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DOE OSTI2021

Nondimensional convection numbers modeling thermally stratified storage tanks: Richardson's number and hot-water tanks

Thermally stratified storage tank studies have spanned over 50 years to increase the thermal storage efficiency and accurate prediction of the outlet temperature particularly for solar applications. The studies have reviewed and modeled the jet and plume flow phenomena inside the tank due to the inlet mixing and stratification level. Kelvin–Helmholtz and Rayleigh–Taylor instabilities are the major drivers of the mixing in these tanks. Momentum jets deflecting off walls at the bottom of the tank also create significant mixing. Reviewing Richardson models shows that the categorization was based on the range of Reynolds numbers at the inlet. Unfortunately, the use of superficial velocity in calculating the Richardson number results in critical values in the literature ranging from below 0.25 to 100. The most used length scale associated with these flows is an inertial scale based on the tank height or diameter although the mixing can occur at a relatively smaller scale. The various inlet devices and a large span of flow rates experienced in thermally stratified storage tanks requisite the use of the Reynolds number in combination with a convection number for accurate one dimensional models that predict performance over the long-term. The evaluation of peak shifting of electric loads leveraging renewable sources for applications, including residential hot-water tanks, commercial water tanks, and large-scale chilled water storage tanks, require these models. Finally, this paper is focused on establishing the significance of the convection numbers in conjunction with the Reynolds number for modeling the thermal stratification in storage tanks.

14 SOLAR ENERGY↗

DOE OSTI2017

Energy Storage Sizing Taking Into Account Forecast Uncertainties and Receding Horizon Operation

Energy storage systems (ESS) have the potential to be very beneficial for applications such as reducing the ramping of generators, peak shaving, and balancing not only the variability introduced by renewable energy sources, but also the uncertainty introduced by errors in their forecasts. Optimal usage of storage may result in reduced generation costs and an increased use of renewable energy. However, optimally sizing these devices is a challenging problem. This paper aims to provide the tools to optimally size an ESS under the assumption that it will be operated under a model predictive control scheme and that the forecast of the renewable energy resources include prediction errors. A two-stage stochastic model predictive control is formulated and solved, where the optimal usage of the storage is simultaneously determined along with the optimal generation outputs and size of the storage. Wind forecast errors are taken into account in the optimization problem via probabilistic constraints for which an analytical form is derived. This allows for the stochastic optimization problem to be solved directly, without using sampling-based approaches, and sizing the storage to account not only for a wide range of potential scenarios, but also for a wide range of potential forecast errors. In the proposed formulation, we account for the fact that errors in the forecast affect how the device is operated later in the horizon and that a receding horizon scheme is used in operation to optimally use the available storage.

25 ENERGY STORAGE↗

DOE OSTI2021

Cold ion beam in a storage ring as a platform for large-scale quantum computers and simulators: Challenges and directions for research and development

The purpose of this paper is to evaluate the possibility of constructing a large-scale storage-ring-type ion-trap system capable of storing, cooling, and controlling a large number of ions as a platform for scalable quantum computing (QC) and quantum simulations. In such a trap, the ions form a crystalline beam moving along a circular path with a constant velocity determined by the frequency and intensity of the cooling lasers. In this paper, we consider a large leap forward in terms of the number of ions that serve as qubits in QC, from fewer than 100 available in state of the art linear ion-trap devices today to an order of 10 5 crystallized ions in the storage-ring setup. This new trap design unifies two different concepts: the storage rings of charged particles and the linear ion traps used for QC and mass spectrometry. In this paper, we use the language of particle accelerators to discuss the ion state and dynamics. We outline the differences between the above concepts, analyze challenges of the large ring with a revolving chain of ions, and propose goals for the research and development required to enable future quantum computers with 1000 times more qubits than available today. The challenge of creating such a large-scale quantum system while maintaining the necessary coherence of the qubits and the high fidelity of quantum logic operations is significant. Performing analog quantum simulations may be an achievable initial goal for such a device. Quantum calculations and simulations of complex quantum systems will move forward both the fundamental science and the applied research. Nuclear and particle physics, many-body quantum systems, lattice gauge theories, and nuclear structure calculations are just a few examples in which a large-scale quantum simulation system will become a very powerful tool to move forward our understanding of nature.

