Shown here is an image of the hydrogen tank, with the hydrogen-pump nozzel attached, BMW plans to implement into 100 luxury sedans next year. Credit: Courtesy of BMW

Next year, BMW plans to produce 100 luxury sedans that can burn liquid hydrogen in addition to gasoline. The hardest part of the job? Manufacturing the hydrogen tank (shown at left with the hydrogen-pump nozzle attached). The tank eats up half of a car's trunk space and weighs 167 kilograms. To keep hydrogen liquid--which ensures there's enough in the tank for a long drive--you need to chill it to -253 °C. So the tank has two walls of stainless steel separated by a vacuum and multiple layers of insulation.

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