In 1980, a BMW 7 Series became the first car in Europe to be powered by cryogenic liquid hydrogen. However, the hydrogen was still obtained using crude oil or natural gas, rather than solar hydrogen technology. The liquid hydrogen was transported in the car at -253 degrees Celsius, while a 93-litre tank enabled a range of around 300 kilometres (186 miles). The hydrogen-powered BMW 7 Series was fitted with a tried-and-tested combustion engine. The key aspect of its development concerned the mixture preparation, which saw BMW working closely with the German Society for Aeronautics and Astronautics. Hydrogen contains less energy than petrol, but employing a gyro-charger opened the door to output figures only around 30 per cent below those posted by petrol engines. The main competitive edge of hydrogen lies without doubt in the environment-friendly way it uses its energy: hydrogen burns with the oxygen in the air to form water again.