Hydrogen fuel cell powered cars aren't new - we've already driven the BMW 5 Series concept, the Hyundai IX35 and the road-ready Toyota Mirai - but Audi's first foray into the tech is an altogether meatier, more powerful concept car. The A7 Sportback h-tron quattro, as it's known, is sleek and sporty, yet large enough to lug around four people in comfort. And at pace. We got to ride this zero-emissions concept on public roads in Madrid, Spain, to see whether it's a glimpse into the future.

As the use of hydrogen fuel increases, so too does our interest in the technology. Partly because so many manufacturers are forging ahead investing in it, as if to assert its viability, and partly because hydrogen and hybrid-electric vehicles generally aren't seen as capable of replacing the more powerful cars we see on the road.

Sat behind the wheel of the A7 h-tron, however, and that assertion about power is totally flipped on its head: this is, without doubt, the most powerful hydrogen fuel cell car we've driven so far. It's full of pep (170-kilowatts of power from its electric motors) responding much like a current A7 you'd drive off an Audi forecourt.

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Dump a foot on the throttle and the h-tron is off like a shot; with a 0-62mph time of 7.9-seconds and top-speed of 111mph from the 170kW of power at its disposal the h-tron might not read like the most powerful car on the planet - because it certainly isn't - but among its hydrogen competition it's a whole grade above.

So how does it all work? Hydrogen is stored in 700-bar tanks in the car, acting as the fuel that, when mixed with oxygen, creates electricity to drive an electric motor and propel the car forward. And as hydrogen (H) plus oxygen (O) equals water (H20), that's the only "emission" you'll get from this car - dripping from the exhaust to the rear and clean enough to drink, so we're told.

Specifically in the A7 Sportback h-tron's case, there are two electric motors. It's doubling-down on the power, with a hybrid electric battery to the rear - the same as found in the Audi A3 e-tron, which we've also driven on the roads of Vienna - that can also be charged just like a plug-in hybrid, should you so wish. It's not an essential though: the hydrogen fuel can deliver the electrical energy to this battery, as can energy recuperated from braking during driving.

This double-down on power makes all the difference in use. We floored the A7 h-tron down an empty open stretch of highway and it zipped along at pace, reactive in its response. Perhaps no surprise given the 398.3 lb-ft torque available on command. Other than the spaceship-like noises from the electrical motors and lack of growl due to the absence of a combustion engine we otherwise wouldn't have known much difference between this and a "normal" A7. It's even got normal and sport modes available by a nudge of the auto gearstick.

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There are some other clues to the hydrogen concept, of course, with the power meter tucked behind the wheel in the instrument cluster showing the state of power, fuel level and battery charge level. Although at the pace we were hurtling down the road it was a case of all eyes ahead rather than on the displays.

First Impressions

Saying all that, this is hydrogen - a fuel that's a long way away from being viable in the UK market at present. We doff our hats to Toyota for bringing the Mirai to the UK (albeit only 50 of the cars will make it to these shores in 2016), but with a mere four UK hydrogen fuelling stations in existence at present, right now it's premature for the technology to be on the roads. Hence, we suppose, the A7 h-tron being a concept at this stage.

Elsewhere in the world, such as the 20 stations in Germany, or many more in Japan, the want for hydrogen to take off is all the more apparent. When the situation does improve on British shores, however, the idea of hydrogen fuel does begin to make sense. Refuelling a tank from empty takes around three minutes, its cost-per-mile is roughly the same as petrol or diesel (and that should come down as production goes up) and, of course, it's emissions-free.

Whether it takes off or not, however, is perhaps irrelevant in this context. Our experience in driving the A7 Sportback h-tron was like no other hydrogen concept that we've driven before. It's ultra comfortable and sees hydrogen go hyper. It's exciting to see what not only this fuel cell technology can do, but how powerful cars propelled by electricity have become.