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

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DOE OSTI2024

2023 Project Peer Review Report

The Bioenergy Technologies Office (BETO) within the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy supports the research, development, and demonstration (RD&D) of technologies aimed at mobilizing domestic renewable carbon resources for the reduction of greenhouse gas emissions across the U.S. economy. BETO systematically prioritizes RD&D into technology opportunities across a range of emerging scientific breakthroughs and technology readiness levels in the subprogram areas illustrated in Figure 1. This approach supports a diverse portfolio while developing the most promising and widely applicable technologies, testing technologies as integrated processes, and demonstrating integrated processes to support scale-up. These technologies will use a broad variety of renewable carbon resources to produce increasing volumes of biofuels and bioproducts. More information on BETO’s mission, goals, and strategic approaches can be found in the Bioenergy Technologies Office Multi-Year Program Plan. The biennial Peer Review process enables external stakeholders to provide feedback on the responsible use of taxpayer funding and develop recommendations for the most efficient and effective ways to accelerate the development of a bioenergy industry. This report includes the results of the Project Peer Review meeting held on April 3–7, 2023, in Denver, Colorado.

09 BIOMASS FUELS↗
DOE OSTI2024

Exploring the Potential of Second-Life Batteries for Mobile Charging Infrastructure: A Review

This review paper investigates the potential applications of second-life batteries (SLBs) specifically for mobile charging stations. As the adoption of electric vehicles (EVs) continues to rise, the need for accessible and efficient charging infrastructure becomes increasingly critical to address range anxiety of EV owners. The repurposing of SLBs presents a promising solution to address this need, offering cost-effective and sustainable alternatives to traditional stationary charging infrastructure. This paper examines key technical considerations, including battery chemistry, state of health assessment, heterogeneity and battery management system design, and safety protocols tailored to SLBs. The paper also highlights economic and environmental implications of utilizing SLBs in mobile charging applications, encompassing techno-economic analysis techniques and sustainability metrics. Through an exploration of challenges, opportunities, and emerging trends, this review aims to provide valuable insights to stakeholders involved in the development and deployment of SLBs in mobile charging infrastructure.

Gautam, Mukesh (ORCID:0000000305715825)↗
DOE OSTI2023

Incremental Threshold Scheme Enabled IoT Group Key Management

Cyber landscape evolves rapidly. Internet of Things (IoT) and Edge Computing (EC) have rapidly become an integral part of the modern computing infrastructure. It is expected that there will be more than 50 billion active and connected IoT devices by 2025 [1]. Pervasive IoT/EC creates unprecedented opportunities bridging the gap between previously segregated cyber and physical spaces. However, this progress also brings along new security challenges. IoT devices typically have limited computation, communication, and storage resources. This leads to security architecture designs such as using symmetric keys for group communication. While secure and efficient in stable network settings, symmetric key solutions are ill-adapted for IoT's highly dynamic device mobility behavior and frequent group membership turnover. Whenever IoT members leave a group, the known symmetric keys cannot be made forgotten, posing a serious vulnerability. This leads to frequent re-groupings that require expensive re-authentication, key regeneration, and key redistribution in order to maintain IoT/EC security. We present a novel symmetric key management framework that integrate an Incremental Threshold Scheme (ITS) cryptographical function into communication protocol's key rotation mechanism to allow for secure and efficient symmetric key communication group member node revocation. This ITS-enabled key management framework alleviates the need of frequent and expensive re-grouping and re-keying needed by today's large and dynamic IoT/EC operations. We further applied this ITS-enabled key management framework to a distributed IoT/EC-integrated publish and subscribe framework for applicability validation.

Li, Mingyan↗
DOE OSTI2020

Ultrafast terahertz spectroscopy provides insight into charge transfer efficiency and dynamics in artificial photosynthesis

