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

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All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Concrete Thermal Energy Storage Enabling Flexible Operation without Coal Plant Cycling

The work described in this report is responsive to the Office of Fossil Energy program “Energy Storage for Fossil Power Generation.” The pilot plant built as a result of this project demonstrated the feasibility and performance of a concrete thermal energy storage (CTES) system integrated with a supercritical coal power plant. The 10 MWh electrical (>25 MWh thermal) CTES unit, developed by Storworks Power, was designed to enable flexible operation of coal plants without cycling damage. The project's key technical achievements showcase a significant advancement in energy storage technology. A modular CTES system using 42 “Bolderblocs” units was successfully designed and constructed at Alabama Power’s Plant Gaston Unit 5, with each block containing embedded stainless-steel coils in specialized, cost-effective high-temperature concrete. The system interfaced seamlessly with the plant's 3500 psig (241 barg), 1000°F (538°C) supercritical steam, demonstrating operational flexibility. Over 86 full cycles, the CTES exhibited rapid charging and discharging capabilities, effectively mimicking steam turbine feed conditions and handling varying load profiles and storage durations. Performance validation confirmed the system's ability to consistently meet design target steam conditions of 75 bar-a and ~400°C for nominal baseline discharge. The concrete material withstood repeated thermal cycling without degradation, validating earlier lab-scale tests. Integration of balance of plant components, including a condensate management system with storage tank and air-cooled condenser, minimized plant interfaces and water consumption. A robust control scheme ensured safe, automated operation across various scenarios. Key learnings from the project were invaluable: 1. Initial concrete drying and commissioning procedures were refined for future deployments, enhancing efficiency in subsequent installations. 2. System flexibility exceeded expectations, with rapid response to changing conditions. 3. Design improvements were identified including optimized insulation and piping that will enhance overall system efficiency in future deployments 4. Full cycle thermal roundtrip efficiencies exceeded 88%. While the roundtrip electrical efficiency was somewhat limited by known challenges using input steam, such constraints may be mitigated by swapping steam for hot air as thermal input. 5. A summary of key performance parameters for the pilot test and predicted performance of a full scale commercial system with specified improvements determined from the pilot are shown in Section 8. The project faced challenges, including COVID-19 delays and host plant availability constraints. However, these were overcome through adaptive planning and execution. The successful management of these obstacles demonstrated the resilience and adaptability of the project team and the robustness of the CTES technology. This successful pilot demonstrates the potential for CTES to enhance coal plant flexibility, supporting grid stability as renewable penetration increases. The validated design and operational data provide a solid foundation for scaling up to utility-scale implementations, potentially transforming how thermal plants operate in evolving energy landscapes. The system's ability to rapidly respond to changing grid conditions while maintaining high efficiency makes it a promising solution for balancing intermittent renewable energy sources. Furthermore, the project highlighted the potential for even greater efficiencies in future iterations. The use of air as an input medium could potentially eliminate the limitations observed with steam input, opening new possibilities for energy storage applications beyond coal plant integration. In conclusion, this pilot project not only achieved its primary goals but also uncovered additional benefits and potential applications of the CTES technology. It represents a significant step forward in addressing the challenges of grid stability and flexibility in an increasingly renewable-driven energy landscape.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2025

Examination of Factors Affecting the Cost and Performance of a Natural Gas Combined Cycle Equipped with Carbon Dioxide Capture

The purpose of this Technical Note is to report the findings of an examination of the effect of plausible deviations in select study assumptions on the reported cost and performance estimates for a power plant case drawn from NETL’s “Cost and Performance Baseline for Fossil Energy Plants Volume 1: Bituminous Coal and Natural Gas to Electricity” (known as the Fossil Energy Baseline). An F-Class NGCC power plant equipped with state-of-the-art, solvent-based, post-combustion carbon dioxide (CO2) capture (95 percent carbon capture rate)—designated as Case B31B.95—was selected for this work. This sensitivity analysis provides insight into the effects of parameter variations within and across selected categories—ambient conditions, construction cost, natural gas (NG) price, capacity factor, and finance—on the plant performance and capital and operating and maintenance (O&M) costs, and the subsequent impact on common figures of merit.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2024

