Red Bull KERS: Floor Mounted Super Capacitors?

In the second year of their use of RenaultSport’s KERS, Red Bull appear to have found a new mounting position and format for their KERS energy storage with what appear to be floor mounted super capacitors.  Super Capacitors (Supercaps) are an alternative energy storage to Lithium Ion batteries, using very much the same technology as smaller capacitors used in electronics

2011 was Red Bulls first year with KERS, having chosen not to run it in 2009 as it compromised their design too much. As is typical for Newey, Marshal and their design team the KERS installation was unique and uncompromising, with its energy storage in two packs either side of the gearbox and a smaller unit inside the gearbox. Reliability issues plagued the team throughout the year, with the batteries succumbing to heat and vibration.

Floor mounting


So with a year’s understanding under their belt and the newly confirmed status as the RenaultSport factory team, the RB8 has taken a step forwards in KERS packaging. Now the energy storage appears to be slightly revised, with the unit inside the gearbox swapped for floor mounted units. In this exclusive picture from MichaelD in Melbourne, we can see the units remain fitted to the floor when it’s removed. The two carbon fibre cases are closed with aluminium tops and are provided with electrical and cooling connections. They sit in the final section of flat floor known as the boat tail.
Having the units placed on the floor, as opposed to between the gearbox and engine, means they can lower the Centre of Gravity. Also being quite heavy they are placed near the rear axle line to suit the mandatory weight distribution. As mentioned the units are supplied with a common cooling circuit, one pipe routes around the back of the floor to link the devices. There are also a number of electrical connections for both connecting to the KERS Power Control Unit and for monitoring their status. Quickly detachable connectors are used to allow rapid removal of the floor keeping the units in place.

What are they?
While trying to confirm these items as part of KERS, I’ve learnt some new facts about KERS in F1, which might help to explain these devices. It might convenient to call these units ‘batteries’; however their actual design and purpose might not accurately tally with that term.
It’s possible they could be part of the energy storage system for the KERS, either as Li-ion Batteries or Super Capacitors (supercaps), or they could be an energy dump used to reduce the load on the battery when harvesting power under braking.

Energy dump
The way the FIA F1 KERS rules are written there is a limit on the amount of energy that can be stored and reused. These limits are not in line with what is actually achievable with current technology. Teams are effectively capped on energy, as they could store and re-use far more. Part of the problems is that under braking, the energy harvesting is capable of producing more power than they are allowed to put into the battery. So the teams control the harvesting rate according the driver’s style and the circuits demands. Even then the harvesting potential is hard to predict. Rather than stopping the harvesting mid braking, which would unsettle the car. The teams keep the same harvesting rate, but dump the energy through a series of fixed rate resistors. Obviously these resistors quite large and create a huge amount of heat. This would explain their low position and cooling requirement.
These floor mounted devices might be the energy dumps, but they are particularly large and with increased experience of KERS teams are getting better at controlling the harvest rate, so shouldn’t need such a large dump. So it’s possible, but unlikely these are energy dumps.

Energy storage solutions

Li-ion batteries
Typically current F1 cars use dozens of Li-ion cells packed into an array forming a ‘battery’ pack. This KERS Battery Pack is commonly a single part sat under the fuel tank. Although often used as a single battery, the unit can be broken up into a set of batteries in series.
In 2011 Red Bull clearly split this part up into several smaller Battery Packs, there being the two aforementioned units either of the gearbox and another in the gearbox. Although interconnecting these parts with cooling pipes, high current cable and sensor cabling adds some weight, this does provide a nicer packaging solution. It’s logical to explain these new floor mounted parts as batteries. However they do not look like the battery packs seen in the gearbox last year, or on other cars. Being on the floor of the car they are subject to even more danger from impacts as well as the heat and vibration that caused issues last year.