Terahertz (THz) spectroscopy provides a noncontact method to measure the ultrafast dynamics and photoconductivity of mobile carriers in semiconducting materials. This has proven useful in studying artificial photosynthesis devices which use semiconductor photoelectrodes. In this work, we present a brief introduction to optical-pump THz-probe (OPTP) spectroscopy, a technique that provides unique and useful insight into interfacial electron transfer (from the surface-attached dye to the conduction band of the semiconductor) in dye-sensitized photoelectrochemical cells. Compared with more familiar methods like visible transient absorption spectroscopy, OPTP spectroscopy stands out in offering both sub-picosecond time resolution as well as sensitivity to mobile carriers (electrons and holes) in the semiconductor portion of artificial photosynthesis devices. The mobile carriers are crucial to device performance as only they pass to the other half cell to complete the reaction. In order to highlight these advantages and illustrate the types of questions OPTP spectroscopy can address, we discuss three case studies. In the first, OPTP spectroscopy is used to measure the injection rates from a set of six different dyes, revealing the effect of the energetics and lifetimes of the dye excited states on interfacial electron transfer. The subsequent case studies investigate the influence of varying the moieties which bind to the surface (anchors), as well as the moieties that connect the chromophore with these anchors (linkers). OPTP spectroscopy was used to measure the interfacial electron transfer rate as these moieties were varied.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Highly efficient removal and sequestration of Cr(VI) in confined MoS 2 interlayer Nanochannels: Performance and mechanism

Environmental contamination by Cr(VI) is of particular concern because of its severe toxicity and high mobility. In this study, we employed two-dimensional MoS 2 nanosheets in the removal of Cr(VI), with an emphasis on revealing the removal mechanisms, and how the compositional and structural uniqueness of 2D MoS 2 nanomaterials intrinsically impact the Cr removal efficiency. Through batch experiments with dispersed nanosheets, we found that MoS 2 nanosheets exhibited a high Cr(VI) removal capacity at ~1100 mg/g via a phase-dependent mechanism. Particularly, the 1T polymorph in the MoS 2 nanosheets removed Cr(VI) through a redox-reaction mechanism, which was different from the adsorptive removal of Cr(VI) by MoS 2 reported previously, highlighting the compositional effects on the removal mechanism and performance. More importantly, the reduced product Cr(III) was concurrently removed via precipitation and adsorption onto the MoS 2 nanosheets, which could avoid the additional pH-elevation step that is typically needed in the conventional treatment. The unique 2D flake-like structure of MoS 2 nanosheets enabled the formation of aligned and ion-accessible nanochannels, where Cr(VI) species were accommodated, reduced and sequestered. The irreversible shrinking of the nanochannels under drying modified the interior of the layer-stacked structure into confined compartments preventing the release and re-oxidation of the immobilized Cr(III). In conclusion, the compiled results highlight the effects of MoS 2 composition and structure on the Cr removal efficiency and mechanism, which has substantial implications on future studies tailoring these unique features of 2D nanomaterials for various remediation scenarios.

42 ENGINEERING↗
DOE OSTI2022

Predicting Solar Cell Performance from Terahertz and Microwave Spectroscopy

Abstract Mobilities and lifetimes of photogenerated charge carriers are core properties of photovoltaic materials and can both be characterized by contactless terahertz or microwave measurements. Here, the expertise from fifteen laboratories is combined to quantitatively model the current‐voltage characteristics of a solar cell from such measurements. To this end, the impact of measurement conditions, alternate interpretations, and experimental inter‐laboratory variations are discussed using a (Cs,FA,MA)Pb(I,Br) 3 halide perovskite thin‐film as a case study. At 1 sun equivalent excitation, neither transport nor recombination is significantly affected by exciton formation or trapping. Terahertz, microwave, and photoluminescence transients for the neat material yield consistent effective lifetimes implying a resistance‐free JV‐curve with a potential power conversion efficiency of 24.6 %. For grainsizes above ≈20 nm, intra‐grain charge transport is characterized by terahertz sum mobilities of ≈32 cm 2 V −1 s −1 . Drift‐diffusion simulations indicate that these intra‐grain mobilities can slightly reduce the fill factor of perovskite solar cells to 0.82, in accordance with the best‐realized devices in the literature. Beyond perovskites, this work can guide a highly predictive characterization of any emerging semiconductor for photovoltaic or photoelectrochemical energy conversion. A best practice for the interpretation of terahertz and microwave measurements on photovoltaic materials is presented.

14 SOLAR ENERGY↗
DOE OSTI2025

Unequal {110} Facets: The Potential Role of Intraparticle Heterogeneity and Facet Termination in Photoelectrochemical Activity of Single BiVO 4 Particles

