[Land-speed] Hydraulic Hybrids

[Elon]

I think the intent is only to supplement initial acceleration during the
typical city stop-and-go scenario. Regenerative braking can do this task
well, at low cost. You only need enough energy to accelerate to city road
speed (25-35) and no more.  Even a truck van requires only about 20%-30% of
engine HP to cruise at 30 mph. Most fuel consumption is used during the
initial acceleration from a stop. If the regenerative power is applied to
initial acceleration the effect is about the same as perpetual cruise-mode.
Tremendous gas savings can be attained with relative simplicity and low
cost.  Steady-state, flat cruise of big trucks is fairly efficient. A
regenerative system to make up for the long pull up the Rockies would not be
practical.



F-1 has mandated regenerative braking. After the rule was introduced, and
after some preliminary testing a year ago, they quickly add a rule change
limiting maximum power input to 80KW!  I'm not clear on this but the power
limit may be for the total race. Nothing like money and ingenuity-in-action
to scare the rule makers. It was estimated that applying limited
regenerative power for acceleration out of the turns would give a car about
a 1 second lap advantage. At 120 mph average that would be about 12 car
lengths each lap. Both battery and fly wheel technologies are being used.
Some numbers I have heard about flywheels (probably carbon filament wrapped
cylinders) are 6"-10" in diameter around 120,000 RPM. I'm not aware of
hydraulic systems.  -Elon.