Supercaps
As their design does not tally with existing Li-ion battery packs, then they might still form part of the energy storage element of KERS. So if not Li ion batteries then they might be the next bet alternative ‘super capacitors’. Supercaps have far more energy storage than the capacitors we common see on household electronics. They are far more efficient in storing and releasing energy quickly, with less losses and do not degrade as quickly as Li Ion batteries do. However they are not as efficient in storing larger amount of energy for longer periods.
A link between Red bull and supercaps is RenaultSport. Renault already uses supercaps as onboard storage for both formula Renault 2.0 and 3.5. In the 2012 FR3.5 series, the KERS only uses Supercaps, not a conventional battery.
So it’s possible the Red Bull RenaultSport KERS uses hybrid storage with a mix of Li ion cells and Supercaps, using the supercaps for short term storage and for more immediate bursts of acceleration. While the Battery provides the longer term storage between corners and for more sustained discharges of energy.
It’s believed that other teams are already using a mix of supercaps in their KERS Battery Packs to reduce the unit’s size and provide the option for a quick storage\release of energy.  So I believe that most likely these devices are Supercaps.  With revised KERS regulations coming for the new Powertrain in 2014, more use canbe made of Supercaps in both the Kinetic and Thermal Energy Recovery systems.  Experience of these componenents now, will be an important part of the development of the 2014 systems.

More on Supercap KERS via Race Engine Technology Magazine

30 thoughts on “Red Bull KERS: Floor Mounted Super Capacitors?

  1. Reblogged this on pptf1car and commented:
    This is quite clever. I guess I need to think of using a similar system now for MY designs. Even tighter rear end packaging. Top marks Scarbs, thanks for doing this!

    • Actually, they are using a capacitor instead of a battery, but with no harvesting.

      From Autosport:

      “The battery is replaced by an advanced ‘SuperCaps’ electronic control unit, which has been developed by Nîmes-based XAP Electronique.”

  2. Scarbs,

    You mentions that in 2014 the teams will be able to do thermal energy recovery. Any ideas on what means the teams will use to harness the energy?

      • Solid state thermo electric power generation is able to recover heat from just about anything hot. This is done via the peltier effect and there is a commercial interest in it as a means to recover waste heat from all ICEs (internal combustion engines). I believe BMW has implemented just such a system to recover heat from the exhaust on their 5-series a few years back. With the stated goal of driving the development of technologies to trickle down to consumer autos it would make sense to drive development of just such a system. The efficiency of recovery is generally limited by the Zt, the so call figure of merit. There have been a number of developments in this area over the past decade that have significantly driven the efficiency upward.

  3. Interesting. I wondered when F1 would embrace super/ultra capacitors. Toyota’s LMP1 machine is running ultracapacitors while Audi R18 Hybrid is running the Williams designed flywheel battery. AFAIK capacitors generate very little heat if at all any since there is no heat generating chemical reaction. So I’m not sure whether the photos really are of supercapacitors

  4. Great write-up as usual Scarbs! Excellent (rarely seen) photos of the floor diffuser area as well, you can clearly see how the starter hole feeds the ‘monkey seat’ and Red Bull’s beautiful aerofoil-section Gurney flap (why haven’t all the other teams adopted this?).

    • Turbos do not recover waste heat, they recover wasted mechanical energy. That is, they are primarily energized not by the temperature of the exhaust but rather by the physical force it exerts on the turbine blades.

      Please feel free to let me know if I am wrong but I was (at one point in time) pretty sure I knew how these things worked.

      Cheers!

      • Turbochargers are placed in such a way that they utilise the waste energy from the engine. Placed in the exhaust gas flow, they convert the energy there in the turbine side of the t/c into energy by driving the compressor part of the t/c, as you have stated above. One by product Of this process is the large reduction in the exhaust gas heat.

        Atb

        Drew

      • Yes. it recovers energy, which would otherwise be wasted heat mainly. This is one of the reasons you want the turbine as close as possible to the engine where maximum thermal energy and greatest potential exist. There is a large exhaust temperature drop as it flows through the turbine.

