GM, Honda & Fuel Cells

No confusion. The Mazda hydrogen RX-8 power output drops by half, and torque by nearly a third. The BMW doesn't lose power, but it's fuel efficiency with hydrogen is horrendous. The V12 gets 16.9mpg, which is bad to begin with, and drops to 4.7mpg on hydrogen. Tractor trailer trucks do better.

Maintaining the power output is probably why BMW used liquid hydrogen. It has some advantages over high pressure H2. The tank on the BMW is empty in 10 to 12 days do to venting in order to keep the liquid cold.

BMW Hydrogen 7 - Wikipedia, the free encyclopedia
Mazda RX-8 Hydrogen RE - Wikipedia, the free encyclopedia

" EERE’s Fuel Cell Technologies Program claims that, as of 2011, fuel cells achieved a 42 to 53% fuel cell electric vehicle efficiency at full power,"
Fuel cell vehicle - Wikipedia, the free encyclopedia
The best engines might be that efficient, but that is measuring efficiency for the engine alone. For a vehicle, there are going to be losses taking the engine's work to the wheels.

The Honda Clarity is now available as a limited lease. It has a EPA rated 60mpge. The only cars doing better are running on batteries. A hydrogen ICE car is only going to match, at best, a gasoline ICE one in fuel economy.

 

Ah...you said the BMW had no power. Now it does.

As for the '"efficiency" of hydrogen, we don't really care since we have a non-polluting fuel that is created without pollution. And you don't measure hydrogen efficiency by the gallon but by the kilogram.

Keep in mind that this is a prototype built using a non-purpose built car to demonstrate how little manufacturing change is needed to convert from gasoline to hydrogen fuel.

It is more efficient to direct burn hydrogen vs. the energy loss of conversion to electricity in a fuel cell and the energy loss of transmission and the electric motors.

And much less expensive, a type of economic efficiency, using much less natural resources to construct. The natural resources do not exist to convert current cars and trucks to fuel cell or EV or even hybrid. The natural resources do exist to convert to natural gas, what is happening now, and to hydrogen, what will happen if science, self preservation and a long view of industrial economy prevail.

 

Since it was liquid H2, they used volume. Going by kg the BMW only went 1.39 miles per kilogram, or 0.33mpge.

A purpose built hydrogen ICE will do better, but it will never by as efficient as a FCV. If the BMW engine efficieny was improved an hundred fold, it would still be around half as efficient as a FCV on the road today.

If we had the non polluting energy energy to make hydrogen, we'd still go about 4 times as far putting the energy into a BEV than into a FCV. Or eight or more times compared to a H2 ICE. Even if pollution free, there is still a cost for making this energy. SO the BEV, and even the FCV, will be cheaper to run than the H2 ICE.

If the natural resources don't exist for the batteries or fuel cells, it will be cheaper making bio gas or methanol than hydrogen.