* Posts by Technopete

1 post • joined 17 Mar 2007

Electric cars may not be solution to all world problems


Why Lewis Page will eat his words

Lewis is surely wrong about the Electric Car, for the following reasons:-

A company called Eestor has recently made infrequent and quiet but highly encouraging noises about their ultracapacitor electricity storage unit. They expect to ship a small unit in production quantities this year (2007) but are expected to scale this up to deliver around 50 KW Hours in a unit weighing approx 150-200 Kg and a charging time of 4-6 minutes. That compares with the Tesla Roadster Lithium Ion battery at 50 KW Hours, approx 450 Kg and a charging time of 4-6 hours.

Three of these ultracapacitor units wired in parallel would deliver a range of around 750 miles between recharges and a recharge time of 4-6 minutes (assuming you just charge at 3 times the charge current for the smaller units). All that with a possibility of 0-60 time of 4 seconds (as the weight is similar - 450-600kg), though this depends on the size of the electric motor.

Now who in their right mind would want to drive 750 miles in a day without even a 6 minute break for a refill? Clearly there is a miles per recharge threshold somewhere between 250 and 750 miles per recharge which tips the balance in favour of the electric car. What is it Lewis? How much does battery technology have to improve for you to believe in electric cars?

And the fuel costs would be around 2 UK pence or 4 USA cents per mile for an electric car compared with around 10+ UK pence or 20 USA cents per mile for the most efficient hybrid petrol cars, or perhaps 20+ UK pence or 40 USA cents for a performance petrol sports car achieving 0-60 in less than 5 seconds. (Prices are for UK electricity and petrol).

A factor of at least two improvement in cost per mile comes from a "well to wheels" efficiency doubling for electric cars compared with the best hybrid petrol cars. This means that if you fed the power station with crude oil using the most efficient of today's electricity generation equipment you would get twice as many miles out of a given quantity of oil in an electric car at the far end than if you refine it and power the car with petrol. The rest of the price difference seems to be due to the different tax rates on electricity and petrol.

Given the recent EEC commissioner interest in the speed limits on German autobahns, it seems likely that there will be no public roads within the EEC where you can go faster than 80 mph (130 kph). The fact is that electric motors can deliver much better torque at lower speeds than petrol engines. If you double the capacity of an electric motor you can accelerate twice as fast without significant reduction in efficiency. If you do the same with a petrol engine you probably get around half the number of miles per gallon. If it is important to the driver to do 190 mph as well as 0-60 in 4 seconds then you can design the car with a bigger electric motor.

The above facts will be enough to influence the most ardent road hog who cares nothing for the environment in favour of buying an electric car once the price is right - and in 6 years it ought to be cheaper to make than a petrol car. The maintenance costs will be much less too.

Of course Eestor may not deliver the spec, though the internet gossip is encouraging. If they are just a year late then we will to excuse them as their power storage unit will still be a game changer. Even if they fail completely then a 17% annual improvement in Lithium Ion battery technology will produce a three times battery energy to weight ratio improvement in 6 years with the same result.

Personally I reckon 500 miles between charges removes the problem of range for all practical purposes. A 17% annual improvement in batteries over 4 years or a 10% improvement over 6 years will deliver this. Is Lewis really going to bet against a 10% annual improvement with all the investment from the laptop makers?

Either way, electric power storage in batteries or ultracapacitors is going to tip the balance for a significant proportion of car buyers in favour of electric cars and my best guess is that this will happen around the time of the London Olympics (2012), possibly with the aid of a little government financial inducement.

Lewis does not even seem to have heard of Eestor or done any sums for himself. Why not, I ask? Perhaps he will answer this.

If a driver also happens to care about the environment then an added factor is that the CO2 emissions of a performance electric car are about 25% of the most efficient of today's hybrid petrol cars. This is because power stations on average generate electricity from fuels which produce half the CO2 for a given energy output. With capital investment you can also remove the CO2 from fossil fuel power station exhaust and reduce this still further (to end up close to zero) or use renewables such as wind or solar - or even nuclear (but only if you happen to be French).

Finally, what about ethanol or hydrogen? Well, it turns out that the efficiency of producing these from whatever source is very significantly worse than using the source fuel to generate electricity, pump it through the grid, store it in a battery and use it to drive an electric motor in a car. The maths can be found in a white paper on the Tesla Motors web site at www.teslamotors.com/display_data/21stCentElectricCar.pdf. Clearly Tesla have an axe to grind, but the maths do look plausible to me.



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