Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “DIRECT ENERGY CONVERSION”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Carbon neutral manufacturing via on-site CO 2 recycling

The chemical industry needs to significantly decrease carbon dioxide (CO 2 ) emissions in order to meet the 2050 carbon neutrality goal. Utilization of CO 2 as a chemical feedstock for bulk products is a promising way to mitigate industrial emissions; however, CO 2 -based manufacturing is currently not competitive with the established petrochemical methods and its deployment requires creation of a new value chain. Here, we show that an alternative approach, using CO 2 conversion as an add-on to existing manufactures, can disrupt the global carbon cycle while minimally perturbing the operation of chemical plants. Proposed closed-loop on-site CO 2 recycling processes are economically viable in the current market and have the potential for rapid introduction in the industries. Retrofit-based CO 2 recycling can reduce annually between 4 and 10 Gt CO 2 by 2050 and contribute to achieving up to 50% of the industrial carbon neutrality goal.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2024

Predictive model using artificial neural network to design phase change material-based ocean thermal energy harvesting systems for powering uncrewed underwater vehicles

Uncrewed Underwater Vehicles (UUVs) are a major beneficiary of the phase change material (PCM)-based ocean thermal energy harvesting technology for their mission needs. However, this technology relies on different parameters and energy conversion steps that could be critical to the general energy generation efficiency. Sea trials showed that the design performed lower than their laboratory design specifications. This underperformance results from different factors, mainly the UUV’s trajectory, travel time, underwater ocean currents, temperature fluctuations, and biofouling on the heat exchanger due to long term underwater operations. Therefore, there exists a need to continuously monitor the ambient energy harvesting system and predict system performance, for mission planning purposes. Two major parameters influencing the energy harvesting system include the final pressure inside the hydraulic energy storage vessel or accumulator, and the electrical load value. Here, this work focuses on the hydraulic to electric energy conversion system. Therefore, a combination of numerical model and experimental testing is used to develop a predictive model using artificial neural network using MATLAB. After validation with experimental testing, 1000 data samples obtained from the numerical model are used to train the ANN. Compared to the experimental results, the developed ANN model can predict in less than a second the designed benchtop system’s total efficiency with less than 15 percent maximum error range. This predictive model development represents a cost-effective way for optimization and a computational energy efficient mode aboard UUVs for mission planning for deployed UUVs using PCM-based ocean thermal energy harvesting technology.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2023

Electrochemical Measurement of Water Transport Numbers in Anion-Exchange Membranes

Anion-exchange membranes (AEMs) are a possible replacement for perfluorosulfonic-acid membranes in energy-conversion devices, primarily due to the hydroxide mobile ion allowing the devices to operate in alkaline conditions with less expensive electrocatalysts. However, the transport properties of AEMs remain understudied, especially electro-osmosis. In this work, an electrochemical technique, where the open-circuit voltage is measured between two ends of a membrane maintained at different relative humidities, is used to determine the water transport number of various ionomers, including Versogen and Sustainion AEMs and Nafion cation-exchange membrane (CEM), as a function of water content and temperature. In addition, the CEMs and AEMs are examined in differing single-ion forms, specifically proton and sodium (CEM) and hydroxide and carbonate (AEM). Carbonate-form AEMs have the highest transport number (∼11), followed by sodium-form CEMs (∼8), hydroxide-form AEMs (∼6), and proton-form CEMs (∼3). Finally, a multicomponent transport model based on the Stefan-Maxwell-Onsager framework of binary interactions is used to develop a link between water transport number and water-transport properties, extracting a range for the unmeasured membrane water permeability of Versogen as a function of water content.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2020

A Cost-Performance Analysis of a Sodium Heat Engine for Distributed Concentrating Solar Power

