Translator: André GENNESSEAUX Reviewer: Ivana Korom
I found a means to solve the energy problem
with concrete!
Yes, concrete!
Not to build dams or install windmills,
but concrete to power the grid,
make light and heat.
I am going to explain it to you.
Did you know that the cheapest energy today
is solar energy?
Thanks to the dramatic drop in solar panel price,
if you install now a solar panel in a sunny place,
you get a kilowatthour at 2 cents.
It's half the price of classic polluting energies.
In addition to being the cheapest, solar energy is extremely abundant.
The red square in Sahara, roughly one quarter of France,
represents the area of solar panels
that can power the whole planet with electricity!
So, if solar energy is so cheap and so abundant,
why isn't it our main energy source?
Because there is a problem: intermittence.
In the day there is sun, but in the night there is no sun.
This bell curve shows
that solar energy comes concentrated, in the middle of the day,
whereas our consumption is rather constant: this is the white line.
If we want to power the network with a lot of solar energy,
it is absolutely necessary to store the excess of energy
in the middle of the day, in yellow,
to be able to use it in the evening and the night.
Storing energy is not a technological problem,
it's an economical problem.
Energy can be stored, in batteries.
But energy cannot be stored profitably with batteries.
Batteries, like the lithium ones of your phone,
use a chemical reaction.
After each charge-discharge cycle, they wear, they lose some capacity.
They need to be replaced after a few years.
And when you compute the cost of storing energy in batteries,
you find that it is very high.
It is estimated to be 10 cents per kilowatthour,
so that solar energy, when stored in batteries, is no more interesting.
It is not profitable: it needs subsidies, it cannot develop.
I am not a chemist, I am a mechanical engineer.
A few years ago, I was working for Total and I went to Detroit Auto Show,
and I see a startup willing to replace electric car batteries with "wheels".
Not steering wheels for driving, flywheels.
A flywheel is a disc or cylinder spinning at very high speed
to store energy in a form called kinetic energy.
Flywheels have been made of steel.
Recently some have been made of carbon fiber.
The very large advantage of flywheels over batteries is their unlimited life.
Unfortunately for electric cars, flywheels proved to be too heavy.
But I had the conviction that, when weight is not a problem,
flywheels have a tremendous potential for storing renewable energies,
and I founded my company.
With my team of four, we made flywheels with steel, then with cast iron.
We were in the quest of the graal that everybody is searching now:
low cost storage.
But these classical materials are too expensive.
We had to find something completely different.
Last year I had an intuition: we had to test concrete.
And I found that
concrete is an extraordinary material for energy storage.
Concrete can store energy at a cost ten times lower than classical materials.
And I can tell you that, in an engineer's life,
you don't often make such a large progress in so little time.
Of course you will ask: if it's so easy, why did nobody think about it before?
Because concrete is incompatible with flywheels.
Concrete does not resist traction: if you pull on concrete, it breaks.
When a flywheel spins, there is a huge centrifugal force
that creates intense traction.
If you make a cylinder out of concrete, it bursts as soon as you spin it.
My solution consists in compressing the concrete
with a winding in traction all around
so that concrete stays compressed up to the maximum speed.
To keep things simple, we can say that we wrap it like a roast beef.
This "Flywheel for Solar Energy Storage", we called it VOSS.
How does it work?
When there is an excess of solar energy, needing to be stored,
we use an electric motor to spin the flywheel faster and faster,
and store kinetic energy.
Maximum speed is that of an airplane, slightly less than 1,000 km/h.
This is fast.
But there is no air drag, as we have removed the air - vacuum,
so that we can keep energy for hours.
To recover the energy, the system is reversed, that is:
the flywheel spins the motor,
which produces electricity like an alternator.
Finally, with intuition, a lot of reflexion and some concrete,
we have found a means to store energy at a low cost:
The association of concrete flywheels with photovoltaic panels
produces a renewable energy, available night and day,
at a lower cost than that of polluting energies.
This technology is currently under development.
Our project in the short term is to equip small networks:
like Corsica, Guadeloupe, Réunion, African villages...
that are currently powered by generating sets,
in order to replace their fossil fuel by solar energy.
But our long term project, in 4 to 5 years,
is to create large photovoltaic solar plants
in highly sunny areas such as deserts,
in order to power the global network
with an energy that will be clean and cheap:
solar energy, profitable without subsidies.
Needless to say, after all these years of research,
I am impatient to see our technology reach the energy market,
and revolutionize it,
because with such a low cost of storage,
renewable energies will at last be able to replace polluting energies.
Thank you.
(Applause)