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PROFESSOR: Ladies and gentlemen,
thanks for coming today.

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00:00:29,220 --> 00:00:32,070
I'd like to formally start
the course, The Fundamentals

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00:00:32,070 --> 00:00:33,010
of Photovoltaics.

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That's 2.626/2.627.

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Why don't we dive quickly
into the syllabus,

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and then, a few slides of
motivation, why we're here, why

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we're studying photovoltaics.

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00:00:40,970 --> 00:00:43,380
Hopefully, get you
excited for the course.

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00:00:43,380 --> 00:00:45,440
The syllabus that
you have before you

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00:00:45,440 --> 00:00:47,700
should outline the course
objectives and the course

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00:00:47,700 --> 00:00:49,464
learning objectives.

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00:00:49,464 --> 00:00:51,630
At the end, during the
background assessment survey,

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00:00:51,630 --> 00:00:53,460
we'll take the last
10 minutes of class

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00:00:53,460 --> 00:00:55,810
for you to provide your
feedback to us, the teaching

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00:00:55,810 --> 00:00:58,600
staff, to make sure that
we're addressing your needs

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00:00:58,600 --> 00:01:00,160
and your interests.

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00:01:00,160 --> 00:01:04,730
So take a quick moment to read
over that while I describe

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00:01:04,730 --> 00:01:07,200
the overall flow of the course.

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00:01:07,200 --> 00:01:10,020
The course roadmap, this
little diagram right here,

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00:01:10,020 --> 00:01:12,290
is essentially a
three step component.

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00:01:12,290 --> 00:01:14,820
We first instill
the fundamentals

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00:01:14,820 --> 00:01:17,540
of how light is absorbed
into a material, how charge

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00:01:17,540 --> 00:01:19,612
is excited, how then
charge is separated

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and a voltage
created, and finally,

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00:01:21,070 --> 00:01:22,720
how a charge is collected.

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00:01:22,720 --> 00:01:25,700
And that is the essence
of a photovoltaic device.

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00:01:25,700 --> 00:01:28,690
In 30 years time,
photovoltaic devices

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00:01:28,690 --> 00:01:31,930
probably will still be
using that combination

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00:01:31,930 --> 00:01:33,360
of physical processes.

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00:01:33,360 --> 00:01:35,230
So understanding
these fundamentals

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00:01:35,230 --> 00:01:38,670
will arm you-- will give
you the information needed

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00:01:38,670 --> 00:01:41,250
to be able to assess any
photovoltaic technology that

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00:01:41,250 --> 00:01:43,490
might be presented to you.

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00:01:43,490 --> 00:01:46,300
Then, in the second
component of the course,

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00:01:46,300 --> 00:01:48,890
we'll discuss the technologies,
the specific technologies that

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00:01:48,890 --> 00:01:50,390
are out there in
the market today,

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00:01:50,390 --> 00:01:53,140
and those that are up and
coming that have the potential

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00:01:53,140 --> 00:01:54,470
to replace them.

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00:01:54,470 --> 00:01:56,330
And as a third
part of the course,

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00:01:56,330 --> 00:01:58,130
we'll be discussing
cross cutting themes.

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These include the policy,
economics, and social aspects

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00:02:02,130 --> 00:02:05,080
of photovoltaics that, of
course, are of general interest

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00:02:05,080 --> 00:02:07,740
and are particularly interesting
for scientists and engineers,

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who spend most of
their time thinking

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about the fundamentals, to
take a step back and look

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at the broader picture.

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A note on the fundamentals.

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I recognize that many of you
come from diverse backgrounds,

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some from nontechnical
backgrounds,

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00:02:20,390 --> 00:02:22,880
many from mechanical
engineering who never really

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have looked into semiconductors
or semiconductor devices.

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Not to worry, as you'll
see on page number-- page

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number 2, meeting times, class
recitation, and office hours.

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We provide a number of
opportunities for you

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to get more closely engaged
with us, the teaching staff,

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and to work through
some of the fundamentals

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as you might
experience difficulties

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in the learning process.

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Let's take a quick look
at the course schedule

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just to situate ourselves.

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So the course schedule
follows that three step

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process very closely.

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The first component of the
course, the first third,

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roughly, is focused
on the fundamentals.

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So we'll learn about light
absorption, charge excitation,

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charge separation,
and charge collection.

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And the recitation
times will be used

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to discuss those fundamentals
because, for many of you,

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this is the first time you're
working with this material.

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The second third of the
course, on PV technologies--

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when we discuss the industry
that's out there today,

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how it's evolving, how the
different technologies are

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evolving, this is when
we get to experience

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some of the industry pain
upfront, up close and personal.

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We'll be making solar cells.

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And as part of your take home
quiz number two-- as you'll

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notice, take home
quiz number two

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is distributed right
in the beginning

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of October-- middle of October.

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And then it's due in
the middle of November.

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So it's almost a month.

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And the reason it's
a month long take

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home quiz is because,
during the recitation times,

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we will be making
solar cells with you.

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00:03:54,620 --> 00:03:56,750
And it will be a little
bit of a challenge.

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It's not only to make the
most efficient solar cell,

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but the most cost
effective solar cell.

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And so we'll be making
technology choices

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as we go along, processing
our solar cells,

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00:04:06,180 --> 00:04:08,690
deciding whether we do
process A or process

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B. We'll be doing the
calculations that we learned

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how to do during the
fundamentals section

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00:04:12,668 --> 00:04:14,760
to predict what the
efficiency gains should be.

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And it will have
costs associated

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with each of the different
process steps as well.

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So it will be a little bit of
a game, a little competition

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within the group,
as well, to see

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who can make the most cost
effective solar cell in terms

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of dollars per
unit power output.

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And finally, in the last
third of the course,

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this is really when the
projects kick off in earnest.

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We have several really
interesting projects lined up

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as well as we're open to
hearing your own project ideas.

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This is when you form teams
of three, four, perhaps five,

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00:04:44,840 --> 00:04:47,190
but hopefully three or four.

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And you will be addressing some
of the most important questions

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00:04:50,740 --> 00:04:56,020
of the day, obviously, in a
very bound, well-defined way.

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And some of the projects
that we have lined up

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include looking at actual
photovoltaic installer

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data coming from houses
with temporal resolution

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00:05:06,180 --> 00:05:07,600
on the order of five minutes.

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00:05:07,600 --> 00:05:09,450
So you can obtain
a huge database

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of maybe 10,000, 15,000 homes
distributed geographically,

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and determine to what
degree is the ensemble

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00:05:15,670 --> 00:05:17,730
of photovoltaic
systems predictable.

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Obviously, if a cloud
goes over one home,

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power output drops
pretty dramatically.

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But if you begin averaging over
several homes, how predictable

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is the solar power
output of that ensemble?

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And that's going to be very
important as photovoltaics

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00:05:29,380 --> 00:05:33,430
scales up and assumes a greater
percentage of the total grid.

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Another interesting
project we have lined up

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is with the World Bank.

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This is with folks
in Washington DC who

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are looking into a project
called Lighting Africa.

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00:05:41,230 --> 00:05:44,000
And they're installing
PV on small little lights

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and distributing those to
folks in sub-Saharan Africa.

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And their big question
to the MIT audience

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is, with some of the newer
up and coming technologies

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00:05:52,110 --> 00:05:55,180
out there, how will this
impact their technology?

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00:05:55,180 --> 00:05:57,030
How will this impact
their lighting?

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00:05:57,030 --> 00:05:58,420
And so the
deliverable at the end

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00:05:58,420 --> 00:06:01,270
will be a technology
perspectus-- one page.

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00:06:01,270 --> 00:06:02,970
A lot of thought
has to go into it.

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That will be
delivered to companies

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00:06:04,970 --> 00:06:07,369
that will be selling their
products in Africa to guide

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00:06:07,369 --> 00:06:09,660
them and to inform them about
some of the up and coming

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00:06:09,660 --> 00:06:12,190
technologies and how their
markets will be impacted.

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00:06:12,190 --> 00:06:14,359
Like those two projects,
we have several others.

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And we're open to
your ideas as well.

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So if you're really jazzed
about one particular topic,

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there will be opportunities
to let us know, specifically

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on homework number
2, when there will

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be a specific question
there, are you

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00:06:25,270 --> 00:06:27,350
interested in a particular
topic of your own.

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We'll assemble-- begin
creating teams early on so

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that there's some bonding going
on, especially during the cell

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00:06:31,975 --> 00:06:34,450
fabrication part during the
second third of the course

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00:06:34,450 --> 00:06:37,190
when we make the
actual solar cells.

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But then, the third
part of the course

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will be really focusing on
the class projects themselves.

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So that's the lay of the land.

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And I want to give you some
motivation as to why we're here

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and why this is
really a special time

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00:06:49,620 --> 00:06:52,210
in the field of photovoltaics.

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This is not your parents'
solar energy anymore.

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Things have changed quite a bit.

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And hopefully, over the
course of these slides,

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I'll be able to convey that
message loud and clear.

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We'll go ahead and get started.

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So first question is why
photovoltaics, or why solar.

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Photovoltaics is one particular
embodiment of solar energy

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00:07:12,320 --> 00:07:15,320
where we convert sunlight
into electricity.

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And in most
photovoltaic panels--

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I'll definitely let you guys
come up and have a look at it

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afterwards.

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In most photovoltaic
panels, you have two leads

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coming out, basically,
the equivalent

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of a positive and a negative.

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00:07:26,774 --> 00:07:28,190
And you have a
bunch of cells here

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that are converting the
sunlight into electricity.

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It's different than, let's
say, solar thermal, which

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is converting
sunlight into heat,

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or solar to fuels, which
is converting sunlight

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into chemical energy.

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And the reason we're
studying photovoltaics

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as a starting point is
because PV, photovoltaics-- PV

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00:07:46,180 --> 00:07:49,870
for short-- is the most
widespread technology,

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00:07:49,870 --> 00:07:53,120
widespread solar conversion
technology out there today.

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So the big question is
why solar in general.

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Why are we at all
interested in this?

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Can anybody tell me what
this is a picture of?

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00:08:02,170 --> 00:08:04,971
It's obviously not
from the United States.

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00:08:04,971 --> 00:08:06,970
Does anybody recognize
the language here written

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00:08:06,970 --> 00:08:08,005
on the side of the boat?

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00:08:08,005 --> 00:08:09,640
It's very small.

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00:08:09,640 --> 00:08:10,905
[SPEAKING PORTUGUESE]

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00:08:10,905 --> 00:08:11,780
AUDIENCE: Portuguese.

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PROFESSOR: It's Portuguese.

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It's from Brazil.

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It's form the
northeast of Brazil.

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It's a small island
called Morro de Sao Paulo.

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00:08:18,500 --> 00:08:22,040
It's located about an hour
south of Salvador in Bahia.

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00:08:22,040 --> 00:08:26,590
These are folks arriving at
the island with gas cylinders.

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00:08:26,590 --> 00:08:28,970
There is no underwater
cable linking the island

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with the mainland.

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So they're arriving by
boat with gas cylinders.

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They're tossing them
into the salt water.

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They're pushing
them onto the beach,

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00:08:37,419 --> 00:08:38,990
rolling them on the
beach, until they

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00:08:38,990 --> 00:08:42,490
get to the little sandy
roads-- of course,

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00:08:42,490 --> 00:08:45,390
getting grains of sand
embedded inside of the nozzle

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and so forth.

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This illustrates to
me the great risks

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that we go through to supply
ourselves with energy.

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00:08:52,910 --> 00:08:55,830
It's just one, what might
be considered by our safety

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00:08:55,830 --> 00:08:59,990
standards here, extreme
example of associated risk

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00:08:59,990 --> 00:09:03,170
with supplying of energy
and effort, of course.

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00:09:03,170 --> 00:09:06,020
But if you look at our energy
supply to the United States,

217
00:09:06,020 --> 00:09:08,260
it's no less heroic.

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00:09:08,260 --> 00:09:09,862
It just has
different dimensions.

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00:09:09,862 --> 00:09:11,320
And so the energy
that we use today

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00:09:11,320 --> 00:09:13,444
is often produced in some
faraway land, not always,

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00:09:13,444 --> 00:09:16,220
but often, transported,
sometimes over thousands

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00:09:16,220 --> 00:09:19,960
of miles, and brought home at
significant risk and peril.

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00:09:19,960 --> 00:09:22,470
And the question is, why
do we go to such extremes.

224
00:09:22,470 --> 00:09:24,887
And second question is,
is there a better way.

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00:09:24,887 --> 00:09:26,470
So to answer the
first question, here,

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00:09:26,470 --> 00:09:30,920
why we go to such extremes, if
you look at the world at night,

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00:09:30,920 --> 00:09:33,470
and then look at our human
development map, which

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00:09:33,470 --> 00:09:36,790
I use Facebook-- what better
indicator of human development

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is there than Facebook?

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This map right here shows
you the number of linkages

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between people on Facebook.

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And of course, the density
of the bright lights

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00:09:45,590 --> 00:09:47,480
there is representing
the number of users.

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And you can see that the
two maps, the electricity

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00:09:50,140 --> 00:09:54,510
consumption and the
technology adoption

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00:09:54,510 --> 00:09:56,950
map very closely,
one on to another.

