General Motors' latest fuel cell stack sets a new world standard

FOR RELEASE: September 13, 2001

General Motors Introduces World's Most Powerful Fuel Cell Stack

LONDON - General Motors' latest fuel cell stack sets a new world standard for power density that packs 60 percent more power than any competitor, GM announced at a technical conference here today.

The new GM stack generates 1.75 kilowatts (kW) per liter, setting an industry benchmark for volumetric efficiency - the measurement of the stack's power output in kilowatts vs. its volume.

The highest power density announced by any other fuel cell manufacturer to date is 1.1 kW per liter by Ballard Power Systems, according to GM scientists.

"Reducing the size and weight of the fuel cell stack while maintaining or improving its power output is important for packaging, design and affordability," said Matthew Fronk, chief engineer of fuel cell systems for GM's Global Alternative Propulsion Center (GAPC).

Smaller stacks create more space for other components and allow their use in smaller vehicles and stationary units. They require less material, providing an opportunity for further cost savings. Stack volume can be tailored to the power needs of the vehicle in which it is installed.

"We achieved this efficiency through further developments in materials, and improving how we form parts of the fuel cell and how the stack is put together," said Gary Stottler, director of stack development at GAPC.

The new stack has 640 cells with a continuous power output of 102kW (134 horsepower) and a peak power output of 129kW (173 hp). It weighs 82 kg (180 pounds) and measures 32 1/4 inches by 5 1/2 inches by 20 inches, or 82 cm by 14 cm by 50 cm (58 liters).

Continuous power is the power that systems are designed to run on indefinitely, while peak power is the power that systems are designed to support for brief periods. Continuous power is what engines and other propulsion systems run at the majority of the time.

GM's previous industry-best fuel cell stack - Stack 2000 - has a power density of 1.6 kW per liter and weighs in at 190 pounds. Stack 2000's continuous power output is 94 kW (126 hp) with a peak power output of 129 kW. As a point of comparison, Ballard's top stack has been quoted at 75 kW of continuous power.

As with Stack 2000, the membrane at the core of each cell in the new stack does not need external moisture to maintain its efficiency. This is accomplished with a unique and proprietary method of water management inside the stack. Fuel cells need humidification to properly function.

The new stack continues to have Stack 2000's excellent cold start performance: full power in 30 seconds at minus 20 degrees Celsius (minus 4 degrees Fahrenheit). This cold-start performance is critical in colder climates. Despite the ability to start quickly in extreme cold, GM engineers continue to improve the stack's cold weather capabilities.

General Motors Corporation , the world's largest vehicle manufacturer, designs, builds and markets cars and trucks worldwide. In 2000, GM earned $5 billion on sales of $183.3 billion. It employs about 372,000 people globally.