We present that a sodium thermal electrochemical converter (Na-TEC) generates electricity directly from heat through isothermal expansion of sodium ions across a beta"-alumina solid-electrolyte. This heat engine has been considered for use with conventional concentrating solar power (CSP) systems before. However, unlike previous single-stage devices, the improved design uses two stages with an interstage reheat, allowing more economical and efficient conversion up to 29% at a hot side temperature of 850 °C. Herein, a cost-performance analysis for this improved design assesses opportunities for distributed-CSP in the context of micro-combined heat and power systems. A high-level techno-economic analysis (TEA) is presented that explores four scenarios where a Na-TEC is used as the heat engine for a distributed-CSP system. Overnight capital cost and levelized cost of electricity (LCOE) are estimated for a system lifetime of 30 years, revealing that overnight capital costs in a range from $3.57 to $17.71 per W e are feasible, which equate to LCOEs from 6.9 to 17.2 cents kWh e -1 . This analysis makes a significant contribution by concurrently quantifying the efficiency and unit costs for a range of multistage configurations, and demonstrating that a Na-TEC may be a promising alternative to Stirling engines for distributed-CSP systems at residential scale of 1–5 kW e .

14 SOLAR ENERGY↗
DOE OSTI2024

Direct conversion of methane to aromatics and hydrogen via a heterogeneous trimetallic synergistic catalyst

Abstract Non-oxidative methane dehydro-aromatization reaction can co-produce hydrogen and benzene effectively on a molybdenum-zeolite based thermochemical catalyst, which is a very promising approach for natural-gas upgrading. However, the low methane conversion and aromatics selectivity and weak durability restrain the realistic application for industry. Here, a mechanism for enhancing catalysis activity on methane activation and carbon-carbon bond coupling has been found to promote conversion and selectivity simultaneously by adding platinum–bismuth alloy cluster to form a trimetallic catalyst on zeolite (Pt-Bi/Mo/ZSM-5). This bimetallic alloy cluster has synergistic interaction with molybdenum: the formed CH 3 * from Mo 2 C on the external surface of zeolite can efficiently move on for C-C coupling on the surface of Pt-Bi particle to produce C 2 compounds, which are the key intermediates of oligomerization. This pathway is parallel with the catalysis on Mo inside the cage. This catalyst demonstrated 18.7% methane conversion and 69.4% benzene selectivity at 710 °C. With 95% methane/5% nitrogen feedstock, it exhibited robust stability with slow deactivation rate of 9.3% after 2 h and instant recovery of 98.6% activity after regeneration in hydrogen. The enhanced catalytic activity is strongly associated with synergistic interaction with Mo and ligand effects of alloys by extensive mechanism studies and DFT calculation.

03 NATURAL GAS↗
DOE OSTI2020

Modified alkaline peroxide pretreatment: An efficient path forward for bioethanol production from bamboo

To overcome the typical delignification saturation point of alkaline peroxide pretreatment and further facilitate lignin removal, a novel modified alkaline hydrogen peroxide pretreatment (MAHP) was proposed by introducing ethanol into the reaction system. The dosages of H 2 O 2 , ethanol, and pretreatment temperature were optimized, and the results revealed that a maximum lignin removal as high as 79.25% could be achieved at only 100 °C, 3 wt% H 2 O 2 concentration and 1 wt% ethanol concentration. Meanwhile, 76.5% of glucan and 56.0% of xylan were preserved at this pretreatment condition. By overcoming the delignification saturation point, enzymatic hydrolysis efficiency was remarkably enhanced, achieving 96.76% and 97.38% of glucan and xylan conversion, respectively, which are 7.4 and 11.4 times as compared to that of the untreated bamboo. Furthermore, the simultaneous saccharification and fermentation (SSF) result indicated an identical ethanol yield of ~75% when elevating the SSF solid loading from 5% to 30%. Based on the sequential SSF and xylose fermentation results, about 5.6 tons of bamboo would be consumed to produce 1 ton of ethanol. Finally, the energy balance revealed that a positive balance of 1255.4 KJ could be generated via processing 1 kg bamboo. Here, the results demonstrate that the MAHP is a promising high-efficiency pretreatment technology for bamboo due to the mild pretreatment severity and robust ethanol yield.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2023

