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use shall serve not only to reduce CO2 emissions, but also to set a new
milestone in a new area of automobile production, initiating a true revolution
in the automotive industry.
By and large, only the pressure- and temperature-proof coupling for filling in
hydrogen distinguishes the liquid hydrogen tank filling system from the
conventional process of pumping in gasoline at a regular filling station. In all
other respects the process of filling the tank is the same as with gasoline,
the small number of manual operations required of the driver being more or
less the same: Before filling up the tank, the vehicle must be parked safely
in position by operating the electromechanical parking brake in transmission
position P. Then, pressing a button to the left of the steering wheel,
the driver opens up the tank filler flap for the hydrogen tank. The next step is to
insert the liquid hydrogen coupling on the fuel pump into the car s hydrogen
tank filler pipe like a conventional pump nozzle. Then, after the connection has
been established manually, the tank coupling is automatically locked firmly
in position, the car informing the filling station by itself via an electronic contact
that the tank may now be filled up, without requiring any intervention on
the part of the driver. Ultimately, therefore, the process of filling up the tank
with hydrogen can start automatically by means of system control.
The filling station receives the electronic go-ahead for filling up the tank only
when the car has been parked safely in position, if battery voltage is sufficient,
if there is neither a gas warning nor a crash signal, if the level of fuel in the
tank is not higher than 80 per cent, and if the pressure within the tank is more
than 5.5 bar. Further requirements are that the tank filler flap is fully open
and the leakage test on the tank coupling has been successfully completed.
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Media
Information
11/2006
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In the system-controlled process of filling the tank, the spherical pump taps
are opened automatically, the transfer pipe is inserted, the process of filling in
fuel is completed, the filler pipe is rinsed, the transfer pipe returned to
its original position, the spherical pump taps are closed and the system is
unlocked fully automatically. So all the driver has to do is disengage the tank
coupling and close the tank filler flap by once again pressing the tank button.
This entire process takes less than eight minutes. Indeed, filling the tank is just
as safe and even cleaner than the conventional process of filling a gasoline
or diesel tank, since complete encapsulation prevents the release of ignitable
vapour otherwise virtually inevitable in the case of gasoline or diesel.
And should there be any kind of malfunction at the filling station or in the
vehicle itself, the process of filling the tank is either interrupted or does
not even start in the first place.
Co-axial hydrogen filling process.
Cooled to a temperature of approximately 250 Celsius, the liquid hydrogen
is able to precipitate into the hydrogen tank of BMW Hydrogen 7, hydrogen
gas above the liquid phase in the tank condensing on the droplets flowing in to
reduce the pressure of the hydrogen gas within the tank.
The process of filling the tank is co-axial, meaning that liquid hydrogen is
transported in the inner section of the tank hose made up of two layers while
gaseous hydrogen is able to return through the outer layer after being
forced out of the tank by the liquid hydrogen and thus returning to the filler
pump through the co-axial tank coupling.
En route to worldwide standardisation.
To ensure the introduction of a standardised liquid hydrogen tank filling
coupling suitable for the automobile the world over, the BMW Group has
established an open consortium in cooperation with General Motors/
Opel and Honda as well as Linde, a major supplier of hydrogen, and Walther,
the manufacturer of the mechanical systems and components for filling up
the hydrogen tank. This consortium seeks to standardise the liquid hydrogen
tank filling coupling on a worldwide level.
Linde contributing significant know-how in hydrogen technology.
Numerous hydrogen projects in the past have already borne the distinctive
stamp of close cooperation between the BMW Group and Linde, a major
supplier of hydrogen: Linde is one of the world s largest manufacturers of
hydrogen production systems and has already built a large number of
hydrogen liquefaction plants. At the same time Linde is one of the most
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Media
Information
11/2006
Page 45
significant suppliers of liquid hydrogen, provides the components and
equipment for nearly all liquid hydrogen filling stations currently in existence,
and, inter alia, supplies liquid and gaseous hydrogen to the filling stations in
both Berlin and Munich.
Filling up the tank both cold and warm.
Apart from the practical process of filling up the tank in a cold state initiated by
manual intervention and then controlled by an automatic system, the hydrogen
tank in BMW Hydrogen 7 may also be filled in exceptional cases when in a
warm state. This may be required when the tank is completely empty or when,
after the car has been parked for a particularly long period, the tank is too
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