significant differences in the relevant metrics were prospectively defined for the testing of all hypotheses. Results and Discussion: Data showed a significant 14% increase in available science time (AST) during Lead-and-Follow mode compared with Divide-and-Conquer, primarily because of the minimal overhead required to maintain communications during Lead-and-Follow. In Lead-and-Follow mode, there was a non-significant 2% increase in AST during Twice-a-Day vs. Continuous communications. Situational awareness of the other vehicle?s location, activities, and contingency return constraints were enhanced during Lead-and-Follow and Twice-a-Day communications modes due to line-of-sight and direct SEV-to-SEV communication. Preliminary analysis of Scientific Data Quality and Observation Quality metrics showed no significant differences between modes.

Abercromby, Andrew F. J.↗

NASA NTRS2004

Heat Control via Torque Control in Friction Stir Welding

In a proposed advance in friction stir welding, the torque exerted on the workpiece by the friction stir pin would be measured and controlled in an effort to measure and control the total heat input to the workpiece. The total heat input to the workpiece is an important parameter of any welding process (fusion or friction stir welding). In fusion welding, measurement and control of heat input is a difficult problem. However, in friction stir welding, the basic principle of operation affords the potential of a straightforward solution: Neglecting thermal losses through the pin and the spindle that supports it, the rate of heat input to the workpiece is the product of the torque and the speed of rotation of the friction stir weld pin and, hence, of the spindle. Therefore, if one acquires and suitably processes data on torque and rotation and controls the torque, the rotation, or both, one should be able to control the heat input into the workpiece. In conventional practice in friction stir welding, one uses feedback control of the spindle motor to maintain a constant speed of rotation. According to the proposal, one would not maintain a constant speed of rotation: Instead, one would use feedback control to maintain a constant torque and would measure the speed of rotation while allowing it to vary. The torque exerted on the workpiece would be estimated as the product of (1) the torque-multiplication ratio of the spindle belt and/or gear drive, (2) the force measured by a load cell mechanically coupled to the spindle motor, and (3) the moment arm of the load cell. Hence, the output of the load cell would be used as a feedback signal for controlling the torque (see figure).

Venable, Richard↗

NASA NTRS2014

Integrating Land Cover Modeling and Adaptive Management to Conserve Endangered Species and Reduce Catastrophic Fire Risk

Land cover modeling is used to inform land management, but most often via a two-step process where science informs how management alternatives can influence resources and then decision makers can use this to make decisions. A more efficient process is to directly integrate science and decision making, where science allows us to learn to better accomplish management objectives and is developed to address specific decisions. Co-development of management and science is especially productive when decisions are complicated by multiple objectives and impeded by uncertainty. Multiple objectives can be met by specification of tradeoffs, and relevant uncertainty can be addressed through targeted science (i.e., models and monitoring). We describe how to integrate habitat and fuels monitoring with decision making focused on dual objectives of managing for endangered species and minimizing catastrophic fire risk. Under certain conditions, both objectives might be achieved by a similar management policy, but habitat trajectories suggest tradeoffs. Knowledge about system responses to actions can be informed by applying competing management actions to different land units in the same system state and by ideas about fire behavior. Monitoring and management integration is important to optimize state-specific management decisions and increase knowledge about system responses. We believe this approach has broad utility for and cover modeling programs intended to inform decision making.

adaptive management↗

NASA NTRS2015

Laser Remote Sensing From ISS: CATS Cloud and Aerosol Level 2 Data Products (Heritage Edition)

