Development of a Ceramic Heat Exchanger for Application as Solid Oxide Fuel Cell Cathode Air Preheater

Author(s):  
José Luis Córdova ◽  
Hooshang Heshmat

A ceramic heat exchanger with high effectiveness and low-pressure drop is being developed for application as a cathode air preheater for a Solid Oxide Fuel Cell (SOFC). At the operating conditions of SOFCs, typical metallic alloys as those used in commercial heat exchangers may undergo chromium volatilization, which is a known cathode degradation mechanism that reduces SOFC performance and life. Use of ceramics such as alumina or alumina-silicate instead of chromium-containing metal is one approach to eliminate the effects of chromium on the SOFC cathode. This project leverages the geometric design of a heat exchanger previously prototyped and tested, and demonstrated to have a nearly constant heat transfer effectiveness of 92% with low pressure drop [1], to fabricate a novel heat exchanger made from a ceramic material. This paper calculates heat exchanger performance requirements based on state of the art SOFC operating conditions, presents a thermal-based tradeoff analysis for ceramic material selection, and presents a modular heat exchanger and its heat exchange elements. The modular concept presented allows for incremental aggregation of modules to target a broad range of operating conditions typical of present and upcoming SOFC applications (e.g., 25 to 400 kWe). A fabricated sample ceramic heat exchange element is shown to demonstrate the viability of the concept for a real SOFC application.

2021 ◽  
Vol 9 ◽  
Author(s):  
Mar Pérez-Fortes ◽  
Victoria He ◽  
Arata Nakajo ◽  
Jürg Schiffmann ◽  
François Maréchal ◽  
...  

With a growing energy demand in a carbon-constrained society, fuels cells powered by renewable fuels, and specifically solid waste, are seen as interesting contributors to the energy portfolio. The alternative energy industry needs to reduce costs, enhance efficiency, and demonstrate durability and reliability to be economically feasible and attractive. This paper addresses biomass waste gasification in distributed energy systems, using a solid oxide fuel cell (SOFC) to produce electricity and heat. The potential and optimal plant efficiency and layout (i.e., anode off-gas (AOG) recirculation point via small-scale turbomachinery and heat exchanger network) are analyzed through a multi-stage approach that includes scenario evaluation and multi-objective optimization via a hybrid optimization strategy with heuristics and mathematical programming. The results in this paper summarize the most convenient operating conditions and provide an optimized heat exchanger network (HEN). The AOG recirculation toward the gasifier combustor is the preferred option; the electrical and thermal efficiencies can separately go up to 49 and 47%, respectively. The combined total efficiency ranges between 76 and 82%, and the area of heat exchange, which corresponds to an amount of heat exchanged between 91 and 117 kW, is within 6–14 m2.


Author(s):  
Y. Haseli

Optimum pressure ratios of a regenerative gas turbine (RGT) power plant with and without a solid oxide fuel cell are investigated. It is shown that assuming a constant specific heat ratio throughout the RGT plant, explicit expressions can be derived for the optimum pressure ratios leading to maximum thermal efficiency and maximum net work output. It would be analytically complicated to apply the same method for the hybrid system due to the dependence of electrochemical parameters such as cell voltage on thermodynamic parameters like pressure and temperature. So, the thermodynamic optimization of this system is numerically studied using models of RGT plant and solid oxide fuel cell. Irreversibilities in terms of component efficiencies and total pressure drop within each configuration are taken into account. The main results for the RGT plant include maximization of the work output at the expenses of 2–4% lower thermal efficiency and higher capital costs of turbo-compressor compared to a design based on maximum thermal efficiency. On the other hand, the hybrid system is studied for a turbine inlet temperature (TIT) of 1 250–1 450 K and 10–20% total pressure drop in the system. The maximum thermal efficiency is found to be at a pressure ratio of 3–4, which is consistent with past studies. A higher TIT leads to a higher pressure ratio; however, no significant effect of pressure drop on the optimum pressure ratio is observed. The maximum work output of the hybrid system may take place at a pressure ratio at which the compressor outlet temperature is equal to the turbine downstream temperature. The work output increases with increasing the pressure ratio up to a point after which it starts to vary slightly. The pressure ratio at this point is suggested to be the optimal because the work output is very close to its maximum and the thermal efficiency is as high as a littler less than 60%.


2005 ◽  
Author(s):  
Comas L. Haynes ◽  
J. Chris Ford

During latter-stage, “start-up” heating of a solid oxide fuel cell (SOFC) stack to a desired operating temperature, heat may be generated in an accelerating manner during the establishment of electrochemical reactions. This is because a temperature rise in the stack causes an acceleration of electrochemical transport given the typical Arrhenius nature of the electrolyte conductivity. Considering a potentiostatic condition (i.e., prescribed cell potential), symbiosis thus occurs because greater current prevalently leads to greater by-product heat generation, and vice versa. This interplay of the increasing heat generation and electrochemistry is termed “light off”, and an initial model has been developed to characterize this important thermal cycling phenomenon. The results of the simulation begin elucidating the prospect of using cell potential as well as other electrochemical operating conditions (e.g., reactants utilization) as dynamic controls in managing light off transients and possibly mitigating thermal cycling issues.


2020 ◽  
Vol 167 (4) ◽  
pp. 044517
Author(s):  
Congying Jiang ◽  
Yuchen Gu ◽  
Wanbing Guan ◽  
Meng Ni ◽  
Junkang Sang ◽  
...  

Author(s):  
Aristide F. Massardo ◽  
Loredana Magistri

The aim of this work is to investigate the performance of Internal Reforming Solid Oxide Fuel Cell (IRSOFC) and Gas Turbine (GT) combined cycles. A mathematical model of the IRSOFC steady-state operation was presented in Part A of this work (Massardo and Lubelli, 1998), coupled to the thermodynamic analysis of a number of proposed IRSOFC-GT combined cycles, taking into account the influence of several technological constraints. In the second part of this work, both an exergy and a thermoeconomic analysis of the proposed cycles have been carried out using the TEMP code developed by the Author (Agazzani and Massardo, 1997). A suitable equation for IRSOFC cost evaluation based on cell geometry and performance has been proposed and employed to evaluate the electricity generation cost of the proposed combined systems. The results are presented and the influence of several parameters is discussed: external reformer operating conditions, fuel to air ratio, cell current density, compressor pressure ratio, etc. Diagrams proposed by the Author (Massardo and Scialo’, 2000) for cost vs. efficiency, cost vs. specific work, and cost vs. system pressure are also presented and discussed.


2010 ◽  
Vol 171-172 ◽  
pp. 319-322
Author(s):  
Hong Bin Zhao ◽  
Xu Liu

The simulation and analyses of a “bottoming cycle” solid oxide fuel cell–gas turbine (SOFC–GT) hybrid system at the standard atmospheric condition is presented in this paper. The fuel cell model used in this research work is based on a tubular Siemens–Westinghouse–type SOFC with 1.8MW capacity. Energy and exergy analyses of the whole system at fixed conditions are carried out. Then, comparisons of the exergy destruction and exergy efficiency of each component are also conducted to determine the potential capability of the hybrid system to generate power. Moreover, the effects of operating conditions including fuel flow rate and SOFC operating temperature on performances of the hybrid system are analyzed.


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