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DOE OSTI2025

Effects of Particle Mixing and Gravitational Settling on Charge Transport in Carbon Flow-Electrode Cells

Flowable carbon slurries are actively studied and under development for charge transport in various electrochemical systems including flow capacitors, capacitive deionization cells, semi-solid flow batteries, and lithium extraction. However, much less is known about in operando slurry flow dynamics and their corresponding effect on charge transport. We performed an experimental study of mixing and settling dynamics of slurry electrodes within an electrochemical flow cell during continuous operations. The electrochemical cell consisted of two horizontal co-flowing channels, separated by a cation-exchange membrane (CEM). Here we used high-speed optical imaging of planes parallel to gravity and simultaneous electrochemical measurements. At low flow rates, dense yet dynamic particle beds formed on the bottom electrode in each channel, which unexpectedly yielded the highest currents. This approach enables the operation of the flow cell at low system-average particle concentrations while leveraging gravity-driven particle settling to locally enhance carbon concentrations precisely at the current collector sites. Conversely, high flow rates were characterized by thin particle beds and well-mixed particle flows. In the latter case, the electrodes in closest proximity (located on either side of the CEM) achieved a current higher than the other electrode pairs. The observations have implications for slurry control and electrode designs in electrochemical systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2019

Scaleup of a Single-Mode Microwave Reactor

Widespread use of microwave technology requires quantitative scale-up models. Currently, microwave models are typical qualitative in nature. This work focuses on rendering models quantitative and elucidating the scale-up behavior of microwave heating using numerical simulations. A commonly used bench-scale microwave reactor from the CEM Corp. (CEM Discover SP) is used for benchmarking. To enable quantitative modeling, microwave heating experiments are conducted and compared to COMSOL calculations to develop a calibration curve for the set point vs the actually delivered microwave power. Using the validated computational model, microwave-heating of various liquids in a wide range of vial sizes is investigated. The computational study shows that during the scale-up, the volumetric power absorbed passes through a maximum, whereas the energy efficiency and heating uniformity exhibit strongly nonlinear behavior. As a result, this work introduces a method for quantitative microwave models and insights into the scale-up of commercial microwave reactors.

42 ENGINEERING↗

DOE OSTI2023

Modulation-doping a correlated electron insulator

Abstract Correlated electron materials (CEMs) host a rich variety of condensed matter phases. Vanadium dioxide (VO 2 ) is a prototypical CEM with a temperature-dependent metal-to-insulator (MIT) transition with a concomitant crystal symmetry change. External control of MIT in VO 2 —especially without inducing structural changes—has been a long-standing challenge. In this work, we design and synthesize modulation-doped VO 2 -based thin film heterostructures that closely emulate a textbook example of filling control in a correlated electron insulator. Using a combination of charge transport, hard X-ray photoelectron spectroscopy, and structural characterization, we show that the insulating state can be doped to achieve carrier densities greater than 5 × 10 21 cm −3 without inducing any measurable structural changes. We find that the MIT temperature (T MIT ) continuously decreases with increasing carrier concentration. Remarkably, the insulating state is robust even at doping concentrations as high as ~0.2 e − /vanadium. Finally, our work reveals modulation-doping as a viable method for electronic control of phase transitions in correlated electron oxides with the potential for use in future devices based on electric-field controlled phase transitions.

36 MATERIALS SCIENCE↗

DOE OSTI2024

The cluster decomposition of the configurational energy of multicomponent alloys

Abstract The cluster expansion method (CEM) is a widely used lattice-based technique in the study of multicomponent alloys. Despite its prevalent use, a clear understanding of expansion terms is lacking. We present a modern mathematical formalism of the CEM and introduce thecluster decomposition—a unique and basis-independent decomposition for functions of the atomic configuration in a crystal. We identify the cluster decomposition as an invariant ANOVA decomposition; and demonstrate how functional analysis of variance and sensitivity analysis can be used to interpret interactions among species. Furthermore, we show how the mathematical structure of the cluster decomposition enables numerical evaluation that scales with the number of clusters and is independent of the number of species. Overall, our work enables rigorous interpretations of interactions among species, provides opportunities to explore parameter estimation beyond linear regression, introduces a numerical efficient implementation, and enables analysis of cluster expansions based on established mathematical and statistical principles.