Degradation and recovery of solid oxide fuel cell performance by control of cathode surface acidity: Case study – Impact of Cr followed by Ca infiltration

Solid oxide fuel cells (SOFC) have attracted attention as clean and efficient energy conversion devices with low emissions. However, several degradation mechanisms limit the electrochemical performance of current SOFCs, with cathode degradation due to Cr-poisoning from metal interconnects particularly problematic. The acidity/basicity of binary additives has been found to be a sensitive descriptor of the oxygen exchange kinetics, indicating that acidic Cr-species/basic Ca-species can be expected to deactivate/activate the cathode surface, respectively. Inspired by recent advances, the feasibility of relative acidity as a tool for reviving degraded SOFCs is demonstrated by neutralizing Cr-poisoned SOFCs by subsequent serial infiltration of Ca-species. Furthermore, a model mixed ionic and electronic conducting oxide, Pr 0.1 Ce 0.9 O 2-δ (PCO), is selected as the cathode material. Area-specific resistances (ASR) of symmetric cells obtained by electrochemical impedance spectroscopy show that Cr-infiltration results in a seven-fold increase in ASR, while subsequent infiltration of Ca-species leads to complete recovery. Performance degradation and recovery are attributed to depressed/enhanced redox properties at the PCO surface, as supported by XPS analysis. Experiments using anode-supported fuel cells show a reduction in peak power density by 26% upon Cr-infiltration, reversed following Ca-infiltration, after which no degradation is observed during subsequent operation for 100 h.

(Pr,Ce)O2-δ↗
DOE OSTI2020

Chapter 3 - Harvesting Thermal Energy with Ferroelectric Materials

Thermal energy is considered the ubiquitous form of energy as all other forms of energy ultimately degrade to thermal energy. Thermal to electrical energy conversion is currently an important method for electricity generation. The traditional power cycles, however, become technically and economically unviable when heat source temperature reduces below 100 °C. Thermal energy harvesting has been proposed as a viable alternative for low-grade thermal to electrical energy conversion. Thermal energy harvesting is a method of generating electricity using temperature-induced variations in material properties. It is particularly useful when the heat sources are available free-of-cost, either in the form of natural heat or waste heat. While there are several thermal energy harvesting techniques, pyroelectricity is the most promising as it can be used in situations where spatial thermal gradients are difficult to establish or the temperature of the heat source is changing. Despite the fact that the pyroelectric effect in ferroelectric materials has been known for past several decades, thermal energy harvesting using ferroelectric materials has not been much explored in the literature. In this chapter, we would explore various aspects of thermal energy harvesting using ferroelectric materials. We have first established the physics behind ferroelectricity, then provided a detailed description on ferroelectric thermal energy harvesting, discussed various ferroelectric thermodynamic cycles and devices proposed in the literature, and finally described various other emerging applications of ferroelectricity.

DIRECT ENERGY CONVERSION,MATERIALS SCIENCE,OTHER I↗
DOE OSTI2021

Component Development for Alkaline URFCs

Performance, cost, and durability of the catalyst materials are the key factors that govern commercialization of H 2 -based energy conversion devices such as unitized regenerative fuel cells (URFCs). Compared to existing battery systems, URFCs offer superior energy density and performance over prolonged operation. In addition, alkaline URFC systems, can utilize low-cost platinum group metal-free (PGM-free) catalysts, resulting in much lower overall system costs. This project seeks to address the major obstacles faced in URFC systems such as cost and efficiency and establish a URFC technical capability through the strategic partnership between UofSC and SRNL. The research focuses on the development of low-PGM and PGM-free based bifunctional oxygen catalysts and electrodes, as well as the development of a URFC testing capability at SRNL.