The Cloud-Aerosol Transport System (CATS) instrument was developed at NASA's Goddard Space Flight Center (GSFC) and deployed to the International Space Station (ISS) on 10 January 2015. CATS is mounted on the Japanese Experiment Module's Exposed Facility (JEM_EF) and will provide near-continuous, altitude-resolved measurements of clouds and aerosols in the Earth's atmosphere. The CATS ISS orbit path provides a unique opportunity to capture the full diurnal cycle of cloud and aerosol development and transport, allowing for studies that are not possible with the lidar aboard the CALIPSO platform, which flies in the sun-synchronous A-Train orbit." " One of the primary science objectives of CATS is to continue the CALIPSO aerosol and cloud profile data record to provide continuity of lidar climate observations during the transition from CALIPSO to EarthCARE. To accomplish this, the CATS project at NASA's Goddard Space Flight Center (GSFC) and the CALIPSO project at NASA's Langley Research Center (LaRC) are closely collaborating to develop and deliver a full suite of CALIPSO-like level 2 data products that will be produced using the newly acquired CATS level 1B data whenever CATS is operating in science modes 1. The CALIPSO mission is now well into its ninth year of on-orbit operations, and has developed a robust set of mature and well-validated science algorithms to retrieve the spatial and optical properties of clouds and aerosols from multi-wavelength lidar backscatter signals. By leveraging both new and existing NASA technical resources, this joint effort by the CATS and CALIPSO teams will deliver validated lidar data sets to the user community at the earliest possible opportunity. The science community will have access to two sets of CATS Level 2 data products. The "Operational" data products will be produced by the GSFC CATS team utilizing the new instrument capabilities (e.g., multiple FOVs and 1064 nm depolarization), while the "Heritage" data products created using the existing CALIPSO algorithms and the CATS 532 nm channels and the total 1064 nm channel. " Below is the development of the CATS "Heritage" level 2 software and data along with some initial results with operational data."

Rodier, Sharon↗

NASA NTRS2016

Airborne In-Situ Measurements of Formaldehyde Over California: One Year of Results from the Compact Formaldehyde Fluorescence Experiment (COFFEE) Instrument

Formaldehyde (HCHO) is one of the most abundant oxygenated volatile organiccompounds (VOCs) in the atmosphere, playing a role in multiple atmosphericprocesses, such as ozone (O3) production in polluted environments. Due toits short lifetime of only a few hours in daytime, HCHO also serves astracer of recent photochemical activity. While photochemical oxidation ofnon-methane hydrocarbons is the dominant source, HCHO can also be emitteddirectly from fuel combustion, vegetation, and biomass burning. The CompactFormaldehyde FluorescencE Experiment (COFFEE) instrument was built forintegration onto the Alpha Jet Atmospheric eXperiment (AJAX) payload, basedout of NASAs Ames Research Center (Moffett Field, CA). Using Non-ResonantLaser Induced Fluorescence (NR-LIF), trace concentrations of HCHO can bedetected with a sensitivity of 200 parts per trillion.Since its first research flight in December 2015, COFFEE has successfullyflown on more than 20 science missions throughout California and Nevada.Presented here are results from these flights, including boundary layermeasurements and vertical profiles throughout the tropospheric column.Californias San Joaquin Valley is a primary focus, as this region is knownfor its elevated levels of HCHO as well as O3. Measurements collected inwildfire plumes, urban centers, agricultural lands, and on and off shorecomparisons will be presented. In addition, the correlation of HCHO to othertrace gases also measured by AJAX, including O3, methane, carbon dioxide,and water vapor will also be shown. Lastly, the implications of these HCHOmeasurements on calibration and validation of remote sensing data collectedby NASAs OMI (Aura) and OMPS (SuomiNPP) satellites will be addressed.

wildfire↗

NASA NTRS2020

Probing the Evolutionary History of Comets: an Investigation of the Hypervolatiles CO, CH4, and C2H6 in the Jupiter-Family Comet 21P/Giacobini–Zinner

