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DOE OSTI2012

Thermoelectric energy harvesting from diurnal heat flow in the upper soil layer

We built and tested a subterranean thermoelectric power source that converts diurnal heat flow through the upper soil layer into electricity. This paper describes the operation, design, and performance of the device. Key features of the power source include the use of bismuth-telluride thermopiles optimized for small ΔT and aerogel insulation to minimize thermal losses. The device weighs 0.24 kg and was designed with a flat form factor measuring 12 × 12 × 1.7 cm to facilitate modularity, packing, and assembly into larger arrays. One full year of field testing was performed between June 2009 and May 2010 in Albuquerque, New Mexico where the device generated an average power output of 1.1 mW. The season with the highest performance was spring (March–May) while the season of lowest performance was winter (November–January). During May 2010, the device generated an average power of 1.5 mW and a peak power of 9.8 mW at 9.3 V. Ten years of continuous operation at 1.1 mW would yield an energy density and specific energy of 1384 W h/L and 1430 W h/kg respectively, which is competitive with chemical batteries and is orders of magnitude greater than published subterranean and ambient thermoelectric harvesters. Numerical simulations show that performance is sensitive to the thermal properties of the soil and environmental conditions. This class of energy harvester may provide an option for supplemental power, or possibly primary power, for low power remote sensing applications.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2018

Gelation of plasmonic metal oxide nanocrystals by polymer-induced depletion attractions

Significance Self-supported gelation of optically active nanocrystals offers a modular pathway to harness optoelectronic functionality in multiscale materials by directly controlling volume fraction, bonding, and structure during assembly. We combine depletion attractions that emerge from the incorporation of small polymer chains and electrostatic repulsions to induce the gelation of isotropic metal oxide nanocrystals. We develop a theoretical model to assess our experimental fluid-to-gel-phase progression observations. By preventing nanocrystal fusion during network assembly, we achieve gels with a strong near-infrared absorption, reminiscent of the inherent near-infrared localized surface plasmon resonance of the nanocrystal building blocks.

Saez Cabezas, Camila A.↗

DOE OSTI2015

The long road to groundwater RODs on the ORR: development of a regional groundwater model - 15632

This paper describes the first year of planning and development for the Oak Ridge Reservation (ORR) regional groundwater flow model (ORGFM). The first stage involved the creation of a groundwater model Technical Advisory Group (TAG), made up of local and national industry experts to support the model development. As a first step in the model development process, a smaller-scale model (a Test Case Model) is being developed to test the modeling tools and approach being considered for the regional model. The Test Case Model is allowing the team to identify and develop work-flow processes on a small scale prior to developing the large, regional-scale model. The modeling team currently is testing the combined use of EarthVision{sup R} and MODFLOW-USG (a modular finite-difference flow model using un-structured grids) to develop the regional-scale model. It is anticipated that the ORGFM will be completed by 2016. This paper presents the progress of the ORGFM model development. (authors)

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2014

Generalized Master Equation with Non-Markovian Multichromophoric Förster Resonance Energy Transfer for Modular Exciton Densities

A generalized master equation (GME) governing quantum evolution of modular exciton density (MED) is derived for large scale light harvesting systems composed of weakly interacting modules of multiple chromophores. The GME-MED offers a practical framework to incorporate real time coherent quantum dynamics calculations of small length scales into dynamics over large length scales, and also provides a non-Markovian generalization and rigorous derivation of the Pauli master equation employing multichromophoric Förster resonance energy transfer rates. A test of the GME-MED for four sites of the Fenna-Matthews-Olson complex demonstrates how coherent dynamics of excitonic populations over coupled chromophores can be accurately described by transitions between subgroups (modules) of delocalized excitons. Application of the GME-MED to the exciton dynamics between a pair of light harvesting complexes in purple bacteria demonstrates its promise as a computationally efficient tool to investigate large scale exciton dynamics in complex environments.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2020

