The annual Geneva motor show is a designer's event, and its halls are packed each March with a predicatably dazzling array of concept cars, from the usual suspects along with the occasional unknown. So when a startup called NanoFlowcell arrived in Geneva back in 2014, pulling the wraps off a battery electric grand touring car called the Quant e-SportLimousine, the world was intrigued, if unsurprised. But beyond its dramatic looks and outlandish performance claims (zero to 62mph in 2.6 seconds, a 236mph top speed) this design study made a genuinely audacious promise: It could run on saltwater.

The Quant made use of an ex-Nasa technology, a flow battery powered by 'ionic liquid' – that is, simple saline water. It's not quite as simple as filling the tank with sea water, but there's little question the system is environmentally friendly in ways no other propulsion system (save, perhaps, solar) could be.

Top Gear's Ollie Kew recently enjoyed some seat time in the Quantino, the company's city-car sized concept from the 2015 Geneva show. The car – which has been approved for use on European roads – gets its power from a "flow cell" comprised of two 159-litre tanks, each filled with a different electrolytic liquid­ – one with a positive charge and one with a negative charge. The tanks are separated by a membrane and it is the meeting and interaction of the two fluids that creates an electric charge. Simple, yes? The Quantino’s electric motor produces a modest 136 horsepower, giving it (says its maker) the ability to run from zero to 62mph in five seconds and press on to a top speed of 125mph.

So what did Ollie think of the "electric car that you never have to charge"? Read on.

On its saltwater 'fuel'

Named ‘bi-Ion’, the fluid is a water solution containing both organic and inorganic salts. Nasa gave up on this tech in the 1970s because the energy density was so poor, but NanoFlowcell’s enigmatic and enthusiastic chief technical officer Nunzio la Vecchia’s 16 years of work on the chemistry has apparently yielded the necessary breakthrough to beat a lithium-ion battery’s storage capacity, so far as kWh per kilo are concerned.

What is the breakthrough?

Mr la Vecchia won’t tell us, because the patent is pending.

On the system's chemistry

One batch of ‘bi-Ion’ fluid holds a positive charge, the other a negative charge. The car pumps these liquids through a membrane, where the interaction of the charged electrons generates an electrical charge. The liquid is vapourised and released, harmlessly, we’re told, as ‘water dust’. This allows the tank to empty so you can refill it. [And because] the fuel is essentially saltwater, it’s abundant and can be produced almost anywhere on Earth (again, the exact process is a closely-guarded secret, but la Vecchia says it could be made widespread and totally carbon-free).

On the energy storage system

The charge is stored in a supercapacitor, which is like a giant industrial-strength battery, more resistant to frequent charge-use-charge cycles than a regular battery, and can provide the bursts of power necessary for driving a motorised vehicle. It’s the size of a shoebox.

On the technology's potential

Last year, the superbly coiffured la Vecchia – no arguments, this man is in possession of the greatest hair in the motor industry – apparently competed in a 14-hour, 1100km endurance run in the Quantino. And it still had fuel left in the tanks. It was his backache after 14 hours at the wheel at up to 90mph that called time.

On the Quantino's looks

If Koenigsegg went to Zagato and asked them to construct a Ford Fiesta rival (we can dream), it’d probably look something like this.

On its performance

Just like a regular electric car. [Quantino] accelerates smartly – NanoFlowcell claims a five-second run to 62mph – and though it doesn’t feel quite that snappy, there’s all the performance you’d ever reasonably expect from a small hatch here. The regenerative effort on the brakes is subtle.

On its road manners

Immediately, Quentin feels like it’s been thoughtfully set up. Show it some corners, and despite weighing 1420kg, it’s remarkably agile. The car corners almost completely level and grips tightly on its snaking test course, shrugging off the few bumps there are to run over. The whine of the drive system gets progressively louder as the speed rises, but it’s still perfectly easy to hold a conversation with the giggling la Vecchia in the passenger seat, and once the system has been refined and shrunk behind a bulkhead, it’d be leagues quieter.

On living with the Quantino

[The liquid fuel] is safe – not volatile like petrol – so it’s easy to store and transport around. The bi-Ion doesn’t have a shelf-life either, unlike petrol. And that’s before you get to putting it into the car, which you do via a twin-nozzle pump. Just like filling your car with petrol or diesel, it’s a five-minute pit-stop with no cable adaptor or charging bay anxiety.

On the Quantino's future

NanoFlowcell is adamant they are a tech company, not a carmaker. And the Quantino, and its 920bhp super-limo sister, the Quant e-Sportlimousine, are merely demonstrators of the tech. Both have been road legalised, but will never be sold. Instead, la Vecchia tells us that the company is in talks with a major automaker to sell its propulsion concept on in 2017.

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