      • First of all, sorry for replying to my post rather than your’s, but I can’t seem to reply to your replies for some reason…

        How is it that the turbine converts heat into rotational energy? I am still thinking it just the phsyical force (i.e. mechanical energy) the exhaust gas exerts on the turbine blades that causes it to turn. Heat plays a role in that it causes the exhaust gas to occupy a higher volume than cooler gas. Thus a certain volume of gas exits the head, as it leaves it rapidly cools thus contracting. So in order to maximize the flow rate over the turbine blades you want it hotter (i.e. occupying a higher volume), but this isn’t actually recovering thermal energy so much as it is mechanical energy. I realize I’m kinda getting technical, but it seems to me that a true thermal energy recovery system directly harnesses the thermal energy; a turbo directly havests wasted mechanical energy and heat aids this process.

        I suppose if we wanted to really get into the atomistics of it temperature of a gas is nothing more than a quantification of the sum of the mechanical energy of every atom. I guess its all pretty closely related… I just think about it differently.

      • @mmschnei:
        The basic principle is the transformation:
        waste heat (enthalpy!) -> kinetic energy -> rotational energy
        So, it is all about recovering thermal energy. And yes, it is possible to use the kinetic energy created by the exhaust pulse as well, but not all turbochargers actually do that.

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  7. Craig, absolutely superb articles and this article just reinforces your own pictures of last years RB7 with a tiny KERS ( useless) system whereas I’m sure I’ve seen pictures of the Merc KERS Batteries last year about the size of 4″x15″x 12″ – Craig … Any idea how big the Merc system is this year. ??

  8. Hi Craig, I only discovered your blog at the start of this season and have been enjoying reading it over the last few weeks. I’m a power electronics engineer and have recently been working with this sort of technology, so I feel able to contribute something useful for the first time…

    I’m sorry to spoil your fun, but I’m affraid it looks pretty unlikely to me that what you have a picture of is any sort of super/ultracapacitor energy storage system for KERS. An F1 KERS system needs to be able to store over 400kJ of energy (60kW x 6.7s = 402kJ), and probably more like 450-500kJ if you take efficiency into account.

    The best ultracaps currently available have a capacity in the region of 2000F at 2.7V (approx 7.25kJ) in a cylindrical volume approx. 60mm dia x 100mm long. So to store the amount of energy we’re talking about you would need ~70 of these connected together. Now this is entirely possible, but looking at the photos it just doesn’t look like those modules are anywhere near big enough to fit them all into. They’d need a volume of ~25,000cc and they’d also weigh the best part of 25kg!

    They’re still fascinating photos, like all of what you put up. Please keep up the good work!

    • Andy,
      Thanks for the comment.
      I take your comments on board, due to poor super cap energy density, I never thought super caps could be used alone. These supercaps aren’t the entire 400kj energy store. The rb8 still carries two very large li ion battery packs. These two small units probably only contribute a small proportion of the energy.
      Does this make it more plausible, that these are a super cap solution?

      • Yeah, that does actually sound much more plausible; to use supercaps as a sort of energy storage buffer. They have a much lower internal resistance than any battery, so they can handle far greater bursts of current and generate a lot less heat in the process (both of which are advantageous considering Mr Newey’s famous lack of compromise on cooling!).
        I’m interested to see what happens when they increase the power to 120kW in a couple of years time!🙂
        But firstly lets just hope everything goes well for all the teams this weekend!

  9. why doesn’t the FIA just let KERS be unlimited? then we could see the real potential of this technology and where the true line of compromise is between weight and performance using this technology.

    amazing write-up and sleuthing.

  10. Batteries and capacitive systems both have their benefits and drawbacks. The capacitive systems can be charged/discharged more rapidly and are mostly lighter weight. But the voltage of the capacitors drops as they discharge, so the power electronics must be made to compensate for this effect. Battery designs like Li-ion are getting quite good, but they still require active cooling for duty cycles like those used in F1.

    As a side note, I recently saw a development version of a PM motor and controller for an F1 KERS system that was rated at better than 0.12 kg/kW. That is a pretty impressive power/weight figure!

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