36 MATERIALS SCIENCE↗

DOE OSTI2016

Determination of water equivalent content in fuel rods

In water-cooled reactors, hydriding failure of zircaloy cladding tubes can be easily caused by high content of total water in fuel rods. WEC, which is the water equivalent content within the cold space of a fuel rod, directly reflects the total water content of the fuel rod. A device measuring WEC has been designed, manufactured and tested. This extraction device is a hermetically sealed system consisting of six parts: the break-off part, the heating unit, the reduction unit, the sample storage part, the collecting unit and the gas flow system. Each part is connected to another one using a special connection, and the device's end part is connected to a gas chromatograph. The determination procedure can be briefly summarized as follows: first, a test fuel rod should be put into the sealed device after lathing two circular grooves on both ends, so that it can be easily broken at these points in the break-off part. Driven by carrier gas, water and hydrogen both contained in helium gas and absorbed on the rod in-wall pass over the hot uranium filament where water is converted into hydrogen. After being concentrated by the collecting unit, hydrogen flows into the gas chromatograph for measurement and data are calculated as total water content A. UO{sub 2} pellets in the test rod should be taken out from the sample storage part and the total hydrogen content of these pellets is determined according to ASTM C1457 standard, followed by its conversion into total water content B. Finally, the sum of A and B being divided by the free volume of the cold space within the test rod, gives the value of WEC.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2017

Challenges and Opportunities of User-Level File Systemsfor HPC

The performance gap between magnetic disks and data processing on HPC systems has become that huge that an efficient data processing can only be achieved by introducing non-volatile memory (NVRAM) as a new storage tier. Although the benefits of hierarchical storage have been adequately demonstrated to the point that the newest leadership class HPC systems will employ burst buffers, critical questions remain for supporting hierarchical storage systems, including: How should we present hierarchical storage systems to user applications, such that they are easy to use and that application code is portable across systems? How should we manage data movement through a storage hierarchy for best performance and resilience of data? How do the particular I/O use cases mandate the way we manage data? There have been many efforts to explore this space in the form of file systems, with increasingly more implemented at the user level. This is because it is relatively easy to swap in new, specialized user-level file systems for use by applications on a case-by-case basis, as opposed to the current mainstream approach of using general-purpose, system-level file systems which may not be optimized for HPC workloads and must be installed by administrators. In contrast, file systems at the user level can be tailored for specific HPC workloads for high performance and can be used by applications without administrator intervention. Many user-level file system developers have found themselves “having to reinvent the wheel” to implement various optimizations in their file systems. Thus, a main goal of this meeting was to bring together experts in I/O performance, file systems, and storage, and collectively explore the space of current and future problems and solutions for I/O on hierarchical storage systems in order to begin a community effort in enabling user-level file system support for HPC systems. We had a lively week of learning about each other’s approaches as well as unique I/O use cases that can influence the design of a community-driven file and storage system standards. The agenda for this meeting contained talks from participants on the following high level topics: HPC storage and I/O support today; what do HPC users need for I/O; existing userlevel file system efforts; object stores and other alternative storage systems; and components for building user-level file systems. The talks were short and intended to be conversation starters for more in-depth discussions with the whole group. The participants engaged in lengthy discussions on various questions that arose from the talks including: Are we ready to program to a memory hierarchy versus block devices? Are the needs of HPC users reflected in our existing file systems and storage systems? Should we drop or keep POSIX moving forward? What do we mean when we say “user-level file system”? Do we all mean the same thing? How should the IO 500 benchmark be defined so it is fair and useful? and How are stage-in and stage-out actually going to work? The report for this seminar contains a record of the talks from the participants as well as the resulting discussions. Our hope is that the effort initiated during this seminar will result in long-term collaborations that will benefit the HPC community as a whole.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2018

DRILL Interface Makes Ion Soft Landing Broadly Accessible for Energy Science and Applications

