Braking power and the F1 energy recovery system

All that has to do with the power train, gearbox, clutch, fuels and lubricants, etc. Generally the mechanical side of Formula One.
xpensive
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Braking power and the F1 energy recovery system

Post by xpensive » Sun Jun 22, 2014 10:00 pm

This is Brembo's braking data for the past weekend's F1 race at Red Bull Ring, click on corner 02 and you get the numbers.

http://www.formula1.brembo.com/index.ph ... 36&lang=en

1849 kW of braking power for 2.8 sec, that's 5.2 MJ, but the 120 kW MGU-K can only pick up 0.34 MJ over that time.

See, it's all just cosmetics, 6.5% of the available energy is harvested, the entire thing is just a charade.

How they lose the remaining 1729 kW from the brakes is a mystery to me however.
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NTS
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Re: Braking power and the F1 energy recovery system

Post by NTS » Sun Jun 22, 2014 10:15 pm

xpensive wrote:How they lose the remaining 1729 kW from the brakes is a mystery to me however.
Massive heat in all four brakes. That's why Hamilton had a small brake-fire and JEV had a complete brake failure. I also noticed black clouds of brake dust on some other cars such as the McLaren.

xpensive
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Re: Braking power and the F1 energy recovery system

Post by xpensive » Sun Jun 22, 2014 10:37 pm

You don't get the point, you cannot contain that kind of power/energy in the brakes, how do they transfer it to the air?
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gruntguru
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Re: Braking power and the F1 energy recovery system

Post by gruntguru » Mon Jun 23, 2014 12:31 am

Same ways they have been doing it for hundreds of years.

https://www.google.com.au/search?q=brak ... gws_rd=ssl
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xpensive
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Re: Braking power and the F1 energy recovery system

Post by xpensive » Mon Jun 23, 2014 12:41 am

Why don't you just give us some figures in W/A*deltaT?
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wuzak
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Re: Braking power and the F1 energy recovery system

Post by wuzak » Mon Jun 23, 2014 1:38 am

You have to know that 60-70% of that braking effort is going through the front wheels. So, to get a whole lot more you will need front braking recovery. Which then means that you can have ERS on the front wheels. And 4wd.

The size of teh MGUK is set, mainly, I think, to limit the amount of power that it can deploy to the engine. Limiting the recovery power allowed at the same level seems wholly sensible.

xpensive
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Re: Braking power and the F1 energy recovery system

Post by xpensive » Mon Jun 23, 2014 1:42 am

The problem is that you have sub 3s to make the most of some 2000 kW, how much will a 120 kW MGU-K gain then?
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wuzak
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Re: Braking power and the F1 energy recovery system

Post by wuzak » Mon Jun 23, 2014 1:47 am

2000kW is the total barking effort - front and rear. Some 60-70% of that effort will come from the front brakes.

I

xpensive
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Re: Braking power and the F1 energy recovery system

Post by xpensive » Mon Jun 23, 2014 1:48 am

Agreed, and?
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wuzak
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Re: Braking power and the F1 energy recovery system

Post by wuzak » Mon Jun 23, 2014 1:56 am

xpensive wrote:Agreed, and?
It isn't quite as bleak as you put it in the OP.

The question is, if you are allowed to recover 600kW or more (say it is unlimited) from rear wheel braking, but only deploy 120kW, would you have the super-sized MGUK to recover that energy? Or would you maintain the smaller MGUK to save weight and for packaging considerations?

If you have the 600kW+ rated MGUK you will carry the extra weight of the MGU, cabling and power electronics to be used for 10 or 15s a lap, at most.

And you would need a higher storage limit per lap and a larger (and heavier) ES.

xpensive
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Re: Braking power and the F1 energy recovery system

Post by xpensive » Mon Jun 23, 2014 2:10 am

It was obviously a rethorical question, there is no chance of employing a 600 kW MGU-K, the point is that today's braking distances are way to short to make anything useful of this idea, far too much power over too short time.
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Lycoming
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Re: Braking power and the F1 energy recovery system

Post by Lycoming » Mon Jun 23, 2014 3:00 am

don't forget that at F1 speeds a good portion of the braking force comes from aerodynamic drag, so there's quite a bit of energy leaving there as well, though that's speed dependent.
xpensive wrote:It was obviously a rethorical question, there is no chance of employing a 600 kW MGU-K, the point is that today's braking distances are way to short to make anything useful of this idea, far too much power over too short time.
It's not that ludicrous; Toyota's LMP1 car can harvest at ~360 kW from front and rear by using supercapacitors, which are more amenable to large currents than batteries.

And it's not like the energy they store is negligible. I wouldn't say that they're not making anything useful of it.

But how about this, let's talk numbers. First, that 1849 kW is peak, not average. Assuming a 700 kg car, 304 km/h down to 67 km/h amounts 850 kW average and 2.374 MJ. If peak is 1849 kW, then a significant amount of time is spent with braking power below that average. This makes sense. As speed decreases, so does downforce and with it the amount of braking force that can be applied.

If we take the above, that means MGU-K is picking up 14% of the available energy. Except that's not entirely true because MGU-K only harvests from the rear wheels. Let's account for aerodynamic drag and front wheel work. Let's assume front wheels are responsible for 65% of the work done, which if you don't think is reasonable, feel free to dispute. But that's 65% of total braking work done by the wheels. What about drag? They say that an F1 car makes 1g of braking at top speed. Let's assume the car makes 1g of drag at 304 km/h. Using the same weight assumption as above, 700 kg, that makes drag force at 304 km/h is equal to about 7 kN

Now let's use the equation F = .5 * rho *Cd * A * V^2. Since Cd and A are invariant, let's combine them into one variable, CdA, and now we can solve for it if we assume rho = 1.225. We get CdA = 1.571. So now we have drag force as a function of speed. Let's integrate between 67 and 304 km/h. This tells us that the energy dissipated by aero drag is about 0.191 MJ.

Now let's combine everything. Total work done by brakes is 2.374 - .191 = 2.184 MJ. Multiply that by .35 to get .764 MJ. MGU-K can theoretically harvest 44% of the energy available to it. That doesn't sound so bad, does it?

xpensive
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Re: Braking power and the F1 energy recovery system

Post by xpensive » Mon Jun 23, 2014 5:57 am

I think we have to take this from the top so that I can think straight, a 700 kg object going from 304 to 67 km/h is 2.37 MJ.

Then you deduct the integrated aerodynamic resistance which comes to some 0.19 MJ, where I trust you are correct.

Remaining kinetic energy to harvest is thus 2.37 minus 0.19 equals 2.18 MJ

A 120 kW MGU-K can pick up 0.34 MJ over 2.8 seconds, which is indeed 15% of what is available.

Why I stand corrected and can only argue that it is still a rather small portion of the energy at hand.
"I spent most of my money on wine and women...I wasted the rest"

gruntguru
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Re: Braking power and the F1 energy recovery system

Post by gruntguru » Mon Jun 23, 2014 7:36 am

So, how log before the rules allow MGUK on the front wheels? Lots more waste energy to be harvested plus AWD capability..
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xpensive
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Re: Braking power and the F1 energy recovery system

Post by xpensive » Mon Jun 23, 2014 7:57 am

:arrow:
gruntguru wrote:So, how log before the rules allow MGUK on the front wheels? Lots more waste energy to be harvested plus AWD capability..
It will probably happen in WEC long before it reaches F1.
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