Chemistry↗

DOE OSTI2023

Energy storage solutions to decarbonize electricity through enhanced capacity expansion modelling

To meet ambitious global decarbonization goals, electricity system planning and operations will change fundamentally. With increasing reliance on variable renewable energy resources, energy storage is likely to play a critical accompanying role to help balance generation and consumption patterns. As grid planners, non-profit organizations, non-governmental organizations, policy makers, regulators and other key stakeholders commonly use capacity expansion modelling to inform energy policy and investment decisions, it is crucial that these processes capture the value of energy storage in energy-system decarbonization. Here we conduct an extensive review of literature on the representation of energy storage in capacity expansion modelling. We identify challenges related to enhancing modelling capabilities to inform decarbonization policies and electricity system investments, and to improve societal outcomes throughout the clean energy transition. Additionally, we further identify corresponding research activities that can help overcome these challenges and conclude by highlighting tangible real-world outcomes that will result from pursuing these research activities. Capacity expansion modelling (CEM) approaches need to account for the value of energy storage in energy-system decarbonization. A new Review considers the representation of energy storage in the CEM literature and identifies approaches to overcome the challenges such approaches face when it comes to better informing policy and investment decisions.

25 ENERGY STORAGE↗

DOE OSTI2023

Cecal microbiota composition differs under normal and high ambient temperatures in genetically distinct chicken lines

Modern broilers, selected for high growth rate, are more susceptible to heat stress (HS) as compared to their ancestral jungle fowl (JF). HS affects epithelia barrier integrity, which is associated with gut microbiota. The aim of this study was to determine the effect of HS on the cecal luminal (CeL) and cecal mucosal (CeM) microbiota in JF and three broiler populations: Athens Canadian Random Bred (ACRB), 1995 Random Bred (L1995), and Modern Random Bred (L2015). Broiler chicks were subjected to thermoneutral TN (24 °C) or chronic cyclic HS (8 h/day, 36 °C) condition from day 29 until day 56. HS affected richness in CeL microbiota in a line-dependent manner, decreasing richness in slow-growing JF and ACRB lines, while increasing richness in faster-growing L1995 and L2015. Microbiota were distinct between HS and TN conditions in CeL microbiota of all four lines and in CeM microbiota of L2015. Certain bacterial genera were also affected in a line-dependent manner, with HS tending to increase relative abundance in CeL microbiota of slow-growing lines, while decreases were common in fast-growing lines. Predictive functional analysis suggested a greater impact of HS on metabolic pathways in L2015 compared to other lines.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2023

Mechanism of monovalent and divalent ion mobility in Nafion membrane: An atomistic simulation study

Polymer cation exchange membranes (CEMs) are widely used in water treatment processes. The fundamental factors that control the separation and selectivity of cations with different valences in CEMs are not fully understood. In this study, we use atomistic molecular dynamics simulations to investigate the underlying molecular mechanisms that control the mobility of cations with different valences in Nafion membranes. Our results indicate structural differences in binding of monovalent and divalent cations, which gives rise to differences in ion diffusion in Nafion. Monovalent cations are shown to be “territorially” bound, i.e., bound while partially hydrated, to the fixed charge groups whereas divalent cations are shown to be “site” bound, i.e., bound while fully dehydrated, to the charge groups on the polymer. This difference in binding structure gives rise to differences in transport characteristics of cations in Nafion.

Chemistry↗

DOE OSTI2021

Achieving 5,000-h and 8,000-h Low-PGM Electrode Durability on Automotive Drive Cycles

Whereas total Pt loading in anode and cathode catalysts below 0.125 mg cm −2 is required to meet the stringent cost target for automotive fuel cell systems (FCS) for light duty vehicles, low-loaded cathode catalysts are susceptible to unacceptable aging-related performance losses at high current densities. A framework model, validated by accelerated stress test data, has identified cell voltage, relative humidity (RH) and temperature as the key operating variables that affect degradation of a high-activity d-PtCo/C cathode catalyst with 0.1 mg cm −2 Pt loading. Drive cycle simulations indicate that these can be controlled by properly selecting the minimum FCS power, compressor-expander module (CEM) turndown, and stack coolant temperature. The optimum system parameters are 4-kW e minimum power for an 80-kW e FCS, CEM turndown of 12.5, and 66 °C average coolant exit temperature that combine to limit the maximum cell voltage to 850 mV and outlet RH to 90%–100%. Depending on Pt loading, the mismatch between actual and allowable degradation for 10% power loss over 5,000-h lifetime requires the stack to be oversized by 2.4%–5%, resulting in 8.4%–41% lower Pt utilization and 7.1%–20.5% penalty in stack cost. The corresponding results for 8,000-h lifetime are 10.3%-14% stack oversizing, 23%–51.8% lower Pt utilization, and 24.1%–35.4% stack cost penalty.