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00:09:56,950 --> 00:09:59,236
And it's almost down
to the specific region

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00:09:59,236 --> 00:10:00,360
once in a specific country.

239
00:10:00,360 --> 00:10:03,730
This is especially noticeable
in some of the developing world

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00:10:03,730 --> 00:10:08,100
where you see these pockets of
high concentration of people,

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00:10:08,100 --> 00:10:09,980
essentially capital cities.

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00:10:09,980 --> 00:10:14,090
You have Lagos, Nairobi,
and so forth-- Jakarta.

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00:10:14,090 --> 00:10:15,640
And you have this
huge concentration

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00:10:15,640 --> 00:10:19,270
of people that, of course,
are using electricity.

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00:10:19,270 --> 00:10:21,882
And more and more people
flock to those cities,

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00:10:21,882 --> 00:10:23,340
especially in
developing countries,

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00:10:23,340 --> 00:10:25,830
because the standard of
living tends to be higher.

248
00:10:25,830 --> 00:10:30,030
There is a certain indicator,
called Human Development Index,

249
00:10:30,030 --> 00:10:32,402
that was put together
by the World Bank, which

250
00:10:32,402 --> 00:10:33,860
pulls together a
number of factors,

251
00:10:33,860 --> 00:10:38,260
including expectation of
life, infant mortality, and so

252
00:10:38,260 --> 00:10:40,240
forth-- education levels.

253
00:10:40,240 --> 00:10:42,990
So in some hand
wavy way, comes up

254
00:10:42,990 --> 00:10:46,580
with a metric that indicates
quality of life, roughly.

255
00:10:46,580 --> 00:10:50,300
And on the x-axis here, we have
annual per capita electricity

256
00:10:50,300 --> 00:10:52,960
use-- not energy, but
electricity specifically.

257
00:10:52,960 --> 00:10:56,062
And we see some form of
correlation between the two.

258
00:10:56,062 --> 00:10:57,770
So one could naturally
conclude from this

259
00:10:57,770 --> 00:11:01,540
that energy is
fueling development,

260
00:11:01,540 --> 00:11:06,110
and energy is also fueling per
capita income, as a result.

261
00:11:06,110 --> 00:11:09,660
This little bubble chart
hear, courtesy of UC Berkeley,

262
00:11:09,660 --> 00:11:12,570
is showing you the size
of the bubble here,

263
00:11:12,570 --> 00:11:15,470
indicating the size of the
population, and of course,

264
00:11:15,470 --> 00:11:17,060
the position on this
graph indicating

265
00:11:17,060 --> 00:11:21,010
the per capita energy use
and per capita income.

266
00:11:21,010 --> 00:11:26,520
The reality is that many of the
up incoming energy consumers

267
00:11:26,520 --> 00:11:29,260
aren't quite there yet in
terms of their energy use.

268
00:11:29,260 --> 00:11:32,160
There will be a drastically
increasing demand

269
00:11:32,160 --> 00:11:35,710
as several regions
of the world turn on

270
00:11:35,710 --> 00:11:38,940
as they begin plugging in and
demanding more electricity.

271
00:11:38,940 --> 00:11:42,880
So somehow we have to
satisfy that growing demand.

272
00:11:42,880 --> 00:11:44,950
So to put things in
perspective as well,

273
00:11:44,950 --> 00:11:47,560
here we have the world
somewhat at night.

274
00:11:47,560 --> 00:11:50,730
World population in millions.

275
00:11:50,730 --> 00:11:54,380
And so we have somewhere around
10 billion approaching by 2050.

276
00:11:54,380 --> 00:11:56,380
And you can see that the
majority of the growth,

277
00:11:56,380 --> 00:11:59,620
what's driving world
population, is Asia and Africa.

278
00:11:59,620 --> 00:12:01,400
Those are the two lines.

279
00:12:01,400 --> 00:12:02,830
My apologies for the small text.

280
00:12:02,830 --> 00:12:04,550
But that's the yellow
line right here.

281
00:12:04,550 --> 00:12:06,770
And the black line right here.

282
00:12:06,770 --> 00:12:10,020
They're the two largest
bars in that Pareto chart.

283
00:12:10,020 --> 00:12:12,180
And the projected
human energy use

284
00:12:12,180 --> 00:12:15,880
is only going to
go up as a result.

285
00:12:15,880 --> 00:12:19,809
So again, we look at
the world at night.

286
00:12:19,809 --> 00:12:21,600
Now instead of looking
at the bright areas,

287
00:12:21,600 --> 00:12:23,900
we're going to focus on
the dark areas instead.

288
00:12:23,900 --> 00:12:26,275
The regions of the world where
we do have high population

289
00:12:26,275 --> 00:12:29,100
densities-- some of the regions,
not the deserts, obviously.

290
00:12:29,100 --> 00:12:31,680
Some of the regions we do have
high population densities,

291
00:12:31,680 --> 00:12:34,180
like sub-Saharan Africa,
but don't have a whole lot

292
00:12:34,180 --> 00:12:36,290
of electricity use right now.

293
00:12:36,290 --> 00:12:40,150
Then we'll take another map,
which is the solar resource.

294
00:12:40,150 --> 00:12:41,740
Again here, the
red is indicating

295
00:12:41,740 --> 00:12:43,170
a lot of solar resource.

296
00:12:43,170 --> 00:12:46,430
And the blue is
indicating not so much.

297
00:12:46,430 --> 00:12:48,610
But still, it's pretty
amazing that the entire world

298
00:12:48,610 --> 00:12:50,290
is falling within
about a factor of two,

299
00:12:50,290 --> 00:12:52,010
maybe a factor of three.

300
00:12:52,010 --> 00:12:54,040
So even if you
compare Scandinavia

301
00:12:54,040 --> 00:12:58,400
against-- let's say,
Scandinavia against Kenya,

302
00:12:58,400 --> 00:13:01,910
you're still looking at about a
variation of a factor of three,

303
00:13:01,910 --> 00:13:03,310
right?

304
00:13:03,310 --> 00:13:05,140
So the solar resource
is pretty well

305
00:13:05,140 --> 00:13:07,069
matched with the regions
of the world that

306
00:13:07,069 --> 00:13:09,360
don't have electricity right
now, where the demand will

307
00:13:09,360 --> 00:13:10,730
be coming online.

308
00:13:10,730 --> 00:13:13,410
And to put that into
another nice chart,

309
00:13:13,410 --> 00:13:15,480
I don't think this
is very common yet.

310
00:13:15,480 --> 00:13:18,260
You've seen the HDI
versus per capita income.

311
00:13:18,260 --> 00:13:21,530
But this is HDI
versus insulation,

312
00:13:21,530 --> 00:13:25,180
showing that those regions of
the world that are ranked lower

313
00:13:25,180 --> 00:13:28,410
on the HDI scale are
precisely those regions that

314
00:13:28,410 --> 00:13:31,570
have higher insulation,
that have greater

315
00:13:31,570 --> 00:13:34,740
access to that solar resource.

316
00:13:34,740 --> 00:13:37,370
Now the big question is, is
that solar resource big enough

317
00:13:37,370 --> 00:13:40,530
to supply necessary
energy needs.

318
00:13:40,530 --> 00:13:44,480
And this is a quick intro to
next lecture, where we discuss

319
00:13:44,480 --> 00:13:46,260
the solar resource in detail.

320
00:13:46,260 --> 00:13:48,390
But the short answer
is absolutely,

321
00:13:48,390 --> 00:13:50,070
yes, by orders of magnitude.

322
00:13:50,070 --> 00:13:52,150
The volumes of these
cubes represent

323
00:13:52,150 --> 00:13:55,980
the volume of either energy
resource or energy need.

324
00:13:55,980 --> 00:13:58,190
Energy need here,
on the far right--

325
00:13:58,190 --> 00:14:01,980
that little blue cube
represents the human energy use.

326
00:14:01,980 --> 00:14:05,920
Some are very small compared
to the solar resource

327
00:14:05,920 --> 00:14:07,060
on the Earth's surface.

328
00:14:07,060 --> 00:14:09,547
This obviously is including
the ocean as well.

329
00:14:09,547 --> 00:14:11,880
If we're to be realistic,
instead of calling this planet

330
00:14:11,880 --> 00:14:14,110
Earth, we should probably
call it ocean or water

331
00:14:14,110 --> 00:14:17,100
since oceans do
comprise about 2/3.

332
00:14:17,100 --> 00:14:21,820
But even if we discount
this for usable land area,

333
00:14:21,820 --> 00:14:23,700
we're still an
order of magnitude

334
00:14:23,700 --> 00:14:25,200
greater than total
human energy use.

335
00:14:25,200 --> 00:14:26,920
So the resource base is there.

336
00:14:26,920 --> 00:14:27,770
It's available.

337
00:14:27,770 --> 00:14:30,020
It's up to us to figure
out how to use it, up to us

338
00:14:30,020 --> 00:14:32,540
scientists and engineers.

339
00:14:32,540 --> 00:14:34,630
So the potential
for solar energy

340
00:14:34,630 --> 00:14:36,740
is represented on this chart.

341
00:14:36,740 --> 00:14:38,166
I'm not a huge
fan of this chart,

342
00:14:38,166 --> 00:14:39,760
and I'll explain
why in a minute.

343
00:14:39,760 --> 00:14:41,990
But there is something very
valuable to be taken away

344
00:14:41,990 --> 00:14:42,489
from here.

345
00:14:42,489 --> 00:14:46,660
These black dots, one, two,
three, four, five, six,

346
00:14:46,660 --> 00:14:49,550
represent around 18
terawatt equivalent,

347
00:14:49,550 --> 00:14:52,850
which is total human energy
use in a few years time.

348
00:14:52,850 --> 00:14:56,571
And you can see the total land
area there is not astronomical.

349
00:14:56,571 --> 00:14:58,320
The reason I don't
like this chart so much

350
00:14:58,320 --> 00:15:01,902
is because we're not going to
cover up vast swaths of Nevada,

351
00:15:01,902 --> 00:15:03,860
for instance, with solar
panels for the benefit

352
00:15:03,860 --> 00:15:05,160
of the rest of the country.

353
00:15:05,160 --> 00:15:08,260
We're going to distribute those
solar panels over larger areas.

354
00:15:08,260 --> 00:15:10,210
But this is just meant
to emphasize the point

355
00:15:10,210 --> 00:15:13,610
that the land area usage
does work out in our favor.

356
00:15:13,610 --> 00:15:15,880
So the way we distribute
solar panels typically

357
00:15:15,880 --> 00:15:19,560
is either on residential
installations, like this one,

358
00:15:19,560 --> 00:15:21,600
or in large field installations.

359
00:15:21,600 --> 00:15:24,400
This one, the Sarnia
Solar Farm in Ontario

360
00:15:24,400 --> 00:15:28,440
is currently the largest
solar farm in the world.

361
00:15:28,440 --> 00:15:32,090
We call it a solar farm because
it's just a massive land

362
00:15:32,090 --> 00:15:34,330
area comprised of solar panels.

363
00:15:34,330 --> 00:15:37,300
This is the covering half
of Nevada scenario, right?

364
00:15:37,300 --> 00:15:39,450
This here on the left hand
side, on the other hand,

365
00:15:39,450 --> 00:15:42,030
is a residential neighborhood
in California indicating

366
00:15:42,030 --> 00:15:43,970
the more distributed variety.

367
00:15:43,970 --> 00:15:48,350
And both have their distinct
strengths and weaknesses.

368
00:15:48,350 --> 00:15:52,680
So solar isn't about those
small, little, rinky dinky,

369
00:15:52,680 --> 00:15:54,640
20 or 30 watt panels
that are sitting

370
00:15:54,640 --> 00:15:56,260
on a remote thatched hut.

371
00:15:56,260 --> 00:16:00,330
Solar is really growing up to
be a grid tied, grid integrated,

372
00:16:00,330 --> 00:16:04,260
renewable energy source that
is now probably skirting a $100

373
00:16:04,260 --> 00:16:06,360
billion industry worldwide.

374
00:16:06,360 --> 00:16:09,020
So it's growing up, and
certainly professionalizing

375
00:16:09,020 --> 00:16:11,220
quite a bit.

376
00:16:11,220 --> 00:16:12,440
Historical perspective.

377
00:16:12,440 --> 00:16:15,959
It's time to take a
look back and trace

378
00:16:15,959 --> 00:16:18,500
through some of the technical
history of how solar cells came

379
00:16:18,500 --> 00:16:19,380
into being.

380
00:16:19,380 --> 00:16:22,310
And that really
will inform why it

381
00:16:22,310 --> 00:16:25,830
is we're at where we are today,
why the industry has some

382
00:16:25,830 --> 00:16:28,880
of the biases it
has today, and what

383
00:16:28,880 --> 00:16:31,580
are some of the
intangible barriers that

384
00:16:31,580 --> 00:16:33,940
could be needed to
be overcome if we are

385
00:16:33,940 --> 00:16:36,390
to develop new technologies.

386
00:16:36,390 --> 00:16:38,890
So aside from just
general knowledge

387
00:16:38,890 --> 00:16:41,800
and general edification, this
has an important technical

388
00:16:41,800 --> 00:16:43,310
aspect as well.

