3 ms·

Buses sometimes have flywheels for that purpose, too. Although that also has weight and space, so may not be worthwhile for a vehicle where both are needed for

• blagie 2y ago
  Interesting. Where I live, the stops are too long for a flywheel to make any sense. The postal worker will usually deliver to a mailbox serving several houses, and will often have packages. Perhaps in the suburbs, where there are individual mailboxes for each house, it could work well. Still, if we take 8000 lbs, times (10mph)^2, and divide by 2, we get about 35kJ. First supercap which came up in a Google search does 1kJ for <$10. So it's like $350, and will have far less maintenance and better efficiency than a flywheel. If we do 20mph -- although goodness knows mail trucks here don't go nearly that fast for start-and-stop between mailboxes -- it's $1400. Even 40mpg would be around $5k. So it's very cheap (and, electronically, very easy), at least for this use case. For highway speeds, it'd be a different story.