25 ENERGY STORAGE↗
DOE OSTI2026

Empirical Comparison of Machine Learning Approaches for Black-Box Modeling of Power Conversion System Dynamics

Inverter-based resources are key components in modern power systems, but accurately modeling their complex behavior can be challenging. Standard, generic converter models often oversimplify inverter dynamics, leading to significant errors in predicting performance. In this work, we compare several data-driven machine learning (ML) approaches for inverter modeling, performing experiments on power conversion systems, systematically varying input conditions, and recording the resulting voltages and currents. The ML models were then trained on this measured data to capture the inverter's dynamic response and to predict the inverter's output current. A performance comparison between the four ML models under study is conducted, laying the foundation for future work on hardware implementation for real-time inference.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2021

DOE Support for the North American meeting of the International Society for Microbial Electrochemistry and Technology

The objective of the North American meeting of the International Society for Microbial Electrochemistry and Technology (NA-ISMET 2021, postponed from 2020 due to COVID-19) was to provide a welcoming space for an interdisciplinary group of researchers, primarily based in North America, to discuss their latest discoveries and innovative ideas on both basic science and applied technology in the field of microbial electrochemistry. After two years of limited travel and research interactions due to COVID-19, an in-person meeting was urgently needed to facilitate conversations and collaborations that help move the field forward. NA-ISMET 2021 was co-organized by Moh El-Naggar from the University of Southern California (USC) and Orianna Bretschger from Aquacycl Inc. The meeting took place on November 17 – 19, 2021 at the Michelson Center for Convergent Biosciences of USC. We hosted a total number of 65 registered participants from across the United States and several international participants. Thanks to the generous support from the Department of Energy, Air Force Office of Scientific Research, Office of Naval Research, the Army Research Office, the ISMET organization, and Gamry Instruments Inc., we were able to waive registration fees for all participants and reduce travel cost for several early-career researchers. The scientific program included 28 talks (16 from early-career researchers) and 24 posters that highlighted recent advances in microbial electrochemistry.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2023

High-efficiency purification of CH 4 and H 2 energy sources enabled by a phosphotungstic acid-supported Os single-atom catalyst

Methane (CH 4 ) and hydrogen (H 2 ) show promise as low-carbon energy sources, but their impurities, including H 2 and CO, pose challenges for storage and use. To address these challenges, a robust purification protocol for CH 4 and/or H 2 , combined with the catalytic conversion of impurities into CO 2 and H 2 O, is a compelling solution. Here, in this work, we investigated 11 phosphotungstic acid (PTA)-supported single-atom catalysts (SACs) by density functional theory (DFT) computations. Os 1 /PTA SACs exhibited superior catalytic activity, and the ease of oxidation follows the CO > H 2 > CH 4 order. It facilitated efficient purification of CH 4 in solvents such as water, MeOH, and various others. For H 2 purification, Os 1 /PTA SACs demonstrated excellent performance in gas, water, and MeOH. Notably, in water and MeOH, it selectively removed CO without consuming H 2 with low free energy barriers. The strong Os-PTA interactions and charge transfer mechanism contributed to its exceptional catalytic activity. Our findings shed light on SAC behavior and their potential for efficient CH 4 and H 2 purification. By addressing impurity challenges and improving clean energy utilization, these findings contribute to the development of sustainable energy technologies.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2020

A Robust, Scalable Platform for the Electrochemical Conversion of CO 2 to Formate: Identifying Pathways to Higher Energy Efficiencies

This work demonstrated a robust, scalable cell architecture for electroreduction of CO 2 (CO 2 R). An up to 90% faradaic efficiency for the conversion of CO 2 R to formate at 500 mA/cm 2 was realized at a 25 cm2 gas diffusion electrode (GDE) with a carbon-supported SnO 2 electrocatalyst. Furthermore, a 1.27 mm thick catholyte was used between the bipolar membrane and cathode GDE, which could be further reduced to tens of micrometers upon refinement. The deconvolution of the potential drop from each individual component/process guides the pathways to higher energy efficiencies of CO 2 R at this platform. Significant changes in the agglomerate size and aspect ratio on the electrode before and after an 11 h test were revealed by nano-CT, suggesting reduced CO 2 accessibility from electrode degradation. The versatility of this CO 2 R testing platform enables the ability to assess materials, components, and interactions at scales more in line with future devices.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2024

