Energy Recovery Systems (ERS) in LMP1

[MyNameIsNigel]

I am trying to find some more precise answers as regards Energy Recovery Systems as used in LMP1, in particular ERS-K (Energy Recovery System - Kinetic) designed to recover energy upon braking and ERS-H (Energy Recovery System - Heat) designed to recover energy from the exhaust gases. I am in particular interested in understanding how much energy can be recovered by both systems.

As regards ERS-K, it was mentioned in a recent RCE article (source to be added) that a lap at Le Mans involves approximately 60sec of braking and that the equivalent of 11 MJ/lap could (in theory ?) be harvested with a double ERS-K (on the front and rear axles) developing a combined power of 450 kW.

The ERS-K used by Audi in 2013 had a power of 2x 80 kW and was apparently capable of harvesting at least 7x 0.5 MJ = 3.5 MJ/lap at Le Mans, the amount of energy that could be released by the ERS-K being limited by the rules.

In view of the above, I therefore assume (or rather speculate) that a single ERS-K of 225 kW on the front axle should be capable of recovering approximately 5.5-6 MJ/lap (maybe more, maybe less) at Le Mans, it being understood that more energy can be recovered on the front axle.

That seems to be a plausible estimation at least.

Very little information is available as regards the amount energy that can be recovered by the ERS-H. Has anybody a clue in that respect ?

[TzeiTzei]

Originally Posted by MyNameIsNigel

Very little information is available as regards the amount energy that can be recovered by the ERS-H. Has anybody a clue in that respect ?

There is a very long thread about this on F1technical. Atleast i've let myself believe that these technologies are similar. On the last page someone mentioned 100kW on full throttle, but that's F1 and i don't know if it's going to be very much different in LMP1.

[gwyllion]

Originally Posted by MyNameIsNigel

As regards ERS-K, it was mentioned in a recent RCE article (source to be added) that a lap at Le Mans involves approximately 60sec of braking and that the equivalent of 11 MJ/lap could (in theory ?) be harvested with a double ERS-K (on the front and rear axles) developing a combined power of 450 kW.

In http://tentenths.com/forum/showthread.php?p=3033923 knighty reported 34 seconds of braking per lap.

60 sec * 450 kW = 27 MJ

[MyNameIsNigel]

Originally Posted by gwyllion

In http://tentenths.com/forum/showthread.php?p=3033923 knighty reported 34 seconds of braking per lap.

60 sec * 450 kW = 27 MJ

Here are Peter Wright's exact words in his article entitled "Opening up the rulebook" in the October 2013 issue of RCE, on page 48:

With around a minute's braking in a 3 1/2 minute lap of Le Mans, and around 11MJ of energy to be harvested with a 600cv (450kW) system, Toyota should be able to fully exploit the 8MJ allowance - just under 18 seconds of full electric power to both axles. (...)

[gwyllion]

Something is definitely wrong with those numbers: 11 MJ / 450 kW = 24.4 seconds!

Peugeot Sport also talked about 20-30 seconds.

In the course of a lap of Le Mans, for example, the system will recuperate energy for between 20 and 30 seconds.

source: http://www.supercars.net/cars/4221.html

[MyNameIsNigel]

Originally Posted by gwyllion

Something is definitely wrong with those numbers: 11 MJ / 450 kW = 24.4 seconds!

Peugeot Sport also talked about 20-30 seconds.
source: http://www.supercars.net/cars/4221.html

Thanks gwyllion. So one should rather assume that we are rather talking about approximately 20-30 seconds of braking during which the ERS-K can harvest energy, i.e. the equivalent of 9 to 13.5 MJ/lap.

What about the energy recovery capability of the ERS-H ?

[TF110]

As per 2013 you recovered energy from the axel you used the power to propel, right? Im sure doing double that with both axels is not hard. I remember reading Toyota said currently they could double what they capture. Possibly even triple the power (10.5mj) with freedom without zones or limits on regenerating. This is probably why Toyota has voiced opinions of allowing them to use the hybrid freely.

[MyNameIsNigel]

Originally Posted by TF110

As per 2013 you recovered energy from the axel you used the power to propel, right? Im sure doing double that with both axels is not hard. I remember reading Toyota said currently they could double what they capture. Possibly even triple the power (10.5mj) with freedom without zones or limits on regenerating. This is probably why Toyota has voiced opinions of allowing them to use the hybrid freely.

It's safe to say that a double ERS-K with a combined power of the order of 450 kW should be sufficient to easily recover more than 8 MJ of energy per lap. There is indeed plenty of energy to harvest, but with a double ERS-K, any excess energy harvested beyond the maximum amount of energy that can be released (i.e. 8 MJ/lap) cannot be exploited and is basically lost. The energy harvested by the double ERS-K can only be released through the MGUs on the front and rear axles and it is the amount of energy released through the MGUs that is restricted by the rules.

Now, the question for me is how much energy the ERS-H (in the case of Audi and Porsche) can harvest on top of the energy recovered by the single ERS-K. Assuming that a single ERS-K with a power of 225 kW can harvest the equivalent of 5.5-6 MJ/lap, you would need at least 2 MJ/lap from the ERS-H in order to achieve the 8 MJ/lap target. In addition, with a combined ERS-K and ERS-H, any excess energy "could" be released back through the ERS-H, in particular to eliminate turbo-lag, which could lead to some performance gains.

On paper at least, it would seem that an 8 MJ/lap combined ERS-K+ERS-H package would make more sense than an 8 MJ/lap double ERS-K package, especially if the amount of energy that can be harvested is in excess of 8 MJ/lap.

