Publication Date

2012

Document Type

Honors Thesis

Department

Engineering

Keywords

Proton exchange membrane fuel cells, Proton exchange membrane fuel cells-Reliability, Humidity, PEM fuel cells, Low humidity, Voltage sensitivity, Humidity estimates

Abstract

A fuel cell is an electrochemical engine that produces electricity. Fuel cells are similar to batteries except that instead of using a form of stored chemical energy that is detrimental to the environment upon disposal, fuel cells use a fuel source such as hydrogen to enable the production of electricity. Fuel cells can perform in a variety of operating conditions. In low humidity applications, however, fuel cells may suffer dramatic voltage losses largely due to membrane water content. In order to achieve better performance for the application of miniature fuel cells in low humidity conditions, the voltage characteristics of PEM fuel cells were studied with a focus on the effect of membrane water content. Using a polarization model derived from fundamental principles, sensitivity to membrane water content and temperature were explored. Since membrane water content, lmb, is difficult to measure and is often estimated, models typically require an assumption for this value. In the sensitivity analysis performed, however, the predicted polarization curves had drastically different ranges depending upon the assumed value of lmb used when tuning the model, with greatest sensitivity for humidified conditions. In addition, at lower temperatures, the model was more sensitive to changes in membrane water content. These observations suggested that assuming a value for lmb would not be appropriate. To further explore ways to circumvent the requirement of actual lmb data, the potential for improving estimation methods for lmb was explored. A membrane water content estimation technique was developed and revealed that voltage is more sensitive to changes in membrane water content at higher humidity. A hypothesis was developed to find the membrane water content tuning value that would be most appropriate for further modeling and understanding the performance dynamics of a cell under those operating conditions. viii

Language

English

Comments

viii, 32 p. : ill. (some col.) Honors project-Smith College, Northampton, Mass., 2012. Includes bibliographical references (p. 31-32)

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