Energy-based break-even transportation distance of biomass feedstocks

The distance a solid biomass feedstock could be used to transport the feedstock when used as biobased fuel is critical information for transportation analysis. However, this information is not available. The break-even transportation distance (BTD) of various fuels from biomass feedstocks and fossil sources was analyzed for truck, rail, and ship transport modes based on bulk density, moisture content, and specific energy. Fourteen different biomass feedstocks, such as crop residues (e.g., corn stover), woody biomass (e.g., wood chips), including thermally pretreated (torrefied) and densified forms (pellets), cattle feedlot compost, and three standard fossil fuels, namely, coal, lignite, and diesel, were considered for BTD analysis and comparison. The BTD values were derived by comparing the energy content of biomass feedstocks with the energy expended in transporting the fuels through selected transportation modes. For ready reference, an alternative derivation of BTD equations and example calculations were also presented. Among the biomass feedstocks, torrefied pellets had the highest BTD (4.16 × 10 4 , 12.47 × 10 4 , and 54.14 × 10 4 km), and cattle feedlot compost had the lowest BTD (1.29 × 10 4 , 3.88 × 10 4 , and 9.23 × 10 4 km), respectively, for truck, rail, and ship. Higher bulk density and higher specific energy of the biomass feedstocks increased the BTD for all modes of transport. Transport is most efficient when mass-limited. Biomass feedstock bulk densities where transportation becomes mass-limited are 223, 1,480, and 656 kg/m 3 for truck, rail, and ship, respectively. Truck transport is typically mass-limited (payload limit restriction; increased BTD), whereas rail transport is entirely volume-limited (cargo space restriction; decreased BTD), and ship transport is mostly volume-limited for biomass feedstocks and mass-limited for densified biomass feedstocks. Ship transport is the most efficient, followed by rail and truck; on average for the materials (17) studied, rail is 3.1 times and ship is 9.2 times the truck's BTD. Based on the bulk density and higher specific energy of the biomass feedstocks, regardless of the refinery location, interstate truck transport of these feedstocks is not a limiting factor in the bio-refining process., with the studied biomass feedstock BTD per truckload representing between 0.89 and 2.88 times the US perimeter.

09 BIOMASS FUELS↗
DOE OSTI2016

EVOLUTION OF GALAXY GROUPS IN THE ILLUSTRIS SIMULATION

We present the first study of the evolution of galaxy groups in the Illustris simulation. We focus on dynamically relaxed and unrelaxed galaxy groups representing dynamically evolved and evolving galaxy systems, respectively. The evolutionary state of a group is probed from its luminosity gap and separation between the brightest group galaxy and the center of mass of the group members. We find that the Illustris simulation overproduces galaxy systems with a large luminosity gap, known as fossil systems, in comparison to observations and the probed semi-analytical predictions. However, this simulation is just as successful as the probed semi-analytic model in recovering the correlation between luminosity gap and offset of the luminosity centroid. We find evolutionary tracks based on luminosity gap that indicate that a group with a large luminosity gap is rooted in one with a small luminosity gap, regardless of the position of the brightest group galaxy within the halo. This simulation helps to explore, for the first time, the black hole mass and its accretion rate in galaxy groups. For a given stellar mass of the brightest group galaxies, the black hole mass is larger in dynamically relaxed groups with a lower rate of mass accretion. We find this to be consistent with the latest observational studies of radio activity in the brightest group galaxies in fossil groups. We also find that the intragalactic medium in dynamically evolved groups is hotter for a given halo mass than that in evolving groups, again consistent with earlier observational studies.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

