Rasa does 300 miles on 1.5kg of fuel. But do you want to drive 10 miles to fill up?
Alun Taylor
| Specs at a glance: Riversimple Rasa | |
|---|---|
| Body type | 2-seat, 3-door hatchback |
| Power source | 8.5kW Hydrogenics hydrogen fuel cell |
| Transmission | Four wheel-mounted electric motors |
| Power | 16kW continuous (55kW peak) |
| Torque | 4x 60Nm continuous (170Nm peak) |
| Chassis | Carbon composite monocoque with aluminium crash structure |
| Bodywork | Self-coloured thermoplastic panels |
| Steering | Unassisted rack and pinion |
| Suspension | Double wishbone (front) Semi-trailing arm (rear) |
| Tyres | Michelin 115/80R15 |
| Top speed | 60mph (97km/h) |
| 0-60mph | Under 10 seconds |
| Fuel tank capacity | 1.5kg (hydrogen) |
| Extra power storage | 1.9MJ (lithium-ion hybrid capacitors) |
| Rated max range | 300 miles (485km) |
| Weight | 580kg (1278lbs) |
| Wheelbase | 2272mm (89.4in) |
| Dimensions | 3673mm (144.6in) x 1630mm (64.1in) x 1332 (52.4in) (LWH) |
| Base price | TBA |
Why not? Well, if you drive seventy-five miles to the south-west from Riversimple’s HQ in Llandrindod Wells, you end up in Swansea, once the home of William Robert Grove who in 1842 pretty much invented the hydrogen fuel cell. And it’s a hydrogen fuel cell that part-powers the Rasa, Riversimple’s funky little two-seater prototype.
"Part-powers?" I hear you ask. While the majority of electric and hydrogen cars currently on the market are essentially conventional designs with battery or fuel-cell-and-battery power sources, the Rasa—the name comes from tabula rasa, the Latin for blank or clean slate—is the result of altogether more clever thinking. I’m inclined to use a word I usually avoid like the plague—holistic—to describe Riversimple’s view of automotive design.
The first clue to what’s afoot here is the fuel cell itself. The unit in the Rasa is an off-the-shelf component with a piffling 8.5kW output that's best known for powering forklift trucks in Walmart warehouses. Compare that to the 100kW fuel cell in the Hyundai ix35 Fuel Cell or the 114kW stack in Toyota’s Mirai. Despite that limp output, the prototype Rasa can hit 60mph (which is also its top speed) in under 10 seconds.
The Rasa uses a number of clever techniques to pull off this low-power but decent performance trick. To start with the vehicle has a low drag coefficient of 0.248. I’ve passed wind with more drag than that. Next is its weight: at 580 kilos (1278lbs) all-in, the Rasa is only 130kg heavier than Renault’s Twizy. And that’s as much scooter as car. Lastly but most importantly is the unusually efficient regenerative braking system that harvests the kinetic energy usually wasted under retardation from the four in-wheel traction motors.
The clever part in all this is that the fuel cell only solely powers the Rasa when it is cruising. An average family car uses about twenty percent of the engine's output when wafting along at a steady 70mph. For acceleration or climbing hills, the Rasa summons extra power from four banks of lithium-ion hybrid capacitors that store the energy recuperated from the braking system.
The advantage of super capacitors over batteries is that you can dump a large amount of energy into them quickly without anything going “bang” and without doing long-term damage. The downside is limited storage capacity.
The lithium-ion hybrid capacitors used in the Rasa consist of 120 cells with a capacitance of 3300F each and a total energy storage capacity of 1.9MJ or 0.53kWh. They offer a best-of-both-worlds compromise: only slightly less robust energy capture than a supercapacitor but higher energy storage capacity.
What all this means is that the power sources for cruise and acceleration are decoupled. This is the reason Riversimple calls the Rasa a “network electric car." The electric drive system uses power from varying sources as and when needed.
