Hydrogen fuel cells turn hydrogen into electricity which then is stored in a battery and used to drive one or more electric traction motors. Though fuel cell vehicles are basically electric cars, this concept enables significantly higher driving ranges compared to today's battery electric cars (BAVs) - Toyota claims a range of 480 km (300 miles) whereas the battery capacity of most standard electric vehicles (save Tesla) is only enough for some 120 to 160 km. What's more, refilling the hydrogen tank at a filling station takes only some three minutes and thus is much shorter than recharging the battery of a BAV which takes at least 20 minutes even with quick charging technology.
Fig. 1: Toyota's Mirai is ready for series production
Toyota undoubtedly has the most advanced technology for fuel cell cars. The Japanese company will make its Mirai available to the public in Japan as early as mid-December (2014, of course). The Mirai offers a system power of 113 kW (154 hp). Toyota's fuel cell, located beneath the floor of the passenger compartment, offers a specific power of 3.1 kW per litre of volume, a value that makes it the most efficient fuel cell worldwide. The system of fuel cell stacks, up-converters and high-presure hydrogen tank is the result of some 20 years of research.
Toyota's fuel cell stacks for the first time utilise finely-woven 3D channels that ensure even current generation at the cell surface and this guarantee maximum efficiency at compact dimensions. For instance, the power density of the new Mirai is 2.2 times as high as it was the case with Toyota's FCHV-adv research vehicle. The up-converter offers an output voltage of up to 650 V, which enabled the vehicle designers to shrink the size of the electric motor as well as the number of the fuel cells.
The hydrogen is stored at a pressure of 700 bar in a tank made of three