Polyoxometalates (POM) have been deposited onto carbon nanotube (CNT) electrodes using benchtop ion soft landing (SL) enabled by a vortex-confined electrohydrodynamic desolvation process. The device is based on the dry ion localization and locomotion (DRILL) mass spectrometry interface of Fedorov and co-workers. By adding electrospray emitters, heating the desolvation gas, and operating at high gas flow rates, it is possible to obtain stable ion currents up to -15 nA that are ideal for deposition. Coupled with ambient ion optics, this interface enables desolvated ions to be delivered to surfaces while excluding solvent and counterions. Electron microscopy of surfaces prepared using the device reveal discrete POM and no aggregation that degrades electrode performance. Characterization of POM-coated CNT electrodes in a supercapacitor showed an energy storage capacity similar to that achieved with SL in vacuum. For solutions that produce primarily a single ion by electrospray ionization, benchtop SL offers a simpler and less costly approach for surface modification with applications in catalysis, energy storage, and beyond.

Johnson, Grant E.↗

DOE OSTI2015

Recent Developments and Trends in Redox Flow Batteries

Stationary energy storage systems are needed to facilitate the widespread integration of intermittent renewable electricity generators, such as solar photovoltaic and wind turbines, and to improve the energy efficiency of the electrical grid. While no single technology can meet all needs, redox flow batteries (RFBs) have shown a favorable balance of cost, safety, and performance for many high-value applications. RFBs are rechargeable electrochemical devices that utilize the reversible redox reactions of two soluble electroactive species for energy storage. A compelling feature of the RFB configuration is the independent scaling of power and energy which enables cost-effective implementation of electrochemical couples with low energy density. Aqueous RFBs have been the subject of the vast majority of research efforts to date, which have yielded industry-level demonstrations. By comparison, non-aqueous RFBs are still in their infancy but have the potential for high energy density due to the extended stability window of non-aqueous electrolytes and the enriched selection of redox materials due to the broad variety of organic solvents. This chapter aims to introduce emerging, potentially transformative, strategies for enhancing RFB technologies through molecular design, electrolyte development, and cell-level engineering. Detailed discussions focus on recent developments in redox active materials (inorganic – aqueous, organic – aqueous, inorganic – non-aqueous, and organic – non-aqueous) and in system design (interdigitated flow fields, semi-solid flow cells, and hybrid flow cells). Future research directions and key challenges for RFB technologies are also highlighted.

Su, Liang↗

DOE OSTI2016

NSLS-II commissioning and operation

The National Synchrotron Light Source II at Brookhaven National Lab is a third-generation synchrotron radiation facility that has been commissioned in 2014. The facility is based on a 3 GeV electron storage ring, which will circulate 500 mA of beam current at 1 nm rad horizontal emittance. The storage ring is 792 meters in circumference and will accommodate more than 60 beamlines in the final built-out. The beamline sources range from insertion-devices located in straight sections, bending magnets or three-pole-wigglers configured in multiple branches. The NSLS-II storage ring commissioning was successfully completed in July 2014 and the facility delivered the first user light on October 23, 2014. Currently the storage ring reached 300 mA beam current and achieved 1 nm rad of horizontal emittance with 3 sets of Damping Wigglers. At this point six NSLS-II project beamlines are routinely taking photons with beam current at 150 mA. This paper reviews the NSLS-II accelerator design and commissioning experience.

43 PARTICLE ACCELERATORS↗

DOE OSTI2022

Elucidating the Determinants of Alkali Ionic Conductivity in Oxide and Sulfide Frameworks

