Here is another innovative look at a future technology. The car is a BMW 7-series 6.0-liter V12 modified to run on both gasoline and liquid hydrogen rather than employing a hydrogen fuel-cell. The car looks like any other 7-series with the exception the engine cover. There is a switch that allows the driver to switch between the two fuel sources.
The BMW Hydrogen 7 is unlike the other Hydrogen powered vehicles. The Honda Clarity, and vehicles from General Motors, Mercedes Benz use a fuel cell technology to create electricity to power the automobile. BMW directly ignites the hydrogen directly in its standard internal combustion engine.
BMW has built 100 Hydrogen 7s, with fifty percent dedicated to customers around Berlin and most of the rest bound for Los Angeles. There is no current liquid hydrogen infrastructure so BMW has to provide a fleet of hydrogen tankers to keep the hydrogen tanks refilled.
BMW put a cryogenic tank into the trunk of the Hydrogen 7 to store the liquid hydrogen at a temperature of minus 423 degrees Fahrenheit. The tank is capable of holding 17.6 pounds of liquid hydrogen, which provides a range of approximately 125 miles. The Hydrogen 7 is also equipped with a 19.5 gallon gasoline tank. Refueling the hydrogen tank is fairly simple, with the pump hose easily attaching to the coupler on the car, behind that c-pillar door. The entire refueling process takes roughly 8 minutes.
The hydrogen fuel is stored in a large, nearly 30-gallon (110 liters), bi-layered and highly insulated tank that stores the fuel as liquid rather than as compressed gas, which BMW says offers 75% more energy per volume as a liquid than compressed gas.
One of the technical problem with the car when not using fuel, the Hydrogen 7’s hydrogen tank starts to warm and the hydrogen starts to vaporize. Once the tank’s internal pressure reaches 87 Psi, at roughly 17 hours of non-use, the tank will safely vent the building pressure. Over 10-12 days, it will completely lose the contents of the tank.
It is obvious that auto manufacturers have a ways to go before hydrogen becomes commercially feasible. It appears that Honda is the technological leader in hydrogen drivetrains.
The main concern when using liquid hydrogen is safety....since hydrogen gas is highly flammable. My concern would be a serious accident....could this turn into a replay of the Hindenberg Disaster.