Mechanistic Insights into the Electrochemical Oxidation of 5-Hydroxymethylfurfural on a Thin-Film Ni Anode

The electrochemical oxidation of alcohols is being explored as a favorable substitute for the oxygen evolution reaction owing to its capability to generate high-value products and lower overpotentials. Herein, we present a systematic investigation into the electrochemical oxidation of 5-hydroxymethylfurfural (HMF), a model biomass platform chemical, on a thin-film nickel catalyst, aiming to investigate the underlying reaction mechanism and shed light on the role of the catalyst’s microenvironment and phase on activity and product selectivity. Utilizing a combined experimental and computational approach, we demonstrate that NiOOH is the active phase for HMF oxidation. Additionally, we find a substantial impact of the electrochemical environment, particularly the electrolyte pH, on the reaction. Under highly alkaline conditions (pH = 13), higher activity for HMF oxidation is observed, accompanied by an increased selectivity toward 2,5-furandicarboxylic acid (FDCA) production. Conversely, a less alkaline environment (pH = 11) results in diminished HMF oxidation activity and a higher preference for the partial oxidation product 2,5-diformylfuran (DFF). Mechanistic insights from DFT studies reveal that geminal diols that are present under highly alkaline conditions undergo hydride transfer via HMFCA, while a shift to an alkoxide route occurs at a lower pH, favoring the DFF pathway. Hydride transfer energetics are also strongly affected by the surface Ni oxidation state. Finally, this integrated approach, bridging experimental and computational insights, provides a general framework for investigating the electrochemical oxidation of aldehydes and alcohols, thereby advancing rational design strategies in electrocatalysts for alcohol electro-oxidation reactions.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2021

A Multiport DC Transformer to Enable Flexible Scalable DC as a Service

The rapid adoption of new DC loads and sources, including photovoltaic arrays, DC fast charging of electric vehicle, battery energy storage and data centers, requires a large amount of DC power conversion. A majority of new deployments also necessitate the integration of multiple DC loads and sources at one site. The traditional approach to serve these new applications relies on multiple standard power converters, each dedicated to a source or load, and results in highly customized systems, with challenging control coordination, complex protection strategies, and poor scalability. Instead, this paper proposes the concept of a multiport DC transformer (MDCT) as a modular building block for realizing a flexible, scalable DC as a Service system and address this rapidly growing need. The MDCT uses the S4T to achieve very tight control of cycle-by-cycle energy exchange between multiple ports, with high efficiency. A single multiport converter replaces 4-6 distinct converters, integrates all energy flows and manages protection. As a result, a new layered control architecture is introduced to ensure stability and scalability of the MDCT, with multiple S4T power converter building blocks connected in parallel to realize a fully modular system and reach the target power levels.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2020

Techno-Economic Analysis of Synthetic Fuels Pathways Integrated with Light Water Reactors

The purpose of this work is to identify, model, and compare two possible synfuel production routes utilizing CO 2 as the feedstock. Heat from an LWR nuclear plant is integrated wherever possible as a means to positively affect the economics of the LWR. Process and economic modeling for a conceptual synfuel production plant co-located (or in near proximity) with an LWR is presented, including the cost of CO 2 captured from an ethanol plant, compressed, and transported to the LWR hybrid plant, co-electrolysis of the CO 2 with water in a solid oxide electrolyzing cell (SOEC) system to produce syngas, and thermo-catalytic conversion of the syngas to transportation fuel. The hybrid LWR/synfuels plant is assumed to be located within 50-150 miles of an ethanol plant, e.g., located in the Midwest region of the United States. Performance and nth plant economics for the co-electrolysis-based processes are evaluated and compared with biomass-gasification-based technology for the synfuel routes considered. Sensitivity analysis around the price of CO 2 and electricity, two of the major cost drivers, is presented for each case. Consideration of a carbon credit is also included in the sensitivity analysis.

