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DOE OSTI2021

OPFLearn.jl [SWR-21-109]

OPFLearn.jl is a Julia package for creating datasets for machine learning approaches to solving AC optimal power flow (AC OPF). It was developed to provide researchers with a standardized way to efficiently create AC OPF datasets that are representative of more of the AC OPF feasible load space compared to typical dataset creation methods. The OPFLearn dataset creation method uses a relaxed AC OPF formulation to reduce the volume of the unclassified input space throughout the dataset creation process. Over time this input space tightens around the relaxed AC OPF feasible region to increase the percentage of feasible load profiles found while uniformly sampling the input space. Load samples are processed using AC OPF formulations from PowerModels.jl. More information on the dataset creation method can be found in our publication, "OPF-Learn: An Open-Source Framework for Creating Representative AC Optimal Power Flow Datasets". To use OPFLearn.jl a PowerModels network data dictionary is required (can be loaded from Matpower ".m" files) to define the network the dataset is being created for.

Joswig-Jones, Trager↗

DOE OSTI2023

Experimental Evaluation of Refrigerant Leak Characteristics for Different HVAC&R Equipment Types–Phase 2

The US Department of Energy (DOE) Building Technology Office (BTO) and the Air-conditioning, Heating & Refrigeration Technology Institute (AHRTI) collaborated to sponsor an experimental study of refrigerant leak characteristics at Oak Ridge National Laboratory (ORNL); AHRTI project 9012. The project has been conducted in two phases with objectives to conduct refrigerant leak tests on several heating, ventilating, air-conditioning and refrigeration (HVAC&R) systems under operating conditions representative of actual applications to document the pressure decay rate and the mass flow rate of leaked refrigerant as a function of time. Phase 1 of the project ran from late 2017 to late 2018 with refrigerant leaks imposed on five systems and the collection of data to meet the project objectives. Systems chosen covered three air-conditioning (AC) applications (packaged terminal AC or PTAC, 3-ton residential split system AC, and 5-ton packaged rooftop AC) and two refrigeration applications (split system unit cooler, and standalone display case). AHRTI members donated the test systems used for the project. The systems were tested at two different leak rates (catastrophic high rate simulating full line break and a lower flow rate), two leak locations (high-pressure side and low-pressure side), and two operating conditions (compressor ON or OFF). Phase 1 results were summarized in a project report by Baxter, et al. (2019)1. The leak rates imposed in Phase 1 led to much more rapid charge releases than the more typical much slower rates seen in practice that would take days, weeks, or months to empty a system of its entire charge. For Phase 2, the project sponsors asked that the “higher” leak rate target a total charge release time of about 4 min. This was intended to represent a “reasonable” worst case release scenario to match the refrigerant leak rate assumption used in the International Electrotechnical Commission (IEC) standard IEC 60335-2-40 (2016 version [IEC 2016]. A charge release time of about 20–40 min (leak release rate 5 to 10 times lower than higher rate) was targeted for the “lower” leak rate. This report provides a summary of the Phase 2 effort. Two additional HVAC systems were selected for testing in this phase. First was a multi-split air-conditioning (MS-AC) system with one outdoor section and two indoor units and a nameplate refrigerant charge of 1.75 kg (3.86 lb.) of R-410A. The MS-AC was tested in cooling only or AC operation. Second was a split system heat pump coupled to two different representative supply duct systems (HP-duct) and a nameplate charge of 3.83 kg (8.44 lb.) of R-410A. This system was tested in both space heating and AC modes. As in Phase 1 of the project, all tests were conducted using R-410A.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2021

Integration of Air Classification and Hydrothermal Carbonization to Enhance Energy Recovery of Corn Stover

