Thursday, March 24, 2011

What I was looking at last night

The Nissan Leaf , that is looking at it on the Wikipedia.  The Leaf comes with a 24kwh battery pack.

I'm looking at what kind of combination of fuel cell and battery that you would need to make it an all electric vehicle.  It looks like if you were to fit it with a 20 kwh fuel cell, that would fill the bill for most scenarios that you may encounter while driving.  Here's a chart to illustrate it


The most challenging scenario was on the highway with the a/c running and outside temperatures in the nineties.  As you can see, I added some notes to the far left.  The discharge rate for that scenario is 19 kwh per hour.  With a fuel cell of that capacity, it should be able to keep the battery charged while driving under these conditions.  All other conditions are easily met.

Nissan believes it can reduce production costs of the battery in half.  That would put the battery cost at $8000 per car.  Given that Nissan is already absorbing this cost, then halving the cost of the battery would still allow it to be sold for the same price, presumably with a profit.  What about the fuel cell?

Here's an estimate of the cost per kwh of a fuel cell from a page that is undated.  The claim is $225 per kwh according to the DOE.  For a 20 kwh fuel cell, that would cost $4500.

If you used the Ford configuration, with only a 25 mile range ( 8 kwh battery), the cost of the battery goes down to about 2500 dollars.  A 20 kwh fuel cell could keep this battery charged as well.

If you were to meet Ballard's estimate of the mass produced cost of a fuel cell,  which was 73 dollars back in 2005, the price of the fuel cell drops to $1460.  The latest numbers for this estimate (50 dollars) are here.

These costs are not at all prohibitive.

The cost of the electrolyzer may not be possible to estimate here.  Let's assume that the electrolyzer is left out and the electrolysis takes place at the refueling station.  At that point, you can buy the hydrogen for $2 per kg plus the cost of compressing it or cryolyzing it.  Let's say that doubles the price.  It would then be $4 per kg.

If you get 60 mile per kg, the operating cost would be $4.00/60 mile per kg, yielding a cost per mile of 6.7 cents per mile.  That compares to 16 cents per mile at $4 gal gas for 25 mpg conventional car.  Every mile would save 9 cents in operating costs.  That means $9 thousand for every 100,000 miles.

Assuming the sale price could be held at 32000 dollars, which may be possible under mass production, the vehicle could be economically feasible.  Whatever the reason for it not being built, it probably doesn't have to be economic.

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