The aim of this project is to elucidate the structural and chemical factors determining alkali conductivity in oxide and sulfide frameworks using large scale first principles calculations and topological analysis. The facile conduction of alkali ions in oxide and sulfide host structures is of critical importance in energy storage. Today, the dominant form of energy storage in portable electronics is the rechargeable alkali-ion battery, a device that functions entirely on the basis of the reversible transport of alkali ions. The Li+/Na+ conductivity of a cathode has a direct influence on the rate capability of a Li/Na-ion battery, i.e., the speed at which it can be charged and discharged. Alkali conductivity is arguably of even greater importance in the solid electrolytes currently being investigated for high safety, high energy all-solid-state batteries. The research performed in this project has provided critical new insights into the diffusion mechanisms in state-of-the-art alkali superionic conductors such as Li 7 P 3 S 11 , Li 3 OCl 1-x Br x anti-perovskite, argyrodite Li 6 PS 5 Cl. Two potential novel lithium superionic conductors (Li 3 Y(PS 4 ) 2 and Li 5 PS 4 Cl 2 ) with improved electrochemical stabilities were predicted. We have also conducted in-depth studies into alkali conduction in several important classes of electrodes, including the layered P2 NaMO 2 oxides and the highly promising novel disordered rock salt Li 3+x V 2 O 5 anode for high-rate applications. This project has resulted in more than 10 peer-reviewed articles in highly regarded journals as well as a new open-source software framework (pymatgen-analysis-diffusion) that is widely used by the materials research community for the study of diffusion in materials.

25 ENERGY STORAGE↗

DOE OSTI2019

Oriented porous LLZO 3D structures obtained by freeze casting for battery applications

All solid-state lithium batteries are, potentially, higher energy density and safer alternatives to conventional lithium-ion batteries (LIBs). These are particularly attractive characteristics for large-scale applications such as electric vehicles and grid energy storage systems. However, the thin film deposition techniques used to make current devices are not readily scalable, and result in low areal capacities, which translate to low practical energy densities. To overcome these deficiencies, it is necessary to design thicker electrodes similar to what are used in LIBs (30–100 μm), in which the active material is composited with an ionic conductor and an electronically conducting additive, to overcome transport limitations. In this paper, we propose a method for making such an electrode, starting with a porous scaffold, i.e. Li 7 La 3 Zr 2 O 12 (LLZO), made by freeze casting, which is then infiltrated with the active material LiNi 0.6 Mn 0.2 Co 0.2 O 2 (NMC-622) and other components. The freeze casting technique results in the formation of oriented channels with low tortuosity, which run roughly parallel to the direction of the current. The scaffolds were characterized with synchrotron X-ray micro-tomography for structural analysis, as well as synchrotron X-ray fluorescence to map the elemental distribution in the infiltrated composite. A hybrid half-cell was constructed and cycled as proof of principle, and it showed good stability. In addition, a bilayer structure consisting of a porous layer combined with a dense LLZO film was successfully made as a prototype of an all solid-state battery. Finally, a mathematical model was established to propose optimized scaffold structures for battery performance.

25 ENERGY STORAGE↗

DOE OSTI2018

Evaluation of a self-regulated in vitro hypoxic system by using chemical reactions

Highlights: • A self-regulated in vitro hypoxic system has been established using chemical reactions. • The chemical reaction was able to sustain the basic requirements of CO{sub 2} and pH levels of cell culture. • The hypoxia box design may provide countless applications for the study of hypoxia. In this study, we established an in vitro hypoxic system driven by a self-regulated chemical reaction that proved effective for cell culture. The hypoxic device was modified from a 1.5 L polypropylene preservation box normally employed for food storage. Pyrogallic acid, sodium hydroxide, and sodium carbonate were dissolved in water and injected into the box. Sodium dihydrogen phosphate solution was injected into the box after 15 min. We measured the concentrations of oxygen and carbon dioxide in the box to determine viability of the hypoxic system. It maintained low levels of oxygen less than 0.2% and stabilizing levels of carbon dioxide at 5% for at least 96 h. Therefore, this device sustained a stable hypoxic environment that may be applicable for cell culture and in vitro studies of hypoxia.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2023

Impact of heating and cooling loads on battery energy storage system sizing in extreme cold climates

Efficient operation of battery energy storage systems requires that battery temperature remains within a specific range. Current techno-economic models neglect the parasitic loads heating and cooling operations have on these devices, assuming they operate at constant temperature. In this work, these effects are investigated considering the optimal sizing of battery energy storage systems when deployed in cold environments. Here, a peak shaving application is presented as a linear programming problem which is then formulated in the PYOMO optimization programming language. The building energy simulation software EnergyPlus is used to model the heating, ventilation, and air conditioning load of the battery energy storage system enclosure. Case studies are conducted for eight locations in the United States considering a nickel manganese cobalt oxide lithium ion battery type and whether the power conversion system is inside or outside the enclosure. The results show an increase of 42% to 300% in energy capacity size, 43% to 217% in power rating, and 43% to 296% increase in capital cost dependent on location. This analysis shows that the heating, ventilation, and air conditioning load can have a large impact on the optimal sizes and cost of a battery energy storage system and merit consideration in techno-economic studies.