Air classification (AC) is a cost-effective technology that separates the energy-dense light ash fraction (LAF) from the inorganic-rich high ash fraction (HAF) of corn stover. HAF could be upgraded into energy-dense solid fuel by hydrothermal carbonization (HTC). However, HTC is a high-temperature, high-pressure process, which requires additional energy to operate. In this study, three different scenarios (i.e., AC only, HTC only, and integrated AC–HTC) were investigated for the energy recovery of corn stover. AC was performed on corn stover at an 8 Hz fan speed, which yielded 84.4 wt. % LAF, 12.8 wt. % HAF, and 2.8 wt. % below screen particles. About 27 wt. % ash was reduced from LAF by the AC process. Furthermore, HTC was performed on raw corn stover and the HAF of corn stover at 200, 230, and 260 °C for 30 min. To evaluate energy recovery, solid products were characterized in terms of mass yield, ash yield, ultimate analysis, proximate analyses, and higher heating value (HHV). The results showed that the energy density was increased with the increase in HTC temperature, meanwhile the mass yield and ash yield were decreased with the increase in HTC temperature. Proximate analysis showed that fixed carbon increased 18 wt. % for original char and 27 wt. % for HAF char at 260 °C, compared to their respective feedstocks. Finally, the hydrochar resulting from HAF was mixed with LAF and pelletized at 180 bar and 90 °C to densify the energy content. An energy balance of the integrated AC–HTC process was performed, and the results shows that integrated AC with HTC performed at 230 °C resulted in an additional 800 MJ/ton of energy recovery compared to the AC-only scenario.

09 BIOMASS FUELS↗

DOE OSTI2021

OPFLearn.jl v0.1.2 5/18/2023 [SWR-21-109]

Joswig-Jones, Trager↗

DOE OSTI2020

Materials Data on AcTh3 by Materials Project

Th3Ac is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are three inequivalent Th sites. In the first Th site, Th is bonded to eight Th and four equivalent Ac atoms to form ThAc4Th8 cuboctahedra that share corners with four equivalent AcTh12 cuboctahedra, corners with fourteen ThAc4Th8 cuboctahedra, edges with six equivalent AcTh12 cuboctahedra, edges with twelve ThAc4Th8 cuboctahedra, faces with four equivalent AcTh12 cuboctahedra, and faces with sixteen ThAc4Th8 cuboctahedra. There are a spread of Th–Th bond distances ranging from 3.54–3.78 Å. There are two shorter (3.66 Å) and two longer (3.72 Å) Th–Ac bond lengths. In the second Th site, Th is bonded to eight equivalent Th and four equivalent Ac atoms to form ThAc4Th8 cuboctahedra that share corners with four equivalent AcTh12 cuboctahedra, corners with fourteen ThAc4Th8 cuboctahedra, edges with six equivalent AcTh12 cuboctahedra, edges with twelve equivalent ThAc4Th8 cuboctahedra, faces with four equivalent AcTh12 cuboctahedra, and faces with sixteen ThAc4Th8 cuboctahedra. There are two shorter (3.66 Å) and two longer (3.72 Å) Th–Ac bond lengths. In the third Th site, Th is bonded to eight equivalent Th and four equivalent Ac atoms to form ThAc4Th8 cuboctahedra that share corners with four equivalent AcTh12 cuboctahedra, corners with fourteen ThAc4Th8 cuboctahedra, edges with six equivalent AcTh12 cuboctahedra, edges with twelve equivalent ThAc4Th8 cuboctahedra, faces with four equivalent AcTh12 cuboctahedra, and faces with sixteen ThAc4Th8 cuboctahedra. There are two shorter (3.66 Å) and two longer (3.72 Å) Th–Ac bond lengths. Ac is bonded to twelve Th atoms to form AcTh12 cuboctahedra that share corners with six equivalent AcTh12 cuboctahedra, corners with twelve ThAc4Th8 cuboctahedra, edges with eighteen ThAc4Th8 cuboctahedra, faces with eight equivalent AcTh12 cuboctahedra, and faces with twelve ThAc4Th8 cuboctahedra.