Soot microphysical effects on liquid clouds, a multi-model investigation

We use global models to explore the microphysical effects of carbonaceous aerosols on liquid clouds. Although absorption of solar radiation by soot warms the atmosphere, soot may cause climate cooling due to its contribution to cloud condensation nuclei (CCN) and therefore cloud brightness. Six global models conducted three soot experiments; four of the models had detailed aerosol microphysical schemes. The average cloud radiative response to biofuel soot (black and organic carbon), including both indirect and semi-direct effects, is -0.11Wm -2 , comparable in size but opposite in sign to the respective direct effect. In a more idealized fossil fuel black carbon experiment, some models calculated a positive cloud response because soot provides a deposition sink for sulfuric and nitric acids and secondary organics, decreasing nucleation and evolution of viable CCN. Biofuel soot particles were also typically assumed to be larger and more hygroscopic than for fossil fuel soot and therefore caused more negative forcing, as also found in previous studies. Diesel soot (black and organic carbon) experiments had relatively smaller cloud impacts with five Correspondence to: D. Koch (dorothy.koch@science.doe.gov) of the models <±0.06Wm -2 from clouds. The results are subject to the caveats that variability among models, and regional and interrannual variability for each model, are large. This comparison together with previously published results stresses the need to further constrain aerosol microphysical schemes. The non-linearities resulting from the competition of opposing effects on the CCN population make it difficult to extrapolate from idealized experimen

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2011

Biogas Potential on Long Island, New York: A Quantification Study

Biogas is the product of anaerobic digestion of waste, whether occurring spontaneously in landfills or under controlled conditions in digesters. Biogas is viewed as an important energy source in current efforts to reduce the use of fossil fuels and dependency on imported resources. Several studies on the assessment of biogas potential have been made at regional, national, and global scales. However, because it is not economically feasible to transport biogas feedstock over long distances, it is more appropriate to consider local waste sources for their potential to produce biogas. An assessment of the biogas potential on Long Island, based on the review of local landfills, wastewater treatment plants, solid waste generation and management, and agricultural waste, found that 234 x 10{sup 6} m{sup 3} of methane (CH{sub 4}) from biogas might be harvestable, although substantial barriers for complete exploitation exist. This number is equivalent to 2.52 TW-h of electricity, approximately 12% of fossil fuel power generation on Long Island. This work can serve as a template for other areas to rapidly create or approximate biogas potentials, especially for suburban U.S. locations that are not usually thought of as sources of renewable energy.

03 NATURAL GAS↗
DOE OSTI2012

COMBUSTION-ASSISTED CO2 CAPTURE USING MECC MEMBRANES

Mixed Electron and Carbonate ion Conductor (MECC) membranes have been proposed as a means to separate CO{sub 2} from power plant flue gas. Here a modified MECC CO{sub 2} capture process is analyzed that supplements retentate pressurization and permeate evacuation as a means to create a CO{sub 2} driving force with a process assisted by the catalytic combustion of syngas on the permeate side of the membrane. The combustion reactions consume transported oxygen, making it unavailable for the backwards transport reaction. With this change, the MECC capture system becomes exothermic, and steam for electricity production may be generated from the waste heat. Greater than 90% of the CO{sub 2} in the flue gas may be captured, and a compressed CO{sub 2} product stream is produced. A fossil-fueled power plant using this process would consume 14% more fuel per unit electricity produced than a power plant with no CO{sub 2} capture system, and has the potential to meet U.S. DOE's goal that deployment of a CO{sub 2} capture system at a fossil-fueled power plant should not increase the cost of electricity from the combined facility by more than 30%.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2015