Chespa: Streamlining Expansive Chemical Space Evaluation of Molecular Sets

Thousands of chemical properties can be calculated for small molecules, which can be used to place the molecules within the context of a broader “chemical space.” These definitions vary based on compounds of interest and the goals for the given chemical space definition. Here, we introduce a customizable (i.e., modular) Python module, chespa, built to easily assess different chemical space definitions through cluster-ing of compounds in these spaces and visualize trends of these clusters. To demonstrate this, chespa currently streamlines prediction of vari-ous molecule descriptors (predicted chemical properties, molecular substructures, AI-based chemical space, and chemical class ontology) in order to test 6 different chemical space definitions. Furthermore, we investigated how these varying definitions trend with mass spectrometry (MS)-based observability, i.e., the ability of a molecule to be observed with MS (e.g., as a function of the molecule ionizability), using an example data set from the U.S. EPA's Non-Targeted Analysis Collaborative Trial (ENTACT), where blinded samples had been analyzed previously, providing 1,398 data points. Improved understanding of observability would offer many advantages in small molecule identifica-tion, such as (i) a priori selection of experimental conditions based on suspected sample composition, (ii) the ability to reduce the number of candidate structures during compound identification by removing those less likely to ionize, and, in turn, (iii) a reduced false discovery rate and increased confidence in identifications. Factors controlling observability are not fully understood, making prediction of this property non-trivial and a prime candidate for chemical space analysis. Chespa is available at github.com/pnnl/chespa.

Nunez, Jamie↗

DOE OSTI2020

Modeling and Harmonic Stability of MMC-HVDC With Passive Circulating Current Filters

A modular multilevel converter (MMC) is an emerging converter technology widely used in wind power applications using high-voltage direct current (HVDC) transmission, and it has been largely investigated in medium-voltage solar harvesting as well as electric motor drives. Different from studies dealing with active circulating current control loops, this paper focuses on impedance modeling and harmonic stability studies for MMCs with passive circulating current filters (PCCFs). A power stage circuit including a PCCF is transformed and remodeled to obtain small-signal formulations. This transformation leads to additional high-order matrix computing complexity due to the added impedance subnetwork matrix from the PCCF as well as relevant crossed-frequency impacts. To simplify the computational burden, the proposed model aims to solve one arm equation instead of all six MMC arm equations. To achieve this result, additional challenges occur when the MMC is connected to a renewable energy source instead of the grid voltage, where low-level zero-sequence components might exist in the neutral point of three phases, especially in the case of no integrated advanced modular voltage balancing control, which prevents computational simplification. To overcome this challenge, further impedance matrix adjustments are conducted in this paper to theoretically suppress the impact of zero-sequence harmonics when obtaining small-signal impedance, taking into account the frequency coupling effect. Finally, simulations are carried out to validate the developed impedance model under different operating scenarios. Harmonic stability case studies of MMCs with PCCFs connected to renewable energy current sources are also presented, where frequency-domain stability analyses based on Bode diagrams are compared to time-domain simulation waveforms and FFTs, which validate the effectiveness of the proposed impedance model.

24 POWER TRANSMISSION AND DISTRIBUTION↗

DOE OSTI2016

Modular Chemical Process Intensification: A Review

Modular chemical process intensification can dramatically improve energy and process efficiencies of chemical processes through enhanced mass and heat transfer, application of external force fields, enhanced driving forces, and combinations of different unit operations, such as reaction and separation, in single-process equipment. Dramatic improvements such as these lead to several benefits such as compactness or small footprint, energy and cost savings, enhanced safety, less waste production, and higher product quality. Because of these benefits, process intensification can play a major role in industrial and manufacturing sectors, including chemical, pulp and paper, energy, critical materials, and water treatment, among others. This article provides an overview of process intensification, including definitions, principles, tools, and possible applications, with the objective to contribute to the future development and potential applications of modular chemical process intensification in industrial and manufacturing sectors. Drivers and barriers contributing to the advancement of process intensification technologies are discussed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2020

Hybrid EMT-TS Simulation Strategies to Study High Bandwidth MMC-Based HVdc Systems

Modular multilevel converters (MMCs) are widely used in the design of modern high-voltage direct current (HVdc) transmission system. High-fidelity dynamic models of MMCs-based HVdc system require small simulation time step and can be accurately modeled in electro-magnetic transient (EMT) simulation programs. The EMT program exhibits slow simulation speed and limitation on the size of the model and brings certain challenges to test the high-fidelity HVdc model in system-level simulations. This paper presents the design and implementation of a hybrid simulation framework, which enables the co-simulation of the EMT model of Atlanta-Orlando HVdc line and the transient stability (TS) model of the entire Eastern Interconnection system. This paper also introduces the implementation of two high-fidelity HVdc line models simulated at different time steps and discusses a dedicated method for sizing the buffer areas on both sides of the HVdc line. The simulation results of the two HVdc models with different sizes of buffer areas are presented and compared.

