On Sun, 03 Feb 2008 11:52:51 GMT, "Androcles"
<Headmaster@[EMAIL PROTECTED]
> wrote:
>
>"RichD" <r_delaney2001@[EMAIL PROTECTED]
> wrote in message
>news:fc536e3e-6d54-45fc-a36a-31c432e32c58@[EMAIL PROTECTED]
>| What is the efficiency of regenerative brakes?
>|
>|
>| Let's say we have a 3000 lb. vehicle, traveling 30 mph.
>| It hits a red lght. That's 1350000 lb-(mi/hr)^2
>| kinetic energy, dissipated through the disc brakes.
>|
>| Now assume it's a Prius - how much is recovered
>| into the batteries?
>|
>| I'm not looking for a theoretical discussion, just a
>| number. Anybody know the number?
>|
>
>80%. Friction with air still causes some braking but most
>of the KE is recovered and stored as useful energy to get
>going again. Remember that no energy is required to continue
>in a vacuum, so all the energy a car uses is wasted as heat
>directly through the exhaust pipe and radiator and the rest
>warms the atmosphere through friction.
>
Is that a fact and reason based answer or just a guess? A battery is
not as efficient as a capacitor and there is a theorem from sophomore
EE that "proves" no more than 1/2 the energy stored in a capacitor can
be recovered. More personal research would be needed to recover the
proof, but that would imply something like 40% of the KE absorbed by
the regenerative brakes could be recovered.
An Analysis of Hybrid Electric Propulsion Systems for Transit Buses
Milestone Completion Re****t by O’Keefe and Vertin of the
National Renewable Energy Laboratory
http://tinyurl.com/292xyt
gives the efficiency of regenerative braking
as 49-50% at best and 39% as current practice.
|