08 HYDROGEN↗
DOE OSTI2023

Modeling the Environment-Dependent Kinetics of Oxygen Reduction Reaction – a Continuum Model for Electric Double Layer

Here, for proton-exchange-membrane fuel cells (PEMFCs) to achieve broad commercialization, improved energy-conversion efficiency with minimal Pt-based electrocatalyst is required. Because the sluggish rate of oxygen reduction reaction (ORR) limits the efficiency of PEMFCs, the efficiency improvement requires a better understanding of ORR kinetics and mechanism to design better catalyst. To understand the ORR mechanism, theoretical and experimental analyses have been conducted. While previous studies reasonably explained the catalyst-dependent activity on single crystal catalysts in 0.1 M perchloric acid solution, the explicit effect of electrolyte and related microenvironments is not thoroughly understood. The change in the electrolyte alters the electric-double-layer (EDL) structure and thus the local microenvironment at the electrode/electrolyte interface. Thus, the structure of the EDL should be carefully analyzed to uncover the electrolyte-dependent reaction kinetics. In this talk, we propose a multiscale continuum model to predict the EDL structure and examine the effect of perchloric acid concentration on ORR activity on Pt (111). The model includes Density Potential Functional Theory (DPFT) for electron density and Modified Poisson Boltzmann equation for species’ density and electric potential. Also, the interaction between adsorbents and electric field is taken into account by minimizing the grand potential. After model validation with experimentally measured double-layer capacity data as a function of applied potential and concentration, the effect of the perchloric acid concentration (0.02 M – 0.2 M) on ORR activity is analyzed and discussed. It is shown that the model reproduces the specific activity obtained in the experiments when assuming the oxygen adsorption is limiting the rate, which can be attributed to the large energetic barrier for solvent reorganization. Then, extension of the model to PEMFC ionomer electrolytes will be introduced. Overall, the model framework and findings provide insights into the ORR mechanism and guidance on how to tailor catalyst materials for increased PEMFC performance.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2020

Photoinduced charge transfer in transition metal dichalcogenide heterojunctions – towards next generation energy technologies

Increasing interest in using two-dimensional transition metal dichalcogenides (2D TMDCs) in optical energy conversion technologies creates a demand for improving the yields and lifetimes of photogenerated charge carriers. Despite inherently fast photocarrier decay in neat 2D TMDCs, the unique photophysics in these quantum-confined systems motivates continued effort to control the evolution of photoexcited states and create functional devices. Here, an intriguing strategy to accomplish this goal is to employ TMDCs in heterojunctions with appropriate semiconductors, where energy level offsets drive photoinduced charge transfer (PCT) across material interfaces. PCT in TMDC-based systems can be optimized for many different applications, such as driving free carriers to photocatalytic sites for redox reactions like water splitting, extracting charge to perform work in photovoltaics or photodetectors, and manipulating the spin and momentum valley electronic degrees of freedom for quantum computing systems. Here, we review recent strides in optimizing PCT for such applications through greater fundamental understanding of the photophysics that occurs at TMDC/semiconductor interfaces. After giving an overview of isolated TMDC properties, synthetic methods, and the basics of PCT, we discuss TMDCs in heterojunctions with several classes of materials, including other TMDCs, small molecule semiconductors, polymers, single-walled carbon nanotubes, quantum dots, perovskites, and electrolytes. In addition to highlighting the unique benefits of each materials category, we also identify parallels across common themes, such as the roles of charge-transfer states, spin, electronic coupling, delocalization, interfacial atomic morphology, and the precise design of energy landscapes to direct charge and energy motion. We hope to capture a broad range of the valuable work in this fast-paced field to inspire new research directions for employing PCT in targeted TMDC-based systems.

30 DIRECT ENERGY CONVERSION↗