Understanding the cosmogonic record encoded in the parent volatiles stored in cometary nuclei requires investigating whether evolution (thermal or otherwise) has modified the composition of short-period comets during successive perihelion passages. As the most volatile molecules systematically observed in comets, the abundances of CO, CH4, and C2H6 in short-period comets may serve to elucidate the interplay between natal conditions and post-formative evolution in setting present-day composition, yet secure measurements of CO and CH4 in Jupiter-family comets (JFCs) are especially sparse. The highly favorable 2018 apparition of JFC 21P/Giacobini–Zinner enabled a sensitive search for these "hypervolatiles" in a prototypical carbon-chain depleted comet. We observed 21P/Giacobini–Zinner with the iSHELL spectrograph at the NASA Infrared Telescope Facility on four pre-perihelion dates, two dates near-perihelion, and one post-perihelion date. We obtained detections of CO, CH4, and C2H6 simultaneously with H2O on multiple dates. We present rotational temperatures, production rates, and mixing ratios. Combined with previous work, our results may indicate that the hypervolatile coma composition of 21P/Giacobini–Zinner was variable across apparitions as well as within a particular perihelion passage, yet the spread in these measurements is a relatively small fraction of the variation in each molecule from comet to comet. We discuss the implications of our measured hypervolatile content of 21P/Giacobini–Zinner for the evolution of JFCs, and place our results in the context of findings from the Rosetta mission and ground-based studies of comets.

Roth, Nathan X.↗

NASA NTRS2021

Extreme Lows of Wheat Production in Brazil

Wheat production in Brazil is insufficient to meet domestic demand and falls drastically in response to adverse climate events. Multiple, agro-climate-specific regression models, quantifying regional production variability, were combined to estimate national production based on past climate, cropping area, trend-corrected yield, and national commodity prices. Projections with five CMIP6 climate change models suggest extremes of low wheat production historically occurring once every 20 years would become up to 90% frequent by the end of this century, depending on representative concentration pathway, magnified by wheat and in some cases by maize price fluctuations. Similar impacts can be expected for other crops and in other countries. This drastic increase in frequency in extreme low crop production with climate change will threaten Brazil's and many other countries progress toward food security and abolishing hunger.

Brazil↗

DOE OSTI2012

Managing System of Systems Requirements with a Requirements Screening Group

Figuring out an effective and efficient way to manage not only your Requirement’s Baseline, but also the development of all your individual requirements during a Program’s/Project’s Conceptual and Development Life Cycle Stages can be both daunting and difficult. This is especially so when you are dealing with a complex and large System of Systems (SoS) Program with potentially thousands and thousands of Top Level Requirements as well as an equal number of lower level System, Subsystem and Configuration Item requirements that need to be managed. This task is made even more overwhelming when you have to add in integration with multiple requirements’ development teams (e.g., Integrated Product Development Teams (IPTs)) and/or numerous System/Subsystem Design Teams. One solution for tackling this difficult activity on a recent large System of Systems Program was to develop and make use of a Requirements Screening Group (RSG). This group is essentially a Team made up of co-chairs from the various Stakeholders with an interest in the Program of record that are enabled and accountable for Requirements Development on the Program/Project. The RSG co-chairs, often with the help of individual support team, work together as a Program Board to monitor, make decisions on, and provide guidance on all Requirements Development activities during the Conceptual and Development Life Cycle Stages of a Program/Project. In addition, the RSG can establish and maintain the Requirements Baseline, monitor and enforce requirements traceability across the entire Program, and work with other elements of the Program/Project to ensure integration and coordination.

99 GENERAL AND MISCELLANEOUS↗

DOE OSTI2017

Bandwidth Study on Energy Use and Potential Energy Savings Opportunities in U.S. Food and Beverage Manufacturing

Energy bandwidth studies can serve as foundational references in framing the range (or bandwidth) of potential energy savings opportunities in U.S. manufacturing. This bandwidth study examines energy consumption and potential energy savings opportunities in U.S. food and beverage products manufacturing. The study relies on multiple sources to estimate the energy used for processes in six food and beverage manufacturing sub-sectors, representing 40% of sector-wide energy consumption in 2010. Energy savings opportunities for the processes studied in the six sub-sectors are based on technologies currently in use or under development; these potential savings are then extrapolated to estimate sector-wide energy savings opportunity.

energy energy bandwidth study, food, beverage, adv↗

DOE OSTI2017

Second Validation Testing of Canberra-Obayashi Mobile type TruckScan Pre-production Unit - 17214