389
00:16:43,310 --> 00:16:45,540
So historical perspective.

390
00:16:45,540 --> 00:16:48,400
We credit the discovery
of the photovoltaic

391
00:16:48,400 --> 00:16:52,925
to this gentleman here,
Edmond Becquerel, shown here

392
00:16:52,925 --> 00:16:55,020
in his more mature years.

393
00:16:55,020 --> 00:16:59,730
When he wrote this
article, right here-- I'll

394
00:16:59,730 --> 00:17:02,820
probably butcher it, but it's
"sur les effets electriques

395
00:17:02,820 --> 00:17:05,990
produit sous l'influence
des rayons solaires."

396
00:17:05,990 --> 00:17:08,550
Basically, the
electrical effects

397
00:17:08,550 --> 00:17:11,260
produced by the
influence of solar rays

398
00:17:11,260 --> 00:17:14,380
on a contraption that
looked very similar to this.

399
00:17:14,380 --> 00:17:16,205
He noticed a current
flowing, essentially

400
00:17:16,205 --> 00:17:20,540
a photovoltaic, a photon
induced, a light induced effect

401
00:17:20,540 --> 00:17:21,410
current.

402
00:17:21,410 --> 00:17:25,310
And he was very smart to
decouple the effect of heat

403
00:17:25,310 --> 00:17:26,220
from the light.

404
00:17:26,220 --> 00:17:29,350
So his experiment
involved selective filters

405
00:17:29,350 --> 00:17:32,420
that prevented massive amounts
of heat from getting through.

406
00:17:32,420 --> 00:17:35,230
And he essentially produced
what is a spectral response.

407
00:17:35,230 --> 00:17:38,860
Varying the filter color,
he was able to trace out

408
00:17:38,860 --> 00:17:42,750
the response of this
apparatus to the solar light

409
00:17:42,750 --> 00:17:44,362
as a function of wavelength.

410
00:17:44,362 --> 00:17:45,570
This was a clever experiment.

411
00:17:45,570 --> 00:17:46,350
He wrote it up.

412
00:17:46,350 --> 00:17:48,000
It's more of an
electrochemical device

413
00:17:48,000 --> 00:17:50,380
rather than the solid
state photovoltaic device,

414
00:17:50,380 --> 00:17:51,590
like the one we know now.

415
00:17:51,590 --> 00:17:54,410
But nevertheless, it
earned him the credit

416
00:17:54,410 --> 00:17:57,160
of being the discoverer of
the photovoltaic effect.

417
00:17:57,160 --> 00:18:01,640
Does anybody happen to know
how old he was in 1839,

418
00:18:01,640 --> 00:18:06,325
when he discovered this or
when he published this work?

419
00:18:06,325 --> 00:18:07,450
It's a rather nice article.

420
00:18:07,450 --> 00:18:09,750
Very eloquent, very detailed.

421
00:18:09,750 --> 00:18:12,070
He was 19.

422
00:18:12,070 --> 00:18:13,760
He was born in 1820.

423
00:18:13,760 --> 00:18:15,750
Anyway, small aside.

424
00:18:15,750 --> 00:18:18,760
The field evolved
from 1839, when

425
00:18:18,760 --> 00:18:20,930
that first article came out.

426
00:18:20,930 --> 00:18:24,290
Folks began refining
and-- well, first of all,

427
00:18:24,290 --> 00:18:26,820
discovering new elements during
that period in the 1800s,

428
00:18:26,820 --> 00:18:29,320
refining them and then
testing their properties.

429
00:18:29,320 --> 00:18:31,529
And this was before
we really understood

430
00:18:31,529 --> 00:18:32,570
what semiconductors were.

431
00:18:32,570 --> 00:18:35,440
They were a little bit of
a black box, a big mystery.

432
00:18:35,440 --> 00:18:37,360
Their physical,
electrical properties

433
00:18:37,360 --> 00:18:38,950
were all over the map.

434
00:18:38,950 --> 00:18:43,410
We'll explain why over the
course of the next 10 lectures.

435
00:18:43,410 --> 00:18:45,100
And they began refining
these materials

436
00:18:45,100 --> 00:18:47,890
and putting them in various
contraptions testing them

437
00:18:47,890 --> 00:18:48,630
with light.

438
00:18:48,630 --> 00:18:51,005
And lo and behold, they would
get the photovoltaic effect

439
00:18:51,005 --> 00:18:53,720
again, maybe photoelectric
effect first, and then,

440
00:18:53,720 --> 00:18:55,390
the photovoltaic
effect, finally,

441
00:18:55,390 --> 00:18:57,790
when they set up the
experiment properly.

442
00:18:57,790 --> 00:19:01,310
And selenium was a popular
material at the beginning.

443
00:19:01,310 --> 00:19:03,520
So was cuprous oxide, Cu2O.

444
00:19:03,520 --> 00:19:05,970
That was a very common material.

445
00:19:05,970 --> 00:19:07,510
And I love pointing this out.

446
00:19:07,510 --> 00:19:10,000
This is a little
contraption, a vice.

447
00:19:10,000 --> 00:19:12,680
To hold the contact
onto the device.

448
00:19:12,680 --> 00:19:15,010
And as Joe can tell you,
contacting a solar cell

449
00:19:15,010 --> 00:19:16,940
is not the easiest
thing in the world.

450
00:19:16,940 --> 00:19:20,850
So it's a pretty funny
picture, especially

451
00:19:20,850 --> 00:19:23,290
in light of our current
difficulties in 2011

452
00:19:23,290 --> 00:19:25,350
on resolving some contact
issues, especially

453
00:19:25,350 --> 00:19:26,500
with new materials.

454
00:19:26,500 --> 00:19:29,410
But that gives you a little bit
of a historical perspective.

455
00:19:29,410 --> 00:19:31,960
And the references are there.

456
00:19:31,960 --> 00:19:35,900
In 1954, the first
embodiment of what

457
00:19:35,900 --> 00:19:38,840
we consider the modern
solar cell came into being.

458
00:19:38,840 --> 00:19:43,545
This was driven by the
purification, crystallisation,

459
00:19:43,545 --> 00:19:47,510
and growth of silicon, which
is the second most abundant

460
00:19:47,510 --> 00:19:49,050
element on the Earth's crust.

461
00:19:49,050 --> 00:19:50,920
It was noted to be
superior to germanium

462
00:19:50,920 --> 00:19:55,525
for electronic devices because
of its larger band gap,

463
00:19:55,525 --> 00:19:56,430
less leakage current.

464
00:19:56,430 --> 00:19:58,250
We'll get to that
in a few lectures.

465
00:19:58,250 --> 00:19:59,700
It had superior properties.

466
00:19:59,700 --> 00:20:04,690
And it was engineered into,
I would say, the first

467
00:20:04,690 --> 00:20:07,390
what we call a, homojunction
p-n junction based solar cell

468
00:20:07,390 --> 00:20:10,770
device in Bell Labs by
those three gentleman there,

469
00:20:10,770 --> 00:20:12,040
on the upper left.

470
00:20:12,040 --> 00:20:14,320
And in 1954, the paper
came out in the Journal

471
00:20:14,320 --> 00:20:15,670
of Applied Physics.

472
00:20:15,670 --> 00:20:18,990
And that really spurred a
lot of interest in the field.

473
00:20:18,990 --> 00:20:19,720
Why?

474
00:20:19,720 --> 00:20:22,330
Because 6% efficiency
was about a factor

475
00:20:22,330 --> 00:20:25,730
15 higher than anything
that had come before it.

476
00:20:25,730 --> 00:20:28,990
And now, people could see the
potential of this technology

477
00:20:28,990 --> 00:20:31,930
to drive things.

478
00:20:31,930 --> 00:20:34,752
At the time, within a few
years, within a decade or so,

479
00:20:34,752 --> 00:20:37,210
folks were more interested in
sending satellites into space

480
00:20:37,210 --> 00:20:39,660
than they were, perhaps,
powering terrestrial objects.

481
00:20:39,660 --> 00:20:41,530
But we'll get to
that in a second.

482
00:20:41,530 --> 00:20:43,380
But some of the
first examples here,

483
00:20:43,380 --> 00:20:46,180
in Bell Labs in
New Jersey-- they

484
00:20:46,180 --> 00:20:48,490
had a small little
radio communicating

485
00:20:48,490 --> 00:20:50,440
with this little
device, over here.

486
00:20:50,440 --> 00:20:54,810
And the solar cell was
powering the gadget.

487
00:20:54,810 --> 00:20:57,730
And it's interesting
to note here,

488
00:20:57,730 --> 00:21:01,120
the New York Times
article from that time,

489
00:21:01,120 --> 00:21:03,060
"with this modern version
of Apollo's Chariot,

490
00:21:03,060 --> 00:21:04,480
the Bell scientists
have harnessed

491
00:21:04,480 --> 00:21:05,854
enough of the
sun's rays to power

492
00:21:05,854 --> 00:21:08,590
the transmission of voices
over telephone wires."

493
00:21:08,590 --> 00:21:12,670
And they speculate that
at some point-- obviously

494
00:21:12,670 --> 00:21:14,860
this was written
in the 1950s, keep

495
00:21:14,860 --> 00:21:16,699
that social context in mind.

496
00:21:16,699 --> 00:21:18,740
"But eventually leading
to the realization of one

497
00:21:18,740 --> 00:21:20,237
of mankind's most
cherished dreams,

498
00:21:20,237 --> 00:21:21,820
the harnessing of
the almost limitless

499
00:21:21,820 --> 00:21:24,230
energy of the sun for the
uses of civilization."

500
00:21:24,230 --> 00:21:25,910
They saw the opportunity there.

501
00:21:25,910 --> 00:21:27,672
It was not lost to them.

502
00:21:27,672 --> 00:21:29,130
But of course, a
lot of development

503
00:21:29,130 --> 00:21:30,840
had to come under the bridge.

504
00:21:30,840 --> 00:21:32,548
A lot of water had to
go under the bridge

505
00:21:32,548 --> 00:21:34,550
before they were able to
make solar really cost

506
00:21:34,550 --> 00:21:39,520
effective from 1954 at
almost 60 years later.

507
00:21:39,520 --> 00:21:41,310
The way that basic
solar cell device

508
00:21:41,310 --> 00:21:44,530
worked-- I'm going to introduce
you to the full picture now.

509
00:21:44,530 --> 00:21:46,730
And I will begin dissecting
it piece by piece,

510
00:21:46,730 --> 00:21:48,480
over the next lectures,
so that we really

511
00:21:48,480 --> 00:21:51,112
understand each component
of how the solar cell works.

512
00:21:51,112 --> 00:21:52,820
And we'll put it all
back together again.

513
00:21:52,820 --> 00:21:54,680
We'll actually
make it, literally.

514
00:21:54,680 --> 00:21:56,305
So the sunlight comes
into this device.

515
00:21:56,305 --> 00:21:58,810
This is a cross section
of a solar cell device.

516
00:21:58,810 --> 00:22:02,160
And today's modern solar
cells are about four times

517
00:22:02,160 --> 00:22:04,590
the thickness of your hair.

518
00:22:04,590 --> 00:22:07,190
So if you can imagine
200 microns in thickness,

519
00:22:07,190 --> 00:22:09,580
that's the thickness
here, the cross section

520
00:22:09,580 --> 00:22:11,950
of this solar cell device.

521
00:22:11,950 --> 00:22:14,770
Light comes inside,
excites bound charge,

522
00:22:14,770 --> 00:22:17,610
and makes it mobile, so it
can move around the material.

523
00:22:17,610 --> 00:22:19,750
There's a built
in electric field,

524
00:22:19,750 --> 00:22:23,120
which serves to separate that
charge and create the voltage.

525
00:22:23,120 --> 00:22:25,420
And so one of the
charges goes here.

526
00:22:25,420 --> 00:22:27,222
The other charge
goes to the back.

527
00:22:27,222 --> 00:22:29,180
So you have a voltage or
a potential difference

528
00:22:29,180 --> 00:22:31,685
across these two terminals,
across the front terminal

529
00:22:31,685 --> 00:22:33,402
and across the back one.

530
00:22:33,402 --> 00:22:35,610
And then, if they're connected
by an external circuit

531
00:22:35,610 --> 00:22:37,340
to an external
load, current will

532
00:22:37,340 --> 00:22:40,850
flow through that external
load to complete the circuit.

533
00:22:40,850 --> 00:22:45,810
And that's essentially how
the solar cell device works.

534
00:22:45,810 --> 00:22:48,900
So three basic steps,
there's charge generation.

535
00:22:48,900 --> 00:22:52,069
So light is exciting
charge within the material.

536
00:22:52,069 --> 00:22:54,360
The second important step,
up there in the upper right,

537
00:22:54,360 --> 00:22:55,727
is charge separation.

538
00:22:55,727 --> 00:22:57,560
Somehow, you have to
induce a voltage inside

539
00:22:57,560 --> 00:22:59,096
of your material.

540
00:22:59,096 --> 00:23:00,470
And the third very
important step

541
00:23:00,470 --> 00:23:03,530
is somehow you have to collect
the charge coming out of it.

542
00:23:03,530 --> 00:23:05,600
That's why those folks
in the earlier days

543
00:23:05,600 --> 00:23:07,470
had that big vice over here.

