Based on the bi-fuel version (gasoline and hydrogen) (earlier post), the BMW Hydrogen 7 mono-fuel is equipped with a 6.0-liter V12 internal combustion engine (ICE) which has been engineered to run exclusively on hydrogen. The hydrogen storage system in the mono-fuel version is the same as in the bi-fuel version: a cryogenic tank that holds approximately 8 kg (17.6 lbs) of liquid hydrogen.
This car runs on liquid hydrogen, not gaseous hydrogen. There are only about 50 hydrogen fueling stations in the United States, and just a handful of those dispense liquid hydrogen. Even if you happen to have access to liquid hydrogen station, you’ll still face a number of other drawbacks and obstacles. First, the BMW Hydrogen 7 has a zero-to-60 time of almost 10 seconds, which is about 45 percent slower than a conventional 7 Series with a V-12. Trunk space has been cut in half to make way for the bulky hydrogen fuel tank.
Speaking of the tank, it’s more accurate to think of it as a giant thermos, because the temperature of hydrogen must drop down to about 400 degrees below zero Fahrenheit before reaching a liquid state. If that chilly temperature is not maintained, then you face the problem known as “boil off,” a process which is difficult to avoid. When the car is not in use—for as little as one day—the liquid hydrogen begins boiling off. Half the fuel is gone in eight days time. Therefore, this car is actually more efficient on the road than in parked in a garage.
The driver is able to switch from hydrogen to gasoline mode manually by pressing a button on the multifunction steering wheel. Because engine power and torque remain exactly the same regardless of the mode of operation, switching from one mode to another has no effect on the driving behavior and performance of the BMW Hydrogen 7.
The control system in BMW Hydrogen 7 gives priority to the use of hydrogen. And, should one of the two types of fuel be fully consumed, the system will automatically switch over to the other type of fuel in the interest of secure, ongoing supply.
For now, the problems of the Hydrogen 7 belong to very short list of people. BMW has leased a limited number to high-profile individuals interested in touting the green attributes of hydrogen fuel.