[syhprum (OP)]

During several recent formula one events cars powered by Renault RS27-2012 engines have failed to finish due to alternator failures.
There seems a simple temporary solution to this problem until the alternator design can be improved, All modern F1 cars carry a kinetic energy recovery system which store a considerable amount of power at I believe 490 v computer power supply units weigh very little and when fed from a KERS battery could more than replace the output of the alternator.
Could not one be carried with automatic switching to replace the alternator output in the event of its failure.

[Bored chemist]

Not my field, but I thought the whole point of the KERS was to take energy from the motion of the car (when slowing down) and store it.
To do that electrically you need a generator of some sort (and a motor to make use of the energy subsequently, though they can be the same thing).
I don't see how you can replace that with a computer PSU.

Of course, if you store the energy in a flywheel you don't need an alternator.

Also, according to this
http://www.renaultsport.com/RS27-2011,61.html?lang=frhttp://www.renaultsport.com/RS27-2011,61.html?lang=fr
the engine is rated for something like half a megawatt. The PSUs in computers deliver about 0.1% of that.

I'm not sure they would help a lot even if you over ran them tenfold (on the basis that the duty cycle is low and reliability is only an issue of a few hours).

[techmind]

I think syphrum is suggesting that the computer PSUs could be used to procure 12V for running systems electronics from the 490V kinetic energy recovery system (which by implication is unaffected by alternator failures).

It sounds reasonable enough a suggestion, but I don't know enough about F1 cars to know whether the idea has any mileage (*groan*).

[CliffordK]

You can buy DC to DC converters to give one 12V from a larger battery pack.  Or, if one can get AC (any frequency) from the kinetic generator, one can drop the voltage using a transformer.

And, of course, any 490V battery is made up of lots of 1 to 3 V cells.  One could recover a little 12V power directly from the battery pack, although one might have an issue of discharging one part of it more than another, unless one also made a complicated balancing system.

How much electricity does a typical F1 car consume during the race?  One can drive a typical car without the headlights for a while without recharging.  At least the older cars, I don't know about all the new electronic wizardry.  Perhaps electronic fuel injectors, or even electronic valves would take much more energy.  But, one option might be to just use a big lithium battery, big enough to last the whole race without recharging.  Then the whole recharging system would be unnecessary.

I would, however, think that in a million dollar car, they could resolve the alternator issues.

[peppercorn]

Maybe they should also fit a Magneto for back-up! []

The topic does lead on to the question of why they need an alternator at all .... []

[syhprum (OP)]

Although there is a large amount of electrical energy in the KERS it is also drained away in about 6 seconds to provide acceleration for the car at crucial moments, if a small part of this energy was required as an alternator backup arrangement's would have to be made so that it could not be completely exhausted providing acceleration for which there would a small cost in performance but much better than a DNF.
I would guess that about half a KW would be required from the alternator while the KERS can supply 50Kw in bursts.

 

[CliffordK]

Maybe they should also fit a Magneto for back-up! []

The topic does lead on to the question of why they need an alternator at all .... []

Many diesel engines...  at least those from before about 1980 would run just fine once you got them started without any electricity.  I think a few manufactures have tried diesel F1 engines.

If I was the engineer, I would certainly evaluate whether carry an adequate sized battery, and no recharging system.  Of course weight is always an issue, but so is the extra drag on the engine.

[syhprum (OP)]

It seems sad that a car should fail to finish for the lack of a Kw or so of power when they are carrying a large battery for KERS purposes holding maybe 100 Kwh and constantly recharged when decelerating.

http://en.wikipedia.org/wiki/Kinetic_energy_recovery_system

[CliffordK]

It would seem to me to be more efficient to put in a DC to DC converter to maintain the battery, and eliminate the the need for the alternator, alternator belt, idler, and etc.

[syhprum (OP)]

Agreed but don't remove the alternator as the output from the KERS is not always available (it is only there when the car is being decelerated under race conditions ) but I suggest a belt and braces approach to have a dc to dc converter available in the event of alternator failure.
The proximity of the alternator to the engine is a pretty hostile place due to high temperatures and vibration Renault have provided a redesigned alternator but it was not 100% reliable.
I suggested a PC PSU as it seemed almost built for the job but no doubt the boffins would want to build their own $10000 unit to show they are needed !