544
00:23:07,470 --> 00:23:09,164
They were trying
to really make sure

545
00:23:09,164 --> 00:23:11,330
that the metal was in good
contact with the material

546
00:23:11,330 --> 00:23:14,010
so they could
extract the charge.

547
00:23:14,010 --> 00:23:16,860
And so that's essentially it.

548
00:23:16,860 --> 00:23:18,600
The advantages of a
solar cell devices

549
00:23:18,600 --> 00:23:21,850
is that there are no moving
parts and no pollution created

550
00:23:21,850 --> 00:23:23,480
at the site of use.

551
00:23:23,480 --> 00:23:25,640
There is, obviously,
the manufacturing

552
00:23:25,640 --> 00:23:27,200
of the module itself.

553
00:23:27,200 --> 00:23:29,250
And we'll get into
detail about that,

554
00:23:29,250 --> 00:23:31,140
and begin quantifying
the amount of energy,

555
00:23:31,140 --> 00:23:34,140
the cost to manufacture it.

556
00:23:34,140 --> 00:23:37,150
Bottom line is that the CO2
production per unit energy

557
00:23:37,150 --> 00:23:41,350
output from the solar panel is
on the order of 10 times less

558
00:23:41,350 --> 00:23:43,930
than coal, 5 times
less natural gas,

559
00:23:43,930 --> 00:23:46,630
so significantly less
than fossil fuel.

560
00:23:46,630 --> 00:23:49,790
It is not a zero energy system.

561
00:23:49,790 --> 00:23:53,060
The reason why the majority--
where the majority of that CO2

562
00:23:53,060 --> 00:23:54,890
comes from is
actually the energy

563
00:23:54,890 --> 00:23:56,830
used to produce the solar panel.

564
00:23:56,830 --> 00:23:59,600
So as we transition
to solar panels made

565
00:23:59,600 --> 00:24:03,200
from other solar panels, as
the solar industry ramps up,

566
00:24:03,200 --> 00:24:05,700
obviously the carbon intensity
of producing the solar panels

567
00:24:05,700 --> 00:24:07,270
will go down, as well.

568
00:24:07,270 --> 00:24:09,354
Likewise, it matters where
you produce the panels.

569
00:24:09,354 --> 00:24:11,186
There's some active
research going on at MIT

570
00:24:11,186 --> 00:24:12,630
to decide where
in the world it's

571
00:24:12,630 --> 00:24:14,620
optimal to produce
the solar panels

572
00:24:14,620 --> 00:24:18,830
and where it's optimal
to actually install them.

573
00:24:18,830 --> 00:24:23,180
The disadvantages,
which really embody

574
00:24:23,180 --> 00:24:25,950
why we haven't seen a mass
of adoption of solar to date

575
00:24:25,950 --> 00:24:29,870
and why there are technical and
nontechnical challenges for you

576
00:24:29,870 --> 00:24:32,170
here to resolve
is because there's

577
00:24:32,170 --> 00:24:33,212
no power output at night.

578
00:24:33,212 --> 00:24:35,003
In other words, when
the sun's not shining,

579
00:24:35,003 --> 00:24:36,420
it's not producing electricity.

580
00:24:36,420 --> 00:24:39,530
And there's lower output
when weather's unfavorable.

581
00:24:39,530 --> 00:24:42,640
And thirdly, today
there's a high cost.

582
00:24:42,640 --> 00:24:44,940
We'll get to that in
a few slides as well.

583
00:24:44,940 --> 00:24:48,320
So it's not economically
competitive in most markets.

584
00:24:48,320 --> 00:24:49,360
In some, there are.

585
00:24:49,360 --> 00:24:51,850
In 1.5 out of the 50
states here in US,

586
00:24:51,850 --> 00:24:53,830
solar is cost
competitive, today.

587
00:24:53,830 --> 00:24:57,970
But in the remainder, it's not.

588
00:24:57,970 --> 00:24:59,450
So this is the really fun part.

589
00:24:59,450 --> 00:25:02,800
This is why when you
pick up your phone,

590
00:25:02,800 --> 00:25:05,630
and text your parents, and
say I'm in a PV course.

591
00:25:05,630 --> 00:25:07,442
And they write
back, ah, PV, I've

592
00:25:07,442 --> 00:25:08,650
heard about that for decades.

593
00:25:08,650 --> 00:25:09,650
That's an old hat.

594
00:25:09,650 --> 00:25:10,760
That's not going anywhere.

595
00:25:10,760 --> 00:25:13,100
You can write back and say
it's very different today

596
00:25:13,100 --> 00:25:14,200
than it was then.

597
00:25:14,200 --> 00:25:17,060
And here's the reason why.

598
00:25:17,060 --> 00:25:19,660
In the 1970s, when
PV really started

599
00:25:19,660 --> 00:25:22,237
to take off for civilian
purposes-- obviously,

600
00:25:22,237 --> 00:25:23,820
they had put satellites
up into space.

601
00:25:23,820 --> 00:25:25,550
They had proven that it worked.

602
00:25:25,550 --> 00:25:26,920
It was robust.

603
00:25:26,920 --> 00:25:30,360
In microwave relay stations up
in remote locations, that they

604
00:25:30,360 --> 00:25:33,440
didn't want to service, they
also would place PV panels.

605
00:25:33,440 --> 00:25:35,930
But in terms of civilian
purposes on houses

606
00:25:35,930 --> 00:25:38,965
and so forth, really
late 1970s, early 1980s

607
00:25:38,965 --> 00:25:41,180
were where things were
beginning to take off.

608
00:25:41,180 --> 00:25:43,100
And driven by the oil crisis.

609
00:25:43,100 --> 00:25:46,190
The OPEC oil crisis of 1970s.

610
00:25:46,190 --> 00:25:48,430
This is a New York
Times article describing

611
00:25:48,430 --> 00:25:50,550
the state of the art of solar.

612
00:25:50,550 --> 00:25:54,420
This is taking a look some
20 years later at solar

613
00:25:54,420 --> 00:25:56,360
and saying how far have we come.

614
00:25:56,360 --> 00:25:59,190
And one of the interesting
things of note in this article,

615
00:25:59,190 --> 00:26:01,530
right here, is
that it cost upward

616
00:26:01,530 --> 00:26:05,750
of $10 a watt for the solar
panels, in that day in 1979.

617
00:26:05,750 --> 00:26:07,700
Meaning it would
take, roughly, $12,000

618
00:26:07,700 --> 00:26:10,550
to run an ordinary
household toaster.

619
00:26:10,550 --> 00:26:12,630
So that was the
impression that folks

620
00:26:12,630 --> 00:26:14,990
had of solar in the 1970s.

621
00:26:14,990 --> 00:26:16,610
And for good reason.

622
00:26:16,610 --> 00:26:21,910
This is the cost of electricity
produced of solar versus time.

623
00:26:21,910 --> 00:26:24,040
In reality, the x-axis,
if you look closely,

624
00:26:24,040 --> 00:26:28,620
it's cumulative PV
electricity production.

625
00:26:28,620 --> 00:26:31,840
That means for each
new panel we make

626
00:26:31,840 --> 00:26:34,780
and for each new unit of energy
that that panel is producing,

627
00:26:34,780 --> 00:26:36,910
the cost of electricity
is coming down.

628
00:26:36,910 --> 00:26:39,940
That's because we learned
how to make panels better.

629
00:26:39,940 --> 00:26:44,492
We learned how to make cheaper
panels faster, with less cost.

630
00:26:44,492 --> 00:26:46,700
So the cost of the electricity
reproduced, over here,

631
00:26:46,700 --> 00:26:48,970
is showing going down with time.

632
00:26:48,970 --> 00:26:50,815
And this is a
little bit of apples

633
00:26:50,815 --> 00:26:52,190
to oranges
comparison, that's why

634
00:26:52,190 --> 00:26:54,523
they're two different colors
for the two different dots.

635
00:26:54,523 --> 00:26:57,850
The black dots represent the
average retail electricity

636
00:26:57,850 --> 00:26:58,670
prices.

637
00:26:58,670 --> 00:27:00,809
Not costs, but price.

638
00:27:00,809 --> 00:27:02,350
This is going to be
a repeating theme

639
00:27:02,350 --> 00:27:03,460
throughout the entire course.

640
00:27:03,460 --> 00:27:04,750
I'm going to emphasize it now.

641
00:27:04,750 --> 00:27:06,416
Can somebody tell me
what the difference

642
00:27:06,416 --> 00:27:08,581
between cost and price is?

643
00:27:08,581 --> 00:27:10,455
AUDIENCE: Price is going
to be more than cost

644
00:27:10,455 --> 00:27:13,664
because the company wants to
make a profit on the product.

645
00:27:13,664 --> 00:27:14,330
PROFESSOR: Yeah.

646
00:27:14,330 --> 00:27:19,220
So let's see I make a gizmo--
this is a great example.

647
00:27:19,220 --> 00:27:22,960
I make a gizmo that costs a
certain amount, x, let's say.

648
00:27:22,960 --> 00:27:25,310
And now, I sell it for 3x.

649
00:27:25,310 --> 00:27:26,980
And I make 2x profit.

650
00:27:26,980 --> 00:27:28,560
So the price would be 3x.

651
00:27:28,560 --> 00:27:30,360
The cost would be x.

652
00:27:30,360 --> 00:27:34,590
And so the cost of solar is
shown here in the white dots.

653
00:27:34,590 --> 00:27:38,260
And the price of retail
electricity price is in black.

654
00:27:38,260 --> 00:27:41,370
Why is this comparison
made right here?

655
00:27:41,370 --> 00:27:43,270
Why would somebody do
that sort of apples

656
00:27:43,270 --> 00:27:44,402
to oranges comparison?

657
00:27:44,402 --> 00:27:45,860
What point are they
trying to make?

658
00:27:49,230 --> 00:27:51,180
AUDIENCE: Because we
need to bring down

659
00:27:51,180 --> 00:27:54,450
how much we need to
put into PV to be at

660
00:27:54,450 --> 00:27:57,042
to compete with the price
that electricity is at,

661
00:27:57,042 --> 00:27:58,989
as opposed to cost.

662
00:27:58,989 --> 00:27:59,780
PROFESSOR: Exactly.

663
00:27:59,780 --> 00:28:02,000
This is a substitution
play, right?

664
00:28:02,000 --> 00:28:05,050
You're looking at
PV substituting what

665
00:28:05,050 --> 00:28:08,860
is, in that case, the
base load and peaking

666
00:28:08,860 --> 00:28:10,790
price of electricity--
probably more driven

667
00:28:10,790 --> 00:28:12,905
by the peaking price
of electricity.

668
00:28:12,905 --> 00:28:14,280
And so what they're
doing here is

669
00:28:14,280 --> 00:28:15,660
they're saying,
OK, how much does

670
00:28:15,660 --> 00:28:19,480
it cost to manufacture
this panel,

671
00:28:19,480 --> 00:28:21,261
and how does that
compare against the grid

672
00:28:21,261 --> 00:28:23,010
if I were to plug into
the wall over there

673
00:28:23,010 --> 00:28:24,593
and extract electricity
from the grid.

674
00:28:24,593 --> 00:28:27,565
How much would that cost me?

675
00:28:27,565 --> 00:28:29,876
How much would I have to
pay for that electricity?

676
00:28:29,876 --> 00:28:31,750
And that's really the
comparison that they're

677
00:28:31,750 --> 00:28:32,874
trying to drive right here.

678
00:28:32,874 --> 00:28:35,680
AUDIENCE: Does that
adjust for inflation?

679
00:28:35,680 --> 00:28:36,770
PROFESSOR: Yes.

680
00:28:36,770 --> 00:28:38,520
The details are in
this paper, right here.

681
00:28:38,520 --> 00:28:41,350
Again, you can access all
this information online.

682
00:28:41,350 --> 00:28:42,980
But it is adjusted.

683
00:28:42,980 --> 00:28:46,810
These are, I believe,
in 2002 prices.

684
00:28:46,810 --> 00:28:49,055
I can't remember
the exact-- yeah.

685
00:28:49,055 --> 00:28:52,025
AUDIENCE: What are some of the
assumptions used to compute

686
00:28:52,025 --> 00:28:56,000
the cost of PV and electricity?

687
00:28:56,000 --> 00:28:57,630
PROFESSOR: Great question.

688
00:28:57,630 --> 00:29:02,520
So the higher density of
data points, over here,

689
00:29:02,520 --> 00:29:06,680
is in part because they
get closer together.

690
00:29:06,680 --> 00:29:08,770
It becomes harder to
drive the cost down.

691
00:29:08,770 --> 00:29:11,490
And of course, we were
looking at it in a log scale.

692
00:29:11,490 --> 00:29:15,040
But also, the
quality of the data

693
00:29:15,040 --> 00:29:17,999
is much better in recent
years because we had access

694
00:29:17,999 --> 00:29:19,540
to-- greater number
of companies were

695
00:29:19,540 --> 00:29:22,790
able to average values
coming from multiple sources.

696
00:29:22,790 --> 00:29:27,930
Some of the earlier
data, especially 1957--

697
00:29:27,930 --> 00:29:31,830
those were some of the
first solar cells produced.

