Emissions from Fuel Processor / Fuel Cell Power Systems

Fuel processor / fuel cell systems promise to provide a means of powering automobiles with low emission levels. Prototype systems have already been built to demonstrate operation on automotive fuels including gasoline, methanol, and ethanol. As these systems evolve it becomes increasingly important to verify that the emission reduction potential is indeed possible. This paper outlines the basic components in a fuel processor / fuel cell system, highlights a few differences between emissions from fuel cell systems and IC engines, and describes the various operation modes which must eventually be considered when testing for emissions from fuel cell systems. In addition, steady state results are presented for a 10 kWe system operating at ¼, ½ and full power on gasoline. Key issues related to emissions from fuel cell systems are identified. The Tail Gas Combustor is identified as the critical component for controlling emissions. A rough comparison shows the steady state emissions of current systems are substantially below those allowed by ULEV standards. Therefore the emissions have the potential of still being below ULEV standards when future systems undergo the transient operation required by the standard driving cycle used to evaluate ULEV compliance.