page_title: BMW Hydrogen 7
section_title: Use of hydrogen technology
hierarchical_section_title: BMW Hydrogen 7 / Use of hydrogen technology
caption_attribution_description: Wasserstoffeinfüllstutzen eines BMW, Museum Autovision, Altlußheim, Deutschland; left: filler neck for hydrogen of a BMW
context_page_description: The BMW Hydrogen 7 is a limited production hydrogen internal combustion engine vehicle built from 2005-2007 by German automobile manufacturer BMW. The car is based on BMW’s traditional gasoline-powered BMW 7 Series line of vehicles, and more specifically the 760Li. It uses the same 6-litre V-12 motor as does the 760i and 760Li; however, it has been modified to also allow for the combustion of hydrogen as well as gasoline, making it a bivalent engine. Unlike many other current hydrogen powered vehicles like those being produced by Hyundai, Honda, General Motors, and Daimler AG – which use fuel cell technology and hydrogen to produce electricity to power the vehicle – the BMW Hydrogen 7 burns the hydrogen in an internal combustion engine.
context_section_description: The BMW Hydrogen 7 burns hydrogen in an internal combustion engine (ICE).  When in hydrogen mode, high-pressure injectors, designed by HOERBIGER ValveTec GmbH, directly inject hydrogen gas into the cylinder combustion chamber with pressures of up to 300 bars (4,400 psi). The combustion technique is a combination of spark-ignition and diesel combustion systems using surface ignition, subsequently followed by a diffusion type of combustion. This combustion system matches the efficiency values of the currently best turbodiesel engines at a maximum of 42 percent.  The car can also switch seamlessly between hydrogen and gasoline at the touch of a button on the steering wheel, and will do so automatically when one of the fuels is depleted.
  The hydrogen fuel is stored in a large, nearly 170-litre (45-US-gallon), 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 at 700 bars of pressure.  The hydrogen tank’s insulation is under high vacuum in order to keep heat transfer to the hydrogen to a bare minimum, and is purportedly equivalent to a 17-metre (56 ft) thick wall of polystyrene Styrofoam.
  To stay a liquid, hydrogen must be cooled and maintained at cryogenic temperatures of, at warmest, −253 °C (20.1 K; −423.4 °F).  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 because of this.
  There have been some accusations of greenwash in reference to their BMW Hydrogen 7. Some critics claim that the emissions produced during hydrogen fuel production outweigh the reduction of tailpipe emissions, and that the Hydrogen 7 is a distraction from more immediate, practical solutions for car pollution. The BBC's Jorn Madslien questioned whether the Hydrogen 7 was "a truly green initiative or merely a cynical marketing ploy"
caption: left: filler neck of a BMW for hydrogen, right filler neck for gasoline, Museum Autovision, Altlußheim, Germany
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