Hydrogen fuel cell vehicles from Honda, Toyota and Hyundai are on the roads now in only small numbers, mostly in California. The prospects for the advanced, clean-running powertrain are not clear, but major suppliers are investing in the field.
A key challenge going forward will be making the fuel cell systems smaller and more efficient so that the powertrain can be installed in conventional vehicles that offer the same interior space as today's vehicles.
That's one of the achievements of the current-generation Honda Clarity Fuel Cell. The fuel cell stack is 30 percent smaller than the one in the previous generation, enabling Honda to increase the Clarity's interior room. The current model seats five, compared with the previous Clarity, which had room for four. That helps make it a benchmark for fuel cell vehicles in the years ahead.
To help make this possible, Garrett Motion Inc. (formerly Honeywell Transportation Systems, best known for its turbochargers) developed for the Clarity a high-performance two-stage air compressor — basically an air pump with a turbine wheel on each end of the shaft — that allowed for a smaller fuel cell stack. The more air forced through the fuel cell stack, the more electricity it generates. The compact, lightweight compressor supplies the air, which passes through at high pressure — more than 58 pounds per square inch. Higher pressure, combined with Honda's more efficient fuel cell stacks, produces enough electric power to equal the performance of a V-6-powered sedan.
"Two different superchargers, one at each end of the air compressor motor's axis, are connected by piping to increase air pressure in two stages," said Ryoichi Yoshitomi, Garrett fuel cell system engineer. "We hadn't mass-produced an electric turbo air compressor before, and we also considered the high costs, but the possibilities were too attractive not to try."