698
00:29:31,830 --> 00:29:34,727
If they had access
to good primary data,

699
00:29:34,727 --> 00:29:36,310
those numbers would
be highly accurate

700
00:29:36,310 --> 00:29:38,059
because it would be
one company making it.

701
00:29:38,059 --> 00:29:38,730
And that's it.

702
00:29:38,730 --> 00:29:39,990
Very little error bar.

703
00:29:39,990 --> 00:29:41,730
But if they were
making guesstimates

704
00:29:41,730 --> 00:29:44,640
based on material
cost of the day,

705
00:29:44,640 --> 00:29:48,030
then there would be some error
bar associated with that data

706
00:29:48,030 --> 00:29:49,070
point.

707
00:29:49,070 --> 00:29:52,910
These curves are very
difficult to produce

708
00:29:52,910 --> 00:29:54,520
when you're in academia.

709
00:29:54,520 --> 00:29:57,550
But I can say that when
we were in industry,

710
00:29:57,550 --> 00:30:01,310
we did this for our company
just for hahas one day.

711
00:30:01,310 --> 00:30:04,280
And it fell on a
very similar slope--

712
00:30:04,280 --> 00:30:06,940
with a similar slope
and a similar value.

713
00:30:06,940 --> 00:30:08,997
So somehow they were
getting the numbers right.

714
00:30:08,997 --> 00:30:12,829
AUDIENCE: In terms
of insulation,

715
00:30:12,829 --> 00:30:15,328
what numbers are you using to
assume-- like you said, do you

716
00:30:15,328 --> 00:30:17,763
use values for
Nevada or do you take

717
00:30:17,763 --> 00:30:21,659
an average of the summation
of the entire US-- US

718
00:30:21,659 --> 00:30:25,080
average for the retail
electricity prices.

719
00:30:25,080 --> 00:30:27,090
PROFESSOR: And so the
retail electricity

720
00:30:27,090 --> 00:30:29,010
prices in the United
States vary quite a bit.

721
00:30:29,010 --> 00:30:33,570
You have some coal rich
states, like Wyoming, that

722
00:30:33,570 --> 00:30:35,260
get $0.05 per kilowatt hour.

723
00:30:35,260 --> 00:30:37,630
You have states
like Massachusetts

724
00:30:37,630 --> 00:30:39,204
at the end of the
energy pipeline.

725
00:30:39,204 --> 00:30:40,870
If you look at the
natural gas pipeline,

726
00:30:40,870 --> 00:30:41,910
for example, we're
at the very end.

727
00:30:41,910 --> 00:30:44,360
We get some of our natural
gas even shipped in by boat.

728
00:30:44,360 --> 00:30:47,640
$0.18 per kilowatt hour
is residential prices.

729
00:30:47,640 --> 00:30:49,641
And in California, which
has a tiered structure,

730
00:30:49,641 --> 00:30:51,890
if you're one of the highest
consumers of electricity,

731
00:30:51,890 --> 00:30:54,070
you're going to be paying
somewhere around $0.30 per

732
00:30:54,070 --> 00:30:57,840
kilowatt hour compared to some
of the lower use folks down

733
00:30:57,840 --> 00:30:58,760
around $0.12.

734
00:30:58,760 --> 00:31:01,330
And so, it varies quite a bit.

735
00:31:01,330 --> 00:31:04,810
Typically, when you're looking
at these sorts of charts,

736
00:31:04,810 --> 00:31:07,950
if the chart is produced,
say, by the USDOE

737
00:31:07,950 --> 00:31:10,390
or some solar
promoter, let's say,

738
00:31:10,390 --> 00:31:14,200
they will typically be choosing
a rosy scenario of the American

739
00:31:14,200 --> 00:31:16,530
Southwest because
that is-- well,

740
00:31:16,530 --> 00:31:19,190
not only do the numbers look
better but, more importantly,

741
00:31:19,190 --> 00:31:21,314
that's where a lot of the
solar is being installed,

742
00:31:21,314 --> 00:31:24,560
today, but not all of the solar.

743
00:31:24,560 --> 00:31:27,820
Because it is a substitution
economics situation,

744
00:31:27,820 --> 00:31:29,460
two parameters are
really of interest

745
00:31:29,460 --> 00:31:31,230
that drive the cost
competitiveness

746
00:31:31,230 --> 00:31:32,540
of the solar installation.

747
00:31:32,540 --> 00:31:35,180
One is the retail
price of electricity.

748
00:31:35,180 --> 00:31:37,894
How much are you
paying out of the wall?

749
00:31:37,894 --> 00:31:39,310
What are you
substituting it with?

750
00:31:39,310 --> 00:31:42,170
And the second is how much
sunlight you get locally.

751
00:31:42,170 --> 00:31:46,290
So our break even point in
the state of Massachusetts

752
00:31:46,290 --> 00:31:49,360
is not too far off from
Arizona because they

753
00:31:49,360 --> 00:31:52,510
have a lot cheaper
price of electricity

754
00:31:52,510 --> 00:31:53,975
even though we have
a lot less sun.

755
00:31:57,090 --> 00:32:00,380
So I wanted to emphasize
a couple more points.

756
00:32:00,380 --> 00:32:02,500
So when Gregory Nemet
put together this chart,

757
00:32:02,500 --> 00:32:07,230
it was within the context of
a really interesting paper

758
00:32:07,230 --> 00:32:10,550
in which he attempted to
decouple the effects of scale

759
00:32:10,550 --> 00:32:11,705
from innovation.

760
00:32:11,705 --> 00:32:13,000
Let me emphasize that.

761
00:32:13,000 --> 00:32:15,710
So if you are making
a widget-- let's

762
00:32:15,710 --> 00:32:18,730
imagine a razor, like Gillette
does here in South Boston,

763
00:32:18,730 --> 00:32:20,600
or if you're making
some other high tech

764
00:32:20,600 --> 00:32:24,760
product-- razors by the
way are very high tech.

765
00:32:24,760 --> 00:32:28,510
How many times have you cut
yourself by a defective razor?

766
00:32:28,510 --> 00:32:31,610
I certainly haven't, and I've
probably used tens of thousands

767
00:32:31,610 --> 00:32:33,532
in my lifetime of
individual blades.

768
00:32:33,532 --> 00:32:34,990
And that's because
they're examined

769
00:32:34,990 --> 00:32:36,070
using laser technology.

770
00:32:36,070 --> 00:32:38,164
They're really manufactured
in a high tech way.

771
00:32:38,164 --> 00:32:40,080
And they get better and
better every time they

772
00:32:40,080 --> 00:32:41,880
produce one razor blade.

773
00:32:41,880 --> 00:32:43,380
And so they follow
a learning curve,

774
00:32:43,380 --> 00:32:44,830
just like photovoltaics does.

775
00:32:44,830 --> 00:32:48,290
With cumulative production, the
cost of producing one widget

776
00:32:48,290 --> 00:32:49,160
goes down.

777
00:32:49,160 --> 00:32:53,710
And likewise, microwave ovens
and other high tech products.

778
00:32:53,710 --> 00:32:57,430
And so the big question is,
how much of this learning curve

779
00:32:57,430 --> 00:33:00,640
cost reduction is
driven by innovation

780
00:33:00,640 --> 00:33:04,240
and how much is driven by
scaling-- just learning

781
00:33:04,240 --> 00:33:05,699
how to do incremental
improvements,

782
00:33:05,699 --> 00:33:08,198
tweaking the manufacturing line
to make it a little bit more

783
00:33:08,198 --> 00:33:09,130
efficient.

784
00:33:09,130 --> 00:33:12,200
So Gregorian Nemet, the author
of this paper right here,

785
00:33:12,200 --> 00:33:14,590
in which this figure appears,
looked into that question

786
00:33:14,590 --> 00:33:17,490
and came up with some answers.

787
00:33:17,490 --> 00:33:19,980
Some of those learnings
were incorporated

788
00:33:19,980 --> 00:33:22,860
onto this beautiful chat
here produced by 1366,

789
00:33:22,860 --> 00:33:27,280
a spinoff from MIT focused on
commercializing really cool

790
00:33:27,280 --> 00:33:30,000
next-gen PV product.

791
00:33:30,000 --> 00:33:33,780
They took that learning curve
from Gregory Nemet's paper,

792
00:33:33,780 --> 00:33:35,590
plotted in a slightly
different scale,

793
00:33:35,590 --> 00:33:38,080
and showed several of the
technology innovations

794
00:33:38,080 --> 00:33:41,280
that drove down that learning
curve for crystalline silicon.

795
00:33:41,280 --> 00:33:43,180
And so those, in
the fine text there,

796
00:33:43,180 --> 00:33:44,990
represent specific technologies.

797
00:33:44,990 --> 00:33:47,890
And we'll be getting
to know some of them

798
00:33:47,890 --> 00:33:51,550
over the course
of the PV course.

799
00:33:51,550 --> 00:33:53,800
And so, we're approaching
this very interesting point.

800
00:33:53,800 --> 00:33:55,883
If you haven't noticed
from this chart right here,

801
00:33:55,883 --> 00:33:57,050
this ended in 2003.

802
00:33:57,050 --> 00:33:59,450
And boy, these two are getting
very close to one another.

803
00:33:59,450 --> 00:34:02,870
We're entering a very
interesting point

804
00:34:02,870 --> 00:34:06,080
where the cost of
producing PV electricity

805
00:34:06,080 --> 00:34:11,719
is rapidly intersecting with the
US retail electricity prices.

806
00:34:11,719 --> 00:34:14,840
And that is represented in
a very broad brush strokes

807
00:34:14,840 --> 00:34:19,110
by this DOE chart that was
produced in approximately 2006

808
00:34:19,110 --> 00:34:21,520
with the Solar America
Initiative, where

809
00:34:21,520 --> 00:34:23,989
you have the system price
range for PV systems.

810
00:34:23,989 --> 00:34:27,429
Again, broad range now,
instead of finite data points.

811
00:34:27,429 --> 00:34:31,199
Residential and commercial
rates and utility generation.

812
00:34:31,199 --> 00:34:33,730
For those who have already
dealt with electricity markets,

813
00:34:33,730 --> 00:34:35,354
the residential
commercial rates-- this

814
00:34:35,354 --> 00:34:37,699
is the price or
the retail price.

815
00:34:37,699 --> 00:34:41,460
And the utility generation,
this is more the wholesale price

816
00:34:41,460 --> 00:34:42,690
over here for utility scale.

817
00:34:42,690 --> 00:34:47,530
So again, just showing you
the range of substitutions

818
00:34:47,530 --> 00:34:48,973
that could be going on.

819
00:34:48,973 --> 00:34:50,639
And we're entering
the regime now where,

820
00:34:50,639 --> 00:34:54,810
finally, solar is starting
to be cost competitive.

821
00:34:54,810 --> 00:34:58,560
And when you start having
this sort of interaction,

822
00:34:58,560 --> 00:35:01,930
you can imagine two Gaussian
curves, one curve representing

823
00:35:01,930 --> 00:35:05,980
the price of solar and the
other the price of electricity.

824
00:35:05,980 --> 00:35:09,160
And as they begin overlapping,
as the price of our electricity

825
00:35:09,160 --> 00:35:12,320
goes up-- it went up
15% over the 2000s

826
00:35:12,320 --> 00:35:14,040
here in Massachusetts,
the retail price

827
00:35:14,040 --> 00:35:15,770
of electricity in residential.

828
00:35:15,770 --> 00:35:18,480
And as the price of
solar comes down,

829
00:35:18,480 --> 00:35:20,950
those two Gaussian curves begin
moving against each other.

830
00:35:20,950 --> 00:35:22,460
And at the edge
of a Gaussian, you

831
00:35:22,460 --> 00:35:23,960
can model that using
an exponential.

832
00:35:23,960 --> 00:35:26,730
And so you have two
exponential curves overlapping.

833
00:35:26,730 --> 00:35:29,450
You have, effectively, an
exponentially growing market

834
00:35:29,450 --> 00:35:31,160
penetration.

835
00:35:31,160 --> 00:35:33,360
In other words, the solar
adoption on the grid

836
00:35:33,360 --> 00:35:36,010
is following a
hockey stick curve.

837
00:35:36,010 --> 00:35:39,840
And that's why you hear a lot
of interest in solar these days.

838
00:35:39,840 --> 00:35:43,100
We had a solar system
installed in our house in 2007.

839
00:35:43,100 --> 00:35:45,790
And now, our neighbors
put them up last year.

840
00:35:45,790 --> 00:35:48,090
The folks across are putting
them up, actually, just

841
00:35:48,090 --> 00:35:49,050
last week.

842
00:35:49,050 --> 00:35:50,758
And there's another
family down the road.

843
00:35:50,758 --> 00:35:54,050
So our little neighborhood is
representing this little hockey

844
00:35:54,050 --> 00:35:56,894
stick, right here, as is
Cambridge as a whole and some

845
00:35:56,894 --> 00:35:58,310
of the places in
the United States

846
00:35:58,310 --> 00:36:00,597
where it does make
economic sense.

847
00:36:00,597 --> 00:36:02,180
You're beginning to
see that take off.

848
00:36:02,180 --> 00:36:05,090
And that's why it's such
an exciting time right now.

849
00:36:05,090 --> 00:36:07,650
This is a much busier chart.

