Promising but...

It looks promising, but one useful bit of information would have been what the size of that the fuel tank is so we might have a clue about the mileage achievable on long runs. To match the economy of my 1.6 Focus turbo diesel (where I average about 12.5 miles per litre) then it's going to have to be no more than 25 litres (and I'd hope that an internal combustion engine tuned for the job and running at the optimal efficient level would do better, especially when helped out with regenerative braking.

I can't, incidentally, see any justification whatsoever for a government funded £5,000 rebate on something like this. Until we have a considerable amount of carbon-free electricity, then this thing will mostly be charged using the standard UK generation mix, and the thermodynamic efficiency of the generation and distribution averages out at 31% (which puts the end to end thermodynamic efficiency of this into the same categories as the mose efficient diesels). The CO2 emissions of the UK electrical generation system is about 0.5Kg per KWh. Assuming that the 40 mile range (64 Km) is achieved on 80% of the charge (12.8KWh) and that the charging process is 100% efficient (which it can't be) then that is 6.4Kg of CO2 using the average UK energy generation mix or about 100gm/km. That's an OK figure, but not startlingly good. Quite apart from any possible rebate, there is a massive government subsidy on such vehicles (compared to petrol/diesel) as there is no duty payable on the electricity it uses and VAT is levied at a lower rate than normal.

Of course if we can use more carbon-free electricity and and/or this can make use of off-peak power that would otherwise be wasted, then it would make more sense. However, the environmental benefits of this (apart from tailpipe emission reductions) are going to be minimal in the UK context compared to an efficient diesel and almost certainly outweighed by the considerable extra embedded energy in its manufacture (it has a smaller engine, but has to carry round electric motors, batteries and a a generator).

So, to make sense of this sort of thing we are going to have to have a rather smarter way of charging these things and to use off-peak sensibly it will require smart meters should large numbers of electrical vehicles be used. On nights when there is a lot of wind energy available then it will make sense to use that to charge these cars. However, simply firing up a lot of fossil-fueled powered stations just to charge up a lot of electrical cars would probably not make much sense - it could well be more thermally efficient to use the "range extender". To do this properly is going to require a revolution in the UK power distribution systems.