SUBTASK 6.1 – STRATEGIC STUDIES

The Energy & Environmental Research Center (EERC) has recently completed 7 years of research through the Cooperative Agreement with the U.S. Department of Energy (DOE) National Energy Technology Laboratory (NETL) focused on fossil energy technology development and demonstration. To support a significant number of the different activities being considered within all of our research contracts with NETL, a subtask (6.1 – Strategic Studies) was created to focus on small research efforts that came up throughout the year that would support an existing EERC–NETL project or would help to develop a new concept for inclusion in future efforts. This subtask was funded through the EERC–DOE Joint Program on Research and Development for Fossil Energy-Related Resources Cooperative Agreement No. DE-FC26- 08NT43291

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2016

Investigation of the Effects of Hydrogen Atoms Concentration on the Tungsten Sigma 5 (310) Symmetric Tilt Grain Boundary Strength

Recently, strict policies are being made by several government agencies, environmentalists, and some people against the usage of fossil fuels as the source of energy generation. Not only because its supply does not meet the booming human population all around the world but also it is not pollution-free; just to mention a few. These setbacks attached to fossil fuels make nuclear fusion energy an important means of energy generation; it is characterized with clean and easy means of energy generation compared to other methods of power production such as hydropower and solar power. The success of fusion power depends on the design of modern fusion materials and the selection of the plasma facing materials (PFMs). ITER and Demonstration Power plant (DEMO) considered Tungsten (W) as part of their PFMs. W is the most preferred plasma facing material (PFM) for the future nuclear fusion reactors such as in the proposed DEMO and ITER- which is at the moment the largest Tokamak nuclear fusion reactor under construction in the world. Tungsten has excellent thermal properties, low-sputtering yield, and high melting point. Hydrogen (H) atoms have an affinity for tungsten grain boundary, and are trapped there permanently. In addition, it makes W prone to failure. In a fusion environment, W is exposed to extremely high fluences of H isotopes and irradiation. The low-energy H isotopes will be retained in the tungsten material leading to the formation of blisters in W and cause degradation of the mechanical and thermal properties of W. For safety reason, the effect of hydrogen atoms concentration at the tungsten S5 (310) grain boundary (GB) needs to be investigated and it will aid in better designing of fusion wall materials. Σ5 (310) is considered in this work because it is one of the most important and dominant GBs in the atomic distribution of materials. GBs affect the strength of W as well. The GBs with superior properties can be increased in the atomic distribution of W relative to others in order to achieve high overall material properties. GBs play a role in determining the properties of materials such as the thermal and electrical conductivity of a material. The crystallography description of the Σ5 (310) grain boundary comprises of Σ, tilt type- symmetric, crystallographic direction [001] and the GB plane. The Σ is related to the coincidence site lattice (CSL) model, which denotes that in a certain orientation between two grains, there are numbers of points where the atoms coincide. For the case of Σ5 (310), the misorientation between the two crystals is 36.9 degree along [001] direction and the GB plane is (310). GB properties differ as result of different sigma values and Σ is the reciprocal of CSL. Thus, Σ5 GB has 1/5 of the atoms in coincident sites. For the case of a tilt boundary, the lattice vector is embedded in the GB plane. Also for a tilt-symmetric GB, the grains directions are mirrored against the GB plane. The classic molecular dynamics method (MD) is an accurate numerical approach that adopts Newton's equation of motion to get atoms trajectories.Studies have been carried out on atomistic simulation of tungsten.The effect of H on GB migration in W was studied by using molecular dynamics simulation and it was discovered that H prevents the GB migration at different H concentrations and temperatures. Others investigated the migration, dissolution and trapping of H in W using MD and first principles method. Atomistic simulations have been used to predict the GB energy in Fe and Mo using embedded atom method (EAM) and it was concluded that the GB energies in the metals are affected more by the orientation of the GB plane than by the misorientation of the lattice. Study was done on symmetric and asymmetric tilt grain boundaries in Cu and Al using MD method and the GB structures and energies were established; EAM was adopted as well. The formation of hydrogen blisters and cracking processes for various tungsten materials were investigated and it was observed that, dopants increase the number of blisters and exfoliations for both stress relieved and recrystallized W. Investigation was carried out on the surface morphology changes in W caused by plasmas heat and particle loadings and their effects on material degradation in ITER. In addition, the study of interactions between low energetic hydrogen and tungsten surface was carried out using molecular dynamics simulations with analytical bond order potential (ABOP) and the results addressed irradiation damage in tungsten. Mechanism of blister formation on W surface was studied using experimental approach and it was observed that the amount of blisters formed depends on the beam fluence. This work investigates the effect of hydrogen atom concentrations at the W Σ5 (310) tilt-symmetric GB on the grain boundary energy and the GB pulling force. (authors)

