Thursday, August 12, 2010

A better way for electric cars? A Better Place.

What are the two main things you worry about with electric cars?
  1. Price
  2. Range
Gasoline is great because it is a well established, subsidized fuel with very high energy density (1.3x10^8 J//kg). That makes it easy to carry around and get pretty far with. Plus, when you run out, there's always a gas station somewhere nearby. Price and range... not a problem.

Electric cars are limited by their batteries. Li-Ion battery's energy density is nowhere near as high as gasoline (5.2x10^5 - 7.2x10^5 J/kg - gasoline has >180 times more energy per kg of "fuel"). Even accepting that a gasoline engine is 30% efficient vs a 90% efficient electric motor (i.e. total energy that would be converted to work per kg of fuel is 3.9x10^7 J/kg for gasoline vs 6.5x10^5 J/kg for Li-ion), that yields ~60 times more energy per kg of "fuel" from gasoline than from batteries. So to get the same range as a gasoline car (from one tank of fuel), requires either:
  1. A very large battery -or-
    • If a typical car holds 15 gal of gasoline (@ ~2.7kg/gal = 40.5 kg) , a battery that contains the same effective energy would need to weigh ~2430kg ... where a Honda Civic weighs about 1270 kg... not practical to carry or to pay for.
  2. The ability to "refuel" the battery in less time than refueling a car 
    •  Even with the best recharger possible, it takes hours (~4 hrs for a Tesla roadster) vs maybe 5 minutes to refill a gas tank.
    • With a 100 mile range per battery charge, that would require about 4 battery charges per tank of gas (assuming CAFE standard of 27.5 mpg and 15 gal tank = 412 mile range). Sixteen hours (battery) vs 5 minutes (gasoline) (assuming both cars start empty).
 Those are pretty bad starting places to catch up from.

So Shai Agassi has an idea: Treat the electric car like a cell phone.
The customer buys miles and gets a subsidized car. The batteries are the medium for the "minutes." You never own them, you just use them.
Which means you can now swap batteries because you don't care about the specific battery that you have, only that you're getting the mileage you're paying for.
Suddenly the range problem goes away (~1min to change the battery).
Suddenly the price has a means of being subsidized (ala cell phone contracts that keep the price of the phone low for the end user).

Kind of like Blue Rhino propane tanks ... but way cooler.

And he created a company Better Place to do it:
  • Get the cars built
  • Get the battery swap system figured out
  • Get the infrastructure in place
  • Prove to the world that it can work
Check out this video (or the video below) of the system working in Tokyo. It's real.


So, admittedly, it only works where you have the infrastructure, but it certainly gives a new direction for addressing the two big problems of EVs.