BiVO 4 photoanodes are promising for solar water splitting, with photogenerated electrons and holes preferentially reacting at top {010} and lateral {110} facets, respectively. However, the mechanisms driving this facet-dependent reactivity remain unclear. Here, in this study, we investigate facet-dependent photocurrent and material heterogeneity using correlative scanning photoelectrochemical microscopy (SPCM), electron beam induced current (EBIC) mapping, and mid-IR scattering scanning near-field optical microscopy (s-SNOM). SPCM measurements of 62 BiVO 4 particles confirmed higher photocurrents at lateral {110} facets compared to top {010} facets, but unexpectedly revealed variations in photocurrent among lateral facets within the same particle. Variations in lateral facet surface termination could explain the intraparticle-level reactivity heterogeneity, consistent with theoretical predictions. Nano-FTIR spectroscopy and Raman microspectroscopy indicated significant materials chemistry heterogeneity within individual particles and facets that could be attributed to variations in lattice vibration distortions that enhance the overlap between Bi 6s and O 2p orbitals. The increased orbital overlap is significant as it potentially increases hole mobility in the valence band and potentially explains the lateral facet-dependent charge separation efficiency observed in photocurrent maps. Facet-dependent electrical and EBIC measurements showed no space charge regions at interfacet junctions or metal-BiVO 4 contacts under vacuum, suggesting that photogenerated holes beneath top {010} facets are unlikely to transport to lateral {110} facets to drive water/sulfite oxidation. These findings indicate the potential influence of distinct bulk properties and surface termination chemistries across different particles and facets, highlighting the importance of carefully controlling defects and surface chemistry during sample growth to optimize photocatalytic performance.

BiVO4↗
DOE OSTI2022

Carbon nanomaterials–polymer composites for perovskite solar cells: preparation, properties and applications

Perovskite solar cells (PSCs) are a rising star in the photovoltaic industry, which achieved an enormous breakthrough in terms of efficiency from an initial 3.8% in 2009 to 25.7% in 2021. Here, the major challenge to bring perovskite solar cells commercially available is the poor long-term device stability. The defects in perovskite and energy loss originating from charge recombination limit the efficiency of perovskite solar cells. Carbon–polymer composites, which feature superb electrical conductivity, outstanding carrier mobility, remarkable flexibility and superior heat and moisture stability, have attracted considerable attention to tackle these issues. With their multifunctional properties, carbon–polymer composites can play various roles in almost every component in the perovskite solar cell architecture. In this review article, recent progress concerning the utilization of carbon–polymer composites in different components in PSCs (i.e., perovskite additives, electrodes, encapsulation layers and charge transport layers) is comprehensively overviewed. Then, future research directions and opportunities toward high-performance perovskite solar cells utilizing carbon–polymer composites are presented.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Hydrogen Infrastructure Modeling and Optimization

HyET, established in 2008, is a small business developing electro-chemical hydrogen compressors. HyET’s goals are for a low-cost, efficient, high-pressure compressor ready for market and installation into hydrogen infrastructure stations servicing mobile fuel cell applications. NLR has been working on hydrogen infrastructure research for over a decade and includes electrolyzer production via electrolysis, storage, compression, dispensing, safety, and performance validation. Accelerating technologies into the marketplace is one goal of NLR’s hydrogen research. Therefore, HyET and NLR have teamed up to provide one year of support for HyET’s modeling and small-scale experiments optimization efforts for HyET’s next-generation electro-chemical compressor.

08 HYDROGEN↗
DOE OSTI2021

A hybrid CoOOH-rGO/Fe 2 O 3 photoanode with spatial charge separation and charge transfer for efficient photoelectrochemical water oxidation

As a promising photoanode for photoelectrochemical (PEC) water oxidation, hematite (Fe 2 O 3 ) still suffers from poor charge mobility and serious charges recombination and sluggish surface oxygen evolution kinetics. Herein, a hybrid photoanode of cobalt (oxy)hydroxide coupled with reduced graphene oxide modified Fe 2 O 3 (CoOOH-rGO/Fe 2 O 3 ) is well crafted by a facile hydrothermal synthesis with a chelation-mediated in-situ growth method. Morphology characterizations indicate rGO forms the internal network among isolated Fe 2 O 3 and CoOOH nanosheets distribute on the terminal of Fe 2 O 3 , forming a spatial separated nanostructure. The resultant CoOOH-rGO/Fe 2 O 3 exhibits an obviously reduced onset potential of ca. 150 mV and a significantly enhanced photocurrent density of 2.56 mA cm -2 at 1.23 V, which is ca. 3.3 times higher than that of bare Fe 2 O 3 . Especially, the functions of rGO and CoOOH are studied by using electrochemical impedance spectroscopy, open circuit potentials and intensity modulated photocurrent spectroscopy. It is found rGO act as conductive network which facilitates the electron transfer from Fe 2 O 3 to the substrate, while CoOOH evidently passivate the surface states of Fe 2 O 3 , improve charge separation and provide catalytic active sites for water oxidation. Additionally, the spatial charge separation and charge transfer caused by CoOOH and rGO are responsible for the enhanced PEC performance of water oxidation. The rational design and the facile fabrication strategy exhibit great potential to be used for other PEC system with great efficiency.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

