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January 18, 2007

Look Ma, No Gas

No, I’m not selling cars on Fractals of Change. The Tesla’s an expensive toy for rich people which points to a possible future for all of us.

No matter whether you think that we have a burning strategic need to reduce our dependence on Middle Eastern oil, an economic need to reduce the cost of energy imports, or that further CO2 emissions will catastrophically accelerate global warming or any combination of the above, you probably agree that using less oil for transport is a good – in fact, a very good – idea.

No question that the Tesla Roadster is pretty.  Its electric induction motor takes it from zero to sixty in four seconds; it has a top speed of 130mph, and a range of 250 miles between charges.  Of course, it has no tailpipe emissions.  Even if the electricity to charge its batteries is all generated by burning fossil fuels, there is a claimed significant decrease both in fossil fuel used and atmospheric carbon dioxide emitted compared to running either a traditional gasoline engine or a gas/electric hybrid.  With all of its blazing performance, the Tesla claims twice the efficiency of a Toyota Prius measured on a “well to wheel” basis.

The hitch: with a base price of $92,950 including destination charges, the Tesla isn’t about to cure our addiction to oil.  But it’s worth looking at as an early indicator of what’s to come.  Also points out some of the obstacles to getting to an oil-less nirvana.

You aren’t going to make up for the extra cost by what you save on gas.  Suppose you’re now getting 20 mpg and paying $2.50/gallon; the gas to go 100,000 miles costs you $12,500.  Here in Stowe, Vermont electricity currently costs us $.15 per additional kilowatt hour (kwh).  Based on information from the Tesla site, we’d need to buy .206 kwh per mile to charge batteries so the cost for 100,000 miles of electric fuel is $3,090.  Nice but the savings doesn’t pay for the car even allowing for the fact that the iPod connection is in the base price.

First question that comes to mind is why isn’t there a cheaper version for people who don’t need an electric Lotus?  Unfortunately, there’s an answer to that.  Lithium ion batteries (what the Tesla uses) are very expensive.  So is the kind of electric induction motor that drives the Tesla.  These components are not expensive, however, when compared to the cost of the engines and elaborate fuel injection systems which drive gasoline-powered performance cars; but they don’t get much cheaper in versions with lower performance.  The Tesla IS price competitive and performance competitive with other high end sport cars so it makes sense to introduce it first for that market.

GM has announced it’ll use lithium ion batteries in its plug-in electric hybrid (which is, so far, car show vapor).  However, mass production SHOULD lower the price of these technologies and get them down market.

The Tesla is pretty much only useful as a second (or third) car and that for local travel since it takes hours to recharge after going its 250 miles.  Another reason for it to be introduced first as a green toy for a luxury market.

There’s lots of good technical detail on the measurement of “well to wheel” efficiency in a white paper on the Tesla site. First the definition:

“To compute the well-to-wheel energy efficiency of any car, we start with the energy content of the source fuel (e.g. coal, crude oil or natural gas) as it comes from the ground. We then track the energy content of this fuel as it is converted to its final fuel product (e.g. gasoline or electricity), subtracting the energy needed to transport the fuel to the car. Finally, we use the fuel efficiency of the car itself (e.g. its advertised mpg) to complete the equation.”

Got that part?  Ok, working backward, they say that the Tesla uses, on the average, 110 watt-hours to drive a kilometer. They then take into account the energy loss in battery charging (14%), electricity transmission over the grid (8%), electricity production from natural gas (40%), natural gas extraction (2.5%) and processing (2.5%). Do all the math and the Tesla ends up going 1.145 kilometers on a mega-joule of energy supply.  The Prius (using less-efficient gasoline to generate its electricity) gets only .556 kilometers per mega-joule.

The assumption that all electricity in the US is generated by natural gas is a bit misleading.  More comes from coal.  On the other hand some comes from even cheaper hydro and some comes from nuclear plants – no CO2.

Speaking of CO2 emissions, Tesla claims that only 46.1 grams of the gas are released when generating the electricity (again with natural gas) needed to take the Tesla a kilometer.  The Prius, they say, emits 130.4 grams when you do the math in both cases from well to wheel.  That’s impressive.

Hat tip to friend Marc for pointing me to the Tesla site.

Driving in The Wind is about the infrastructure to support electric cars.

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