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BMW has gone to great lengths to publicize the “Hydrogen 7,” the hydrogen powered 7 Series loaned to stars with great publicity.

But is there any reality to what BMW is doing, or is the Hydrogen 7 really just a very effective publicity stunt?

Though hydrogen powered vehicles are generally thought of when fuel cells are the actual source of power creation, the Hydrogen 7 is not a fuel cell car. And, therein, lies the real story.

The Hydrogen 7 burns hydrogen in modified BMW V-12 engine. In that respect, it’s a lot like cars that are converted to burn propane. A different fuel is being substituted for gasoline, but it creates power the same way as any other internal combustion engine: moving pistons in cylinders. In fact, the Hydrogen 7 can also burn regular gasoline. Selecting the fuel is simply a matter of moving a switch on the dashboard.

But, in order to burn hydrogen in an internal combustion engine, it must be stored in liquid form. That requires the ability to keep the hydrogen very, very cold. The hydrogen fuel tank in the Hydrogen 7 is insulated, using an insulating material which BMW says has the equivalent properties of 17 meters of Styrofoam in the one inch thick tank insulation. Even though the tank is so well insulated that, according to BMW, it could keep coffee hot for three months, it can’t keep hydrogen inside it for more than a day. The fuel builds pressure in the tank, to the point that it must be vented when the pressure reaches 87 psi. That happens automatically, but it can also vent out half the hydrogen fuel supply into the atmosphere. The car is equipped with a catalytic converter to add oxygen to the venting hydrogen to turn the escaping gas into water vapor.

Then, there is cost: hydrogen is more expensive than gasoline. Even though it creates water vapor as its exhaust, there has been virtually nothing done to assess either the environmental impact of the energy used to manufacture hydrogen or maintain it in liquid form in storage tanks around the country. Similarly, there has been no apparent consideration given to the effect of increasing the atmospheric water content, particularly in areas with concentrated automotive populations.

BMW claims that it is hoping the Hydrogen 7 will encourage more stations selling liquid hydrogen. But, it’s not willing to take the gasoline tank out of the car before loaning it to the stars. That’s probably just as well, for both stars and company. On hydrogen, the range of the Hydrogen 7 is a mere 100 miles with a full tank.