36 MATERIALS SCIENCE↗
DOE OSTI2024

Life-Cycle Assessment Integration into Scalable Open-Source Numerical Models (LiAISON) for Analyzing Emerging Low-Carbon Technologies

Decarbonizing the industrial sector is a significant challenge in achieving a net-zero greenhouse gas (GHG) emissions economy by 2050 and the Paris Agreement, i.e., a global climate change mitigation target of achieving a maximum average temperature change potential of 1.5 degrees C or less by 2100 with respect to pre-industrial levels. In the United States (US), the industrial sector accounts for 23% of total GHG emissions and is home to a number of hard-to-electrify activities. The chemicals subsector has the single largest subsector emissions profile after direct emissions from fossil fuel combustion and leakage from fossil fuel distribution systems. Within the chemicals subsector, many processes depend on hydrogen or ammonia precursors. Decarbonizing these two commodities would contribute significantly to decarbonizing the industrial sector as hydrogen could also be used for low carbon steel production (e.g., hydrogen-based direct reduction of iron) and other industrial applications. Emerging technologies require the application of prospective life cycle assessment (LCA), which can account for technology (foreground) scaling and process improvements via learning-by-doing, among others. In many cases, the future system context (background) in which the technologies are assumed to operate in is equally relevant. Background scenarios generated by integrated assessment models (IAM) can coherently incorporate potential future dynamics of the energy-climate-human-land system. Further, IAM scenarios are harmonized across socioeconomic and climate change mitigation pathways, which facilitates the comparability of prospective LCAs using different IAMs. We introduce an open source prospective LCA framework, the Life-cycle Assessment Integration into Scalable Open-source Numerical models (LiAISON), to analyze the non-linear relationships between technology foreground and the future energy system background across a series of midpoint and resource use metrics The integration of LCA and IAM data is achieved using prospective environmental Impact assessment (PREMISE). We showcase it by assessing two Power-to-Hydrogen (PtH2) processes, namely Solid Oxide Electrolysis (SOE) and Polymer Electrolyte Membrane Electrolysis (PEME). We compare the technologies to a baseline of hydrogen production via natural gas-based Steam Methane Reforming (SMR) in a US context of multiple energy system and climate change mitigation futures. Besides providing an analysis that specifies the LCA results ranges with temporal and geospatial explicitness across the two technologies, metrics, and impact assessment methods, this research also aims to establish a base framework that can be expanded to use other IAM generated scenarios and US open-source life cycle inventory (LCI) databases. We find that the temporal environmental performance of either technology or their difference to SMR is directly influenced by the underlying background dynamics. Under baseline projections (i.e., no decarbonization goals), neither process reaches parity with the incumbent technology across several environmental metrics. Under the decarbonization scenarios, the underlying sectoral shifts result in declining impacts over time, compared to 2020 levels, except for metal depletion levels, which increase. The background shifts postulate a heavily decarbonized economy and energy system, which help technologies reach parity with SMR between 2040-2050 (RCP2.6) and 2030-2040 (RCP1.9) for global warming. Despite declines across several other metrics over time, neither PtH2 technology break even with SMR by 2100 besides for global warming.

decarbonizing↗
DOE OSTI2024

Towards Prospective LCA Using Life-Cycle Assessment Integration into Scalable Open-Source Numerical Models (LiAISON) Framework for Analyzing Emerging Low-Carbon Technologies

