Con el KERS, esa energía no se pierde, si no que se almacena en algún sitio para utilizarla en la conducción; ese sitio puede ser una batería (energía química), en un volante de inercia (mecánica), en un acumulador (hidráulica) y de muchas otras formas. Esa energía almacenada puede reutilizarse para darle potencia extra al motor y la normativa permite un máximo de potencia KERS de 60kW y una salida de energía de 400 kJ en una vuelta. En términos simples, eso significa 60 kW para poco más de seis segundos para ‘impulsar’ el coche en cada vuelta.
¿Por qué eligió Renault la opción de la batería? Cuando empezó el proyecto KERS, la principal prioridad fue estudiar todas las soluciones posibles para el almacenamiento de energía. Fue una decisión difícil escoger entre las baterías y un volante de inercia, pero la solución de la batería resultaba más prometedora y ofrece potencia para adaptar esta tecnología a los coches eléctricos normales en los próximos años. El sistema KERS de Renault utiliza almacenamiento químico en una batería de litio-ion suministrada por SAFT, una empresa francesa con una gran experiencia en la creación de soluciones de alta tecnología para baterías.
El KERS necesita algo más que almacenar la energía para ser un sistema completo; necesita formas de ‘traspasar’ la energía a sus distintas formas, cinética, eléctrica y química. Este ‘traspaso’ se consigue con una unidad de motor eléctrico-generador (MGU) que puede convertir la energía cinética del coche en energía eléctrica y viceversa. Sin embargo, esos aparatos de transformación requieren unos 50 kg y mucho espacio: dos cosas que los equipos de Fórmula Uno intentan evitar a toda costa. Por tanto, era de la mayor importancia que el MGU pesara lo menos posible, y ahí es donde entró Magneti Marelli que, trabajando con el equipo, pudo producir una solución compacta y ligera para cumplir nuestros requisitos.
El MGU que se creó es muy pequeño y solo se activa durante la frenada y durante unos seis segundos de aceleración, mientras que durante el resto de la vuelta puede relajarse y disipar el calor generado en los momentos de actividad. Mientras más eficiente sea el sistema KERS, menor es la pérdida de calor y el sistema Renault F1 consigue un 70% de eficacia en la captura de energía del eje trasero, su conversión a electricidad, almacenado en la batería, salida de la batería y finalmente, su conversión a energía, de nuevo en el eje trasero.
El impulso adicional de 60kW (que son 80 cv), limitados a 400 kJ por vuelta, reducirá el tiempo de vuelta en 0,2-0,3 segundos. Para sacar el máximo partido del KERS, todo el sistema debe ser tan ligero y compacto como sea posible, porque si no, la ventaja puede desaparecer rápidamente. El peso de la solución de cada equipo se guarda en secreto, pero cuando se tiene en cuenta que cada 10 kg de peso innecesario pueden costar 0,35 segundos por vuelta, no resulta raro que tantos coches hayan seguido una dieta de adelgazamiento durante el invierno.
En realidad, sin embargo, hay otros efectos más sutiles que se interponen al intentar lograr esos teóricos 0,2-0,3 segundos de reducción de tiempo, como la distribución del peso, no solo longitudinalmente (delante hacia atrás) sino también en vertical. Sería fácil perder todo el potencial de tiempo de vuelta del KERS si no se han estudiado bien esos puntos. Sin embargo, si se consigue la solución ideal, el impulso de 60 kW al motor podría ayudar a los adelantamientos, al menos entre coches con KERS y sin KERS.
————————————–
Renault explain KERS
KERS is the new buzzword of Formula One. We know that it’s supposed to encourage overtaking and lead the sport towards a greener future, but just how does it work and how effective is this new technology? Renault explain…
The basics: what exactly is KERS?
Let’s start with a definition: KERS stands for Kinetic Energy Recovery System and was introduced by the FIA to direct the Formula One engineering community towards developing greener technologies. Kinetic energy is energy stored in motion and can be thought of as the energy that is required to stop that motion. For example, stopping a bicycle, a car or a train is all about removing its kinetic energy.
Most commonly kinetic energy is removed using friction brakes, turning the kinetic energy into heat energy that goes towards warming up our planet that little bit more. With KERS, that energy is not lost but stored somewhere to be used to drive the car – that somewhere could be in a battery (chemical energy) in a flywheel (mechanical), in an accumulator (hydraulic) and in many others ways too. This stored energy can then be reused to give extra power to the engine with the regulations allowing maximum KERS power of 60kW and energy release of 400kJ in any one lap. In simple terms this means 60kW for a little over six seconds to ‘boost’ the car each lap.
Why did Renault choose the battery option?
When the KERS project began, the first priority was to study all possible energy store solutions. It was a tough call deciding between batteries and a pure mechanical flywheel, but the battery solution was more promising and offers the potential for adapting this technology for road cars over the next ten years. Renault’s KERS device therefore uses chemical storage in a Lithium-ion battery provided by SAFT, a French company with a track record of providing cutting-edge battery solutions.
What comes next?
KERS needs more than just energy storage to be a complete system – it needs devices to ‘translate’ the energy between its various forms of kinetic, electrical and chemical. This energy ‘translation’ comes from an electric motor-generator unit (MGU) which can turn the kinetic energy of the car into electrical energy and vice versa. However, such translation devices normally weigh in the region of 50kg and require a lot of space: two things which Formula One teams go to great lengths to avoid.
