Opportunities For Portable Ballard Fuel Cells

H. H. Voss and J. R. Huff Ballard Power Systems Inc. 9000 Glenlyon Parkway Burnaby, British Columbia, Canada V5J 5J9

Introduction

With the increasing proliferation and sophistication of portable electronic devices in both commercial and military markets, the need has arisen for small, lightweight power supplies that can provide increased operating life over those presently available. A solution to this power problem is the development of portable Ballard Fuel Cell power systems that operate with a hydrogen fuel source and air. Ballard has developed PEM fuel cell stacks and power systems in the 25 to 100 watt range for both of these markets.

For military use, Ballard has teamed with Ball Corporation and Hydrogen Consultants, Inc. and has provided the Ballard Fuel Cell stack for an ambient PEM fuel cell power system for the DoD. The system provides power from idle to 100 watts and has the capability of delivering overloads of 125 watts for short periods of time. The system is designed to operate over a wide range of temperature, relative humidity and altitude. Hydrogen is supplied as a compressed gas, metal hydride or chemical hydride packaged in a unit that is mated to the power/control unit. The hydrogen sources provide 1.5,5 and 15 kWh of operation, respectively. The design of the fuel cell power system enables the unit to operate at 12 volts or 24 volts depending upon the equipment being used.

For commercial applications, as with the military, fuel cell power sources in the 25 to 500 watt range will be competing with advanced batteries. Ambient PEM fuel cell designs and demonstrators are being developed at 25 watts and other low power levels. Goals are minimum stack volume and weight and greatly enhanced operating life with reasonable system weight and volume.

This paper will discuss ambient PEM fuel cell designs and performance and operating parameters for a number of power levels in the multiwatt range.

Military Applications

The team of Ballard, Ball Aerospace and Technologies Corporation, and Hydrogen Consultants, Inc. has developed a 100 watt PEM fuel cell based power system that operates on hydrogen and air. The power system is comprised of two separate parts; a power module containing the fuel cell system and controls and a fuel module containing the hydrogen fuel supply system. The power module utilizes a 100-watt nominal Ballard hydrogen/air fuel cell stack that is configured to provide either 12 or 24 volt operation, as required, over a wide range of operating conditions; including from 0° to 50°C, from 0 to 95% relative humidity, and from sea level to 8000 feet elevation. The fuel cell uses air as the oxidant and coolant; supplied and controlled by small fans. Hydrogen energy storage options include a metal hydride storage vessel (1.3 kWh); a high pressure, composite gas cylinder (5 kWh); or a chemical hydride system, which is under development (15 kWh). The complete power system is man-portable and fits into a standard military backpack. (The unit's volume is less than 1 ft3 with any of the hydrogen storage options and the weight of the unit is approximately 27 pounds.) The power system can deliver 2 to 100 watts continuous power and short duration peak power of 125 watts. It is also capable of up to 15 kWh of energy storage at 10 watts continuous power. The electrical interface characteristics of voltage, voltage overshoots, settling time, and response to load changes are well within normal specifications.

The portable fuel cell power system has been thoroughly tested and has successfully met the required electrical characteristics. The system also has been operated at the four extreme points defined by combinations of the required operating conditions. In addition, the system has undergone shock and vibration testing. Units have been successfully field tested by military personnel using both 12 and 24 volt equipment.

Commercial Applications

Ballard has begun development of portable hydrogen/air PEM fuel cell systems for commercial applications that require power in the 25 to 500 watt range. Ambient PEM fuel cell designs and demonstrators are being developed at 25 watts and other power levels at the lower end of this range. The goals for these efforts are minimum stack volume and weight, greatly enhanced operating life, and reasonable system weight and volume. These designs use ambient air as the source of reactant oxygen and for cooling. Metal hydrides are used for hydrogen fuel storage. An initial 25 watt prototype is shown in Figure 1.

Figure 1:25 Watt Prototype

This system contains a 16-ceII fuel cell stack and has a 12 VDC nominal output. The hydrogen storage capability is sufficient to provide 300 Wh of operation at 25 watts. The metal hydride and power unit plus controls are packaged separately; therefore, it is possible to increase the energy storage of the system by increasing the size of the hydride hydrogen storage module. This prototype has demonstrated the feasibility of portable hydrogen/air PEM fuel cells systems for providing power in the lower end of the power range being evaluated. Design and development of the system for commercial applications is continuing.

Acknowledgment

The 100 watt power plant system for military applications effort was supported by the U.S. Department of Defense.

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