08 HYDROGEN↗

DOE OSTI2024

GRid Analysis and Visualization Interface (GRAVI) [SWR-24-16]

GRAVI (GRid Analysis and Visualization Interface) is a web application for viewing and analyzing nodal Production Cost Model (PCM) and Capacity Expansion Model (CEM) simulations. The web application provides the ability to animate geospatially coupled timeseries data in an agnostic way regardless of the underlying simulation tool used to generate the data. GRAVI also provides capabilities to animate non-geospatial data relevant to a PCM or CEM model. Furthermore, this web application can be tailored as an real-time operational tool to better understand a live grid.

Webb, Micah↗

DOE OSTI2026

GAT (Grid Analysis Toolkit) [SWR-25-41]

Grid Analysis Toolkit (GAT) is a unified Python API and plotting for power system PCM and CEM results (Sienna, PLEXOS, ReEDS™). It's a toolkit for wrangling data for Bulk Grid Dispatch and Transmission Analysis. GAT aims to provide simplified access to PCM and CEM results in a standard format while also allowing raw data access to underlying datasets specific to the model. This software can also be found on PyPI at For plotting, GAT defaults to standard National Lab of the Rockies (NLR) color schemes and standard styles while allowing customization.

Webb, Micah [National Laboratory of the Rockies (N↗

DOE OSTI2022

Methods for Translating ReEDS Solutions to Production Cost Modeling Tools

Capacity expansion modeling tools are increasingly being utilized to investigate a wide range of potential future scenarios, particularly with high penetrations of variable and energy-constrained resources that may be operated differently than current dispatch paradigms. While capacity expansion models are particularly adept at making investment decisions for future years, they must make compromises in operational aspects to maintain computational tractability. However, it is of high interest to determine if such future systems would be able to maintain reliability during a variety of grid conditions, and to identify any potential operational challenges for these systems at finer temporal resolution than is typically captured in CEMs. As such, there is value in having an automated tool that can convert many CEM investment pathways into inputs for a more detailed production cost model, in this case the PLEXOS commercial software package. This paper describes the methodology used to make that translation for the NREL-developed ReEDS model, making use of two internally developed tools - PIDG and beetle - along with a set of processing scripts. We describe the current assumptions, data sets, and important operational characteristics of these translations along with an example of the extended analyses that may be done through this connection.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗

DOE OSTI2022

Advanced Hydropower and PSH Capacity Expansion Modeling (Final Report on HydroWIRES D1 Improvements to Capacity Expansion Modeling)

Hydropower and pumped-storage hydropower (PSH) have played a key role in providing flexible, low-carbon electricity to the U.S. electricity system for over a century. As variable generation (VG) deployment increases the demand for flexible, dispatchable generation, it is important to use all available methods for understanding how hydropower and PSH interfaces with VG in a future low-carbon grid. Capacity expansion models (CEMs) of electricity systems are often used to study future electricity scenarios, but these tools often have difficulty representing site- and technology-details of hydropower and PSH due to limited spatial, temporal, or process resolution. This report demonstrates a set of model advancements to improve hydropower and PSH representations in CEMs and other models that consider hydropower and PSH's role in electricity systems. Model advancements include new data integration to define closed-loop PSH resource availability and cost, along with site-level parameterizations of existing PSH capacity and energy storage specifications. Shifting energy across seasons for both hydropower and PSH is explored to demonstrate the potential value of long-duration storage. New representations of hydropower upgrades offer opportunities to increase dispatchability, add pumps, or independently add capacity or energy depending on what is most valuable. New model structures and data are demonstrated individually and in combination to observe their impact on model results and provide initial insights into what is most important for analysts, electricity system planners, and hydropower decision-makers to consider when assessing future roles of hydropower. Improving flexibility of existing hydropower assets has the potential to reduce CO 2 emissions through complementing VG technologies and/or improve electricity system economics by reducing the need to deploy higher-cost systems. Large-scale energy storage is also shown to provide opportunities for balancing seasonal differences in VG, particularly solar photovoltaics (PV). Initial analysis with a new closed-loop PSH resource and cost dataset also demonstrate the potential for new PSH deployment to offer new grid flexibility opportunities. Future analysis and modeling of hydropower's role in the U.S. and other electricity systems could include methodological improvements based on those discussed here along with sensitivity analysis to better represent current and future potential hydropower and PSH flexibility. Improvements to geospatial and site-level data can further improve the understanding of how hydropower and PSH can be upgraded and operated in response to future electricity system needs. This work lays the groundwork to use advanced planning models to explore the range of roles hydropower and PSH can play in the grid of the future.

