A fuel cell system has been developed to provide backup power to a Variable Message Sign (VMS) used in traffic control. The VMS is powered from a bank of batteries that are normally kept charged by a solar photovoltaic array with specialized control electronics. Under certain conditions the solar charging system is unable to maintain the batteries at a sufficient state of charge. This can be due to unfavorable weather conditions, a location that does not receive sufficient sunlight, or a malfunction of the solar charging system. Low battery voltage then causes a malfunction of the sign, to the point where it must be taken out of service. When the system is equipped with the fuel cell system, an electronic system senses low voltage and turns on the fuel cell to bring the batteries up to an acceptable voltage. The sign continues to function normally, and the result is lower maintenance, improved traffic safety, and longer battery life due to avoidance of deep discharge. The backup power system contains two complete fuel cells, each of which can provide the required power; this redundant design provides high reliability for the critical traffic-information application. The VMS trailers are modified to contain four 2000-psi hydrogen cylinders, each weighing about 20 kg and easily handled by one person without special lifting equipment.
Highly reliable 50-watt fuel cell system for variable message signs
50-Watt-Brennstoffzellensystem mit hoher Zuverlässigkeit für veränderbare Verkehrslenkungszeichen
Portable Fuel Cells, 1999 ; 107-112
1999
6 Seiten, 4 Bilder
Conference paper
English
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