Canberra Industries, Inc., (Now, Mirion Technologies (Canberra), Inc.), has developed and validated a new truck monitoring system 'Mobile TruckScan (MTSCAN)' for use with the Interim Storage Facilities (ISF) in Japan. MTSCAN consists of eight shielded LED-stabilized 3x3' NaI detectors. Each detector has a lead shield with a collimated view of the truck. Four detectors are placed on each side of the truck, thus 8 in total, each at about 1.1 meter from the side of the truck. These NaI detectors and collimators were calibrated by the Canberra In-Situ Object Counting System (ISOCS) mathematical efficiency calculation tool. Around the Fukushima Daiichi NPS area, the decontaminated waste was put into flexible containers called Super Sacks (SS), for transportation to the ISF, typically in 10 metric ton dump trucks. The MTSCAN pre-production unit was used to measure multiple SSs loaded into 10 ton trucks, and was able to accurately report the activity of each individual SS, with around 10-20 second acquisition time. The system can also accommodate smaller 2 ton and larger 20 ton trucks. The system is relatively compact, and therefore easy to move and setup at a different location. MTSCAN is expected to measure the SSs after loading onto trucks at the Temporary Storage Area (TSA), and at the entrance of the ISF. The MTSCAN assay results showed good accuracy in this demonstration which simulated the actual operation. From these tests, the combined standard deviation for each SS is about 20%, when compared to the reference activity from multiple Ge measurements of each sack. (authors)

07 ISOTOPE AND RADIATION SOURCES↗

DOE OSTI2014

Class II algorithm for charged-particle transport simulation - Paper 142

Simulation of the transport of high-energy charged particles is difficult because of the large number of interactions experienced by these particles before being brought to rest. Possible strategies to deal with this difficulty were analyzed by Berger. Most modern Monte Carlo codes use a mixture of complete-grouping (class I) and mixed (class II) schemes. In class I simulations, the global effect of all the interactions that occur along a trajectory segment of a given length s is described by means of precalculated distributions derived from multiple-scattering theories. In class II simulations, hard (or catastrophic) interactions (with energy loss W or polar scattering angle {theta} larger than given cutoff values) are sampled individually, while the effect of soft interactions (with energy losses and scattering angles smaller than the respective cutoffs) is described using a multiple-scattering approach. Although Berger effectively employed class II simulation only for energy-loss events, he did recognize the advantages of class II over class I also for multiple elastic scattering. On the one hand, because hard interactions are described exactly according to the adopted differential cross sections (DCSs), class II schemes are more accurate. On the other hand, multiple-scattering approximations, which are still required to describe the cumulative effect of soft interactions, are simpler and more accurate when individual interactions are limited to small energy transfers and angular deflections. For instance, for path lengths that are not too small, but still much less than the CSDA range, the energy-loss distribution due to multiple soft events is approximately Gaussian, by virtue of the central limit theorem. Similarly, the angular distribution caused by multiple small-angle deflections is also approximately Gaussian. However, class II schemes are more difficult to implement because of their dependence on specificities of the DCSs. In this article we briefly present the essentials of the class II algorithm for charged particles implemented in the last version of the penelope code, and provide evidence of its accuracy and stability with the simulation parameters. (authors)

61 RADIATION PROTECTION AND DOSIMETRY↗

DOE OSTI2014

Luteolin inhibits Cr(VI)-induced malignant cell transformation of human lung epithelial cells by targeting ROS mediated multiple cell signaling pathways

