Kers (kinetic energy regeneration)

Originally Posted by Red__Zed

Back on topic, KERS is a pretty cool idea that I think is quite a ways away from being feasible in a car at a reasonable price point, and a really long way away from being something you can readily retro-fit.

I've done a bit of research into a staged supercap / li-ion arrangement that winds up pulling a lot more energy from braking, but you still run into issues getting that power back to the wheels. Electric motor technology has not progressed much in the last 50 years, and they're fairly heavy to add on to a gasoline vehicle.

KERS is likely to be hot stuff on every electric vehicle going forward, but it gets really hard to justify the weight of the extra motors over other options for adding power...not to mention programming a control system is a non-trivial task (for one-off applications).

The mechanical systems you are talking about are pretty neat, although I haven't really seen any that seem particularly streetable. There's usually a pretty steep dropoff in efficiency if the flywheel isn't operating at insane speeds, and the materials generally wind up being extremely expensive. I have seen some pretty cool applications on transit buses, and I know Volvo just got a big grant for development of one, but I still haven't seen much that looks like it would make sense on a sporty street car.