Decarbonizing the industrial sector is a significant challenge in achieving a net-zero greenhouse gas (GHG) emissions economy by 2050 and the Paris Agreement, i.e., a global climate change mitigation target of achieving a maximum average temperature change potential of 1.5 Degrees Celsius or less by 2100 with respect to pre-industrial levels. In the United States (US), the industrial sector accounts for 23% of total GHG emissions and is home to a number of hard-to-electrify activities. The chemicals subsector has the single largest subsector emissions profile after direct emissions from fossil fuel combustion and leakage from fossil fuel distribution systems. Within the chemicals subsector, many processes depend on hydrogen or ammonia precursors. Decarbonizing these two commodities would contribute significantly to decarbonizing the industrial sector as hydrogen could also be used for low carbon steel production (e.g., hydrogen-based direct reduction of iron) and other industrial applications. Emerging technologies require the application of prospective life cycle assessment (LCA), which can account for technology (foreground) scaling and process improvements via learning-by-doing, among others. In many cases, the future system context (background) in which the technologies are assumed to operate in is equally relevant. Background scenarios generated by integrated assessment models (IAM) can coherently incorporate potential future dynamics of the energy-climate-human-land system. Further, IAM scenarios are harmonized across socioeconomic and climate change mitigation pathways, which facilitates the comparability of prospective LCAs using different IAMs. We introduce an open source prospective LCA framework, the Life-cycle Assessment Integration into Scalable Open-source Numerical models (LiAISON), to analyze the non-linear relationships between technology foreground and the future energy system background across a series of midpoint and resource use metrics The integration of LCA and IAM data is achieved using prospective environmental Impact assessment (PREMISE). We showcase it by assessing two Power-to-Hydrogen (PtH2) processes, namely Solid Oxide Electrolysis (SOE) and Polymer Electrolyte Membrane Electrolysis (PEME). We compare the technologies to a baseline of hydrogen production via natural gas-based Steam Methane Reforming (SMR) in a US context of multiple energy system and climate change mitigation futures. Besides providing an analysis that specifies the LCA results ranges with temporal and geospatial explicitness across the two technologies, metrics, and impact assessment methods, this research also aims to establish a base framework that can be expanded to use other IAM generated scenarios and US open-source life cycle inventory (LCI) databases. We find that the temporal environmental performance of either technology or their difference to SMR is directly influenced by the underlying background dynamics. Additionally we compare our results by linking two other prospective models with LiAISON - GCAM(Global Change Assessment Model) and ReEDS (Regional Energy Deployment System) to analyze the effect of changing background scenarios using varying predictions in life cycle analysis.

emissions↗
DOE OSTI2016

Strong regional atmospheric 14 C signature of respired CO 2 observed from a tall tower over the midwestern United States

Radiocarbon in CO 2 ( 14 CO 2 ) measurements can aid in discriminating between fast (<1 year) and slower (>5–10 years) cycling of C between the atmosphere and the terrestrial biosphere due to the 14 C disequilibrium between atmospheric and terrestrial C. However, 14 CO 2 in the atmosphere is typically much more strongly impacted by fossil fuel emissions of CO 2 , and, thus, observations often provide little additional constraints on respiratory flux estimates at regional scales. Here we describe a data set of 14 CO 2 observations from a tall tower in northern Wisconsin (USA) where fossil fuel influence is far enough removed that during the summer months, the biospheric component of the 14 CO 2 budget dominates. We find that the terrestrial biosphere is responsible for a significant contribution to 14 CO 2 that is 2–3 times higher than predicted by the Carnegie-Ames-Stanford approach terrestrial ecosystem model for observations made in 2010. This likely includes a substantial contribution from the North American boreal ecoregion, but transported biospheric emissions from outside the model domain cannot be ruled out. The 14 CO 2 enhancement also appears somewhat decreased in observations made over subsequent years, suggesting that 2010 may be anomalous. Furthermore, with these caveats acknowledged, we discuss the implications of the observation/model comparison in terms of possible systematic biases in the model versus short-term anomalies in the observations. Going forward, this isotopic signal could be exploited as an important indicator to better constrain both the long-term carbon balance of terrestrial ecosystems and the short-term impact of disturbance-based loss of carbon to the atmosphere.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

