Making it hydrogen-powered doesn't necessarily make it green

BMW’s Hydrogen 7

BMW launched its BMW Hydrogen 7 last month. BMW calls it the first 'commercial hydrogen-powered luxury saloon'. It will not be sold, but leased to prominent personalities in the world of politics, media, and show business who want to be perceived as focusing on a sustainable lifestyle. Those personalities might get a green conscience by driving this car, but the truth is that it is not nearly as green as the BMW marketing department would have us believe.

Fortunately this has already been widely recognized in the media. 'Merely a cynical marketing ploy', says BBC News. Der Spiegel Online calls it 'A farcical ecomobile'. It is 'a pointless activity […], the least efficient conceivable vehicle that you could invent', according to Joseph Romm in the MIT Technology Review. The fundamental problem is that an internal combustion motor fuelled by liquid hydrogen is such an inefficient concept that it is unlikely to ever be the solution of the future.

Hydrogen is not an energy source

Firstly, hydrogen is not an energy source but merely an energy carrier. Today, the only way to produce hydrogen at a reasonable cost is from fossil fuels, resulting in a system that has a lower well-to-wheel performance than petrol or diesel. The BMW publicity presents the car in a setting of wind turbines, thereby suggesting that the required hydrogen could be made out of renewable electricity. True, but today renewable energy sources furnish only two percent of the world’s electricity (not counting hydropower). And if this scarce renewable energy has to be used to power cars, then why not use it directly? Simple laws of physics ensure that electric vehicles will always beat hydrogen vehicles in terms of efficiency, since they require one less conversion step.

Burning hydrogen is inefficient

Secondly, if hydrogen is the energy carrier of choice, then why not use fuel cells instead of an internal combustion motor? A fuel cell car needs about 14 litres of hydrogen for a 100 kilometre trip, while the BMW Hydrogen 7 needs 50 litres for the same distance. Moreover, for use as a liquid in an internal combustion engine, hydrogen has to be cooled down to -253 °C. This requires an additional level of unnecessary energy expenditure. When you add all this up, the consumption rate of the BMW Hydrogen 7 corresponds to more than 20 litres fossil fuel for a 100 kilometre trip, or about the same amount as a heavy truck with diesel engine.