Liu, Yuan↗

DOE OSTI2025

Effects of break geometry and orientation on helium-air mixing in simulated reactor cavities of high temperature gas reactors

Here, this study experimentally examined the spatial and temporal variations in air and helium concentrations and temperature fields within simulated reactor cavities of a High Temperature Gas Reactor (HTGR) following helium discharge into an initially air-filled reactor cavity system. Detailed temperature maps were generated using a combination of fiber optics temperature sensor and multiple thermocouple probes within the simulated reactor cavities. The research scenario involved a hypothetical small pipe break in the Reactor Pressure Vessel, resulting in the release of high-temperature helium into the surrounding cavity. A scaled multi-compartment experimental facility, modeled after the General Atomics Modular High Temperature Gas Reactor (GA-MHTGR) design, was constructed for helium and air mixing experiments. Oxygen sensors and thermocouple probes were installed in all five cavities to measure the concentrations of oxygen (or helium) and the temperature distributions of the gas mixture. The experimental findings highlighted the significant impact of the injected helium jet velocity on the gas mixing process and demonstrated how the direction of the helium jet influences the air-helium temperature profiles within the cavities.

Air-ingress↗

DOE OSTI2024

RAFT: Reconfigurable Array of High-Efficiency Ducted Turbines for Hydrokinetic Energy Harvesting

Diversifying the energy harvesting portfolio is crucial to achieving the ambitious goal of transitioning to clean energy by 2030. Marine hydrokinetic energy has garnered renewed interest due to its high harvesting potential in the U.S., and the resource's reliability and predictability—remaining relatively constant on a daily basis and available 24/7. However, there are currently few commercial devices capable of harnessing the energy from flowing water. This project aims to bridge that gap by designing and evaluating a novel hydrokinetic turbine concept that can efficiently harvest energy from both rivers and tidal streams. The RAFT (Reconfigurable Array of High-Efficiency Ducted Turbines) concept introduces a duct surrounding the turbine rotor and creates an array of small 5-kW units. The duct serves two primary purposes: (1) it enhances hydrodynamic efficiency by accelerating flow to the rotor, and (2) it functions as a structural component, facilitating the formation of modular arrays that lower costs. This project focuses on demonstrating this concept and validating these benefits through simulations and scaled prototype testing. The project team includes 8 faculty members and over 20 students from 3 universities, organized into three core areas: hydrodynamics, electrical systems, and structural analysis, with additional teams dedicated to system integration, environmental assessment and risk management, and tech-to-market strategy. The team successfully demonstrated the increased hydrodynamic efficiency of a ducted turbine compared to an unducted version using high-fidelity simulations and prototype tests. Moreover, design optimization efforts led to surpassing the SHARKS program's goal of 60% reduction of the levelized cost of energy with a significant margin.

13 HYDRO ENERGY↗

DOE OSTI2022

A Blockchain Based Co-Simulation Framework for Integrating DERs to Wholesale Electricity Markets

As the number of distributed energy resources (DERs) continue to increase across energy-delivery systems, there remains a need for integrating their capabilities into traditional grid operations. In this paper, a blockchain-based solution is proposed to facilitate FERC's Order No. 2222 implementations. The presented use-case enables small-scale DERs to participate in wholesale market operations through DER aggregators, while also enabling local distribution system operators to enforce distribution system constraints in a secure and traceable manner. The presented use case is built around the Unified Testing Platform (UTP) being developed as a part of the Blockchain for Optimized Security and Energy Management (BLOSEM) project. This is a multi-lab effort intended to simplify the deployment of blockchain-powered grid solutions by enabling the integration of simulation tools, and blockchain technologies through the use of system-agnostic interfaces that provide a modular, interoperable, and reusable connectivity layer.

blockchain interoperability↗

DOE OSTI2022

Modular Approach for the Synthesis of Bottlebrush Diblock Copolymers from Poly(Glycidyl Methacrylate)-block-Poly(Vinyldimethylazlactone) Backbones

