A. Peter Jardine, Ph.D.
DCH Technology Inc.
Valencia, CA

Introduction

In the coming conversion from fossil fuel energy sources, safety and a clean source of hydrogen will be paramount in the utilization of hydrogen as a source of clean abundant energy. Effective hydrogen sensors and ancillaries, to accurately and quickly respond to hydrogen gas leaks, will be critical in the safe deployment of mobile, hydrogen-based vehicles and stationary hydrogen-derived power sources.

Hydrogen is emerging as a primary fuel source to replace oil-based fuels. Hydrogen-based fuel cells, based on a variety of technologies, will be the mechanism by which electrical energy will be derived from the reaction of hydrogen and oxygen gases within the fuel cell to make water. Hydrogen generation can come from a variety of methods, including the following: reforming alcohols (ex. methanol), natural gas, electrolysis of water and biomass generation, as well as from purely synthetic chemical decomposition of hydrogen-containing compounds.

All fuel cell technology ultimately utilizes hydrogen in a gaseous form. In addition, fuel cells generally use platinum catalysts to break down the diatomic hydrogen gas into monatomic hydrogen ions. Key differences in fuel cell technology are in the electrolytes that are used to carry the monatomic hydrogen ions to O₂ to form H₂O. Platinum catalysts are prone to poisoning by other chemical species, such as sulphur-containing chemicals, which means that the hydrogen gas stream has to be kept as pure as possible to avoid degradation of the catalyst and concomitant performance degradation of the fuel cell.

The economics of hydrogen fuel cells are based on three large markets: automotive fuel cells, stationary or residential fuel cells, and portable fuel cells. All fuel cells require two types of sensors; the first monitors the quality of the hydrogen feed gas and the second, more important sensor system, for leak detection.

As hydrogen fuel cells are an emerging technology, the codes and standards for the fuel cells and the sensors supporting the fuel cells are still in development by a number of bodies, including European and American regulators. Sensor specifications for these applications are still being written, with no definite standard in place.

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