PhD Thesis - Cranfield University

Chapter 4
Angular
Velocity
(rad/s)
ω2
ω1
t0
Deceleration rate =(ω2-ω1)/t dcel
t1 t2
108
t dcel
Figure 4.6 Generic deceleration profile
As for the energy storage system, the ability to restore the recoverable energy depends on a
parameter that can be defined as the ‘source receptivity’, ϖ, where
⎛ Eregen
− Eloss
⎞
ϖ =
⎜
⎟
(4.13)
⎝ Eres
⎠
and,
Eregen is the regenerative energy caused by vehicle deceleration, Eloss is the energy loss during
conversion and Eres is the energy recaptured by the energy storage system. In an ideal system
with full recuperation, ϖ = 1.
For maximum recuperation to occur, change in kinetic energy will equal the charge in stored
energy such that,
∆ E = ∆E
(4.14)
kin
sto
As such, for an EV that utilises ultracapacitors as the energy storage system for recuperation
of regenerative braking power, the capacity of the ultracapacitor bank is dimensioned based
on the following,
t(s)