25 ENERGY STORAGE↗

DOE OSTI2015

All-optical switching of magnetoresistive devices using telecom-band femtosecond laser

Ultrafast all-optical switching of the magnetization of various magnetic systems is an intriguing phenomenon that can have tremendous impact on information storage and processing. Here, we demonstrate all-optical switching of GdFeCo alloy films using a telecom-band femtosecond fiber laser. We further fabricate Hall cross devices and electrically readout all-optical switching by measuring anomalous Hall voltage changes. The use of a telecom laser and the demonstrated all-optical switching of magnetoresistive devices represent the first step toward integration of opto-magnetic devices with mainstream photonic devices to enable novel optical and spintronic functionalities.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2016

Charge storage and tunneling mechanism of Ni nanocrystals embedded HfO{sub x} film

A nano-floating gate memory structure based on Ni nanocrystals (NCs) embedded HfO{sub x} film is deposited by means of radio-frequency magnetron sputtering. Microstructure investigations reveal that self-organized Ni-NCs with diameters of 4-8 nm are well dispersed in amorphous HfO{sub x} matrix. Pt/Ni-NCs embedded HfO{sub x}/Si/Ag capacitor structures exhibit voltage-dependent capacitance-voltage hysteresis, and a maximum flat-band voltage shift of 1.5 V, corresponding to a charge storage density of 6.0 × 10{sup 12} electrons/cm{sup 2}, is achieved. These capacitor memory cells exhibit good endurance characteristic up to 4 × 10{sup 4} cycles and excellent retention performance of 10{sup 5} s, fulfilling the requirements of next generation non-volatile memory devices. Schottky tunneling is proven to be responsible for electrons tunneling in these capacitors.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2022

Device Voltage Stress from Ground Leakage Current in Medium-Voltage Solid-State Transformer

Grounding related issues are critical for safe and reliable operation of solid-state transformer (SST) in medium-voltage (MV) applications, e.g., solar photovoltaic and energy storage integration, date center, electric vehicle fast charging, etc. This article presents for the first time the issue of additional device voltage stress due to grounding-loop current in current-source SST, using the soft-switching solid-state transformer (S4T) as an example. The S4T features single-stage isolated AC-AC, AC-DC, or DC-DC conversion with full-range ZVS, derived from flyback converter or current-source converter (CSC). However, the flyback operation for CSC-based SST means that magnetizing current flows through the reverse-blocking devices on only one side of the medium-frequency transformer (MFT) at a time. Then, the voltages across the devices, especially those on the other side of the MFT, can be influenced by parasitic current. A parasitic model of a modular S4T (M-S4T) prototype is developed from direct measurements and datasheets. Using the developed parasitic model and equivalent circuits, the causes of the voltage stress are analyzed. A voltage-stress mitigation scheme of connecting additional grounding capacitors is proposed. Damping resistors are also installed to damp out the grounding-loop resonance. A robust parameter design of the proposed scheme is given. The existence of the voltage stress issue and the effectiveness of the proposed scheme are verified experimentally on an MV SiC M-S4T prototype with inherent parameter variations among the five modules in the prototype. Here, both single-module and stacked-module operation are demonstrated during steady state and dynamic conditions up to 4 kV peak.

