Ultra Cool: A Ride in BMW's Hydrogen 7

“In some cases, the exhaust from the Hydrogen 7 is cleaner than the actual air,” Dave Buchko tells me. We are standing in my driveway next to his charge, a heavily art-directed BMW, which has the words “Clean Energy” emblazoned on its side. I am not tempted to breathe in its exhaust, however clean it may be.

Buchko, who is an advanced powertrain spokesman for BMW, delivered the car to me and brought his young son, Jamie, along for the ride. Given that his family's involved, I believe what he's saying about the safety of hydrogen (no visions of the Hindenburg for him) and the bullet-proof, drop-proof and crash-resistant nature of its hydrogen tank.

BMW's Dave Buchko, son Jamie and BMW's Hydrogen 7.

The Hydrogen 7 has a detuned 12-cylinder, internal-combustion engine. Normally cars with V-12s are horrible gas guzzlers. The standard-issue big boy known as the 760Li gets a miserable combined fuel economy of 15 miles per gallon, and will if allowed consume 22.8 barrels of oil annually. The fairly luxurious H7 runs on gasoline if you want it to, but a push of the “H2” button and its taking in hydrogen from the big cryogenic tank that occupies half the trunk.

Why cryogenic? Well, the car carries eight kilograms (17.6 pounds) of liquid hydrogen, which is stored at an amazing -423 degrees Fahrenheit. A drop of it could burn through your skin, but you're not likely to ever encounter it in a liquid state because it instantly vaporizes when exposed to ambient temperatures.

Liquid hydrogen is much denser than hydrogen gas, which is why the car can eke out a 125-mile range on it. But leave the car sitting (at an airport, for instance) for 17 hours or more and the hydrogen will start to warm up, or “boil off.” The car captures the escaping gas, mixes it with air and turns it into water.

Driving the Hydrogen 7 is fun, and not overly dramatic. It's super-quiet in gasoline mode, and only slightly more ratchety (the unique fuel injection) on hydrogen. The engine starts (with an intense whirring noise) on hydrogen only, which avoids the pollution associated with a warming catalytic converter. At 80 on the American autobahn, it's lazing along.

The Hydrogen 7 is nominally a production car, but don't expect to see many on the road. Our hydrogen pumping network is vestigal at best, and the liquid form is hardly the affordable alternative to gasoline. The German Der Spiegel, in a grumpy piece downplaying the car's environmental benefits, concludes that a trip of 62 miles will use up $38 of hydrogen. Fuel economy on hydrogen amounts to 17 mpg.

BMW has never been into fuel cells, preferring to burn the mysterious, 15-times-lighter-than-air gas known as hydrogen. No other carmaker is currently showing such enthusiasm. I think fuel cells still have the edge, but with all the remaining hurdles it remains highly speculative to think the hydrogen energy economy will save us from fossil fuel tyranny. But let's hope!