|
Adressing the issue of the amount of power from a fully charged accumulator. You have a choice for range or weight. Balancing the two means you can increase range but you also increase system weight. Electric cars face this same issue with the additional consideration of battery cost as a factor.
In my opinion you want enough capacity for a single 0-70 acceleration event, as well as the capacity to recover the same energy in a single panic stop. This is your worst case scenario. Higher accumulator operating pressures mean greater storage capacity. Some here try to compare battery capacity to accumulator capacity, but you must understand the purpose of the two systems is not the same. One is the primary energy source, the other is a demand "shock absorber" with a high percentage of recovery capability.
Ian made a good point about the efficiency of electric regeneration. My counterpoint is a worst case scenario where you are forced to make a panic stop. In 20 revolutions of the wheels you have to recover your several hundreds of horsepower-seconds of energy in a vehicle weighing over 1 ton. That basically means every revolution of each wheel needs to be able to recover about 10 horsepower seconds of energy in a total time of a few seconds. In this scenario I am not aware of any electric powered vehicle with this capability. Maybe the KERS system in the new Formula 1 designs, but at what cost?
Primary propulsion is the "fuel tank", be it a battery or a tank of liquid fuel. A capacitive energy recovery system has a different purpose which is to smooth out the extreme variations in energy demand in a vehicle. Considering that coasting in neutral is 0 energy demand (engine off), the graph of energy demand goes from positive to negative, with positive being when you require primary fuel to provide power and negative when you have regenerative opportunities. Capacitive energy storage covers the extemes of the two demands, with negative being recovered for positive applications.
The resultant graph of energy demands goes from vasty changing points to a very flat graph with periods of replenishment when primary fuel sources provide for accumulator recharging. In either IC or electric vehicles the graph remains the same and in an electric vehicle you no longer need to modulate the amount of current to control vehicle speed. You only need an on or off switch to operate either the electric motor or the iC engine. No power modulation is necessary since the HH system performs that function irrelevant of engine-motor power production.
regards
Mech
|