850
00:36:07,650 --> 00:36:09,330
There's a lot going on.

851
00:36:09,330 --> 00:36:12,690
But to sensitize you, this
is the PV residential.

852
00:36:12,690 --> 00:36:15,850
In other words, it's either
the cost or the price

853
00:36:15,850 --> 00:36:18,400
to install PV on a
residential home.

854
00:36:18,400 --> 00:36:20,480
In other words, it's
a smaller system.

855
00:36:20,480 --> 00:36:22,240
So there's a larger
overhead per system.

856
00:36:22,240 --> 00:36:24,170
The architect needs
to spend more time

857
00:36:24,170 --> 00:36:27,245
per unit energy produced to
design your system because it's

858
00:36:27,245 --> 00:36:28,576
a smaller one.

859
00:36:28,576 --> 00:36:32,780
A lot of people go out there
per panel to install it.

860
00:36:32,780 --> 00:36:36,140
Whereas PV utility, those large
fields filled with PV panels,

861
00:36:36,140 --> 00:36:39,620
it's cheaper per unit
panel to install.

862
00:36:39,620 --> 00:36:42,835
One architect can sit down
and design the whole thing--

863
00:36:42,835 --> 00:36:43,970
maybe a team of architects.

864
00:36:43,970 --> 00:36:47,290
But the overhead
costs are lower.

865
00:36:47,290 --> 00:36:49,920
And you can bargain with
the module manufacturers

866
00:36:49,920 --> 00:36:51,640
to get a better rate
on your modules.

867
00:36:51,640 --> 00:36:53,050
So get a better price.

868
00:36:53,050 --> 00:36:57,120
And as a result, the PV
utility costs and prices

869
00:36:57,120 --> 00:36:59,640
tend to be lower
than PV residential.

870
00:36:59,640 --> 00:37:03,140
And the blue and the
red, here, just represent

871
00:37:03,140 --> 00:37:04,974
the wholesale and retail
electricity costs--

872
00:37:04,974 --> 00:37:07,140
what they're substituting
here in the United States.

873
00:37:07,140 --> 00:37:09,160
So a bit more
detailed chart, again,

874
00:37:09,160 --> 00:37:11,760
showing the grid penetration
down here at the bottom.

875
00:37:11,760 --> 00:37:13,350
Also, in terms of percent.

876
00:37:13,350 --> 00:37:16,900
So back here, a few
years ago, the 0.2%

877
00:37:16,900 --> 00:37:21,450
of total worldwide electricity
was generated by photovoltaics.

878
00:37:21,450 --> 00:37:25,310
And projections are that by
2020, we'll be at around 1%,

879
00:37:25,310 --> 00:37:30,740
by 2030 around 5% using these
just two overlapping Gaussian

880
00:37:30,740 --> 00:37:31,580
curves.

881
00:37:31,580 --> 00:37:34,660
And it's interesting to
note that this is global.

882
00:37:34,660 --> 00:37:36,780
On a local level,
Germany has already

883
00:37:36,780 --> 00:37:39,560
well surpassed 2% in Bavaria.

884
00:37:39,560 --> 00:37:42,700
I think it might be up 3%
or 4% now in photovoltaics,

885
00:37:42,700 --> 00:37:45,940
in the southeastern
region of Germany.

886
00:37:45,940 --> 00:37:49,040
There's a small island in
the Hawaiian chain that

887
00:37:49,040 --> 00:37:52,020
has, I believe in peak days,
around 40% of its electricity

888
00:37:52,020 --> 00:37:53,390
produced from solar.

889
00:37:53,390 --> 00:37:55,100
So there are regions
that already, you

890
00:37:55,100 --> 00:37:58,240
have a very large percentage
of the total electricity being

891
00:37:58,240 --> 00:38:01,345
produced by solar because of
that distribution of prices.

892
00:38:04,720 --> 00:38:07,700
And lastly, this is a
really exciting chart.

893
00:38:07,700 --> 00:38:11,380
This is the convergence between
PV and conventional energy--

894
00:38:11,380 --> 00:38:13,070
essentially, what
this chart over here

895
00:38:13,070 --> 00:38:15,780
was attempting to capture
in its percentages.

896
00:38:15,780 --> 00:38:17,650
This is explicitly
laid out, now.

897
00:38:17,650 --> 00:38:21,950
And I took data going
back to the 1970s,

898
00:38:21,950 --> 00:38:26,660
and plotted the average
terawatts installed

899
00:38:26,660 --> 00:38:30,790
of new PV installations
versus total primary energy--

900
00:38:30,790 --> 00:38:34,470
new primary energy
installations.

901
00:38:34,470 --> 00:38:37,880
So for those energy wonks
here in the audience, what

902
00:38:37,880 --> 00:38:41,540
is the primary energy
burn rate in the world,

903
00:38:41,540 --> 00:38:44,230
right now, in terms
of terawatts average?

904
00:38:44,230 --> 00:38:46,930
Around 15, right?

905
00:38:46,930 --> 00:38:49,230
And so the average
new energy installed

906
00:38:49,230 --> 00:38:50,840
each year is represented here.

907
00:38:50,840 --> 00:38:54,520
It's somewhere between 100
gigawatts and a terawatt,

908
00:38:54,520 --> 00:38:55,720
typically.

909
00:38:55,720 --> 00:38:58,850
And this is the new PV installs.

910
00:38:58,850 --> 00:39:01,570
You can see that we're within
about two orders of magnitude,

911
00:39:01,570 --> 00:39:04,520
now, of total new
energy installs.

912
00:39:04,520 --> 00:39:06,270
This is primary energy.

913
00:39:06,270 --> 00:39:08,440
For electricity, it
looks even rosier.

914
00:39:08,440 --> 00:39:10,190
And so we're rapidly
approaching the point

915
00:39:10,190 --> 00:39:12,520
where substitution will begin.

916
00:39:12,520 --> 00:39:14,780
We're going to
start replacing, not

917
00:39:14,780 --> 00:39:17,010
only we're going
to take a larger

918
00:39:17,010 --> 00:39:19,730
share of total new
installed energy,

919
00:39:19,730 --> 00:39:22,060
but we may even start
putting some existing power

920
00:39:22,060 --> 00:39:23,250
plants out of business.

921
00:39:23,250 --> 00:39:25,430
And we'll get into that
in the economic section

922
00:39:25,430 --> 00:39:27,884
in the third part of our course.

923
00:39:27,884 --> 00:39:30,300
Interesting to note, these
three distinct phases of growth

924
00:39:30,300 --> 00:39:31,770
of the industry over time.

925
00:39:31,770 --> 00:39:33,330
Phase one was right
at the beginning,

926
00:39:33,330 --> 00:39:35,520
when we had the OPEC
oil crises, when people

927
00:39:35,520 --> 00:39:37,603
were really interested in
solar, but it was really

928
00:39:37,603 --> 00:39:38,620
a boutique thing.

929
00:39:38,620 --> 00:39:44,820
And solar cute, great PR,
but not really impactful.

930
00:39:44,820 --> 00:39:48,330
In this regime, right here,
where most of you were born,

931
00:39:48,330 --> 00:39:51,340
solar went kind of
through a down cycle.

932
00:39:51,340 --> 00:39:54,020
So while the price of
oil was really high,

933
00:39:54,020 --> 00:39:57,860
right back here, it
crashed in the early 1980s.

934
00:39:57,860 --> 00:40:00,360
And symbolically,
Ronald Reagan ended up

935
00:40:00,360 --> 00:40:03,020
taking down the solar
panels from the White House

936
00:40:03,020 --> 00:40:05,650
some time in '86, '87.

937
00:40:05,650 --> 00:40:07,950
And big oil companies
were the ones

938
00:40:07,950 --> 00:40:10,410
who kept the solar industry
going, interestingly enough.

939
00:40:10,410 --> 00:40:11,340
It was Mobil-Tyco.

940
00:40:11,340 --> 00:40:12,840
It was BP Solar.

941
00:40:12,840 --> 00:40:15,090
The largest companies that
were producing solar panels

942
00:40:15,090 --> 00:40:19,350
in the world were ones that were
small divisions of larger oil

943
00:40:19,350 --> 00:40:22,840
companies, which viewed
themselves as energy companies.

944
00:40:22,840 --> 00:40:24,760
And then finally,
this phase three,

945
00:40:24,760 --> 00:40:26,140
this really rapid growth here.

946
00:40:26,140 --> 00:40:27,830
Again, a cumulative
annual growth

947
00:40:27,830 --> 00:40:30,430
rate somewhere between
40% and 50% average.

948
00:40:30,430 --> 00:40:34,240
That took off when generous
government subsidies,

949
00:40:34,240 --> 00:40:35,850
whether it be for
the manufacturing

950
00:40:35,850 --> 00:40:37,836
or the installation.

951
00:40:37,836 --> 00:40:39,210
In the case of
the United States,

952
00:40:39,210 --> 00:40:40,780
it's mostly been on
the installation side.

953
00:40:40,780 --> 00:40:42,238
In the case of
China's, it's mostly

954
00:40:42,238 --> 00:40:43,600
been on the manufacturing side.

955
00:40:43,600 --> 00:40:46,340
Japan and Germany
had a bit of both,

956
00:40:46,340 --> 00:40:48,810
but more heavily toward
the installation.

957
00:40:48,810 --> 00:40:51,154
And we saw a massive
growth of the PV industry

958
00:40:51,154 --> 00:40:53,320
because, now, the government's
realized, well, wait,

959
00:40:53,320 --> 00:40:56,920
the cost is coming down, and
we will need new electricity

960
00:40:56,920 --> 00:40:58,060
coming on board.

961
00:40:58,060 --> 00:41:00,367
And our oil supply is
a little unreliable.

962
00:41:00,367 --> 00:41:01,950
So let's invest in
this new technology

963
00:41:01,950 --> 00:41:03,420
and see where it takes us.

964
00:41:03,420 --> 00:41:07,130
And I think the Germans,
now, are paying somewhere

965
00:41:07,130 --> 00:41:09,250
on the order of a euro,
maybe a little over euro,

966
00:41:09,250 --> 00:41:11,430
per month on their
electricity bills

967
00:41:11,430 --> 00:41:14,590
as a result of having financed
a lot of this growth right

968
00:41:14,590 --> 00:41:17,930
here in the PV industry, which
allowed the costs to come down

969
00:41:17,930 --> 00:41:19,710
for the entire world.

970
00:41:19,710 --> 00:41:22,130
So it was a successful program.

971
00:41:22,130 --> 00:41:25,470
And as a result, many
pure play companies

972
00:41:25,470 --> 00:41:27,640
saw the financial opportunities.

973
00:41:27,640 --> 00:41:30,360
The case Q Cells, which
is highlighted down here,

974
00:41:30,360 --> 00:41:32,100
is not unusual in those days.

975
00:41:32,100 --> 00:41:35,820
In the late 1990s, a group
of executives at McKinsey

976
00:41:35,820 --> 00:41:38,050
got together and
said, wow, the numbers

977
00:41:38,050 --> 00:41:40,150
look really promising
in the solar business.

978
00:41:40,150 --> 00:41:41,550
Why don't we form
our own company

979
00:41:41,550 --> 00:41:43,500
and only do solar
instead of being

980
00:41:43,500 --> 00:41:45,480
part of a much larger
one where they have

981
00:41:45,480 --> 00:41:48,110
their interests dispersed among
many different product lines

982
00:41:48,110 --> 00:41:49,090
and technologies?

983
00:41:49,090 --> 00:41:50,730
Let's focus
exclusively on solar,

984
00:41:50,730 --> 00:41:53,150
burn our bridges behind
us, and just go for it.

985
00:41:53,150 --> 00:41:54,040
And they went for it.

986
00:41:54,040 --> 00:41:55,726
And for a while,
for a few months

987
00:41:55,726 --> 00:41:58,100
Q Cells was the largest solar
cell producer in the world.

988
00:42:00,710 --> 00:42:03,950
It was, I would
say, a poster child

989
00:42:03,950 --> 00:42:05,580
of this new generation
of PV companies

990
00:42:05,580 --> 00:42:07,310
coming in this third phase here.

991
00:42:07,310 --> 00:42:12,250
And as we'll learn over the
course of this semester's

992
00:42:12,250 --> 00:42:15,780
course, many of the
leading solar producers

993
00:42:15,780 --> 00:42:18,380
today are now located in China.

994
00:42:18,380 --> 00:42:21,524
So this is, basically, the
history of PV development.

995
00:42:21,524 --> 00:42:23,690
And the important thing to
note is this closing gap,

996
00:42:23,690 --> 00:42:24,620
right here.

997
00:42:24,620 --> 00:42:27,509
So when folks are saying solar,
it's the same old, same old.

998
00:42:27,509 --> 00:42:28,300
It's been gimmicky.

999
00:42:28,300 --> 00:42:29,410
It's been around
for a long time,

1000
00:42:29,410 --> 00:42:30,620
but it's not going anywhere.

1001
00:42:30,620 --> 00:42:32,620
You can point to some of
this data and, say, no.

1002
00:42:32,620 --> 00:42:34,240
Actually, it's on the cusp.

1003
00:42:34,240 --> 00:42:36,660
It really is
beginning to take off.