NEXT Generation Energy Technologies for Connected and Automated On-Road Vehicles (NEXTCAR Phase I & II)

The Ohio State University’s ARPA-E NEXTCAR project was a multi-phase, multi-year research, development, and demonstration program focused on improving the energy efficiency of connected and automated vehicles (CAVs). The team developed and validated advanced vehicle motion and powertrain control algorithms that coordinate propulsion and automation systems to optimize energy use. Key technologies included Dynamic Skip Fire engine control, predictive eco-driving functions such as Eco-Approach and Departure (Eco-AND) and Eco-Adaptive Cruise Control (Eco-ACC), and powertrain-agnostic optimization frameworks for hybrid, plug-in hybrid, and battery electric vehicles. The project successfully demonstrated up to 30% energy-efficiency improvement during real-world testing at the Transportation Research Center and the American Center for Mobility. The outcomes provide a foundation for scalable, cost-effective deployment of energy-optimized CAV technologies across the automotive industry.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2023

Automated Electric Vehicle Fleet Operations for On-Demand Service: Challenges and Opportunities

Automated/autonomous vehicle fleet operations within automated mobility districts have been studied over the past five years by the National Renewable Energy Laboratory, a US Department of Energy federally funded research and development center. This paper extends the analysis in this third phase of research underway to include considerations for electric vehicle operations and charging within a fleet of right-sized automated vehicles providing on-demand public mobility services. The current focus of research is on the operational complexities and associated challenges for automated/autonomous vehicles employing electric drivetrains and the resultant need for an efficient battery charging process while vehicles are operating in an "on-demand" mode of service. The blossoming of microtransit with shared-ride and point-to-point dispatching of each vehicle instills complex operations, with multiple mobility-on-demand transit operating sites being deployed, studied, and analyzed across North America. As a starting point, the authors' experience over the past 20 years with the analysis of automated transit network systems operating on and within dedicated and protected transitways provides initial insights into the system-level operational implications for maintaining a sufficient battery charge for a fleet of automated vehicles. Lessons learned through the prior analyses of automated transit network systems operating in on-demand service are identified, along with the capital cost implications for the requisite operating fleet size and charging station infrastructure for various approaches. These costs are summarized in juxtaposition with the benefits of realizing the higher goals of reducing environmental impacts and energy use within automated mobility districts as automated/autonomous vehicle technology matures. Finally, the discussion addresses key aspects of battery-electric propulsion for managed fleets in fully automated operation that will be studied as the third phase of research continues.

ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2021

Compromise between band structure and phonon scattering in efficient n-Mg 3 Sb 2-x Bi x thermoelectrics

n-type Mg 3 Sb 2 -based materials have become a top candidate for efficient thermoelectric applications within 300–700 K, due to its high band degeneracy, inherently high carrier mobility and low lattice thermal conductivity, as well as its advantages of less toxicity and abundance. Existing works showed that Mg 3 Bi 2 -alloying largely help ensure the exceptional performance, leaving a key issue to be uncovered on the primary mechanisms favoring or limiting the thermoelectric performance of Mg 3 Sb 2-x Bi x alloys. Furthermore we focus on the alloy composition dependent transport properties at various temperatures, with a large volume of experimental data. It is revealed that, with increasing x, the reduction in both inertial mass and lattice thermal conductivity is significantly beneficial, but the closure in band gap leads to a strong compensation due to the bipolar effect. Such a compromise between band structure and phonon scattering results in optimal Mg 3 Bi 2 -alloying concentrations to be about 50%–75% at 300 K, 50%–60% at 450 K and 50% at 600 K, which successfully guiding this work to realize extraordinary thermoelectric figure of merit at these temperatures.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Quantized electronic transitions in electrodeposited copper indium selenide nanocrystalline homojunctions

