Sunday, March 20, 2005

More Battery Nerdishness (Enough Already!)

I've mentioned the Rocky Mountain Institute from time to time. Via How To Save the World, this collection of progressives on the old moving picture. Including Amory Lovins, co-founder and director of the Rocky Mountain Institute. In the video, he's hawking his latest book, the perhaps optimistic Winning the Oil Endgame.

One of the points he mentions twice in the video (in the first and last segments) is that Carbon-fibre fabrication technology has come so far down in cost that using it instead of steel is now essentially free - that is, the higher materials cost is offset by the smaller amount of materials used. This was news to me, and apparently it was news to the RMI people when they found it. Despite being half the weight, a carbon fibre car would be much safer than its steel counterpart, and get far better mileage. As an example, Lovins says a carbon-fibre Prius would get close to 100 miles per gallon, instead of the 45 or so that current models get.

If you've been paying attention, you know I favor plug-in hybrids and battery-electric cars. Lightweighting the body is obviously something which can cross over to any advanced car design, but I'd like to point again to the Stanford EV Project, which features a carbon-fibre body and a 150kwh battery pack made up of lithium-ion cell phone batteries. Via The Ergosphere, we find the EPRI estimates that a compact car would need 250 watt-hours per mile of range. This means, even if we assume the lighter body doesn't improve mileage, that a 150kwh battery pack on the Stanford can get us a range of 600 miles, or 1000 kilometres. Unfortunately, this battery pack would cost upwards of $100,000, not including the car. Ouch. Again according to Engineer-Poet at the Ergosphere, a battery-pack would need to come down to $2000-3000 to compete with internal combustion. This means that the price of batteries needs to come down a factor of 35-50. The only thing that this is better than is current fuel cells, which need to come down a factor of 100.

But look at some of the technologies we've seen come up just in the few months I've had this blog. Lithium-sulphur Batteries, new anode materials from Altair Nanomaterials, and now cheap carbon-fibre bodies. Lightweighting reduces the power requirements by half, those two battery technologies each advertise capacity increases by a factor of five (Sion Power) and 3 (Altair Nanomaterials). Taken together, these three things combined should reduce the battery cost by a factor of 30. Maybe more.

(Note: not an engineer. I could be waaaaay off. In particular, the Sion and Altair technologies may not be compatible.)

In the near term, I think it's obvious that a lightweight battery pack powering a plug-in hybrid is the way to go. However, mass-production of batteries on the scale required for the automobile industry could conceivably bring prices down to the point where batteries are the only way to go.

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