Transcriber: Midori Takagi Reviewer: Elisabeth Buffard
Tonight, I want to share with you a vision.
A vision to bring renewable solar energy into each one of your homes,
and to make Arizona an exporter of the same,
clean solar energy to the rest of the nation.
(Cheering and Applause)
So let’s start out by talking about solar.
So when I think about “solar”,
a picture kind of like this comes to mind.
The sun is shining, it’s a blue sky, maybe one cloud in the sky...
there’s even a sunflower.
It’s just a beautiful picture of renewable energy
and how clean that can be.
So let me show you another picture.
This is a map of the United States,
with Tucson and Phoenix kind of in that white circle right there.
And what you can see is that we’re in the very center
of the best solar resource in the country.
Right in the middle of that red-orange zone.
So let’s put these two things together.
We’ve got clean, solar power, and we’ve got the best solar resource.
So how come we don’t see solar
just sprouting up everywhere, all over the state?
Well, there are a couple of things that solar has to overcome.
In fact, there are three big hurdles.
The first one, is it has to be cheap.
Right now, installed solar is about 50 % to 66 % subsidized
by the government for every installation.
If you’re going to compete with coal and nuclear,
somehow you have to get beyond needing that subsidy.
Second, it’s got to be reliable.
When you build a coal or nuclear plant,
it lasts for 20 or 30 years,
in order to pay off the capital cost of building it.
Now, a solar plant is going to have to last just as long,
but it would be out in the desert, dealing with monsoons,
dealing with the hot Tucson summers for 20 years.
And that’s a real challenge.
Third, it has to be scalable.
If you take a look at this circle right here,
that’s about the area you would have to cover in Arizona
to power the whole US.
And if you think about solar panels right now,
that’s going to be a lot of solar panels.
So whatever solution you use, it has to be something
you can scale to real quantity,
really be able to make it mass produced
and make a real effect on the way we use power in this country.
So that brings me to the very basic problem of solar power:
that the sun is actually a very diffuse source of energy.
So let me give you an example.
If I were to go to a solar power plant
and stand right in the center of the solar power plant
for eight hours, twelve hours, the whole day,
at the end of the day I’ll probably have a sunburn, I might peel —
that might be the worst thing that happens.
If I were to go to the center of a coal or nuclear plant,
say , (Laughter)
I would last maybe a second before being incinerated,
and the difference there is that in those plants,
the energy is concentrated,
and it’s much easier to convert into electricity
when your energy source is concentrated.
So some of you may have already come up with a solution in your heads.
I’m sure many of you have done this before in the backyard.
The solution therefore is to concentrate the sun.
And I’m sure many of you have had that experience concentrating the sun
on dry leaves, unsuspecting insects?
(Laughter)
And with this concentrated energy,
it’s now much more easily converted into electricity.
So this is the kind of experiment you can do in your backyard.
But Roger Angel and the researchers at the University of Arizona
took this to the next level.
So they took a 10–foot–diameter mirror, or segments of a mirror,
and focused that much sunlight on a single point.
And instead of focusing on a dry leaf or an insect,
they chose a quarter–inch–thick plate of steel.
And this was the result.
Within about 10 seconds, there was a quarter–size hole in a plate of steel.
So that’s the power of concentrated energy.
So now that we’ve solved the problem of concentration,
now the problem is to convert that concentrated energy into electricity.
And we’re actually fortunate in the solar world
to have photovoltaic cells that are capable
of transforming sunlight directly into electricity
without any moving parts
and [are] highly reliable.
So you’ve probably seen these before:
this is a picture of some being installed on a roadway in Oregon —
you’ve seen them on rooftops,
you’ve seen them on parking garages,
things like that.
And now this is a great technology, but it’s fairly expensive right now.
And the reason that two thirds of the price
is in the solar cells is because sunlight is diffuse.
You have to cover a huge area with these expensive semiconductors,
which ends up making it pricey.
So let’s take the concept of concentration
and let’s take the photovoltaic cells,
and put them together.
Let’s imagine that you can concentrate the sun
1,000 times onto one of these cells.
You would immediately need only one thousandth the area of cell,
cutting the cost dramatically.
Now you’re right to say that these cells maybe can’t take a thousand times,
maybe we want to use more efficient cells
because we’re concentrating the light, etc, etc,
but at the end of the day, we see a 95 % reduction
in the cost of the cells with concentrating.
And that’s better than any of the sales I saw last Friday for Black Friday.
(Laughter)
So now that we’ve solved the PV problem,
the only thing left to do is to take these cells and this concentration,
put it in the ground and point it at the sun.
And follow the sun throughout the day to really maximize the energy we get.
So the other thing they looked at at the University
was how do we do that in an inexpensive way.
How do we do that cheaply, reliably, in a way that we can scale.
And they came up with the design that you’re also probably familiar with.
Something that moves,
something that can potentially track the sun,
something that’s really pretty inexpensive.
So the Ferris wheel, in fact, moves around,
carries pieces around the outside,
and can actually be disassembled in a day,
put on a truck and taken to the next carnival.
What a great solution.
So it’s actually a steel space frame,
and steel is cheap, steel is abundant,
and now we can support these concentrating mirrors
and do all of these solar things cheaply and effectively.
So let’s put all of these things together.
We’ve got the concentration, we’ve got the photovoltaics,
and we’ve got the space frame structure to hold it.
And let’s look at what the prototype looks like.
So some of you may recognize this — if you’re familiar with the university —
as being the pool behind Bear Down Gym,
that is actually no longer in use
but is now the Steward Observatory Solar Lab.
And this contraption actually
can carry eight different mirrors to concentrate the light,
and you can see where those will start to go,
and you can see a little bit of where the sun is being concentrated right now
on that spot making power.
So let me zoom in just a little bit,
and this is an example of four mirrors
focusing 2,000 Watts of sun energy on a ball lens
to distribute that over the photovoltaic cells.
And to give you an idea of scale,
this right now produces 500 Watts of electricity.
If you were to do that with solar panels that you have on your roof,
it would take about 4 ft by 4 ft — about two panels.
This much space. Pretty good area.
We were able to do that
with enough cells that can fit in the palms of your hands.
We use three square inches of solar material
at 1000x concentration to make that same amount of power.
And that’s where we think the real cost savings will come.
So looking forward,
this is what the final artist’s rendition
of one in a desert environment will look like.
It’s got eight parabolic mirrors, concentrating light at 1000x
onto individual photovoltaic receivers, at each of the focuses.
So to give you an idea of scale again,
if these were to supply even 1% of the power in the US,
it would take 500,000 of these units to do that.
Now it’s certainly not insurmountable, but it is certainly a challenge.
And if I can leave you with one final thought tonight,
I want you to imagine a future:
a future that’s free of smoke stacks,
it’s free of piles of coal outside our power plant,
it’s even free of coal power plants.
And replace that with fields of solar generators
that are using the power of the sun to make electricity,
and not only enough to provide energy for Arizona,
but enough to power the rest of the nation.
Thank you very much.
(Applause)