Pairing semiconductors with electrochemical processing offers an untapped opportunity to create novel nanostructures for practical devices. Here we report the results of one such pairing: the in-situ formation of highly-doped, interface-matched, sharp nanocrystalline homojunctions (NHJs) with single step electrodeposition of two copper-indium-selenide (CISe) compounds on flexible foil. It produces a homogenous film, comprising inherently ordered, 3-dimensional interconnected network of pn -CISe NHJs. These CISe NHJs exhibit surprising non-linear emissions, quantized transitions, large carrier mobility, low trap-state-density, long carrier lifetime and possible up-conversion. They facilitate efficient separation of minority carriers, reduce recombination and essentially function like quantum materials. This approach mitigates the material issues and complex fabrication of incumbent nanoscale heterojunctions; it also overcomes the flexibility and scale-up challenges of conventional planar pn junctions. The self-stabilized CISe NHJ film can be roll-to-roll processed in ambient atmosphere, thus providing a promising platform for a range of optoelectronic technologies. This concept exemplified by CISe compounds can be adapted to create nano-scale pn junctions with other inorganic semiconductors.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Evolving Architectures and Considerations to address Distributed Energy Resources and Non-Wired Alternatives

The electric grid is in the beginning stage of a transformation, driven by a combination of shutdowns of coal-fired plants, commissioning of new natural-gas plants, and tremendous growth in energy supply from renewables such as wind, and solar. As utilities navigate this transformation, their progress is supported by advances in Operational Technologies (OT), and Informational Technologies (IT), such as automation, smart inverters, cloud computing, mobile computing, machine learning, big data analytics, which have the potential to enable advanced capabilities more efficiently and at a lower cost. This white paper focuses on the architectural considerations that will allow the industry to transition in a planned manner. It introduces and formalizes two architectural constructs –the data bus and the control bus. The data bus is responsible for carrying all non-operational models and information necessary to drive utility decisions. In contrast, the control bus is responsible for carrying all operational data and control actions taken at the local level, centralized level, or other levels in-between. The paper reviews those architectural considerations, their requirements and how they will evolve. This paper intends to provide a context for vendors, utilities, and their service providers to review and understand the changes that are coming and get ready for them.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2026

Meeting the Challenges of Modern Transit through the Integration of Traditional Transit, On-Demand Micro-Transit Services and Vehicle Automation - A Case Study in Chandler, Arizona

Current technology trends of vehicle automation, electrification and on-demand transit are providing new tools to develop effective public mobility services, yet need to be balanced with traditional modes to serve the spectrum of demand effectively and efficiently. Automated vehicle transportation network company (TNC) services, better known as 'Robotaxis' are beginning to proliferate and scale across the US, with Waymo as the lead commercial entity. Chandler, AZ was the first fully automated deployment of Waymo technology. Chandler was also one of the first municipalities in Arizona to roll out micro-transit service to its citizens in 2022. At present the Chandler Flex micro-transit program is beginning to partner with Waymo to augment micro-transit services during peak demands, another first in the nation. However, the mix of services in Chandler relies not only on new technology, but also on traditional modes including fixed route transit and para-transit services. These are blended and balanced such that both old and new modes are applied within the context in which each excel. This presentation will provide background on the Chandler, AZ public mobility services, and the performance metrics that govern their use and selection within the spectrum of development and population density as well as socio-demographics within Chandler. Additionally, the behavioral response of the use of unmanned, automated vehicles employed to augment micro-transit is novel, the first in the nation - and initial feedback from public transit constituents in Chandler will be shared.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2022

Highly Efficient Layer-by-Layer Processed Quaternary Organic Solar Cells with Improved Charge Transport and Reduced Energy Loss

We report how to improve charge transport properties and reduce energy losses are the two main challenges of organic solar cells (OSCs). Herein, a new device fabrication strategy that combines the layer-by-layer (LBL) method and a quaternary active layer is demonstrated to realize highly efficient photovoltaic performance of the OSCs based on PM6:PM7/Y6:O1-2F. The introduction of the second donor, PM7,forms a cascade energy-level alignment with PM6 that facilitates effective charge transfer. The second acceptor, O1-2F, which is poorly miscible with the donors, helps to reduce the miscibility between the donors and acceptors, and thus delivers a more desirable vertical phase separation of the active layer. Furthermore, the alloy acceptor of O1-2F and Y6 can optimize the horizontal and vertical morphology of the active layer, forming an effective charge separation and continuous charge transport channel. As a result, the PM6:PM7/Y6:O1-2F system shows a distinct increase in charge mobility and a reduced nonradiative lossΔVnrof 0.231 V compared to the PM6/Y6 system, achieving a high-power conversion efficiency of18.23%. The results indicate that the quaternary LBL OSCs are promising for future large-scale and industrial manufacture of the OSCs.

14 SOLAR ENERGY↗