Engineering topics
Publications and source records attributed to Hackett, Gregory.
Neural networks and computer vision techniques are used to rapidly predict solid oxide fuel and electrolysis cell performance from low-resolution tomographic data.
47th International Conference and Expo on Advanced Ceramics and Composites (ICACC 2023), Daytona Beach, FL, January 22-27, 2023
47th International Conference and Expo on Advanced Ceramics and Composites (ICACC 2023), Daytona Beach, FL, January 22-27, 2023
47th International Conference and Expo on Advanced Ceramics and Composites (ICACC 2023), Daytona Beach, FL, January 22-27, 2023
47th International Conference and Expo on Advanced Ceramics and Composites (ICACC 2023), Daytona Beach, FL, January 22-27, 2023
Fracture and crack growth is one of the main degradation mechanisms in solid oxide cells (SOCs). However, the modeling of crack growth in SOCs is challenging due to their complex microstructures and possible plasticity development within the Ni particles in Ni-based SOC electrodes. In this study, a phase-field fracture model is developed, which incorporates the SOC microstructures and phase-dependent material properties, including yield strength, fracture toughness in the bulk and at the interphase boundaries. The model is employed to study crack initiation and growth under thermal and redox cycling on the hydrogen electrode side of SOCs. The simulation results demonstrate that under thermal cycling, work-zone cracking dominates in electrolyte-supported SOCs with cracks initiated at the triple-phase boundaries, while only minor mechanical degradation occurs in hydrogen-electrode-supported SOCs after hundreds of thermal cycles. Under redox cycling, through-cracking of yttria-stabilized zirconia (YSZ) in the hydrogen electrode and electrolyte layers dominates. Finally, the simulation results suggest several crack-mitigation strategies, including decreasing the porosity in the hydrogen electrode support layer and synchronizing thermal strain to balance oxidation strain.
As conventional strategies of engineering new MIEC materials for SOFCs over the past few decades would have eliminated a material like BFCZ75 from contention, this work suggests there is a need to re-think existing design criteria and develop and understand new rational materials design strategies that challenge conventional wisdom and chemical intuition. The ultimate goal of cathode design of SOFCs is to achieve a balance among electrical conductivity, ionic conductivity, oxygen exchange activity and long-term stability. Instead of searching for a replacement for unstable MIEC like LSCF, which works well in a ceria based composite electrode, some stable composites contain a highly conductive material mixing with a less conductive but highly ORR active and stable MIEC such as BFCZ75 or even triple-phase composites could be an alternative way to advance the current SOFC technology. (This work is published in May 2022 issue of Advanced Energy Materials. https://doi.org/10.1002/aenm.202201203 -->)<br>
23rd Annual Solid Oxide Fuel Cell (SOFC) Project Review Meeting, Pittsburgh, PA, October 25-27, 2022
23rd Annual Solid Oxide Fuel Cell (SOFC) Project Review Meeting, Pittsburgh PA, October 25-27, 2022
23rd Annual Solid Oxide Fuel Cell (SOFC) Project Review Meeting, Pittsburgh, PA, October 25-27, 2022
23rd Annual Solid Oxide Fuel Cell (SOFC) Project Review Meeting, Pittsburgh, PA, October 25-27, 2022
Density functional theory-based thermodynamic modeling was performed to determine the effect of humidity and H 2 /O 2 gas pressure on the defect chemistry and transport properties of proton conducting oxide BaZr 1-x Y x O 3-δ (x ≤ 0.1) in the temperature range of 800–1200K, relevant for solid oxide fuel/electrolysis cell applications. The first-principles charge defect analysis was carried out to obtain the defect energetic ensembles as a function of Fermi level as well as the dependence of the hydration and oxidation reaction energies on complex defect-dopant configurations. It is shown that oxygen vacancies introduced to compensate for the extra Ba vacancies may cause a slight increase in the concentration of hydroxyl and proton species upon hydration of Ba deficient BaZr 1-x Y x O 3-δ , while the overall proton diffusivity is predicted to decrease with increased proton hopping barriers upon trapping near the Ba vacancies. The developed defect model is further demonstrated to be able to describe the bulk defect chemistry and transport properties of BaZr 0.9 Y 0.1 O 3-δ under the solid oxide cell operating conditions. Finally, the theoretical framework developed in this work further allows the inclusion of configurational, energetic and electronic characteristics of the defects that can be used as a complementary tool to experimental measurements for testing various mechanistic pathways or to provide essential mechanistic data.