Hexavalent chromium [Cr(VI)] is a well-known human carcinogen associated with the incidence of lung cancer. Inhibition of metal induced carcinogenesis by a dietary antioxidant is a novel approach. Luteolin, a natural dietary flavonoid found in fruits and vegetables, possesses potent antioxidant and anti-inflammatory activity. We found that short term exposure of human bronchial epithelial cells (BEAS-2B) to Cr(VI) (5 μM) showed a drastic increase in ROS generation, NADPH oxidase (NOX) activation, lipid peroxidation, and glutathione depletion, which were significantly inhibited by the treatment with luteolin in a dose dependent manner. Treatment with luteolin decreased AP-1, HIF-1α, COX-2, and iNOS promoter activity induced by Cr(VI) in BEAS-2B cells. In addition, luteolin protected BEAS-2B cells from malignant transformation induced by chronic Cr(VI) exposure. Moreover, luteolin also inhibited the production of pro-inflammatory cytokines (IL-1β, IL-6, IL-8, TNF-α) and VEGF in chronic Cr(VI) exposed BEAS-2B cells. Western blot analysis showed that luteolin inhibited multiple gene products linked to survival (Akt, Fak, Bcl-2, Bcl-xL), inflammation (MAPK, NF-κB, COX-2, STAT-3, iNOS, TNF-α) and angiogenesis (HIF-1α, VEGF, MMP-9) in chronic Cr(VI) exposed BEAS-2B cells. Nude mice injected with BEAS-2B cells chronically exposed to Cr(VI) in the presence of luteolin showed reduced tumor incidence compared to Cr(VI) alone treated group. Overexpression of catalase (CAT) or SOD2, eliminated Cr(VI)-induced malignant transformation. Overall, our results indicate that luteolin protects BEAS-2B cells from Cr(VI)-induced carcinogenesis by scavenging ROS and modulating multiple cell signaling mechanisms that are linked to ROS. Luteolin, therefore, serves as a potential chemopreventive agent against Cr(VI)-induced carcinogenesis. - Highlights: • Luteolin inhibited Cr(VI)-induced oxidative stress. • Luteolin inhibited chronic Cr(VI)-induced malignant transformation. • Luteolin inhibited chronic Cr(VI)-induced inflammation. • Luteolin inhibited chronic Cr(VI)-induced angiogenesis.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2018

Iterative genome editing of Escherichia coli for 3-hydroxypropionic acid production

Synthetic biology requires strategies for the targeted, efficient, and combinatorial engineering of biological sub-systems at the molecular level. Here, we report the use of the iterative CRISPR EnAbled Trackable genome Engineering (iCREATE) method for the rapid construction of combinatorially modified genomes. We coupled this genome engineering strategy with high-throughput phenotypic screening and selections to recursively engineer multiple traits in Escherichia coli for improved production of the platform chemical 3- hydroxypropionic acid (3HP). Particularly, we engineered i) central carbon metabolism, ii) 3HP synthesis, and (iii) 3HP tolerance through design, construction and testing of ~162,000 mutations across 115 genes spanning global regulators, transcription factors, and enzymes involved in 3HP synthesis and tolerance. The iCREATE process required ~1 month to perform 13 rounds of combinatorial genome modifications with targeted gene knockouts, expression modification by ribosomal binding site (RBS) engineering, and genome-level site-saturation mutagenesis. Specific mutants conferring increased 3HP titer, yield, and productivity were identified and then combined to produce 3HP at a yield and concentration ~60-fold higher than the wild-type strain.

3-hydroxypropionic acid↗

DOE OSTI2024

Methane Pyrolysis for CO2-free H2 and Carbon Nanomaterials - CRADA 576 (Final Report)

In this CRADA project we continued to develop the Pacific Northwest National Laboratory (PNNL) patent-pending Regenerable Catalytic Pyrolysis (ReCaP) process technology for producing CO 2 -free hydrogen (H 2 ) from inexpensive and domestically-abundant natural gas (NG), while simultaneously reducing H 2 ’s net production cost to $\$$1.0/kg through the sale of valuable crystalline solid carbon co-product. Producing clean hydrogen at this price is a DOE Hydrogen Energy Earthshot goal. This effort builds on our prior catalyst and processing advances made thermocatalytic decomposition of methane (TCD). The additional scope performed here accelerated the commercial deployment of TCD for CO 2 -free H 2 and valuable solid carbon nanotubes (CNT) co-product, by i) scaling up the production of CNT co-product using a fluidized bed reactor (25 g catalyst scale versus the 1 g catalyst scale demonstrated prior), ii) producing approximately 1 kg of CNT byproduct, produced via multiple cycles of TCD, carbon-catalyst separation, and catalyst re-synthesis, to enable the production of sufficient quantities of solid carbon so as to explore its market potential, iii) understanding the quality of the co-product CNTs, produced at larger scale, using advanced characterization, and iv) beginning to explore multiple promising high volume carbon product applications (e.g., aluminum and polymer composites, steel additive, and cement reinforcement applications). We are in discussions with Department of Energy and potential commercial partners to continue funding of this effort with the goal to facilitate eventual commercial deployment.