Does vapor pressure deficit drive the seasonality of δ 13 C of the net land-atmosphere CO 2 exchange across the United States?: The Influence of VPD on δ 13 C of NEE

The seasonal pattern of the carbon isotope content (δ 13 C) of atmospheric CO 2 depends on local and nonlocal land-atmosphere exchange and atmospheric transport. Previous studies suggested that the δ13C of the net land-atmosphere CO 2 flux (δsource) varies seasonally as stomatal conductance of plants responds to vapor pressure deficit of air (VPD). We studied the variation of δ source at seven sites across the United States representing forests, grasslands, and an urban center. Using a two-part mixing model, we calculated the seasonal δsource for each site after removing background influence and, when possible, removing δ 13 C variation of nonlocal sources. Compared to previous analyses, we found a reduced seasonal (March–September) variation in δ source at the forest sites (0.5‰variation). We did not find a consistent seasonal relationship between VPD and δ source across forest (or other) sites, providing evidence that stomatal response to VPD was not the cause of the global, coherent seasonal pattern in δsource. In contrast to the forest sites, grassland and urban sites had a larger seasonal variation in δ sourc e (5‰) dominated by seasonal transitions in C 3 /C 4 grass productivity and in fossil fuel emissions, respectively. Our findings were sensitive to the location used to account for atmospheric background variation within the mixing model method that determined δsource. Special consideration should be given to background location depending on whether the intent is to understand site level dynamics or regional scale impacts of land-atmosphere exchange. The seasonal amplitude in δ 13 C of land-atmosphere CO 2 exchange (δ source ) varied across land cover types and was not driven by seasonal changes in vapor pressure deficit. The largest seasonal amplitudes of δsource were at grassland and urban sites, driven by changes in C 3 /C 4 grass productivity and fossil fuel emissions, respectively. Mixing model approaches may incorrectly calculate δs ource when background atmospheric observations are remote and/or prone to anthropogenic influence.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Strategies for Semiconductor/Electrocatalyst Coupling toward Solar‐Driven Water Splitting

Abstract Hydrogen (H 2 ) has a significant potential to enable the global energy transition from the current fossil‐dominant system to a clean, sustainable, and low‐carbon energy system. While presently global H 2 production is predominated by fossil‐fuel feedstocks, for future widespread utilization it is of paramount importance to produce H 2 in a decarbonized manner. To this end, photoelectrochemical (PEC) water splitting has been proposed to be a highly desirable approach with minimal negative impact on the environment. Both semiconductor light‐absorbers and hydrogen/oxygen evolution reaction (HER/OER) catalysts are essential components of an efficient PEC cell. It is well documented that loading electrocatalysts on semiconductor photoelectrodes plays significant roles in accelerating the HER/OER kinetics, suppressing surface recombination, reducing overpotentials needed to accomplish HER/OER, and extending the operational lifetime of semiconductors. Herein, how electrocatalyst coupling influences the PEC performance of semiconductor photoelectrodes is outlined. The focus is then placed on the major strategies developed so far for semiconductor/electrocatalyst coupling, including a variety of dry processes and wet chemical approaches. This Review provides a comprehensive account of advanced methodologies adopted for semiconductor/electrocatalyst coupling and can serve as a guideline for the design of efficient and stable semiconductor photoelectrodes for use in water splitting.