This National Energy Technology Laboratory presentation was given at the Carbon Conversion Procurement Grant Program Regional Workshops. The workshops are organized collaboratively by the DOE Office of Fossil Energy and Carbon Management and the United States Energy Association. There are a series of four workshops scheduled: 1) August 30, 2022 in Knoxville, TN (University of Tennessee) 2) September 13, 2022 in Emeryville, CA (Lawrence Berkeley National Laboratory 3) September 27, 2022 in New York, NY (Orrick, Herrington, & Sutcliffe LLP) 4) October 18, 2022 in Minneapolis, MN (TBD) The intent of the workshop is to provide potential applicants with background on the Procurement Grants program and the types of information requested. The specific purpose of this presentation is to give a high-level overview of techno-economic analysis to an audience that has little to no experience conducting them. The intent is to help the audience understand why techno-economic analysis is requested in the application process and to educate on its utility.
Ni redistribution in the hydrogen electrodes of solid oxide cells is an important degradation mechanism. Its driving force is still under debate. This work focuses on the interplay between Ni(OH) 2 diffusion and Ni-YSZ wettability change. With a Ni(OH) 2 diffusion model developed in our previous work, we further employ three models for the Ni-YSZ contact angle to quantify the Ni-YSZ wettability change. The microstructure evolutions in a reconstructed Ni-YSZ electrode are simulated under selected experimental operating conditions. It is shown that the phenomenological model can capture the driving force of Ni spreading/detachment on YSZ surface and the Ni migration reported in experiments can be qualitatively reproduced through the competition between Ni(OH) 2 diffusion and Ni-YSZ wettability change. It is also found that the initial microstructure of the active layer and the microstructure characteristics in the support layer can strongly affect the distribution of steam partial pressure and overpotential, hence the Ni redistribution, in the active layer, which may explain the inconsistencies in experiments. Further, our results show that there are two missing pieces in current theory of Ni redistribution: a mechanism of fast Ni diffusion under humid atmosphere and the physical reason behind the Ni spreading/detachment.
23rd International Conference on Solid State Ionics (SSI-23), Boston, MA, July 17-22, 2022
Computer vision techniques are combined with NETL’s machine learning based model trained on results from NETL's long-term SOFC/SOEC performance prediction tool, in order to produce a rapid assessment tool for evaluation and improvement of SOC electrodes from more easily collected microstructural data.
This presentation was delivered as part of the Global CO2 Initiative and NETL sponsored workshop, 2022 CCU TEA and LCA Guidance - A Harmonized Approach. The presentation highlights the intent and content of forthcoming NETL guidance documents and toolsets on conducting techno-economic analysis on carbon conversion technologies. Specifically discussed are the "Performing a TEA for Carbon Conversion Technologies" guidance document, the "Cost Scaling Methodology Specific to Carbon Conversion Technologies," and brief highlights of upcoming work products.
This National Energy Technology Laboratory (NETL) study describes the results of a pathway study for coal-based integrated gasification and solid oxide fuel cell (IGFC) power systems with and without carbon capture and storage. Two pathway scenarios are considered, based on the operating pressure of the SOFC. Three gasification technologies, including a conventional technology, differing in the syngas methane content, which has a significant effect on the IGFC system performance, were considered. The performance and cost benefits were estimated for a series of projected gains made through the development of advances in the component technologies or improvements in plant costs and availability. The objective of the study is to provide targeted research and development guidance to the FECM SOFC Program and SOFC commercial developers.