08 HYDROGEN↗

DOE OSTI2022

Operating Strategies for Dispatchable PEM Electrolyzers that Enable Low-Cost Hydrogen Production

Hydrogen is a pathway to enabling decarbonization across multiple economic sectors that cannot be directly decarbonized with electricity including heat for industrial operations, medium- and heavy-duty transportation applications, long-duration energy storage, and as a feedstock for chemical synthesis. Producing hydrogen at low costs and carbon footprint is likely essential to economically decarbonize these otherwise "hard to decarbonize" sectors. Low-temperature polymer electrolyte membrane (PEM) electrolysis produces hydrogen from water and electricity and is a rapidly developing pathway towards making hydrogen at the scales required for decarbonization applications. The levelized cost of electrolytic hydrogen is dependent on the capital cost, efficiency, and durability of the electrolyzer system as well as the price of electricity supplied to the electrolyzer and the annual utilization of the electrolyzer (capacity factor). Electricity price and capacity factor depend on the source of energy that the system uses and impact other economic factors. Electricity price and capacity factor and the connections between other aspects of hydrogen production via PEM electrolyzers are the focus of this work. PEM electrolyzers have conventionally been operated at high capacity factors using electricity purchased from utilities with a constant price throughout the year. To achieve lower effective electricity prices, recent work has investigated opportunities for electrolyzers to purchase electricity in wholesale markets, where the cost of electricity varies hourly. This option can lead to lower electricity costs when the electrolyzer is a controllable load that ramps up and down rapidly and turns on and off frequently. This configuration and operating strategy capitalizes on times of low wholesale electricity prices and results in lower hydrogen levelized costs than constant operation due to reduced electricity costs even though the reduced capacity factor increases the cost of recovering the capital investment. Cycling on and off frequently also has implications for electrolyzer durability. An electrolyzer configuration where it is directly connected to renewable generation such as wind or solar, only running when the generator is producing energy, has similar implications on operating strategy, hydrogen levelized cost, capacity factor, and durability. This work provides insight into the relationships between dispatchable electrolyzer operating strategies and the cost of producing hydrogen from these systems, outlining strategies and opportunities to minimize production costs while minimizing operations that are likely to negatively impact system durability and efficiency. We find strategies that minimize electrolyzer cycling and the resulting durability impacts while increasing the hydrogen levelized cost only slightly above the minimum. We also find opportunities for batteries to minimize the number of cycles in systems directly connected to renewable generation. These findings outline key opportunities for future electrolyzer deployments and the synergistic benefits between electrolyzers and increased deployment of renewable energy generation like wind and solar. They also inform research and development that is reducing electrolyzer capital cost while managing durability impacts.

electricity markets↗

DOE OSTI2021

Mapping the catalytic conformations of an assembly-line polyketide synthase module

Assembly-line polyketide synthases, such as the 6-deoxyerythronolide B synthase (DEBS), are large enzyme factories prized for their ability to produce specific and complex polyketide products. By channeling protein-tethered substrates across multiple active sites in a defined linear sequence, these enzymes facilitate programmed small-molecule syntheses that could theoretically be harnessed to access countless polyketide product structures. Additionally, using cryogenic electron microscopy to study DEBS module 1, we present a structural model describing this substrate-channeling phenomenon. Our 3.2- to 4.3-angstrom-resolution structures of the intact module reveal key domain-domain interfaces and highlight an unexpected module asymmetry. We also present the structure of a product-bound module that shines light on a recently described “turnstile” mechanism for transient gating of active sites along the assembly line.

59 BASIC BIOLOGICAL SCIENCES↗