1004
00:42:36,660 --> 00:42:39,890
And these are some
of the data you can

1005
00:42:39,890 --> 00:42:42,720
point to if you care to do so.

1006
00:42:42,720 --> 00:42:45,710
Let me spend a few minutes
talking about the broader

1007
00:42:45,710 --> 00:42:49,230
picture beyond just
solar photovoltaics

1008
00:42:49,230 --> 00:42:51,710
into some of the other
solar technologies.

1009
00:42:51,710 --> 00:42:53,710
We won't be addressing
too many of these

1010
00:42:53,710 --> 00:42:56,075
over the course of the lecture
because we have to focus

1011
00:42:56,075 --> 00:42:58,150
and we have to become
very good at something,

1012
00:42:58,150 --> 00:42:59,787
otherwise we spread
ourselves to thin.

1013
00:42:59,787 --> 00:43:01,620
But I did want to give
you a sense of what's

1014
00:43:01,620 --> 00:43:04,120
out there so that you can
situate solar photovoltaics

1015
00:43:04,120 --> 00:43:05,730
within a broader context.

1016
00:43:05,730 --> 00:43:08,030
And so this is a solar
energy technology framework

1017
00:43:08,030 --> 00:43:11,900
that encompasses all conversion
technologies from sunlight

1018
00:43:11,900 --> 00:43:13,470
into energy.

1019
00:43:13,470 --> 00:43:16,340
And so first off, I start with
a rationale for framework.

1020
00:43:16,340 --> 00:43:19,160
Why invest the time to
come up a the framework?

1021
00:43:19,160 --> 00:43:21,820
I'll explain why.

1022
00:43:21,820 --> 00:43:24,360
There are several hundreds
of technologies out there

1023
00:43:24,360 --> 00:43:26,280
that can convert
sunlight into energy.

1024
00:43:26,280 --> 00:43:28,750
And to make sense of
the technology space

1025
00:43:28,750 --> 00:43:31,360
and to provide some meaningful
technology assessments,

1026
00:43:31,360 --> 00:43:34,610
there have to be some
performance driven,

1027
00:43:34,610 --> 00:43:37,090
technology neutral
performance metrics

1028
00:43:37,090 --> 00:43:40,130
that you can use to evaluate
one technology against another.

1029
00:43:40,130 --> 00:43:42,470
And that's why coming up
with some sort of framework

1030
00:43:42,470 --> 00:43:44,460
is very helpful.

1031
00:43:44,460 --> 00:43:47,350
So the three criteria
that I chose together

1032
00:43:47,350 --> 00:43:50,010
with Vladimir Bulovic
when we put the together,

1033
00:43:50,010 --> 00:43:52,770
to design a technology
framework was

1034
00:43:52,770 --> 00:43:54,630
an exhaustive categorisation.

1035
00:43:54,630 --> 00:43:57,550
In other words, our framework
had to encompass more than 90%

1036
00:43:57,550 --> 00:43:59,002
of all technologies out there.

1037
00:43:59,002 --> 00:43:59,960
The 30 years challenge.

1038
00:43:59,960 --> 00:44:02,700
Again, in 30 years,
the PV technologies

1039
00:44:02,700 --> 00:44:05,110
should be able to fit
into this framework still.

1040
00:44:05,110 --> 00:44:06,930
And it should be a
useful analysis tool.

1041
00:44:06,930 --> 00:44:09,140
It should be able
to give insight

1042
00:44:09,140 --> 00:44:11,330
into the complex space
that's out there,

1043
00:44:11,330 --> 00:44:13,780
and allow folks, like
yourselves, to make sense

1044
00:44:13,780 --> 00:44:16,250
of it, whether you're trying
to develop cost models

1045
00:44:16,250 --> 00:44:18,580
or if you're trying to
develop technology prospectus.

1046
00:44:18,580 --> 00:44:21,870
This should allow you to
gain a foothold in it.

1047
00:44:21,870 --> 00:44:24,320
So we have solar energy
conversion technology.

1048
00:44:24,320 --> 00:44:27,350
And we chose an output
oriented rationale

1049
00:44:27,350 --> 00:44:30,810
for dividing the solar
energy conversion space.

1050
00:44:30,810 --> 00:44:34,912
So the output would be either
electricity, heat, or heat

1051
00:44:34,912 --> 00:44:37,370
which is then used to power,
say, a turbine which generates

1052
00:44:37,370 --> 00:44:39,960
electricity, or fuels.

1053
00:44:39,960 --> 00:44:43,857
And those are the four primary
outputs of solar energy, today.

1054
00:44:43,857 --> 00:44:45,440
Yes, there are
technologies out there,

1055
00:44:45,440 --> 00:44:47,430
for example, that convert
sunlight and store it

1056
00:44:47,430 --> 00:44:50,960
in some way and convert
light on the other end.

1057
00:44:50,960 --> 00:44:53,660
But we're not including
those in here because,

1058
00:44:53,660 --> 00:44:55,310
again, the 90% rule.

1059
00:44:55,310 --> 00:44:57,560
We're focusing on
the major ones.

1060
00:44:57,560 --> 00:44:59,700
And then, we do a
further subdivision

1061
00:44:59,700 --> 00:45:01,520
between the non-tracking
and tracking.

1062
00:45:01,520 --> 00:45:03,149
Tracking means if
the sun is moving

1063
00:45:03,149 --> 00:45:04,940
through the sky over
the course of the day,

1064
00:45:04,940 --> 00:45:07,850
your apparatus is
following the sun so as

1065
00:45:07,850 --> 00:45:10,320
to maximize the cross section
between the incoming rays

1066
00:45:10,320 --> 00:45:12,760
in your device.

1067
00:45:12,760 --> 00:45:14,890
The reason we chose
tracking non-tracking

1068
00:45:14,890 --> 00:45:17,350
is because tracking
requires motors,

1069
00:45:17,350 --> 00:45:19,900
which will add cost and
reliability questions

1070
00:45:19,900 --> 00:45:22,180
to your system considerations.

1071
00:45:22,180 --> 00:45:26,860
And that's why we chose this
further division right here.

1072
00:45:26,860 --> 00:45:28,140
So on to the assessment.

1073
00:45:28,140 --> 00:45:30,181
Let's look at the technologies
that are out there

1074
00:45:30,181 --> 00:45:31,470
and try to bin them.

1075
00:45:31,470 --> 00:45:32,814
Solar to electricity.

1076
00:45:32,814 --> 00:45:33,980
There are a few embodiments.

1077
00:45:33,980 --> 00:45:36,165
There's the photovoltaic
device, these ones.

1078
00:45:36,165 --> 00:45:37,540
There's the
thermoelectric device

1079
00:45:37,540 --> 00:45:40,570
as well, which convert
solar energy into heat,

1080
00:45:40,570 --> 00:45:42,196
really, and then heat
into electricity.

1081
00:45:42,196 --> 00:45:44,320
So maybe it should have
been in the other category.

1082
00:45:44,320 --> 00:45:47,014
But it is a device that converts
solar energy into electricity.

1083
00:45:47,014 --> 00:45:48,430
So we've seen a
solar cell device.

1084
00:45:48,430 --> 00:45:51,240
We've learned the three steps,
charge generation, charge

1085
00:45:51,240 --> 00:45:53,670
separation, charge collection.

1086
00:45:53,670 --> 00:45:56,330
And we look at the
existing technologies that

1087
00:45:56,330 --> 00:45:58,520
are out there, today,
and say, all right,

1088
00:45:58,520 --> 00:46:00,140
let's start to bin them.

1089
00:46:00,140 --> 00:46:03,950
We have non-tracking systems
that can be non-concentrating,

1090
00:46:03,950 --> 00:46:05,280
like these panels right here.

1091
00:46:05,280 --> 00:46:07,030
Essentially, they're
just flat panels that

1092
00:46:07,030 --> 00:46:09,450
are receiving the sun's rays.

1093
00:46:09,450 --> 00:46:13,130
Or, you can have cheap,
mirror-like materials

1094
00:46:13,130 --> 00:46:16,020
that bounce the sunlight off
of them into the solar panels

1095
00:46:16,020 --> 00:46:17,490
and concentrate sunlight.

1096
00:46:17,490 --> 00:46:19,690
So let's imagine we
put a set of mirrors

1097
00:46:19,690 --> 00:46:21,690
on either side of this
panel, right here.

1098
00:46:21,690 --> 00:46:23,070
And when the sunlight
bounced into the mirror,

1099
00:46:23,070 --> 00:46:24,611
it would reflect
back into the panel.

1100
00:46:24,611 --> 00:46:28,110
That would be a concentrating,
but non-tracking, system.

1101
00:46:28,110 --> 00:46:34,420
And these are common on barriers
along the highway in Germany.

1102
00:46:34,420 --> 00:46:35,510
They're sound barriers.

1103
00:46:35,510 --> 00:46:36,450
They're preventing
the people who

1104
00:46:36,450 --> 00:46:37,690
live on the other
side of that barrier

1105
00:46:37,690 --> 00:46:40,436
from hearing the noise of the
cars going by on the Audubon.

1106
00:46:40,436 --> 00:46:42,060
They're not meant to
be crash barriers.

1107
00:46:42,060 --> 00:46:45,620
Those are separate,
closer to the actual road.

1108
00:46:45,620 --> 00:46:49,110
But these are examples of
concentrating and non-tracking

1109
00:46:49,110 --> 00:46:50,440
photovoltaics.

1110
00:46:50,440 --> 00:46:52,810
There are ground mounted
and roof mounted systems.

1111
00:46:52,810 --> 00:46:55,130
So again, another
way to split the pie.

1112
00:46:58,210 --> 00:47:00,240
In the concentrating
non-tracking system,

1113
00:47:00,240 --> 00:47:01,990
there aren't only
these types, there

1114
00:47:01,990 --> 00:47:04,330
are a variety of other
species of concentrating

1115
00:47:04,330 --> 00:47:06,200
non-tracking devices as well.

1116
00:47:06,200 --> 00:47:08,900
There are so-called
sliver cells--

1117
00:47:08,900 --> 00:47:11,540
which the light comes in,
bounces around a little bit,

1118
00:47:11,540 --> 00:47:14,110
and then eventually gets
absorbed by the device.

1119
00:47:14,110 --> 00:47:18,140
And that even happens, to some
degree, in these modules, too.

1120
00:47:18,140 --> 00:47:20,261
Because the light
comes in-- make sure

1121
00:47:20,261 --> 00:47:21,760
I don't reflect
this into your face.

1122
00:47:21,760 --> 00:47:22,760
There we go.

1123
00:47:22,760 --> 00:47:23,542
Point it up.

1124
00:47:23,542 --> 00:47:25,500
The light can come in
sometimes and reflect off

1125
00:47:25,500 --> 00:47:27,100
of this white back skin.

1126
00:47:27,100 --> 00:47:29,640
If the light is coming in
at an oblique enough angle,

1127
00:47:29,640 --> 00:47:31,990
total internal
reflection by the glass.

1128
00:47:31,990 --> 00:47:34,430
It'll get a second bounce
and go into the device.

1129
00:47:34,430 --> 00:47:37,720
We'll talk about how that
works in a couple of lectures.

1130
00:47:37,720 --> 00:47:40,230
So internal reflections.

1131
00:47:40,230 --> 00:47:46,040
And this is particularly timely.

1132
00:47:46,040 --> 00:47:49,380
Does anybody know--
does the word Solyndra

1133
00:47:49,380 --> 00:47:51,300
ring a bell for anybody?

1134
00:47:51,300 --> 00:47:51,800
Yeah.

1135
00:47:51,800 --> 00:47:53,040
What about Solyndra?

1136
00:47:53,040 --> 00:47:54,211
AUDIENCE: It went bust.

1137
00:47:54,211 --> 00:47:55,210
PROFESSOR: It went bust.

1138
00:47:55,210 --> 00:47:58,055
So it's one of the
three photovoltaics

1139
00:47:58,055 --> 00:47:59,680
start up companies
in the United States

1140
00:47:59,680 --> 00:48:04,230
that went bust over the past few
months over this past summer.

1141
00:48:04,230 --> 00:48:06,330
And that's a really
interesting market dynamic,

1142
00:48:06,330 --> 00:48:08,770
which we'll get to in the
third part of this course.

1143
00:48:08,770 --> 00:48:10,750
And we'll discuss that
head on because it's

1144
00:48:10,750 --> 00:48:12,680
an interesting,
and very important

1145
00:48:12,680 --> 00:48:16,580
dynamic in the evolution
of the solar industry.

1146
00:48:16,580 --> 00:48:19,420
We have some technologies
under development at MIT.

1147
00:48:19,420 --> 00:48:21,520
Marc Baldo's lab and
Vladimir Bulovic and others

1148
00:48:21,520 --> 00:48:25,080
are working on devices that
absorb sunlight, reemit

1149
00:48:25,080 --> 00:48:26,580
the light at a
different wavelength,

1150
00:48:26,580 --> 00:48:30,641
trap it inside of some high
index medium, like glass,

1151
00:48:30,641 --> 00:48:32,140
and then, ultimately,
concentrate it

1152
00:48:32,140 --> 00:48:33,960
on to the cells that
are on the corners.

