Abstract
High Temperature Proton Exchange Membrane (HT PEM) fuel cell based on polybenzimidazole (PBI) polymer and phosphoric acid, can be operated at temperature between 120 °C and 180 °C. Reactants humidification is not required and CO content up to 2% in the fuel can be tolerated, affecting only marginally performance. This is what makes HT PEM very attractive, as low quality reformed hydrogen can be used and water management problems are avoided. Till nowadays, from experimental point of view, only few studies relate to the development and characterization of high temperature stacks. The aim of this work is to present the main design features and the performance curves of a 25 cells HT PEM stack based on PBI and phosphoric acid membranes. Performance curves refer to the stack operating with two type of fuels: pure hydrogen and a gas mixture simulating a typical steam reformer output. The stack voltage distribution analysis and the stack temperature distribution analysis suggest that cathode air could be used as coolant leading to a better thermal management. This could simplify stack design and system BOP, thus increasing system performance
Highlights
A fuel-cell power-source system can generate electrical power with significantly improved: efficiency, energy density, ergonomics and environmental compliance than other conventional power sources
Several technical obstacles hinder their widespread commercialization. These include a complex water and heat management and the intolerance to carbon monoxide (CO) usually contained in the reformates fuels. To overcome these problems research has focused on the development of Proton Exchange Membrane (PEM) fuel cells that can be operated above 100 °C (High Temperature PEM fuel cells, High Temperature Proton Exchange Membrane (HT PEM)) [1, 2]
There are several advantages in operating at higher temperatures: (i) water management can be simplified because only a single phase of water need to be considered; (ii) the cooling system is simplified due to the increased temperature gradient between the fuel cell stack and the coolant; (iii) waste heat can be recovered as a practical energy source; (iv) CO tolerance is considerably increased thereby allowing fuel cells to use lower quality reformed hydrogen
Summary
A fuel-cell power-source system can generate electrical power with significantly improved: efficiency, energy density, ergonomics and environmental compliance (low or no emissions) than other conventional power sources. Several technical obstacles hinder their widespread commercialization These include a complex water and heat management and the intolerance to CO usually contained in the reformates fuels. To overcome these problems research has focused on the development of PEM fuel cells that can be operated above 100 °C (High Temperature PEM fuel cells, HT PEM) [1, 2]. Amongst all types of HT PEM, the ones based on polybenzimidazole (PBI) and phosphoric acid membranes are the most promising They can be operated at temperature between 120 °C and 180 °C, reactants humidification is not required and carbon monoxide (CO) content up to 2% in fuel can be tolerated, affecting only marginally the performance
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