|
The vehicle could begin operation with precharged accumulators. Climbing extended grades with something like Pikes Peak as the most extreme example will test any hybrid to the point where it no longer has the capacity to climb that extreme a grade. How much range owuld a Nissan Leaf have climbing Pike's Peak. It might no make it from the bottom to the top. Climbing grades is where you actually can use peak BSFC in any IC engine, going down the other side of that grade is where you may exceed your storage capacity. remember the vehicle is a constant energy drain regardless of the circumstances so that reduces the potential for regeneration downhill.
The power required to climb a grade is fairly easy to calculate. A 7% grade of 1 mile is .07X5280 feet That's 369.6 feet per mile. I have read about coasting for 35 miles coming down the east side of the Rocky Mountains. Most Interstates are 7% grades or less with a few exceptions. Only a car with good aerodynamics will exceed 70 MPG coasting down the vast majority of grades on US roads, so we are talking about very small percentages of grades where there would be regeneration opportunities. I am not saying never just fairly rare and I am sure many here see excetions to that rule daily.
A 2200 pound car needs 28 horsepower to climb a 7% grade, 7 feet and 4 times 550 pounds per foot. That is in addition to the power required for level speed, so lets assume you need 40 HP to climb a 7% grade. You need to size the engine for that to be at best BSFC for the most efficient grade capability. Could you recover all the energy of any grade imaginable? Of course not. What vehicle can do this, and why design one so it covers every extreme. That ios the problem with vehicles today. They have engines sized to cover every extreme, which means their efficiency is 50% of their potential when they are not in extreme circumstances.
That does not exist in the design of Hh vehicles, the engine shuts off when the loads are light, and runs constantly when loads are extreme. As far as emissions, shutting an engine off for short periods of time is already done in hybrids and they seem to pass emissions easily. no change there.
I am breaking up my posts so that my log in doesn't time out.
regards
Mech
|