Thalluri, Sitaramanjaneya Mouli↗
DOE OSTI2016

An assessment of the potential products and economic and environmental impacts resulting from a billion ton bioeconomy

This study is the summation of several analyses to assess the size and benefits of a Billion Ton Bioeconomy, a vision to enable a sustainable market for producing and converting a billion tons of US biomass to bio-based energy, fuels, and products by 2030. Two alternative biomass availability scenarios in 2030, defined as the (i) Business-as-usual (598 million dry tons) and (ii) Billion Ton (1042 million dry tons), establish a range of possible outcomes for the future bioeconomy. The biomass utilized in the current (2014) (365 million dry tons) economy is estimated to displace approximately 2.4% of fossil energy consumption and avoid 116 million tons of CO 2 -equivalent (CO 2 e) emissions, whereas the Billion Ton bioeconomy of 2030 could displace 9.5% of fossil energy consumption and avoid as much as 446 million tons of CO 2 equivalent emissions annually. Developing the integrated systems, supply chains, and infrastructure to efficiently grow, harvest, transport, and convert large quantities of biomass in a sustainable way could support the transition to a low-carbon economy. Bio-based activities in the current (2014) economy are estimated to have directly generated more than 48 billion in revenue and 285 000 jobs. Our estimates show that developing biomass resources and addressing current limitations to achieve a Billion Ton bioeconomy could expand direct bioeconomy revenue by a factor of 5 to contribute nearly 259 billion and 1.1 million jobs to the US economy by 2030.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2022

Catalytic Processes to Accelerate Decarbonization in a Net-Zero Carbon World

Reducing carbon dioxide emissions is one of the critical challenges to mitigate global climate change, which is having detrimental impacts on society and the environment. Fossil fuel combustion in transportation, power generation, and industrial processes is the dominant contributor to carbon emissions. Over the past decades, sustainable solutions and strategies have been investigated and developed to enable decarbonization. Catalysis plays an essential role to address this global challenge by increasing energy efficiency, reducing carbon emissions, capturing carbon dioxide, and utilizing clean energy sources to displace fossil fuels. In this Review, the role of catalysis in reducing energy demand was discussed, enhancing process efficiency, displacing carbon-intensive feedstocks and products, and therefore, reducing carbon emissions. Here, recent advances in catalyst development were summarized, focusing on applications to enhance industrial processes efficiency and enable utilization of clean energy sources. Emerging approaches in catalysis were reviewed, including the manufacture of iron and steel, direct air capture of CO 2 , production of ethylene, ammonia, and sustainable aviation fuels, plastic recycling, and the synthesis of biobased plastics. The Review was concluded with suggested research directions to achieve a carbon net-zero world.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Photon to plate: A holistic view of photosynthetic and anthropogenic energy fluxes

Modern agriculture couples photosynthetic energy with human-applied energy supplements (e.g., fertilizers, labor, cultivation) to feed a growing population. These energy supplements usually come from fossil fuels, presenting an opportunity to decrease fossil fuel required per calorie by improving photosynthetic efficiency. To quantify how improving photosynthetic efficiency would decrease the supplemental energy needed per calorie, we present a “photon to plate” life cycle analysis of energy flows (photosynthetic and human-applied) needed to produce fresh-cut fries. Our results show that photosynthetic inefficiencies require ~80 times the energy used to cultivate, harvest, transport and prepare fries for consumption and that improvements to photosynthesis could reduce the energy applied by humans per calorie by almost 40%. This study highlights the magnitude of energy used during photosynthesis and the potential for photosynthetic improvements to increase agricultural sustainability.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2024

Design Basis Model for Hosting Small Modular Reactors

An aggressive transition from fossil fuels to other types of energy implies the need to construct a large number of nuclear power plants in the near future. However, the real and perceived risks of nuclear energy remain a significant impediment to this transition. This paper describes a comprehensive work process that combines the rigor of model-based systems engineering (MBSE) with 1) the Idaho National Laboratory's (INL) decades of experience with small reactors and with 2) modern project delivery processes. The objective is to reduce the risk of building new facilities or converting existing facilities to nuclear power generation.

42 ENGINEERING↗