Pinifarina B0 - looks good and has got it where it counts

13 October 2008

Pininfarina B0 side viewPininfarina’s upcoming B0 electric car (that’s a buzzy, efficient bee-zero, not a whiffy bee-oh) is a wonderful thing, and not just because it looks as perfect as a swallow’s egg from every angle. One might expect the Italian styling house responsible for oodles of Ferraris and the Talbot Samba Cabriolet, no less, to turn out a pretty little thing but no, we love the B0 because it aims to put supercapacitors on the road.

The supercapacitors, along with lithium metal polymer batteries, come from the less glamorous half of the partnership behind the B0 – BatScap, part of French electronics group BollorĂ©.

Unlike batteries with their caustic chemicals and exotic materials, capacitors are conceptually simple things – not much more than a bucket in which to store electrons. At their most basic, capacitors are made from two metal plates with a gap between them, across which electricity is not able to jump. Apply a voltage to the plates from a dynamo or battery and the electrons will gather, like penguins at the edge of an iceberg worried about hungry seals in the water. Remove the generator and leave the circuit open and the electrons will happily stay put for quite a while, their energy held in an electric field. Connect a load – like a motor, say – and the electrons will flow back away from the edge, providing a quick burst of eager electrical energy.

In practice, in most ordinary capacitors, the two metal plates are made from sheets of metal foil, separated by an insulating film (called a dielectric) and rolled up tight in a tiny tin can. The larger the surface area of the foil, the closer they are together and the better the insulator between them, the more energy can be crammed into the capacitor before it starts to leak significantly around the edges and across the gap.

Supercapacitors do the same job only more so – sustaining bigger electric fields and a greater density of electrons. Enough, in the case of the B0, to provide worthwhile motive power.

In the B0, the supercapacitors are put to a specific use – storing energy from the regenerative braking system, and immediately feeding it back into the drive system when the car accelerates again.

Pininfarina-Bollore B0 top viewThis is an ideal role for a capacitor, and a much better fit for the job than a battery. Batteries degrade over time, their chemicals gradually falling to pieces over a few tens of thousands of charge-discharge cycles. But capacitors don’t suffer the same degradation. Keep within tolerances and they can, in most cases, happily charge and discharge through billions of cycles. Ideal, in other words, for stop-start city traffic where it seems possible to slow down and speed up an infinite number of times on the way to work.

Capacitors are also fundamentally more efficient than batteries at short-term storage of electrical power, due to the fact that there are no gross energy transformations involved. In a capacitor, electrical energy goes in, is stored in electrical form, and electrical energy comes out again. In a battery, by contrast, electrical energy is converted backwards and forwards through chemical reactions, with associated inefficiencies and heat losses.

Capacitors are also able to store energy in much more rapid bursts than batteries, suiting the short-but-intense role of transforming kinetic energy into stored electricity during sharp braking.

The bottom line? A supercapacitor-equipped electric car ought to go a fair bit further than an equivalent runabout equipped with batteries alone. And that expensive battery pack ought to last a lot longer to boot.

So while we love the fuss-free look of the Pininfarina B0, we really love the nitty-gritty details of its BatScap-built underpinnings.

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