36 MATERIALS SCIENCE↗

DOE OSTI2023

Regulating the properties of activated carbon for supercapacitors: impact of particle size and degree of aromatization of hydrochar

Hydrochar (HC), obtained by the hydrothermal carbonization (HTC) of biomass, is an excellent precursor for preparing activated carbon (AC). However, the effects of the intrinsic properties of HC on the microstructure and electrochemical properties of AC are largely unknown. Here, this study investigates the impact of particle size and the degree of aromatization of in-situ HC on the microstructure and electrochemical properties of AC. Our results show that a large particle size and a high degree of aromatization help protect the HC from overactivation by ZnCl 2 , resulting in an large specific surface area (SSA > 2000 m 2 /g) and high mesopore to micropore volume ratio value ( V mes /V mic > 0.3) of the AC. Electrochemical performance measurements show a maximum specific capacitance of 218 F/g at 0.5 A/g was achieved in all samples where the AC (AC180-10 h) was prepared by activating HC180-10 h with a large size, a high degree of aromatization, and abundant surface oxygen-containing functional groups. After AC180-10 h was assembled into a supercapacitor, the specific capacitance of AC180-10 h still reached 158 F/g at 0.5 A/g, and it showed excellent cycling stability. This study advances the understanding of the impact of HC particle size and degree of aromatization on AC properties, providing new insights into tailoring HC qualities so that improving improve the properties of AC.

36 MATERIALS SCIENCE↗

DOE OSTI2026

Toward Rapid Actinium-225 Purification via Membrane Adsorbers with Covalently Tethered Diglycolamide Ligands

Extractive diglycolamide (DGA) resins are used in several state-of-the-art techniques for purifying 225 Ac, a promising radiometal for targeted alpha therapy. Unfortunately, separation processes that rely on resins are often limited to slow flow rates, high elution volumes, and long processing times. Membrane adsorbers functionalized with DGA ligands are an alternative separation material that may overcome these challenges. This work presents (1) the synthesis of an aminated tetrahexyldiglycolamide ligand, (2) the covalent tethering of the ligand to electrospun poly(vinylbenzyl chloride) fiber mats, and (3) the adsorption and desorption of La(III) and 225 Ac. Chemical and physical characterization supports the covalent tethering of the ligand to the fiber mat, as well as the preservation of the fiber surface area and porosity after functionalization. Equilibrium adsorption experiments were performed with stable La(III) and radioactive 225 Ac. Trends in affinity are consistent between commercial resins and the synthesized membrane adsorbers; however, the Langmuir constants and the maximum binding capacity of the membrane adsorbers were generally lower than the resins. Despite these differences, the modeled selectivity for an equimolar solution of La(III)/ 225 Ac in 10 M nitric acid is 57. Furthermore, 225 Ac is rapidly desorbed from the fibers in 10 M nitric acid (<20 min). The La(III)/ 225 Ac selectivity and rapid 225 Ac desorption indicate this class of materials is promising for rapid radioanalytical separations.

07 ISOTOPE AND RADIATION SOURCES↗

DOE OSTI2020

Structural evolution of amorphous calcium sulfate nanoparticles into crystalline gypsum phase

The involvement of amorphous calcium sulfate (ACS) as a precursor to calcium sulfate crystallization remains an important but poorly understood phenomenon, especially the mechanism by which ACS evolves into crystalline phase. In this study, we captured the ACS nanoparticles as a precursor to calcium sulfate crystallization in a concentrated CaCl 2 solution at 90 °C and observed several stages of its evolution. The ACS nanoparticles grew by simultaneous fusion and internal structural evolution. Aggregation of the ACS nanoparticles gave birth to bulk ACS particles within which nanocrystalline domains sprouted and developed into crystalline gypsum. This work deepens the understanding of the evolution of ACS nanoparticles and its role in multistage crystallization of calcium sulfate.

