Quote:
Originally Posted by JamesH
Agreed the speed is a exponential relationship, but you very quickly get to problems of flywheel materials not being strong enough to cope with the forces involved. Bigger and slower means less danger and also cheaper. But more difficult to package.
Perhaps you should have a leccy generator/motor on each wheel, and a motor/generator attached to the flywheel, which you use to store the energy. Yes, lots of losses in the conversion to leccy and back and forth, but (and I am guessing), perhaps only of the order of the friction losses of the CVT and driveshafts required to physically connect wheels to the flywheel. You capture the energy from all the wheels that way, not just the driven ones. Still, I am sure many people smarter than me have gone through all this stuff!
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I don't think there is any particular virtue in using all wheels or non driven wheels for KERS unless the vehicle is close to traction limited or braking/cornering at the limit, while this is normal use for a racing car I hope it is pretty unusual on the road. Consequently I think there is no disadvantage for mechanical systems connecting to the exisitng drive train.
I do agree with earlier posters that electrical systems are too inefficient and clumsy to be the way forward other than for electric/hybrid cars which already have the hardware in place and in most cases already recover energy under braking anyway.
It is precisely because of the engineering challenges in those high speed spinning flywheels, there bearings and packaging that having a devleopment race around them in F1 could be so good for pushing the technology forward, a process which is well on the way.
It is also worth remembering that to be effective as a fuel saving measure on a road car you don't neccesarily need to store the amount of energy that is already allowed in the F1 systems. Substantial savings could be made in urban driving simply by storing enough energy to get from 0 to 30mph (the in town speed limit at least in the UK). The F1 system gives 80hp for 6.7 seconds which is near enough 400kJ, the energy required to accellerate an 1100kg road car to 30mph is only 100kJ, ie only a quarter the energy allowed in F1. Of course more energy storage=more savings but the relationship is not linear and would rapidly reach the point of diminishing returns, how much energy to store is yet another design trade off. At a fuel efficiency of 30% and an energy content of 38.4 MJ/l this would mean that for every 100 times you used that 100kJ of energy you would save 1l of petrol in round figures.