A strategy that enables the facile synthesis of bottlebrush block copolymers with flexible backbones was developed. A demonstration of the strategy’s utility was carried out by grafting end-functionalized polymethylmethacrylate (PMMA) and polystyrene (PS) to the dually reactive block copolymer, poly(glycidyl methacrylate)-block-poly(vinyldimethylazlactone) (PGMA-b-PVDMA). Five different bottlebrush diblock copolymers were investigated by size-exclusion chromatography (SEC), 1H NMR, Fourier transform infrared (FT-IR), differential scanning calorimetry (DSC), X-ray scattering methods, atomic force microscopy (AFM), rheology and computational simulations using molecular dynamics (MD), and self-consistent field theory (SCFT). A relationship between the glass transition temperature and the fraction of chain ends was demonstrated by DSC and highlights the potential of this synthetic method to tailor polymer properties. All five samples were found to be in a disordered phase exhibiting multiscale structures revealed by two broad peaks in small-angle X-ray scattering (SAXS) that can be attributed to graft-to-graft and backbone-to-backbone density correlations using MD simulations. The SCFT-based simulations justify the observation of a disordered phase due to its stabilization by the grafts. Additionally, this modular approach can be easily extended to other grafts, including responsive, conducting, and charged polymers with the prerequisite end groups. The versatility and ease of assembling these functional bottlebrushes constitute a powerful “toolbox” method for the rapid and scalable synthesis of novel bottlebrush block copolymers with desired properties.

36 MATERIALS SCIENCE↗

DOE OSTI2012

The development of the radio frequency driven negative ion source for neutral beam injectors (invited)

Large and powerful negative hydrogen ion sources are required for the neutral beam injection (NBI) systems of future fusion devices. Simplicity and maintenance-free operation favors RF sources, which are developed intensively at the Max-Planck-Institut fuer Plasmaphysik (IPP) since many years. The negative hydrogen ions are generated by caesium-enhanced surface conversion of atoms and positive ions on the plasma grid surface. With a small scale prototype the required high ion current density and the low fraction of co-extracted electrons at low pressure as well as stable pulses up to 1 h could be demonstrated. The modular design allows extension to large source dimensions. This has led to the decision to choose RF sources for the NBI of the international fusion reactor, ITER. As an intermediate step towards the full size ITER source at IPP, the development will be continued with a half-size source on the new ELISE testbed. This will enable to gain experience for the first time with negative hydrogen ion beams from RF sources of these dimensions.

43 PARTICLE ACCELERATORS↗

DOE OSTI2014

Results from the DOE Advanced Gas Reactor Fuel Development and Qualification Program

Modular HTGR designs were developed to provide natural safety, which prevents core damage under all design basis accidents and presently envisioned severe accidents. The principle that guides their design concepts is to passively maintain core temperatures below fission product release thresholds under all accident scenarios. This level of fuel performance and fission product retention reduces the radioactive source term by many orders of magnitude and allows potential elimination of the need for evacuation and sheltering beyond a small exclusion area. This level, however, is predicated on exceptionally high fuel fabrication quality and performance under normal operation and accident conditions. Germany produced and demonstrated high quality fuel for their pebble bed HTGRs in the 1980s, but no U.S. manufactured fuel had exhibited equivalent performance prior to the Advanced Gas Reactor (AGR) Fuel Development and Qualification Program. The design goal of the modular HTGRs is to allow elimination of an exclusion zone and an emergency planning zone outside the plant boundary fence, typically interpreted as being about 400 meters from the reactor. To achieve this, the reactor design concepts require a level of fuel integrity that is better than that claimed for all prior US manufactured TRISO fuel, by a few orders of magnitude. The improved performance level is about a factor of three better than qualified for German TRISO fuel in the 1980’s. At the start of the AGR program, without a reactor design concept selected, the AGR fuel program selected to qualify fuel to an operating envelope that would bound both pebble bed and prismatic options. This resulted in needing a fuel form that could survive at peak fuel temperatures of 1250°C on a time-averaged basis and high burnups in the range of 150 to 200 GWd/MTHM (metric tons of heavy metal) or 16.4 to 21.8% fissions per initial metal atom (FIMA). Although Germany has demonstrated excellent performance of TRISO-coated UO2 particle fuel up to about 10% FIMA and 1150°C, UO2 fuel is known to have limitations because of CO formation and kernel migration at the high burnups, power densities, temperatures, and temperature gradients that may be encountered in the prismatic modular HTGRs. With uranium oxycarbide (UCO) fuel, the kernel composition is engineered to prevent CO formation and kernel migration, which are key threats to fuel integrity at higher burnups, temperatures, and temperature gradients. Furthermore, the recent poor fuel performance of UO2 TRISO fuel pebbles measured in Chinese irradiation testing in Russia and in German pebbles irradiated at 1250°C, and historic data on poorer fuel performance in safety testing of German pebbles that experienced burnups in excess of 10% FIMA [1] have each raised concern about the use of UO2 TRISO above 10% FIMA and 1150°C and the degree of margin available in the fuel system. This continues to be an active area of study internationally.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2019