36 MATERIALS SCIENCE↗

DOE OSTI2024

Controlled skyrmion ratchet in linear protrusion defects

Using atomistic simulations, we investigate the dynamical behavior of a single skyrmion interacting with an asymmetric linear protrusion array under external ac driving. The linear protrusion array is placed in the xy plane and is composed of magnetic walls near the edge of the nanotrack that have angled linear protrusions into the nanotrack. The structure forms a hard axis for –x direction motion and an easy axis for +x direction motion. When the ac drive is applied along the x direction, the skyrmion moves along the hard direction of the substrate asymmetry in three phases: a pinned phase with localized skyrmion orbits, a constant velocity phase where the orbits become delocalized, and a reentrant pinned phase with larger localized orbits. We measure the dependence of the skyrmion velocity on the frequency and amplitude of the ac drive. All three phases appear for all frequency values simulated here, and in the constant velocity phase the skyrmion velocity depends only on the frequency and not on the amplitude of the ac drive. When ac driving is applied in the y direction, the skyrmion moves along the easy direction of the substrate asymmetry and exhibits the same three phases as for x-direction driving along with a fourth phase which, at high driving frequencies, consists of a series of constant velocity phases, each with different average skyrmion velocities. For low frequencies, the constant velocity phase is lost and the skyrmion speed increases linearly with increasing ac drive amplitude due to a Magnus boost effect. Finally, our findings suggest new ways to create reliable data transport for spintronic devices using skyrmions as information carriers, where the skyrmion direction and speed can be controlled by varying only the ac drive amplitude and frequency.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2026

A Co-Simulation Framework for Steady-State Analyses of Multiple Droop-based MTdc Grids in Continental-Scale Systems

The growing scale and complexity of planning continental hybrid ac and multi-terminal dc (MTdc) systems require scalable steady-state modeling and analysis approaches not currently available in commercial tools. This paper presents a comprehensive multi-fidelity model-conversion framework that enables the efficient transition of MTdc grid models from production cost modeling (PCM) and approximated ac power flow to detailed ac–MTdc power flow for large-scale planning studies. The core of this framework is a scalable co-simulation approach that, for the first time, enables power flow analysis in continental-scale ac–MTdc systems. It seamlessly couples commercial ac solvers with a detailed MTdc grid model that incorporates droop-based control and current-limiting strategies of multiple meshed MTdc grids. Leveraging this capability, an evaluation framework to systematically assess and compare different MTdc power redispatch strategies under ac and dc contingencies is introduced. The proposed framework and algorithm are evaluated using a combined Western and Eastern Interconnection system with 11 MTdc grids of various sizes, showing a coherent transition from PCM to detailed ac–MTdc power flow and improved system performance in voltage regulation and line overload mitigation following typical contingencies.

Nguyen, Quan H.↗

DOE OSTI2024

The Role of Lignin Molecular Weight on Activated Carbon Pore Structure

Over the past decade, the production of biofuels from lignocellulosic biomass has steadily increased to offset the use of fuels from petroleum. To make biofuels cost-competitive, however, it is necessary to add value to the “ligno-” components (up to 30% by mass) of the biomass. The properties of lignin, in terms of molecular weight (MW), chemical functionality, and mineral impurities often vary from biomass source and biorefinery process, resulting in a challenging precursor for product development. Activated carbon (AC) is a feasible target for the lignin-rich byproduct streams because it can be made from nearly any biomass, and it has a market capacity large enough to use much of the lignin generated from the biorefineries. However, it is not known how the variability in the lignin affects the key properties of AC, because, until now, they could not be well controlled. In this work, various fractions of ultraclean (<0.6% ash) lignin are created with refined MW distributions using Aqueous Lignin Purification using Hot Agents (ALPHA) and used as precursors for AC. AC is synthesized via zinc chloride activation and characterized for pore structure and adsorption capacity. We show that AC surface area and the adsorption capacity increase when using lignin with increasing MW, and, furthermore, that reducing the mineral content of lignin can significantly enhance the AC properties. The surface area of the AC from the highest MW lignin can reach ~1830 m2/g (absorption capacity). Furthermore, single step activation carbonization using zinc chloride allows for minimal carbon burn off (<30%), capturing most of the lignin carbon compared to traditional burn off methods in biorefineries for heat generation.