13 HYDRO ENERGY↗

DOE OSTI2023

Nuclear's Role in the U.S. Electricity System: A Multi-Model Inter-Comparison Analysis

A variety of US electric power sector capacity expansion models are used by decision makers and analysts to evaluate competition among generation, transmission, and storage technologies to meeting the demands of the system. CEMs use least-cost optimization to identify optimal portfolios of investments capable of satisfying all specified requirements. While CEMs are a useful tool to inform pathways to meet future needs, projections can differ significantly between tools for apparently similar scenario assumptions. Differences in model structure, scope, and input assumption contribute to this issue. This work compares model response with harmonization between four modeling teams on issues significant to the representation and development of nuclear energy.

capacity expansion model↗

DOE OSTI2023

Insights on Nuclear Energy from Long-Term System Models: Inter-Model Comparison Results

capacity expansion model↗

DOE OSTI2023

European Union's Action Plan for Power Sector Decarbonisation

A collaborative report from the Clean Energy Ministerial (CEM) on Lessons Learned for Rapid Decarbonization of Power Sectors was delivered to energy ministers and presented at CEM13 in the United States in September 2022. In light of these lessons learned and discussed at CEM13, several countries signaled intent to develop Action Plans for power sector decarbonization that will be presented at CEM14 in India. These action plans complement - but are differentiated from - other international power sector initiatives such as the Breakthrough Agenda - whose broad purpose is to raise collective ambition - and the Global Power System Transformation (G-PST) Consortium - whose goals are to convene power system operators to accelerate research innovations and foster peer learning. These action plans, supported by the 21st Century Power Partnership (21CPP) and other CEM workstreams via direct technical assistance and capacity building, are instead intended to focus on implementation actions given each country's existing power sector goals and activities and are an opportunity for countries to display leadership in power sector decarbonization. These action plans are voluntary, developed by each country individually, and can be viewed as a living document that is subject to change.

decarbonization↗

DOE OSTI2023

Chile's Action Plan for Power Sector Decarbonization

A collaborative report from the Clean Energy Ministerial (CEM) on Lessons Learned for Rapid Decarbonization of Power Sectors was delivered to energy ministers and presented at CEM13 in the United States in September 2022. In light of these lessons learned and discussed at CEM13, several countries signaled intent to develop Action Plans for power sector decarbonization that will be presented at CEM14 in India. These action plans complement but are differentiated from - other international power sector initiatives such as the Breakthrough Agenda whose broad purpose is to raise collective ambition and the Global Power System Transformation (G-PST) Consortium whose goals are to convene power system operators to accelerate research innovations and foster peer learning. These action plans, supported by the 21st Century Power Partnership (21CPP) and other CEM workstreams via direct technical assistance and capacity building, are instead intended to focus on implementation actions given each country's existing power sector goals and activities and are an opportunity for countries to display leadership in power sector decarbonization. These action plans are voluntary, developed by each country individually, and can be viewed as a living document that is subject to change.

Chile↗

DOE OSTI2023

Australia's Action Plan for Power Sector Decarbonisation

A collaborative report from the Clean Energy Ministerial (CEM) on Lessons Learned for Rapid Decarbonization of Power Sectors was delivered to energy ministers and presented at CEM13 in the United States in September 2022. In light of these lessons learned and discussed at CEM13, several countries signaled intent to develop Action Plans for power sector decarbonization that will be presented at CEM14 in India. These action plans complement but are differentiated from other international power sector initiatives such as the Breakthrough Agenda whose broad purpose is to raise collective ambition and the Global Power System Transformation (G-PST) Consortium whose goals are to convene power system operators to accelerate research innovations and foster peer learning. These action plans, supported by the 21st Century Power Partnership (21CPP) and other CEM workstreams via direct technical assistance and capacity building, are instead intended to focus on implementation actions given each country's existing power sector goals and activities and are an opportunity for countries to display leadership in power sector decarbonization. These action plans are voluntary, developed by each country individually, and can be viewed as a living document that is subject to change.

Australia↗

DOE OSTI2023

India's Action Plan for Power Sector Decarbonisation

A collaborative report from the Clean Energy Ministerial (CEM) on Lessons Learned for Rapid Decarbonization of Power Sectors was delivered to energy ministers and presented at CEM13 in the United States in September 2022. In light of these lessons learned and discussed at CEM13, several countries signaled intent to develop Action Plans for power sector decarbonization that will be presented at CEM14 in India. These action plans complement but are differentiated from other international power sector initiatives such as the Breakthrough Agenda whose broad purpose is to raise collective ambition and the Global Power System Transformation (G-PST) Consortium whose goals are to convene power system operators to accelerate research innovations and foster peer learning. These action plans, supported by the 21st Century Power Partnership (21CPP) and other CEM workstreams via direct technical assistance and capacity building, are instead intended to focus on implementation actions given each country's existing power sector goals and activities and are an opportunity for countries to display leadership in power sector decarbonization. These action plans are voluntary, developed by each country individually, and can be viewed as a living document that is subject to change.

decarbonization↗