Fuel cells taken for a ride

Fuel cell developer Metallic Power has completed tests of what the company believes is the world’s first refuelable on-road zinc fuel cell powered vehicle.

The technology demonstration, which began in Chula Vista, included more than 100 miles of test-driving on highways and surface streets over various terrains in humid coastal areas and the dry, hot Central Valley of California.

For the demonstration, four of Metallic Power’s prototype telecom backup power zinc fuel cell systems were fitted into a Geo Force sedan converted to Solectria’s electric drive, with a small cargo compartment built into its rear.

The company performed extensive laboratory tests on the system before taking it onto the highway. The test crew drove the vehicle at speeds reaching more than 50 mph and then rapidly refuelled it in approximately 30 minutes using simple fuel hoses that can be optimised to make the process as simple as pumping petrol.

A small lead-acid battery bank connected in parallel with the vehicle’s fuel cells provided extra power for short bursts of acceleration and hill climbing, while the fuel cells supplied the bulk of the energy for long-range driving. The technology holds the promise of delivering as much as five times the energy of the same weight of lead-acid batteries. As a result, such a vehicle could ultimately provide two to three times the range capability of a typical battery-powered electric vehicle.

Metallic Power’s zinc fuel cells are fuelled with small zinc pellets. As this fuel is consumed inside the fuel cell, it is combined with oxygen from the air to form zinc oxide, a common white powder found in sunblock and skin creams. During refuelling, the zinc oxide (which remains dissolved in a liquid electrolyte) is pumped out of the vehicle while fresh fuel and electrolyte are pumped back in. The zinc oxide and spent electrolyte can be completely regenerated back into fresh fuel and electrolyte in a separate, stationary device also under development by the company.

‘It’s a completely closed-loop system,’ said Dr. Jeffrey Colborn, chief executive officer of Metallic Power. ‘There’s nothing added, nothing wasted, and nothing to throw away or pollute the environment. While other metal/air technologies have been used to power vehicles, their implementation has required replacement or rebuilding of the cells rather than a simple refuelling operation that we feel is a more commercially viable approach.’

According to Ray Alstadt, Metallic Power’s vice president of product engineering, ‘These prototype systems performed well under more vibration, shock, dusty conditions, and temperature variation than you would normally see in an indoor telecom backup power application. This project will accelerate our development of extremely robust and reliable telecom backup products in the near term while laying the first groundwork for future applications in transportation.’

Pilot units of Metallic Power’s first commercial product, a 1.25kW 24-hour backup power module for telecom backup power, are scheduled to be available to telecommunications carriers in late 2003.

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