Biochemistry & Molecular Biology↗

DOE OSTI2023

System and method for collecting and isolating radiosotopes

A method for obtaining 225 AC from 225 Ra having the steps of assembling a column having an inorganic stationary phase; priming the column to immobilize 226 Ra 225 Ra and natural decay products therefrom; immobilizing the 226 Ra, 225 Ra, 224 Ra, and natural decay products therefrom onto a stationary phase within the column; and eluting the column containing the 225 Ra with an aqueous sulfate solution to obtain a milking effluent that contains 225 AC. Also provided is a method for obtaining pure 225 AC from its isotope parents, the method comprising assembling a column having a stationary phase comprising an inorganic material; priming the column with the isotope parents to immobilize 225 Ac, and natural decay products of 225 AC; immobilizing the 225 Ac, and natural decay products therefrom onto the stationary phase within the column 226 Ra, 225 Ra, 224 Ra; and eluting the column containing the 225 AC to obtain an effluent that contains the isotope parents.

Brown, Michael A.↗

DOE OSTI2020

Materials Data on Ac3Yb by Materials Project

Ac3Yb is Magnesium-derived structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Ac is bonded to eight equivalent Ac and four equivalent Yb atoms to form AcAc8Yb4 cuboctahedra that share corners with four equivalent YbAc12 cuboctahedra, corners with fourteen equivalent AcAc8Yb4 cuboctahedra, edges with six equivalent YbAc12 cuboctahedra, edges with twelve equivalent AcAc8Yb4 cuboctahedra, faces with four equivalent YbAc12 cuboctahedra, and faces with sixteen equivalent AcAc8Yb4 cuboctahedra. There are a spread of Ac–Ac bond distances ranging from 3.94–3.98 Å. There are two shorter (3.94 Å) and two longer (3.98 Å) Ac–Yb bond lengths. Yb is bonded to twelve equivalent Ac atoms to form YbAc12 cuboctahedra that share corners with six equivalent YbAc12 cuboctahedra, corners with twelve equivalent AcAc8Yb4 cuboctahedra, edges with eighteen equivalent AcAc8Yb4 cuboctahedra, faces with eight equivalent YbAc12 cuboctahedra, and faces with twelve equivalent AcAc8Yb4 cuboctahedra.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on NaAc by Materials Project

NaAc crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Na is bonded to six equivalent Na and six equivalent Ac atoms to form NaNa6Ac6 cuboctahedra that share corners with eighteen equivalent NaNa6Ac6 cuboctahedra, edges with six equivalent NaNa6Ac6 cuboctahedra, edges with twelve equivalent AcNa6Ac6 cuboctahedra, faces with eight equivalent NaNa6Ac6 cuboctahedra, and faces with twelve equivalent AcNa6Ac6 cuboctahedra. All Na–Na bond lengths are 3.88 Å. All Na–Ac bond lengths are 3.96 Å. Ac is bonded to six equivalent Na and six equivalent Ac atoms to form AcNa6Ac6 cuboctahedra that share corners with eighteen equivalent AcNa6Ac6 cuboctahedra, edges with six equivalent AcNa6Ac6 cuboctahedra, edges with twelve equivalent NaNa6Ac6 cuboctahedra, faces with eight equivalent AcNa6Ac6 cuboctahedra, and faces with twelve equivalent NaNa6Ac6 cuboctahedra. All Ac–Ac bond lengths are 3.88 Å.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on CaAc3 by Materials Project

CaAc3 is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Ca is bonded to twelve equivalent Ac atoms to form CaAc12 cuboctahedra that share corners with six equivalent CaAc12 cuboctahedra, corners with twelve equivalent AcCa4Ac8 cuboctahedra, edges with eighteen equivalent AcCa4Ac8 cuboctahedra, faces with eight equivalent CaAc12 cuboctahedra, and faces with twelve equivalent AcCa4Ac8 cuboctahedra. There are six shorter (3.95 Å) and six longer (4.00 Å) Ca–Ac bond lengths. Ac is bonded to four equivalent Ca and eight equivalent Ac atoms to form AcCa4Ac8 cuboctahedra that share corners with four equivalent CaAc12 cuboctahedra, corners with fourteen equivalent AcCa4Ac8 cuboctahedra, edges with six equivalent CaAc12 cuboctahedra, edges with twelve equivalent AcCa4Ac8 cuboctahedra, faces with four equivalent CaAc12 cuboctahedra, and faces with sixteen equivalent AcCa4Ac8 cuboctahedra. There are a spread of Ac–Ac bond distances ranging from 3.96–4.01 Å.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Ac3Th by Materials Project

