Hybrid power units have been part of the F1
regulations for 11 years, though it’s fair
to say they had an unceremonious and bumpy
start.
In 2009, the cars were allowed a fairly small
energy regeneration and deployment system
alongside the combustion engine and this was
expanded substantially in 2014 to turn the
cars into fully hybrid machines with a significant
amount of their power coming from re-captured
energy.
Every car that’s used energy recovery systems
since 2009 has used an electric battery to
store the energy otherwise lost in braking.
While this may seem obvious, using a battery
for this wasn’t mandatory at all and teams
were free to develop whatever they considered
to be the best solution to storing energy.
Williams very nearly changed the whole game
when pointed their research and development
in a completely different direction from the
start.
This video explains how Williams put all their
efforts into designing a revolutionary flywheel
hybrid and how, despite never using it in
F1, it can still be considered a success story
and a piece of engineering genius.
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Now - let’s get back to Williams’ flywheel.
Let’s wind up to discovering Williams novel
flywheel solution by talking about energy
recovery in general.
In fact, let’s start by talking about energy.
The way you power… anything is by transferring
energy from one state to another - whichever
form is useful for the situation.
For example, a gun converts chemical energy
stored in the gunpowder by starting a reaction
that creates heat, sound and kinetic energy
that transfers to the bullet, propelling it
down the barrel of the gun at high speed.
The energy was stored chemically and was transformed
into a useable kinetic (or moving) energy.
We can store and release energy in lots of
ways. For example, we could spend a lot of
mechanical energy lifting a large weight up
to a great height.
A lot of the energy spent in lifting the weight
is stored in the suspension of the mass at
height - a potential energy.
To spend the energy, you simply release the
weight and it accelerates towards to ground,
converting that potential energy into kinetic
energy until it transfers that kinetic energy
to the ground to create a large crater.
The hybrid power units as we know them today
in F1 cars take energy under braking and converts
it into electrical energy to transfer it to
a battery where the energy is stored chemically.
And the reverse it true when the energy is
deployed from the battery back into powering
the wheels.
And by ‘recovering energy under braking’,
what I mean is this: when the wheels are turning,
they carry a lot of rotational energy.
To slow the car down, we need to take that
rotational energy away from the wheels, reducing
their speed.
Normal brakes do that by simply clamping down
on the wheels and using friction to sap the
kinetic energy away by converting it into
heat which simply escapes away from the car
and is lost.
But an Energy Recovery System instead turns
the rotational energy into a different energy
and stores it away, reducing the energy wasted
and hugely improving efficiency.
So: energy recovery was allowed in F1 in 2009
but only a small amount was allowed to be
stored and deployed which allowed teams to
play with and develop the technology without
the pressure of it being a huge amount of
the overall power as it is today.
Cars could only deploy an extra 60 kW (or
80 bhp) of power at the push of a button,
but only for 6 seconds a lap.
That’s a total of 400 kJ extra energy, which
is over 30 AA batteries.
Nowadays, energy storage is ten times higher
and cars can deploy twice as much power for
over 5 times longer per lap.
Under the original KERS rules back in 2009,
only four teams even tried running KERS at
all. No one ran it in 2010 but it came back
with a vengeance in 2011.
In that time, Williams were furiously working
on a flywheel solution to their energy recovery
and deployment. But what does that entail?
This would mean that Williams would have no
battery at all in their energy recovery system
as they would instead store their energy kinetically.
A flywheel is essentially just a heavy wheel
that spins super smoothly on an axle.
You can transfer the spinning rotational energy
from the car’s wheels onto the flywheel;
in doing so, you slow the car down and speed
the flywheel up.
In effect, the flywheel steals spinning energy
from the driving wheels, slowing the car down
which contributes to the braking of the car.
The flywheel then just sits there spinning
happily until it’s ready to be used: at
which point the reverse happens: the rear
wheels steal energy from the flywheel. The
car gains power, and the flywheel slows down.
There are actually many ways to transfer energy
from a flywheel to the driveshaft (and ultimately
the rear wheels) and the most common mechanical
solution is to use a continuously variable
transmission, or CVT.
Unlike a standard transmission, which has
a series of discrete gear ratios, a CVT in
effect allows you to smoothly adjust the gear
ratios infinitesimally like magic. It’s
not in the scope of this video to explain
some of the ways this is done but an advantage
of this system is that everything is linked
mechanically.
Mechanical energy in the rotation of the wheels
converts to mechanical energy in the CVT,
which converts mechanically to the flywheel
- it’s all just one big kinetic system so
you reduce a lot of losses that can happen
converting it to electrical and chemical energy
as with a battery.
The disadvantage here is that you are extremely
limited in where you can put this system as
it has to be right next to the gearbox.
However, Williams didn’t do this either.
In order to save weight and allow them to
position the flywheel further up the car,
they developed an electronically driven flywheel.
The way this worked was that - instead of
a CVT between the driveshaft and the flywheel,
Williams put motor generator units. These
are basically like MGU-Ks you’d find in
the other battery-powered KERS cars that convert
the mechanical energy from the wheels into
electrical energy.
But instead of taking that electrical energy
and using it to charge a battery, they used
it to spin up a flywheel in a very clever
way.
What they did was lace the flywheel’s carbon
mass with magnetic particulate, turning the
wheel into a permanent magnet. The electrical
energy from the MGU would then feel into a
stator in the axle of the flywheel, which
(as you’ll know if you watch my MGUK video)
will spin up the flywheel.
An electric current in the system induces
rotation in the flywheel. Once the flywheel
is charged up with rotational energy, you
can just do the reverse to put power back
into the car. The spinning magnetic flywheel
can induce current in the electrics, sending
electrical energy back to the MGU, which drives
the rear wheels.
It was compact, light weight, relatively easy
to build and could spin at over 50,000 RPM
in good conditions. This type of flywheel
also has a high power-density - essentially
a very good power-to-weight ratio and could
run and run and run without losing efficiency,
unlike batteries which do tend to lose efficiency
over their lifetime.
Ultimately though, Williams never used this
flywheel design in their F1 car. This was
mostly due to packaging problems as, in 2010,
refuelling was banned which increased the
size of the fuel tanks significantly, which
expanded into exactly the area where the flywheel
would sit.
But the tech was a real success. Porsche used
the system in their 911 GT3R and Audi took
a 1-2 at Le Mans with the Williams flywheel
hybrid design.
Though Williams deferred to the standard battery
system for F1, they continued to develop their
flywheel technology, selling their systems
to road cars, sports cars and fleets of London
buses. Eventually, they packaged up Williams
Hybrid Power and sold the venture to huge
engineering firm, GKN.
So the flywheel didn’t quite meet the needs
of F1 - for now at least - but we’ve definitely
not seen the last of its application.
Will we see flywheel systems compete with
batteries in race and road car systems going
forward? Well, it’s important to understand
a crucial limitation: flywheels can only store
so much energy and they can’t hold it forever.
Unlike a battery, which can store energy without
significant loss for a very long time, a flywheel
will eventually slow down and come to a stop.
It only stores energy while it’s spinning
at high speed. And a flywheel is limited in
how much energy it can store at all - it can
only spin safely and practically so fast,
after all.
So, while it’s great at recovering and deploying
energy, it’s not so great at long term,
high density energy storage. So it still has
great application for racing or for public
transport where the frequent braking and accelerating
is the perfect application for flywheels.
Perhaps we will see solutions that involve
a mixture of batteries and flywheels in some
vehicles? A hybrid-hybrid, if you will. Maybe.