[tomerswayler]

With the link and power number of 100kW that TzeiTzei posted above, we can scale down that 100kW to the LMP regulations.

The 2014 F1 engine allows a petrol flow of 100kg/h, Appendix B of the 2014 LMP draft mentions maximum fuel flows of 91,5 to 85 kg/h for the petrol engines and 82 to 75kg/h for the diesel engines if ERS is installed.

As the maximum fuel flow limits directly the ICE power, the power that could be recovered from the MGUH will probably be in the range of 91,5 to 85 kW.

Multiply that by the time on full power around Le Mans (140s?), and the result is:

(91,5kW+85kW)/2 * 140s = 12,355 MJ

[TF110]

The talk of engine and fuel efficiency and you can get lost on that thought without considering the hybrid efficiency. That will be majorly important.

[gwyllion]

Originally Posted by tomerswayler

With the link and power number of 100kW that TzeiTzei posted above, we can scale down that 100kW to the LMP regulations.

According to http://www.omnicorse.it/magazine/217...lla-di-marelli the Magneti Marelli MGU-H is capable of 90 kW at 120 000 rpm.

Turbogenerators that are commercially available, produce substantially less power. According to http://www.cpowert.com/assets/CPT%20TIGERS_5.13_v1.pdf TIGERS48V only produces 4 kW at 60 000 rpm.

[MyNameIsNigel]

Interesting comments from Vasselon were reported by endurance-info.com prior to the race at Spa.

Vasselon claims that Porsche are capable of storing the entire amount of energy allowed by the rules in the energy store (i.e. 4.78 MJ/lap @Spa / 6 MJ/lap @LM) and release it in one step if they want to:

Avec les batteries, ils [Porsche] peuvent stocker de l’énergie jusqu’au maximum réglementaire puis décider de la libérer en une seule fois.

This can be explained by the fact that the batteries as used by Porsche can store a large amount of energy, much more than the supercapacitor used by Toyota or the flywheel system used by Audi.

In the case of Toyota and Audi, due to the more limited capacity of the energy store, the maximum amount of energy that can be released by the ERS can only be released as a result of several successive charge/discharge cycles, which therefore limits the energy release strategies.

In terms of energy release strategies, Porsche's solution therefore appears to provide far greater flexibility in how the energy is or can be released.

[TF110]

Must be nice, but possibly heavy. Vasselon also claims that "back in line after a couple of laps" from google translate. What is this actual meaning "Cependant, en course, le système Porsche rentre dans le rang au bout de plusieurs tours."? Did he expect Porsche to have Toyota to gradually come to terms with the hybrid they have and reel in Porsche?

[Bandicoot17]

Sort of makes sense to me as to why Porsche are pretty consistent with their top speed. I imagine the Toyota dumps everything out of the corner and then has to wait to get more in. The Porsche can store more and so can dump a certain amount out of the corner but then if need be, use a little bit at the end of the acceleration to get the car up to the top speed. This could provide a big advantage on the Mulsanne if they are hindered by traffic whilst battling with Toyota/Audi.


Does anyone know whether the Audi and Toyota have a manual release option? The Porsche apparently does (according to Timo).

[JoestForEver]

Two points to make
1. Personally I believe the chain of power concerning KERS is Recuperative braking system(possibly by-wire, let's call it RBS for short)---energy storage---MGU. Therefore, the power output of a KERS is retricted by the power of RBS/MGU, whichever is lower. The efficiency of KERS=E(RBS energy harvesting)*E(energy storage)*E(MGU)

2. I think during the streaming, Hindy and Collins asked about the battery shaped gauge alongside speedometer whether they are showing full Le Mans 6MJ or Spa-specific 4.78MJ, and the answer is the latter one.
What's more, it automatically recharges fully once crosses the line with still much energy left.

[Articus]

It just struck me and I had to comment. Even though the Porsche can store all 6 MJ in the battery pack (which is not much trust me) they will more often than not only deplete the pack to 50+% or so with recharging taking place several times a lap! This might be how they keep the cycle life of the battery! I'm starting to become a believer...

[GasperG]

I agree, Porsche may have the full 6MJ capacity on board, but higher capacity was chosen because of battery power rating. Even if using highest power density batteries possible it apparently wasn't good enough for 24h of molesting at 180 kW. Even if they have capacity overkill it's not necessary heavier than Toyota's supercap.

And also one thing to note is that Porsche is using ERS-H, this gives energy under full acceleration, they are probably not storing much of that energy but rather using it directly on the electric motor. Kinetic energy on the other hand must be stored and they have "only" >180 kW el. motor. This is a lot less than Toyota charge/discharge capability of 353 kW.

Looking at those two diferent numbers one could conclude that Porsche recuperates almost half of MJ energy from ERS-H, or Toyota has oversized el. motors (I doubt that).

[MyNameIsNigel]

Originally Posted by JoestForEver

Two points to make
2. I think during the streaming, Hindy and Collins asked about the battery shaped gauge alongside speedometer whether they are showing full Le Mans 6MJ or Spa-specific 4.78MJ, and the answer is the latter one.
What's more, it automatically recharges fully once crosses the line with still much energy left.

I could be wrong, but I believe that the gauge only shows the amount of energy that is being released through the MGU, not necessarily the amount of energy stored in the energy store. As a matter of fact, the rules merely limit the amount of energy released through the MGU and the measurement take place at that level. So far I know, there is no provision that limits the amount of energy that can be stored in the energy store or that forces to communicate that amount together with the telemetry data.