Drive

Fuel cell vehicles and their ‘free energy' make their own power

For all the technology that goes into them, battery-electric cars are relatively simple. You plug them into a wall, charge them up, and then drive them until they need to be charged again.

But there’s an even more advanced model that makes its own electricity. Called a fuel cell vehicle, or FCV, it contains a fuel cell stack that produces power from hydrogen.

“It’s a chemical process, not a combustion process,” says Stephen Ellis, manager of fuel cell vehicle marketing for American Honda Motor Company. “In simplest terms, hydrogen is introduced on one side of a membrane and oxygen on the other side, and through the exchange of protons, electricity is made.”

The thin membrane, which resembles cellophane plastic, is sandwiched between layers that form the hydrogen and oxygen electrodes. This “sandwich” is called a membrane electrode assembly. When a separator is attached on either side, the resulting unit is called a cell. Several hundred cells are stacked together —hence the name — to form the fuel cell stack. The separators provide room for hydrogen, air, and coolant to flow between the cells.

The fuel cell receives its hydrogen from a storage tank in the car, while it gets its oxygen from the outside air. The process of creating electricity releases water. Some of it remains in the stack, since the membrane has to stay damp, but the excess goes out the tailpipe. It’s the only emission an FCV creates.

“When you turn the key and press the ‘start’ button, that begins the production of electricity,” Ellis says. While fuel cells from ten years ago needed about 30 seconds to start working, today’s versions take less than five seconds.

Honda’s FCV contains a lithium-ion battery, which stores any excess electricity from the fuel cell. It also captures kinetic energy during deceleration and braking, and stores it as electricity. Ellis calls this “free energy,” since it’s power that’s created without using hydrogen. During start-up and acceleration, when large amounts of power are needed, the battery supplements the fuel cell’s output. The fuel cell also shuts down its electricity production when the car is stationary, so the battery provides power to run the lights, stereo, and other devices.

Honda’s current fuel cell has a range of about 385 km on a tank of hydrogen, but an improved one coming next year will go about 480 km, even though it’s 33 per cent smaller.

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