ThAc3 is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Th is bonded to twelve equivalent Ac atoms to form ThAc12 cuboctahedra that share corners with six equivalent ThAc12 cuboctahedra, corners with twelve equivalent AcAc8Th4 cuboctahedra, edges with eighteen equivalent AcAc8Th4 cuboctahedra, faces with eight equivalent ThAc12 cuboctahedra, and faces with twelve equivalent AcAc8Th4 cuboctahedra. There are six shorter (3.85 Å) and six longer (3.89 Å) Th–Ac bond lengths. Ac is bonded to four equivalent Th and eight equivalent Ac atoms to form AcAc8Th4 cuboctahedra that share corners with four equivalent ThAc12 cuboctahedra, corners with fourteen equivalent AcAc8Th4 cuboctahedra, edges with six equivalent ThAc12 cuboctahedra, edges with twelve equivalent AcAc8Th4 cuboctahedra, faces with four equivalent ThAc12 cuboctahedra, and faces with sixteen equivalent AcAc8Th4 cuboctahedra. There are a spread of Ac–Ac bond distances ranging from 3.80–3.98 Å.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Ac3La by Materials Project

Ac3La is Magnesium-derived structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Ac is bonded to eight equivalent Ac and four equivalent La atoms to form AcAc8La4 cuboctahedra that share corners with four equivalent LaAc12 cuboctahedra, corners with fourteen equivalent AcAc8La4 cuboctahedra, edges with six equivalent LaAc12 cuboctahedra, edges with twelve equivalent AcAc8La4 cuboctahedra, faces with four equivalent LaAc12 cuboctahedra, and faces with sixteen equivalent AcAc8La4 cuboctahedra. There are a spread of Ac–Ac bond distances ranging from 3.93–3.99 Å. There are two shorter (3.92 Å) and two longer (3.96 Å) Ac–La bond lengths. La is bonded to twelve equivalent Ac atoms to form LaAc12 cuboctahedra that share corners with six equivalent LaAc12 cuboctahedra, corners with twelve equivalent AcAc8La4 cuboctahedra, edges with eighteen equivalent AcAc8La4 cuboctahedra, faces with eight equivalent LaAc12 cuboctahedra, and faces with twelve equivalent AcAc8La4 cuboctahedra.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Ac3Sm by Materials Project

Ac3Sm is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Ac is bonded to eight equivalent Ac and four equivalent Sm atoms to form AcAc8Sm4 cuboctahedra that share corners with four equivalent SmAc12 cuboctahedra, corners with fourteen equivalent AcAc8Sm4 cuboctahedra, edges with six equivalent SmAc12 cuboctahedra, edges with twelve equivalent AcAc8Sm4 cuboctahedra, faces with four equivalent SmAc12 cuboctahedra, and faces with sixteen equivalent AcAc8Sm4 cuboctahedra. There are a spread of Ac–Ac bond distances ranging from 3.89–3.98 Å. There are two shorter (3.88 Å) and two longer (3.93 Å) Ac–Sm bond lengths. Sm is bonded to twelve equivalent Ac atoms to form SmAc12 cuboctahedra that share corners with six equivalent SmAc12 cuboctahedra, corners with twelve equivalent AcAc8Sm4 cuboctahedra, edges with eighteen equivalent AcAc8Sm4 cuboctahedra, faces with eight equivalent SmAc12 cuboctahedra, and faces with twelve equivalent AcAc8Sm4 cuboctahedra.

36 MATERIALS SCIENCE↗