It was therefore paramount that the MGU weighed as little as possible, which is where the involvement of Magneti Marelli came in and by working together we have been able to produce a compact, lightweight solution to meet our particular needs.
The resulting MGU is very small as it is active only during braking and for six or so seconds of acceleration, while for the rest of the lap it can relax and dissipate the heat generated in the active moments. The more efficient the KERS system is, the lower the heat losses, with the Renault F1 system achieving over 70% round-trip efficiency from capturing energy at the rear axle, converting it to electricity, storing it in the battery, pulling it out of the battery and then finally converting it to energy at the rear axle again.
What does KERS mean for the fans?
Well, the additional 60kW boost (which equates to 80HP), limited to 400kJ per lap, will reduce lap times by between 0.2-0.3 seconds and, as demonstrated by Fernando Alonso’s and Nelson Piquet’s starts in the Malaysian Grand Prix (gaining six and four places respectively), there are clear benefits in using the system from a standing start. But to get the most from KERS, the whole system needs to be as lightweight and compact as possible; otherwise this advantage can quickly disappear. The weight of each team’s solution is therefore a closely guarded secret, but when you consider that every 10kg of unnecessary weight can cost 0.35 seconds per lap, it’s no wonder so many cars have been on diets over the winter.
In reality, though, there are other more subtle effects that get in the way of achieving the theoretical 0.2-0.3 second lap time reduction, such as weight distribution, not just longitudinally (front to rear) but also vertically. It would be easy to lose all of the KERS lap time potential if these points are not well considered. But, provided you can settle upon the ideal solution and get the gearing of your car right, the 60kW boost to the engine should aid overtaking, at least between KERS cars and non-KERS cars. Of course, it’s still in the earliest stages of development and as the teams learn how to optimise KERS as a racing tool, the advantages are likely to become more apparent as the year unfolds.
————————–
Renault answer 10 questions about KERS
The introduction of Kinetic Energy Recovery Systems, or KERS, is one of the biggest technical challenges of the 2009 Formula One season – and also one of the biggest unknowns. While the basic principles will be shared by all teams’ systems, the specifics could be very different. Understandably, those specifics are closely-guarded secrets, but Renault have been kind enough to reveal just a little more of how the R29’s KERS will work…
KERS?
It’s a system whereby the goal is to store the energy produced under braking in a reservoir (either batteries or flywheel) in order to release it under acceleration. The 2009 technical regulations state that KERS should not deliver power in excess of 60kW, which is equivalent to around 80 horsepower, when the driver presses a button on the steering wheel. He cannot use more than 400kJ per lap.
2. Is there only one way to recover the energy and reuse it?
When the 2009 KERS system was being conceived, the engineers had a choice between two different approaches. The first consisted of using a carbon flywheel in a vacuum linked via a CVT transmission to the differential. This system stores the mechanical energy, offers a big storage capacity and has the advantage of being independent from the gearbox. However, to be driven precisely, it requires some powerful and bulky actuators, and lots of space. The second option was to rely on an electrical motor, which works by charging the batteries under braking and releasing the power on acceleration.
3. Which choice did Renault go with and how does the system work?
Renault chose to go with the electrical solution, as did most other teams. The system consists of three important parts:
• An electric motor (MGU: Motor Generator Unit) situated between the fuel tank and the engine, linked directly to the crankshaft of the V8 to deliver additional power.
• Some latest generation ion-lithium batteries (HVB: High Voltage Battery Pack) capable of storing and delivering energy rapidly.
• A control box (KCU: KERS Control Unit), which manages the behaviour of the MGU when charging and releasing energy. It is linked to the car’s standard electronic control unit.
4. What were the main challenges encountered during the development of the system?
Firstly, it was necessary to deal with the weight and volume of the system, which adds considerable weight in comparison with the 2008 car. This means there is less ballast available for the engineers to redistribute in order to balance the chassis. Also, the cooling of the batteries is of great importance and it was necessary to develop a specific system for them.
5. Where are the batteries situated?
They are positioned under the fuel tank. Some teams have chosen to place them under the driver’s legs or in the sidepods, but Renault opted against this as it felt these solutions presented more problems.
6. Does the MGU have to be positioned between the engine and the fuel tank?
No. It’s possible to situate it parallel to the gearbox in the rear of the car. So it’s connected straight to the rear wheels and releases its power through the differential.
7. Will Renault be the only team to use this system with this set-up?
No, the team will provide its KERS system to another team this season.
8. Why are most teams behind schedule in the development of their systems?
The development timescale was very tight: the system had to be developed in just 18 months and so the number of advanced projects and preliminary studies has been limited. Some teams have suffered from this and may have chosen solutions that are difficult to develop. There has also been the safety of the drivers and mechanics to consider which has required extensive safety training. Finally, the factories have had to install special testing rigs and implement further personnel training
9. Will KERS produce more competitive racing?
Not necessarily. If all the teams use KERS, they will use it in the same way, in the same places, at the same times, and so there will be no advantage. On the other hand, not having the system will be an enormous handicap.
10. Has F1 already helped this technology progress in terms of its relevance to the wider world?
The development of electrical motors capable of delivering 80 horsepower for minimum space and weight while operating in a very harsh environment represents a significant step forward in the world of energy recovery.
www.ing-renaultf1.com/en/media/index.php
