Green technology is driving some of the fastest cars around on planet Earth today. It has taken a while, and there are no top-level divisions in motorsports, yet running all-electric vehicles has developed as a trend.
Most notably, almost all of this year’s Formula One grids feature cars that make use of KERS systems. KERS stands for Kinetic Energy Recovery Systems, a fancy name for technology that takes energy that would otherwise be wasted under braking and turns it into electricity that is stored for later use.
Also known more commonly as regenerative braking, such systems have been used to some degree in most hybrid and electric road vehicles for some time. They were adopted in Formula One in 2009 before being abandoned last year and re-introduced for this year’s season.
Today’s F1 cars use KERS systems that weigh 25kgs. Though this weight fits within the minimum weight limits of the sport’s regulations, some teams eschew use of the KERS as it raises the car’s centre of gravity, slightly degrading the car’s ultimate handling performance.
Those teams that do use KERS are banking on that handling sacrifice being recovered over the course of the race. In practice, the KERS lets the driver hit a button to get a little (but potentially very useful) boost in power – akin to having a turbocharger kick in.
Two main types of KERS systems are available. Mechanical KERS systems use dense flywheels to store the energy recovered under braking. Then there are KERS systems that first convert the recovered energy to electricity, which powers an electrical motor to keep the flywheel spinning. In these systems, the energy then has to be recovered from the flywheel and converted back into electricity, which is again used to drive an electrical motor.
With every conversion of energy, there is a certain amount of energy loss. For this reason, mechanical systems that can recover the energy without conversion and then deploy it again are seen as ideal.
In practice, it can be immensely complex and unreliable to engineer a mechanical KERS system that works within the confines of motorsport. Many of the F1 KERS systems store the recovered energy in electrical batteries or super-capacitors (electrical components that can store large amounts of electrical power for short periods of time). When the driver hits the ‘boost’ button, the electricity is used to drive some form of electrical motor that injects power into the car’s driveline.
Regenerative braking is not a new idea. A mechanical KERS-type system using a flywheel to store energy was reportedly considered some 60 years ago by the colourful physicist Richard Feynman.
Electric locomotives have long operated with regenerative braking systems, with the electric motors used to drive the train used to generate electricity under braking, which is then fed back into the railway’s supply system.
Most diesel-electric locomotives lack the ability to store large amounts of electricity produced under braking. In these machines, the power produced by dynamic braking is turned into heat, some of which can be used to supply the locomotive’s energy needs but much of which is simply lost to the environment.
Back to fast cars, KERS and regenerative braking… why is it taking so long to iron out the kinks in this old technology?
Well, for one thing, it is deceptively difficult to handle the varying voltages in these systems. They tend to run on DC, or direct current, which is hard to manipulate.
In order for these systems to work well, sophisticated electronics are needed to match the voltage expected by the system, the voltage being produced under braking and the voltage the batteries can handle.
Get it right, and you get a handy performance gain with little or no degradation of handling or reliability. Get it wrong, and you’ve basically added 25kgs of unwanted weight that cannot even be shifted around the car (like ballast) to optimise handling.
Get it really wrong, and you end up with a major electrical problem. The Red Bull Racing team saw this lead to a fire at their factory and a major delay in their use of KERS. A little while later, a mechanic at BMW Sauber felt the wrath of KERS when he got a nasty shock from Christian Klein’s car, the performance of which had suddenly become just a little too electric.