Alun Taylor
Body panels can be removed in a trice. Sometimes faster.
The H+ ions pass through the membrane to combine with the oxygen, creating the only byproduct of the process: water. The electrons, meanwhile, are blocked at the anode level and can only move into an external circuit, thus generating an electric current. As a method of power generation it’s roughly twice as efficient as a petrol engine, as well as cleaner, more compact, and more reliable.
Locomotion meanwhile comes courtesy of four radial, flux-wheel, hub-mounted motors developed specially for the Rasa by Printed Motor Works of Alton in Hampshire. The total power output of the drivetrain is 16kW continuous and 55kW peak. Each motor generates 60Nm continuous and 170Nm peak torque.
Thanks to those four motors, the Rasa can recover more than 50 percent of the available kinetic energy when braking. The cunning part of the Rasa’s efficient recuperative braking is due to something Riversimple calls phased braking. In a nutshell: above 5mph braking is entirely down to the electric motors. The wasteful hydraulic disc brakes play no part except in emergency stops or at speeds below 5mph.
Enlarge / Do not adjust your screens... Rasa is actually quite a titchy car. Rather than Ars hack being big.
Alun Taylor
If you are wondering who designed the Rasa, it was Chris Reitz, who has his signature on numerous designs from Volkswagen, Fiat, and Nissan. The shape of the Fiat 500 and Mk. 3 Nissan Micra are both in part down to Reitz’s vision of what a car should look like.
The finished Rasa cars won’t be identical to the current alpha prototype. The company line is that from thirty paces they will be hard to distinguish, but any closer and you will see the differences. I’d be happy if the finished product looks exactly the same as the prototype; as a combination of the practical and futuristic, it’s hard to fault the Rasa.
One change that will be made is the inclusion of a boot. Luggage capacity will never be a Rasa strong point, as it is only a two-seater. There’s more space behind the passenger seats than there is in a Smart Roadster but not a whole lot more. The production cars will have a hatchback and storage volume of about 170 litres; space for a couple of large-ish soft bags, again like the Smart Roadster.
What’s the Rasa like to drive?
Take the Rasa out on the open road and it’s immediately obvious that this is indeed a hand-built prototype. The doors take an effort to swing up; the drivetrain is controlled by a box bolted to the floor in the passenger footwell; the LCD screen on the dash doesn’t work; the fuel cell cooling system is noisy; and the dampers from a Lotus Elise (properly calibrated ones were due to arrive a few days after I visited) make for a bone-jarring ride.None of that matters a jot, though, because there's just so much damn potential. Slotting into the low slung seats under the gull-wing doors gives the Rasa a sense of the dramatic you just don’t get with most eco cars. And the immediacy of the driving experience is truly impressive. The Smart Roadster is once again the best analogy I can think of. The Rasa is similar in size to the Smart Roadster, too; parking the Rasa should not prove to be a problem.
Even in prototype form the cabin is well-appointed, the design and ambience helped by the reduction of controls to a bare minimum. Once the LCD instrument binnacle and touch-sensitive dash display are fully up and running, I suspect it will be a model of less-is-more cabin design. Reading between the lines, I think most of the non-essential functionality—in-car entertainment, navigation, etc.—will come via the likes of Android Auto and Apple CarPlay.
Alun Taylor
Centre console LCD screen not operational in prototype.
But will anyone buy one?
Perhaps most importantly, though, what are the odds that Joe Public will ever get to drive the thing?Riversimple hasn’t just appeared out of nowhere. Its head engineering honcho Hugo Spowers was the driving force behind Morgan’s 2008 LIFECar (LIghtweight Fuel Efficient Car), a hydrogen vehicle research project. Back in June 2009 Riversimple unveiled a hydrogen-powered two-seater technology demonstrator called the Hyrban, or HYdrogen uRBAN car. Neither car was designed to make it into production, so the fact you don’t see either on the road should not lead you to believe that Riversimple are a bunch of dreamy utopians.
