Transcriber: Marcos Vinícius Melo da Silva Reviewer: David DeRuwe
Many of the things that me and my colleagues at academia
have an absolute privilege to do
is to rethink what is it that the world truly needs.
What can be a transformational opportunity
that can indeed transform the way we think about the planet,
and we think about us as humans who live on it,
more sustainably, in a way that would engage others
beyond the ones you see on your everyday experience.
Energy and provision of energy is one of those equalizing factors.
Those who use the most energy in their daily life
happen to be the ones who live the most cushiest lives on this planet.
Provision of energy, hence, might be able to uplift others,
and hence we ask, Where can energy come from?
This little dot in the upper left is an example of, let's say,
19 terawatts of power that all of us use continuously throughout the year.
That’s 19 terajoules per second of energy each one of us, pardon us,
all of us as a society happen to use.
What if I looked at the amount of sunlight that happens to be shining on this planet?
This is, roughly speaking,
174,000 terawatts of sunlight
that hits planet Earth every second.
If we can collect it in a matter of one hour,
we will be able to power the entire planet for one year.
It would require us to cover half the planet Earth with solar cells,
and hence that might be a bit of a challenge,
but all facts put together,
there is a lot of sun’s energy we could use to transform the planet as we know it.
How do we collect it today?
Well, there are three big photovoltaic ways of doing it:
We either install them in large utility systems that cover the fields.
If you don't have a field and maybe there is a rooftop of a commercial building,
we do that.
And if we choose to do it for our own homes,
the residential installations of solar cells are an option.
And that’s not all.
Indeed, if you would like to have a floating system, you can do it.
It’s actually a very practical way of keeping water in reservoirs
from evaporating and at the same time utilizing the electricity,
maybe excess of it, to pump the water up the hill to refill the reservoir.
Agriculture. Turns out, plants don’t need every sun’s photon that’s given.
Plenty of plants can live in the shade and produce very, very effectively.
Plus, if there are animals, they appreciate having a shade
on a very, very sunny day.
You can have an agricultural deployment of solar as well.
Notice in every one of these images I’ve shown and shared with you,
the solar cells are dark blue.
They’re made of silicon.
These large panels, 50 pounds, each of them, 25 kilos.
You need to pick up every one of them,
install it by using some sort of aluminum structure or concrete footing,
and only then can you actually put the solar cell on top.
Solar cells, it turns out, do not cost very much.
It’s the installation that causes us to have the particular price point
that the solar right now reaches.
If you recognize that, you recognize that maybe you have
a transformative opportunity to go from a 50 pound silicon module
to less than one pound solar roll,
if I could only make it; if there’s only a technology
that I can focus on and say, “This is what I need to do.”
Much of the matter around us is really good at absorbing light.
Much of the matter, much beyond silicon.
How do I know this?
Well, anything that's colored around you,
it’s colored because it’s absorbing the light
and reflecting only certain colors.
Dark objects are particularly good at absorbing light,
and they’re colored by pigments, molecules, dyes.
Can I use those dyes as solar cells?
The answer is yes, you can, and actually you can transform
the way we think about what the solar cell is as a result.
You can actually take those dyes and print them on a piece of paper,
add a few electrodes,
and you can make a solar cell that is on the piece of paper.
You can imagine that one day production of solar cells
should be as simple as printing newspapers,
and it should be lightweight and easy to deploy.
Here is one way of doing it:
This is a printer that’s putting down active material,
and it’s crystallizing, turning from clear to dark.
So-called perovskite in films is very good at absorbing light
and very good at making solar cells.
The brilliant thing about this technology is that it's extremely, extremely thin.
So when you bend such a solar cell, it doesn’t mind.
It’s kind of like us standing on planet Earth.
We do know the earth is curved, but we’re too short to notice that.
That’s what these cells experience when you bend them.
They are too thin, nanoscale in thickness,
too thin to notice that they’re actually being stressed and strained,
allowing them to be put on extremely lightweight substrates
like plastics, paper, Saran wrap, if that’s what you wish.
Now to us, that might be a very significant value.
I told you that most of the cost of solar installation
is in the installation itself, not in the cells.
If I gave you free cells,
you would still spend at least two thirds of the money to get those cells installed.
Hmm.
To me, using an extremely lightweight solar cell
will simplify the way I can install it on my roof.
I can make a carpet of it and just unroll it and staple it to the roof.
That can change the paradigm of cost
and ease of deployment to us in developed worlds.
But much more importantly,
it’s these individuals that we need to make a difference for:
Their village is far away, maybe ten-mile walk.
There is no paved road on which you can drive solar cells
in the back of your pickup truck,
and as a result, it needs to be carried on someone’s back.
These individuals, I bet, do not care what is the efficiency
of their solar cells,
and that’s the metric we keep driving towards,
because we want to cover less and less of our rooftop with solar, if possible.
I’d say the transformative metric for them
is how many watts per kilogram am I carrying?
How many trips will I need to make,
knowing that I can only carry 20 kilos of weight on my back.
One way to give you more watts per kilogram is, yes,
make solar cells a little bit more efficient.
Another way is make them weigh a hundred times less, if you can.
That can give you a hundred times more power for the same efficiency
or even 50 times more power per weight for half as efficient of a solar cell.
Opportunities are vast to transform that world.
It is new ways of doing cotton picking or e-rickshaws or solar sprayers,
industrial sheds, shepherd tents.
If this can be a solar cell, those particular individuals would be uplifted
in the way they think about provision of energy
for their little bit of light and a little bit of solar charging.
Here is an example of what we can do.
This is a company called Karma Solar on the east side of India.
They have flexible, lightweight solar cells, we shipped to them,
as a model demo of lightweightedness opportunity for agriculture irrigation.
Unroll the cell, connect to it a pump,
make sure the hose of the pump reaches a stream,
and let’s see if the water comes out.
Oh, it does.
You can transform irrigation of the field by providing solar powered -
easy to deploy on the back of a bicycle -
reach any field you wish power to run the irrigation as needed.
We can make these solar cells extremely light.
This version is as light as a feather.
It sits on top of a soap bubble in these images.
Now it’s so light and so thin that you would easily break it.
So we spent some time asking questions
on can you make things like this?
This is a solar cell.
It’s 120 times less weight than silicon,
per meter square.
You can’t tear it. It’s put on a cloth that’s about as thick as a human hair
and a cloth that doesn’t tear, kind of like the Tyvek envelopes
that you cannot open when you get them.
Same stuff.
This is the way to rethink what solar can be.
And here’s another one:
What if you don’t like the color of the solar cell I make?
Can I give you one that, indeed, looks like a piece of glass?
And the answer is yes.
Through uses of nanoscale,
we can engineer the absorptive molecules to be transparent.
You can look through this, connect if you wish to a voltmeter,
shine some sunlight on it,
and all the cells in series will generate 106 volts of open circuit voltage.
How do they work?
They don’t absorb visible light, that’s why you see through them,
but they do absorb other prevalently available light, the infrared light.
Their efficiency will never reach silicon,
but can reach about two thirds of that of silicon,
and they’ll be able to be deployed on any surface you wish.
Here it is, one version of that cell:
Connect a motor to it, make sure there is infrared light available,
and yes, you will generate electricity and transform the planet as we know it.
Thank you very much.
(Applause)