Electric Heads

Posted on Tue 16 December 2008 in geek

We watched Top Gear last night and I saw a car I'd be happy to buy and still feel good enough about my environmental credentials. I thought Clarkson was a little hard on the Tesla Roadster's range. The rated range of 244 miles on a full charge assumes a level of sensible driving your not going to get throwing the thing around the Top Gear test track. It had echos of the "test" they ran with a Prius racing around the track against a BMW. The Top Gear team are more in favour of the Honda FX Clarity and it's hydrogen fuel cell approach.

The only figure that matters when comparing all these vehicles is how much energy it takes to move for a fixed distance. Both the Tesla and the FCX get their energy from potentially dirty power stations, it's just the FCX's power is indirectly used to separate hydrogen from water before being trucked around to filling stations. Luckily I don't have to look far to get all the numbers I need.

A very efficient petrol car runs at about 62kWh per 100km (roughly equivalent to 43mpg). The Tesla roadster runs at a significantly better 15kWh per 100km, remarkably around the same efficiency as the micro G-Wiz but a lot cooler to drive. The FCX clarity comes in at 69kWh per 100km which is more than an efficient petrol car! Sure it has zero emissions (at least on the road) but it's still using more energy and that will become an increasingly scarce resource. Still it's not as bad as BMW's Hydrogen 7 which comes in at a massive 254 kWh per 100km.

One of the central thrusts of the programmes argument is given the recharge time of pure battery cars we will have to use hydrogen fuel cell cars to get any sort of range. However the average daily commute is 8.7 miles which is well in the range of all battery cars. I suspect the future will be hybrid fuel-cell/battery cars which never need the fuel cell in daily use.

Much as I like the show I do sometimes find myself shouting at the intellectual dishonesty of some of their "tests". However it is heartening that electric cars are starting to become mainstream and even desirable*. Any manufacturer still developing petrol or even hybrid cars at the moment isn't really deserving of government support. The future is electric. Who wants to lay a bet on an all electric Formula 1 within 10 years?

* Technically I could buy one right now. Fliss said no, citing things like buying a house and paying bills as being more important. Bah humbug! ;-)