That’s not to say that “utopian," and other similarly semi-critical aspersions, won't be levelled at Spowers and his team. Riversimple is trying to do a lot more than make and sell a funky little hydrogen runabout: they are out to reinvent how we run and own our cars. And that won't be easy.
Riversimple has no intention of selling people Rasas. Rather, they want you to enter into a leasing scheme that includes the car, insurance, maintenance, and fuel—similar to how Toyota is handling its hydrogen-powered Mirai. Think of it like a mobile phone contract for a car. Hardware, service, and the use of supporting infrastructure all bundled together.
Better Place tried something similar with its electric car project, but the sheer initial scale and outlay of Shai Agassi’s project always worried me. I wasn't surprised when it went pear-shaped in 2013. Riversimple’s plan seems altogether more grounded in reality.
Riversimple says it will partner with a hydrogen supplier who will set up filling stations that will act as a central hub for all the Rasas leased in that area. Riversimple’s initial plan is to target towns and cities with populations of up to 300,000, so think Coventry, Derby, and Plymouth. Since filling up a Rasa takes about three minutes in queues at the solitary filling station, this is unlikely to be an issue, even in towns and cities twice the target size.
One such area—Riversimple is keeping quiet about precisely which at the moment—will be chosen for a test with twenty "beta" Rasas next year, with the leasing scheme rolling out properly in 2018.
Granted this idea may involve people driving ten miles or so to fill up, but since the Rasa can cover 300 miles on a full tank of hydrogen—the fuel tank holds just 1.5 kilos of hydrogen at 350 Bar—this might not be a deal-breaker. I’d happily drive that distance to fill up.
Reducing the environmental impact of hydrogen fuel
The travel-to-refuel problem becomes less of an environmental issue when you consider that, even if the hydrogen originates from natural gas, the Rasa will still deliver wheel-to-wheel CO2 emissions in the region of 40g/km. If we start talking about hydrogen obtained using excess electricity generation from nuclear or renewables, the CO2 question becomes moot. It’s worth pointing out here that Toyota will lease you a Mirai for £750 a month, but you are rather stuck with having to be within range of one of the nine hydrogen filling stations in the UK that are currently open to the public.Riversimple also has some pretty interesting ideas about the component supply chain. Its contention is that, despite the increases made in the government-mandated recyclability of modern cars, they are still inherently pretty wasteful. By constructing a leasing deal with key component manufacturers—that’s fuel cells, traction motors, and such like—it is Riversimple’s belief that it can encourage long-term reusability and improve component quality.
That should result in less waste, lower long-term costs due to a reduction in the write down for obsolescence, and a general lessening of the environmental impact of each Rasa made beyond fuel usage. It’s a brave and bold idea, and most definitely not how the car industry currently does things.
The reasoning is not unsound, though: after ten years and 100,000 miles, the oily bits from a family hatchback have little value. Not so the major components in the Rasa. Granted the fuel cell does degrade, but it also retains a lot of its value. After a few years it will need a new membrane, but one of Riversimple’s fuel cell suppliers reckons that eighty percent of the unit value is recoverable, something not true of a petrol engine. The traction motors from a Rasa could also go into a new vehicle with very little refurbishment.
Did I leave Llandrindod Wells thinking I’d seen the future of automotive transport? At the very least I saw a potentially compelling iteration of it. As I drove back to Manchester, I stuck Arvo Pärt’s classical blank slate on the stereo and silently wished I was behind the wheel of one of Riversimple’s groundbreaking little Rasas.
Alun Taylor is a Manchester-based freelance motoring and technology journalist. Prior to that, he spent much of his life toiling for a major international record label. All of which means he has now managed to pursue two careers that have absolutely nothing to do with his degree in Early Medieval History. In his spare time, Alun works on his debut novel, listens to opera, and yells at his unhinged Norwegian Elkhound.
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