An Investigation to Resolve the Interaction Between Fuel Cell, Power Conditioning System and Application Loads

Solid-Oxide Fuel Cell (SOFC) stacks respond quickly to changes in load and exhibit high part- and full-load efficiencies due to its rapid electrochemistry. However, this is not true for the thermal, mechanical, and chemical balance-of-plant subsystem (BOPS), where load-following time constants are, typically, several orders of magnitude higher. This dichotomy diminishes the reliability and performance of the electrode with increasing demand of load. Because these unwanted phenomena are not well understood, the manufacturers of SOFC use conservative schemes (such as, delayed load-following to compensate for slow BOPS response or expensive inductor filtering) to control stack responses to load variations. This limits the applicability of SOFC systems for load-varying stationary and transportation applications from a cost standpoint. Thus, a need exists for the synthesis of component- and system-level models of SOFC power-conditioning systems and the development of methodologies for investigating the system-interaction issues (which reduce the lifetime and efficiency of a SOFC) and optimizing the responses of each subsystem, leading to optimal designs of power-conditioning electronics and optimal control strategies, which mitigate the electrical-feedback effects. Equally important are ''multiresolution'' finite-element modeling and simulation studies, which can predict the impact of changes in system-level variables (e.g., current ripple and load-transients) on the local current densities, voltages, and temperature (these parameters are very difficult or cumbersome, if not impossible to obtain) within a SOFC cell. Towards that end, for phase I of this project, sponsored by the U.S. DOE (NETL), we investigate the interactions among fuel cell, power-conditioning system, and application loads and their effects on SOFC reliability (durability) and performance. A number of methodologies have been used in Phase I to develop the steady-state and transient nonlinear models of the SOFC stack subsystem (SOFCSS), the power-electronics subsystem (PES), and the BOPS. Such an approach leads to robust and comprehensive electrical, electrochemical, thermodynamic, kinetic, chemical, and geometric models of the SOFSS, PES and application loads, and BOPS. A comprehensive methodology to resolve interactions among SOFCSS, PES and application loads and to investigate the impacts of the fast- and slow-scale dynamics of the power-conditioning system (PCS) on the SOFCSS has been developed by this team. Parametric studies on SOFCSS have been performed and the effects of current ripple and load transients on SOFC material properties are investigated. These results are used to gain insights into the long-term performance and reliability of the SOFCSS. Based on this analysis, a novel, efficient, and reliable PES for SOFC has been developed. Impacts of SOFC PCS control techniques on the transient responses, flow parameters, and current densities have also been studied and a novel nonlinear hybrid controller for single/parallel DC-DC converter has been developed

A structured review of long-term care demand modelling

Long-term care (LTC) represents a significant and substantial proportion of healthcare spends across the globe. Its main aim is to assist individuals suffering with more or more chronic illnesses, disabilities or cognitive impairments, to carry out activities associated with daily living. Shifts in several economic, demographic and social factors have raised concerns surrounding the sustainability of current systems of LTC. Substantial effort has been put into modelling the LTC demand process itself so as to increase understanding of the factors driving demand for LTC and its related services. Furthermore, such modeling efforts have also been used to plan the operation and future composition of the LTC system itself. The main aim of this paper is to provide a structured review of the literature surrounding LTC demand modeling and any such industrial application, whilst highlighting any potential direction for future researchers

A study of high pressure operation of isothermal tubular solid oxide fuel cells and their integration with gas turbines

M.S.William J. Wepfe

Simulation of tubular solid oxide fuel cell behavior for integration into gas turbine cycles

Ph.D.William J. Wepfe

ADVANCING FUEL CELLS TECHNOLOGY VIA ANALOGOUS HEAT EXCHANGER DESIGN PRINCIPLES/7083 (Faxes)

Abstract Fuel cells and heat exchangers have numerous similarities. Both technologies are used to produce an "energy-in-transit." Heat exchangers foster thermal transport (heat) as a result of thermal potential differences between streams; fuel cells foster charge transport across electrodes (current leading to power) as a result of electrochemical/electric potential differences between the reactant streams and fuel cell electrodes. Additional analogs include series resistance formulations, active regions for transport phenomena and pertinent capacity rates. These similarities have motivated the extension of heat exchanger design philosophies to fuel cells development. Pilot simulations have been done wherein solid oxide fuel cell geometries and process settings are being optimized via electrochemical pinch points, electroactive area optimization (patterned after optimal UA allocation within heat exchangers), and electrode "fins" for diminished polarization. The prevailing theme has been to bridge methodologies from the mature field of heat exchanger design to improve fuel cell design practices

Exploring the Mentoring Needs of Early- and Mid-Career URM Engineering Faculty: A Phenomenological Study

While mentoring has been identified as a valuable resource in recruiting and retaining underrepresented minority (URM) faculty, little research has examined the difference in mentoring needs of early- and mid-career engineering URM faculty members. As these needs can change as they navigate academia and the tenure process, mentors can effectively provide guidance and support only when they have been identified. The purpose of this phenomenological study was to determine the mentoring needs and activities of early- and mid-career URM engineering faculty who participated in the IMPACT mentoring program and how their needs were met (Moustakas, 1994). The IMPACT program and the associated research were supported by a National Science Foundation Office for Broadening Participation in Engineering award (15-42728 and 15-42524). The Ideal Mentoring Model for URM Faculty served as the theoretical framework and the study included interviews with 11 early- to mid-career faculty who provided an in-depth understanding of the participants’ needs and activities. Findings indicate all faculty members seek career development support in navigating the engineering promotion and tenure process. However, mid-career faculty display greater interest in receiving sponsorship and coaching from their mentors, as well as an awareness of the importance of having a network of mentors