Coursework - KERS System

[WorboysGP]

Hey Everyone,

Im currently studing a motorsport engineering cousre and working on a project about KERS. CAn you help me by filling out some questions? i will be very gratefull.

1) what do you think of the system? (Good idea, Bad idea, Reasons)
2) What are the main points of the system? (Includ DAngers)
3)What is KERS? (Kinetic Energy Recovery Systems)
4)How Does It Work?
5)Do the regulations place limitations on the use of KERS?
6)How the stored energy is be released by the driver?
7)Why was KERS introduced?
Is a car running KERS heavier than one which is not running the system?
9)Do teams have to use it?
10)What are the Effects on Performance?
11)How much does the system cost?
12)Do you think KERS should come back? (List For or Against reasons)
13)Is Formula 1 Going to the future or back to the Past with KERS?
Thanks, (Note: can you list the question number?)

[747heavy]

one effect as far as performance in F1 goes, is to be able to modify the brake balance with KERS.

This is surely not the intended function of the system, but nonetheless, there where some people, seeing this as one of the main advantages in F1.
Keep in mind that a F1 or high downforce car (LMP,Indy car etc.) will need to change it´s braking balance during braking, to account for the change in wheel loads.
If you can´t modify the balance acticely (and ABS beeing banned in F1) you will need to make a compromise.
This compomise will "cost" you braking performance at one stage.
With KERS and it´s control being not restricted by the FIA, you can use it as a sort of rear wheel ABS, and thereby altering your braking balance.
Which means you can be closer to the optimum brake balance parabel, then you can be with a passive system.

Sure, this is a secondary effect, but maybe one worth to keep in mind.
Just a thought, which you may want to think about

Good luck with your project

[autogyro]

I think it is possible to actively balance rear KERS harvesting with over all braking, without it being ABS. Depends on how it is regulated.

[alelanza]

747,

I think there were specific rules that prevented KERS from doing that?
At least i know that the drivers had a dial to determine how much energy to harvest, so i think how much energy is absorbed is driver controlled. Also i believe energy release can only be engaged by the driver. With that in mind i'm not sure how it could be used in an ABS fashion.
Regards,

[747heavy]

maybe not as an ABS, but surely it will be able to change the brake balance.

I may not expressed myself clearly, I did not mean it was used as ABS, but surely
it will have an effect on the brake balance.
I mean, if the system charges it "absorbs" energy, this "Kinetic Enegry" has to come from somewhere.
It´s like "engine braking", and as the rules outlawed the advanced systems which where at use, teams maybe where looking for a way to get part of the advantage back.

I could be wrong - off course, but I do remeber speaking with some people, who are normaly quite up to date with their knowledge in regards to F1, mentioning this point.
Either way, maybe it is outlawed in F1, but if he considers a KERS system in general, it is something he can take into consideration.
The energy which goes into KERS, does not need to go into the brakes - IMHO, so there is a relation between the two.

For this reason I´m (but this is my personal opinion) not so sure if AWKERS is such
a good idea, from a show point of view.

I accept that the FIA, may prevented the teams from using the electric motor to "drive" the rear wheels under braking and thereby to prevent a "lock-up" in an extreme case, but I´m pretty sure, the FIA can´t control the charging functionof the systems in great detail.
So if you stop charging under braking, it will alter your braking balance, mean you brake less at the rear for the same brake pressure in the brakes.

In my mind, there is at least the possibility to use it as a neat way to alter your brake balance (in terms of brake force at the wheel contact patch) without altering your brake pressure.
By reducing the amount of charging (energy taken from the rotating wheel) you shift the balance slowly forward for a constant brake pressure split.
I would like to look at it, as an equivalent to "tunable engine braking"

But this is just my PoV, and I´m happy for others to have a different one,
or to disagree - no problem at all.

[747heavy]

I think it is possible to actively balance rear KERS harvesting with over all braking, without it being ABS. Depends on how it is regulated.

Sure no doubt about it autogyro, on the other hand it is possible to use it as ABS.
As you say, it depends from how it is regulated.

If you make the MGU´s powerfull enough and if you would have one for each wheel, you don´t need brakes at all - electrical braking.
I think, that this is what you woud like to see in an "perfect EV", no energy waste in the form of heat whatsoever.

At the end of the day your brakes just "waste energy" by turning KE into heat.

[747heavy]

At least i know that the drivers had a dial to determine how much energy to harvest, so i think how much energy is absorbed is driver controlled.

You could be right alelanza,
To me it sounds like a way to change/fine tune the brake balance, by changing the amount of KERS contribution to rear wheel braking

What to you think? It´s possible?

[autogyro]

I think it is possible to actively balance rear KERS harvesting with over all braking, without it being ABS. Depends on how it is regulated.

Sure no doubt about it autogyro, on the other hand it is possible to use it as ABS.
As you say, it depends from how it is regulated.