42 ENGINEERING↗

DOE OSTI2023

Size‐Induced Ferroelectricity in Antiferroelectric Oxide Membranes

Abstract Despite extensive studies on size effects in ferroelectrics, how structures and properties evolve in antiferroelectrics with reduced dimensions still remains elusive. Given the enormous potential of utilizing antiferroelectrics for high‐energy‐density storage applications, understanding their size effects will provide key information for optimizing device performances at small scales. Here, the fundamental intrinsic size dependence of antiferroelectricity in lead‐free NaNbO 3 membranes is investigated. Via a wide range of experimental and theoretical approaches, an intriguing antiferroelectric‐to‐ferroelectric transition upon reducing membrane thickness is probed. This size effect leads to a ferroelectric single‐phase below 40 nm, as well as a mixed‐phase state with ferroelectric and antiferroelectric orders coexisting above this critical thickness. Furthermore, it is shown that the antiferroelectric and ferroelectric orders are electrically switchable. First‐principle calculations further reveal that the observed transition is driven by the structural distortion arising from the membrane surface. This work provides direct experimental evidence for intrinsic size‐driven scaling in antiferroelectrics and demonstrates enormous potential of utilizing size effects to drive emergent properties in environmentally benign lead‐free oxides with the membrane platform.

36 MATERIALS SCIENCE↗

DOE OSTI2019

Machine Learning Applied to a Variable Charge Atomistic Model for Cu/Hf Binary Alloy Oxide Heterostructures [Machine Learning a Variable Charge Atomistic Model for Cu/Hf Binary Alloy Oxide Heterostructures]

Alloy oxide heterostructures are essential for a wide variety of energy applications, including anticorrosion coatings, bifunctional catalysis, energy storage, as well as emerging platforms for multilevel nonvolatile memory and neuromorphic devices. The key role played by oxide composition, density, and stoichiometry in governing electrochemical reactions, interface structure, and ionic transport in alloy oxides remains largely unknown. This is primarily due to the lack of variable charge interatomic potential models that can adequately describe the various atomic/ionic interactions in alloy oxides within a unified framework. Here, we introduce a charge transfer ionic potential (CTIP) model for Cu/Hf/O alloy system and demonstrate its ability to accurately capture the complex potential energy surface owing to dynamically varying interactions, including metallic (Cu/Hf), ionic (Cu/Hf/Ox), mixed environment (interfaces). We leverage supervised machine learning methods powered by genetic algorithms coupled with local simplex optimization to efficiently navigate through a high-dimensional parameter space and identify an optimum set of an independent set of CTIP parameters. We train our model against an extensive first-principles based data set that includes lattice constants, cohesive energies, equations of state, and elastic constants of various experimentally observed polymorphs of hafnia, copper oxide, hafnium, as well as copper. Our machine-learned CTIP model captures the structure, elastic properties, thermodynamics, and energetic ordering of various polymorphs. It also accurately predicts the surface properties of both oxides and their metals. To demonstrate the suitability of our CTIP model for investigating dynamic processes, we employed it to identify the atomistic scale mechanisms associated with the initial nanoscale oxidation and surface oxide growth on Cu-doped hafnia surfaces. Here, our machine-learned CTIP model can be used to probe the dynamic response of Cu/Hf/O alloy interfaces subjected to external stimuli (e.g., electric field, pressure, temperature, strain, etc.) and a variety of atomistic phenomena including the dynamics of switching in emerging neuromorphic platforms.

36 MATERIALS SCIENCE↗

DOE OSTI2015

Core–Shell CdS–Cu 2 S Nanorod Array Solar Cells

As an earth-abundant p-type semiconductor, copper sulfide (Cu 2 S) is an attractive material for application in photovoltaic devices. However, it suffers from a minority carrier diffusion length that is less than the length required for complete light absorption. Core–shell nanowires and nanorods have the potential to alleviate this difficulty because they decouple the length scales of light absorption and charge collection. To achieve this geometry using Cu 2 S, cation exchange was applied to an array of CdS nanorods to produce well-defined CdS–Cu 2 S core–shell nanorods. Previous work has demonstrated single-nanowire photovoltaic devices from this material system, but in this work, the cation exchange chemistry has been applied to nanorod arrays to produce ensemble-level devices with microscale sizes. The core–shell nanorod array devices show power conversion efficiencies of up to 3.8%. In addition, these devices are stable when measured in air after nearly one month of storage in a desiccator. Furthermore, these results are a first step in the development of large-area nanostructured Cu 2 S-based photovoltaics that can be processed from solution.

14 SOLAR ENERGY↗