Crystalix wrote:Hum. I'm a physic student and it was just an idea. Wind mills in the desert are working well, "they get someting for nothing", as you said.
Nevertheless, I understand what you explained to me.
But why can't I say the same thing with KERS : the extra power is given by brake-energy, given by engine (no engine, no velocitie, no braking) and so we are in the same kind of circle...
First off, Lausanne is a beautiful place! I've been lucky enough to travel through there on business a few times. I make a point to always stop and get some coffee overlooking the lake.
I can understand why you would see similarities between your turbine/generator idea and a KERS system. One KEY difference between the two, however. A KERS system is recovering energy that would otherwise be thrown away as heat. You are correct in that the power harnessed by KERS did originate from the engine. In essence energy from the engine that would be thrown away as heat through the brakes is converted back into usable electrical power.
Perhaps I have misunderstood your proposed application, but if turbines could be used under braking ONLY, when the engine is not producing any power, their function would be much the same as KERS. Harnessing the energy of moving the car through the air (or moving the air around the car if you like) to create electrical power. The drag induced would have a braking effect, and the overall effect would be like a braking system based KERS.
To use this system under non-braking circumstances would be 100% ineffective. It would be much like using the brakes to charge up the KERS system while accelerating. Even if the system were 100% efficient, as stated in my previous post, ALL of the car's locomotive energy comes from the engine originally, it cannot come from anywhere else, and converting the braking energy back into electrical power does not increase the net power (not possible)
The situation under braking is different because at that moment in time, the engine is not producing any power, yet the car has a LOT of potential energy that will normally be wasted through the brakes or aero drag. Any system that can harness the car's built up potential energy will NOT increase the overall power created by the engine, but it WILL decrease the overall power created by the engine that is lost.