Forget images of the Hindenburg making its incendiary descent in 1937 – hydrogen fuel is back on the cards. The Volkswagen-group reckons they’ve cracked the technology with their new demonstrators – the A7 Sportback h-tron and Golf Hymotion.
Starting with a regular A7, then ripping out all its dirty, polluting drivetrain components – Audi replaced them with a fuel cell mounted under the bonnet, four hydrogen tanks under the floor and two beefy electric motors, one for each axle. The design of the Golf is much the same but with less power.
Combined power output for the A7 h-tron is 228hp (about as much as the new A7 Ultra), with torque rated at 398lb ft (roughly the same as the rapid S7). This is enough to catapult the 1,950kg A7 h-tron to 62mph from rest in 7.9 seconds and on to an electric class-leading top speed of 111mph. The axles are not linked and both motors are controlled individually by computers.
The fuel cell
Alternative power sources are vital to most manufacturer’s strategies as emissions regulations become increasingly strict. Audi claims the fuel cell in the A7 h-tron is 60% thermally efficient (i.e. it turns 60% of the hydrogen’s potential energy into useful forward motion) – more than twice what most modern petrol engines can manage.
If you do some exceedingly complicated maths you can work out that the A7 h-tron gets the equivalent of 76.4mpg on average and has a range of 310 miles. Unlike electric cars, when you run out of fuel you can refill the tanks in just three minutes, assuming you can find somewhere that sells hydrogen.
To keep the cell running in its optimum range a system has been installed to closely monitor and regulate the temperature. In addition, a compressor forces air into the cell to react with the hydrogen protons and a recirculator that recycles unused hydrogen back into the system. These controls mean Audi can guarantee cold starts down to -28 degrees Celsius.
Unlike most other hydrogen demonstrators, the A7 h-tron also comes with a lithium-ion battery pack borrowed from the A3 e-tron. This means at low speeds its hybrid capacity can save hydrogen that would otherwise be wasted. Regardless of where you drive it, the A7 h-tron only emits water vapour from its lightweight plastic exhaust.
There’s no word on whether either will see production and, if so, how much they’ll cost. Audi, however, is bullish about the technology, claiming it’s ready to put it into production as soon as the infrastructure is available. Even before then, Audi’s already producing hydrogen using wind power to perfect the technology.