If you make the MGU´s powerfull enough and if you would have one for each wheel, you don´t need brakes at all - electrical braking.
I think, that this is what you woud like to see in an "perfect EV", no energy waste in the form of heat whatsoever.

At the end of the day your brakes just "waste energy" by turning KE into heat.

AWKERS might eliminate conventional wheel brakes in F1 and motor racing in general. However, we have found that KERS fitted to road cars do not achieve as much as first thought. An EV on a motorway trip will save more energy by coasting than by recovering energy from braking. Harvesting only becomes worthwhile if the vehicle has more kinetic energy than required for the trip distance, or if the trip involves enough stop/starts to make the KERS use more efficient than the coasting savings.
Racing of course forces heavy braking and is the only obvious place for KERS use.
Coasting into a corner is unlikely to add up to a good lap time though, even though it would save as much energy, if not more than KERS use.
It is interesting technology and hardly touched IMO.

[DaveW]

To me it sounds like a way to change/fine tune the brake balance, by changing the amount of KERS contribution to rear wheel braking

What to you think? It´s possible?

I'm sure it is, 747, but why not left foot brake & reserve the stored energy to supplement acceleration out of corners?

McLaren usually made spectacular race starts when they used it last, & I speculated at the time that they might have been using KERS to control traction. In retrospect, I suspect that they may have been making good use of the fact that an electric motor produces maximum torque at low revs, whilst high revving racing engines do not. Perhaps the combination helps to make good consistent starts.

[autogyro]

A geared down electric motor will produce no wheelspin and there is no need for a clutch.
Unfortunately, to package a high efficiency KERS unit near the fuel tank takes a lot of gearing and negates a lot of the gains.
Gearboxes for KERS and EVs in general are in their infancy.
The torque delivery of electric motors will quickly destroy most conventional layshaft, CVT, or even epicyclic gear trains.

[Caito]

I think that with a generator you can't lock the wheels. The generator will only create a counteracting torque(to the torque making it spin) if it's spinning and generating.

I don't know if the load(in this case the batteries) draw enough current as to slow the car (without the assistance of brakediscs and caliper). And if you don't increase the load, you won't increase your braking.

Anyway, if you added a load(apart from the batteries) it would probably be a resistor, and you would end up with energy transformed as heat, though this time to the resistor. Possible weight savings anyway.

I remember an electric karting in which to brake, they added a reflector light. Everytime they brake hard, the full track would get illuminated, it was very funny.


I believe in some time soon they will be able to use capacitors(size of 3 oreo cookies, 2.5v 200+F, not uF. Farads per se, already available).

There are projects of using supercaps in buses. They can be charged really quickly and although they don't last as long, it doesn't matter because they can be charged at any bus stop(mere seconds to charge).

[DaveW]

Thanks, Caito. Good post. Here is a link to "supercapacitors". The advantages appear to be a high charge rate & long life, disadvantages are energy stored per unit weight, high leakage & safety. Could find an application in F1 if KERS were to become unlimited, I suppose. Be interesting to compute the energy/weight options....

[alexbarwell]

The mechanical braking/loading that an electrical load presents can be very impressive - during power failover tests at one of our buildings, the big 12-pot deltec deisel generator was run up, stabilised and then the load was dropped across - it stopped absolutely dead requiring a full strip-down to see if anything had been damaged like conrods, crank etc.
To back up other comments, as KERS converts some of the KE into an electrical store, there is less KE required to convert to heat energy in traditional braking so brake wear stands to be improved given that we have seen some significant failures especially with no refuelling giving rise to more braking effort as a result of the extra weight.

[autogyro]

If capacitors are improved, they could easily overtake flywheel storage just as developments in sealed induction charged flywheels overtook toloroidal CVT KERS.
IMO it could end with a combination of batteries and capacitors (all solid state).

[Caito]

http://www.batteryspace.com/super-capac ... 70t04.aspx

There's some info on a 3000F 2.7v cap.

Energy=.5*c*v^2= 10935 J

If an F1 weighs 650 kg and we stop it from 300km/h(83.3m/s) to 100 km/h(27.8m/s)

The energy difference would be = .5*m(v1^2-v2^2)=.5*650*(6944.4-771.6)=~2 MJoules.

Let's say we want to store half of it, because we have some aerodynamic braking and something else that we want just half, roughly 1 MJ


1MJ/10935j= 91.44~ 92 caps needed.

Each cap weighs 550g -->92*550=50.6 kg of capacitors. Don't know how much the actual batteries weight.

This may be useful for someone used to batteries.
Energy density = Energy storage in Wh / Weight in Kg = 3.03Wh / 0.55 kg = 5.52 Wh/kg

Continuous discharge current of 150A

92 caps in series would give ~250v and an ESR of 27miliohm.