Experimental Investigation and CFD Analysis of Steam Ingress Accidents in HTGRs

This study focuses on the short-term phenomena due to steam ingress following an SG tube rupture accident in HTGRs, instead of covering a long-term scenario induced by a small amount of steam ingress during plant lifetime. Our ultimate goal is to better understand water/steam ingress accidents in HTGRs, where the Rankine cycle is adopted as the power conversion cycle. General Atomics’ 350 MWth Modular High Temperature Gas-cooled Reactor (MHTGR) was chosen as the prototypic reactor design. The models of steam nuclear graphite oxidation proposed in the literature are surveyed, and will be examined, validated or improved if needed. Furthermore, this study aims to develop and validate a predictive tool for steam ingress accidents. To measure the steam concentration evolution in an integral effect test (IET) facility, a tunable diode laser absorption spectroscopy (TDLAS) measurement system was developed. The TDLAS measuring system is a non-intrusive and non-perturbative diagnostic technique that can be used to measure the steam temperature and concentration at various conditions.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2019

Functional Organic Semiconductors Based on Bay-Annulated Indigo (BAI)

Here, we report the advancement of organic electronics has been continually pushed by the need for stable and high performance acceptor materials. By utilizing inexpensive and stable indigo dye as a starting material, Bay-Annulated Indigo (BAI) provides a new motif for the development of semiconducting materials. Modular and straightforward synthesis makes BAI an outstanding platform for molecular design, while excellent stability, strong absorption, and high ambipolar mobility render BAI-based materials excellent candidates for organic electronics. BAI-based polymers and small molecules have taken advantage of these properties to show promising results in a variety of applications.

36 MATERIALS SCIENCE↗

DOE OSTI2016

Analytical Results from Routine DSSHT and SEHT Monthly Samples

Strip Effluent Hold Tank (SEHT) and Decontaminated Salt Solution Hold Tank (DSSHT) samples from several of the “microbatches” of Integrated Salt Disposition Project (ISDP) Salt Batch (“Macrobatch”) 8B have been analyzed for 238 Pu, 90 Sr, 137 Cs, cations (Inductively Coupled Plasma Emission Spectroscopy - ICPES), and anions (Ion Chromatography Anions - IC-A). The analytical results from the current microbatch samples are similar to those from previous macrobatch samples. The Actinide Removal Process (ARP) and the Modular Caustic-Side Solvent Extraction Unit (MCU) continue to show more than adequate Pu and Sr removal for times when monosodium titanate (MST) is used. Even with no MST strike being performed there exists some small Pu and Sr removal, likely from filtration of fines containing these elements. The Cs removal continues to be excellent, with decontamination factors (DF) averaging 16,400. The bulk chemistry of the DSSHT and SEHT samples do not show any signs of unusual behavior. SRNL recommends that a sample of the strip feed be analyzed for cation and anion content if a further decline in boron concentration is noted in future SEHT samples.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2018

A modular approach for high-flux lactic acid production from methane in an industrial medium using engineered Methylomicrobium buryatense 5GB1

Abstract Convergence of market drivers such as abundant availability of inexpensive natural gas and increasing awareness of its global warming effects have created new opportunities for the development of small-scale gas-to-liquid (GTL) conversion technologies that can efficiently utilize methane, the primary component of natural gas. Leveraging the unique ability of methanotrophs that use methane as carbon and energy source, biological GTL platforms can be envisioned that are readily deployable at remote petroleum drilling sites where large chemical GTL infrastructure is uneconomical to set-up. Methylomicrobium buryatense, an obligate methanotroph, has gained traction as a potential industrial methanotrophic host because of availability of genetic tools and recent advances in its metabolic engineering. However, progress is impeded by low strain performance and lack of an industrial medium. In this study, we first established a small-scale cultivation platform using Hungate tubes for growth of M. buryatense at medium-to-high-throughput that also enabled 2X faster growth compared to that obtained in traditional glass serum bottles. Then, employing a synthetic biology approach we engineered M. buryatense with varying promoter (inducible and constitutive) and ribosome-binding site combinations, and obtained a strain capable of producing l-lactate from methane at a flux 14-fold higher than previously reported. Finally, we demonstrated l-lactate production in an industrial medium by replacing nitrate with less-expensive ammonium as the nitrogen source. Under these conditions, l-lactate was synthesized at a flux approximately 50-fold higher than that reported previously in a bioreactor system while achieving a titer of 0.6 g/L. These findings position M. buryatense closer to becoming an industrial host strain of choice, and pave new avenues for accelerating methane-to-chemical conversion using synthetic biology.

Garg, Shivani↗