1153
00:48:33,960 --> 00:48:36,100
So you can imagine a
window that absorbs

1154
00:48:36,100 --> 00:48:38,120
some of the incoming
light, bounces light

1155
00:48:38,120 --> 00:48:40,985
off, and eventually concentrates
the light in the corners where

1156
00:48:40,985 --> 00:48:42,360
you have your
solar cell devices.

1157
00:48:42,360 --> 00:48:44,151
The advantages, or the
potential advantage,

1158
00:48:44,151 --> 00:48:46,970
here is that you can have
a very high efficiency,

1159
00:48:46,970 --> 00:48:50,060
expensive device, but a
very small area of it.

1160
00:48:50,060 --> 00:48:52,370
Instead of covering this
entire area right here,

1161
00:48:52,370 --> 00:48:54,820
you've now reduced
the total area.

1162
00:48:54,820 --> 00:48:57,770
And then, if this is a
very small percentage

1163
00:48:57,770 --> 00:48:59,430
of the total system
cost, you can just

1164
00:48:59,430 --> 00:49:01,846
switch it right out when a new
and better technology comes

1165
00:49:01,846 --> 00:49:04,900
along, almost like you
switch out your computer.

1166
00:49:04,900 --> 00:49:06,780
So if a better solar
cell device comes along,

1167
00:49:06,780 --> 00:49:08,863
you can take this one out
and put the next one in.

1168
00:49:08,863 --> 00:49:10,852
It's almost like an
upgradable system

1169
00:49:10,852 --> 00:49:12,560
because the majority
of the embedded cost

1170
00:49:12,560 --> 00:49:16,690
is in the concentrator and not
the solar cell device itself.

1171
00:49:16,690 --> 00:49:19,670
Again, just really drinking out
of the fire hose this morning.

1172
00:49:19,670 --> 00:49:21,640
We're drilling you
with data, but it's

1173
00:49:21,640 --> 00:49:24,600
meant to begin to sensitize
you to some of the terms

1174
00:49:24,600 --> 00:49:27,180
and some of the ways of
thinking here in the field.

1175
00:49:27,180 --> 00:49:28,209
Tracking.

1176
00:49:28,209 --> 00:49:29,750
So when we're talking
about tracking,

1177
00:49:29,750 --> 00:49:32,390
there's a rise in the
number of tracking systems

1178
00:49:32,390 --> 00:49:33,830
in the United States.

1179
00:49:33,830 --> 00:49:35,900
It is shown with high
efficiency modules

1180
00:49:35,900 --> 00:49:37,755
that it can be more
cost competitive

1181
00:49:37,755 --> 00:49:39,710
if you have a large
field installation to do

1182
00:49:39,710 --> 00:49:41,390
one axis tracking.

1183
00:49:41,390 --> 00:49:43,417
One axis tracking and
two axis tracking.

1184
00:49:43,417 --> 00:49:45,250
Why would you want one
or two axis tracking?

1185
00:49:45,250 --> 00:49:46,480
What are you tracking?

1186
00:49:46,480 --> 00:49:47,320
One axis tracking.

1187
00:49:47,320 --> 00:49:49,850
What would make sense to
track with a one axis?

1188
00:49:49,850 --> 00:49:52,430
If you had one axis to choose,
would you rotate east west?

1189
00:49:52,430 --> 00:49:54,050
Would you rotate north south?

1190
00:49:54,050 --> 00:49:56,429
Would you rotate
northwest to southeast?

1191
00:49:56,429 --> 00:49:57,220
Where would you go?

1192
00:49:57,220 --> 00:49:58,310
AUDIENCE: East to west.

1193
00:49:58,310 --> 00:49:59,310
PROFESSOR: East to west.

1194
00:49:59,310 --> 00:50:01,120
Why is that?

1195
00:50:01,120 --> 00:50:02,170
[CLASS MURMURS]

1196
00:50:02,170 --> 00:50:03,210
PROFESSOR: Because
you're tracking the sun

1197
00:50:03,210 --> 00:50:04,335
over the course of the day.

1198
00:50:04,335 --> 00:50:06,750
And you're tracking, pretty
much, every day of the year.

1199
00:50:06,750 --> 00:50:10,930
So 365 tracks per year.

1200
00:50:10,930 --> 00:50:13,490
The two axis tracking,
what is this other axis?

1201
00:50:13,490 --> 00:50:15,780
Presumably, it's orthogonal
to the east west.

1202
00:50:15,780 --> 00:50:17,040
In other words, north south.

1203
00:50:17,040 --> 00:50:19,740
Why would you want
to track north south?

1204
00:50:19,740 --> 00:50:20,670
Seasons, right?

1205
00:50:20,670 --> 00:50:25,460
Yeah so from winter to
summer, you're tracking.

1206
00:50:25,460 --> 00:50:29,900
So you would always want your
solar panels facing south,

1207
00:50:29,900 --> 00:50:31,389
I guess, right?

1208
00:50:31,389 --> 00:50:32,930
AUDIENCE: In the
northern hemisphere.

1209
00:50:32,930 --> 00:50:33,790
PROFESSOR: In the
northern hemisphere.

1210
00:50:33,790 --> 00:50:34,540
Exactly.

1211
00:50:34,540 --> 00:50:36,630
So if you're in
Australia or in Brazil,

1212
00:50:36,630 --> 00:50:39,020
your solar panels
are facing north.

1213
00:50:39,020 --> 00:50:42,759
So let's accustomize
ourselves with that.

1214
00:50:42,759 --> 00:50:44,300
And the two axis
tracking, of course,

1215
00:50:44,300 --> 00:50:46,230
would allow for that adjustment.

1216
00:50:46,230 --> 00:50:48,170
The reason one axis
tracking is taking off

1217
00:50:48,170 --> 00:50:54,000
as the most common field
installation tracking

1218
00:50:54,000 --> 00:50:56,346
system is because the
seasonal adjustment,

1219
00:50:56,346 --> 00:50:58,970
if it really needs to be done--
it's not a huge energy benefit,

1220
00:50:58,970 --> 00:51:00,420
but if it really
needs to be done,

1221
00:51:00,420 --> 00:51:02,600
you can probably
just crank by hand

1222
00:51:02,600 --> 00:51:06,860
instead of using a machine or
a motor that can break down.

1223
00:51:06,860 --> 00:51:10,780
And the adjustments still
need to be made very often.

1224
00:51:10,780 --> 00:51:14,500
Non-concentrating
and concentrating PV.

1225
00:51:14,500 --> 00:51:15,390
Tracking.

1226
00:51:15,390 --> 00:51:18,250
So these are one axis
trackers, right here,

1227
00:51:18,250 --> 00:51:20,970
tracking over the course of
the day, but not concentrating.

1228
00:51:20,970 --> 00:51:23,060
In other words, they're
flat panels like this,

1229
00:51:23,060 --> 00:51:24,730
but just mounted
a one axis tracker

1230
00:51:24,730 --> 00:51:27,700
that follows the sun over
the course of the day.

1231
00:51:27,700 --> 00:51:30,760
The system over here
is a two axis tracker

1232
00:51:30,760 --> 00:51:34,250
that includes little lenses
that are focusing the sunlight

1233
00:51:34,250 --> 00:51:36,210
onto tiny little cells.

1234
00:51:36,210 --> 00:51:38,240
And again, very similar
idea that the solar cell

1235
00:51:38,240 --> 00:51:42,600
itself is high efficiency,
but it is a low percentage

1236
00:51:42,600 --> 00:51:43,760
of the total system cost.

1237
00:51:48,220 --> 00:51:50,640
Non-concentrating and tracking.

1238
00:51:50,640 --> 00:51:52,960
Again, several examples of that.

1239
00:51:52,960 --> 00:51:57,377
You have fancy systems, two axis
trackers, again, most common.

1240
00:51:57,377 --> 00:51:59,710
Can anybody guess what this
little gizmo is, right here?

1241
00:51:59,710 --> 00:52:01,709
We're going to get to
that in next lecture but--

1242
00:52:01,709 --> 00:52:04,959
AUDIENCE: A solar sensor that
finds the position of the sun?

1243
00:52:04,959 --> 00:52:05,750
PROFESSOR: Exactly.

1244
00:52:05,750 --> 00:52:07,240
Somehow, you have to
have a measuring device

1245
00:52:07,240 --> 00:52:08,290
if you have a tracker.

1246
00:52:08,290 --> 00:52:09,840
It has to tell you
where the sun is.

1247
00:52:09,840 --> 00:52:10,810
So this little
gizmo, right here,

1248
00:52:10,810 --> 00:52:12,268
is just making sure
that the panels

1249
00:52:12,268 --> 00:52:13,790
are facing the right way.

1250
00:52:13,790 --> 00:52:14,960
Awesome.

1251
00:52:14,960 --> 00:52:16,210
So concentrating and tracking.

1252
00:52:16,210 --> 00:52:18,630
Here's a closer look at
some of the Frenel lenses

1253
00:52:18,630 --> 00:52:20,920
that are used to
concentrate the light down.

1254
00:52:20,920 --> 00:52:25,860
On some cheap microscope-- or
sorry, cheap magnifying glasses

1255
00:52:25,860 --> 00:52:28,800
they also use Frenel lenses.

1256
00:52:28,800 --> 00:52:32,690
And so this is an example
of a low cost apparatus

1257
00:52:32,690 --> 00:52:37,450
here to concentrate the sunlight
onto your high efficiency cell.

1258
00:52:37,450 --> 00:52:38,557
Solar to heat electricity.

1259
00:52:38,557 --> 00:52:41,140
We're not going to talk too much
about this during the course.

1260
00:52:41,140 --> 00:52:43,136
But just to sensitize
you-- that there

1261
00:52:43,136 --> 00:52:45,510
are technologies out there
and some pretty exciting once.

1262
00:52:45,510 --> 00:52:46,555
There are heat engines.

1263
00:52:46,555 --> 00:52:48,180
In other words,
sunlight heats a fluid,

1264
00:52:48,180 --> 00:52:50,330
which moves a turbine or
a piston, either directly

1265
00:52:50,330 --> 00:52:52,420
or by heat exchanger.

1266
00:52:52,420 --> 00:52:53,270
Heat exchangers.

1267
00:52:53,270 --> 00:52:54,370
Thermoelectrics.

1268
00:52:54,370 --> 00:52:56,360
Long wavelengths photovoltaics.

1269
00:52:56,360 --> 00:52:58,490
These are devices
that convert the heat

1270
00:52:58,490 --> 00:53:01,630
portion of the solar
spectrum into usable energy.

1271
00:53:01,630 --> 00:53:04,450
And there are hybrids that
are possible with these.

1272
00:53:04,450 --> 00:53:09,230
So if you heat up a fluid, say,
a salt or a glycol solution,

1273
00:53:09,230 --> 00:53:13,050
then you can store the
energy in terms of heat.

1274
00:53:13,050 --> 00:53:16,380
And if the stored
energy begins to decay

1275
00:53:16,380 --> 00:53:18,230
with time because
of poor insulation,

1276
00:53:18,230 --> 00:53:21,360
you can augment that
heat with natural gas

1277
00:53:21,360 --> 00:53:23,540
or with some other fossil fuel.

1278
00:53:23,540 --> 00:53:27,290
So you get these hybrid,
renewable solar and natural gas

1279
00:53:27,290 --> 00:53:29,930
power plants that are
possible with the solar

1280
00:53:29,930 --> 00:53:31,750
to heat electricity.

1281
00:53:31,750 --> 00:53:35,200
And there are some really
fancy designs out there.

1282
00:53:35,200 --> 00:53:37,740
And I'm happy to dive
into these in more detail.

1283
00:53:37,740 --> 00:53:41,240
The most common one
are sunlight coming

1284
00:53:41,240 --> 00:53:44,720
into some sort of reflector, and
then concentrating the sunlight

1285
00:53:44,720 --> 00:53:49,800
into a thin tube that contains
your high heat capacity

1286
00:53:49,800 --> 00:53:52,910
material, liquid
usually-- so a glycol

1287
00:53:52,910 --> 00:53:56,380
based liquid or even
a salt, sometimes.

1288
00:53:56,380 --> 00:53:57,880
It has to have a
high heat capacity.

1289
00:53:57,880 --> 00:54:00,255
In other words, it has to be
able to absorb a lot of heat

1290
00:54:00,255 --> 00:54:01,610
and retain it.

1291
00:54:01,610 --> 00:54:04,780
But it also has
to have, ideally,

1292
00:54:04,780 --> 00:54:08,790
a minimum amount of corrosion so
that the longevity of the parts

1293
00:54:08,790 --> 00:54:10,450
is sustained.

1294
00:54:10,450 --> 00:54:12,330
And you can see,
here, these tubes that

1295
00:54:12,330 --> 00:54:15,550
are running along here and going
down these fields of collectors

1296
00:54:15,550 --> 00:54:16,800
all the way to the other side.

1297
00:54:16,800 --> 00:54:20,500
And somewhere off in the
distance is the heat exchanger.

1298
00:54:20,500 --> 00:54:23,690
So that's solar thermal for you.

1299
00:54:23,690 --> 00:54:26,610
We have parabolic dishes
concentrating sunlight

1300
00:54:26,610 --> 00:54:28,320
into Stirling engines.

1301
00:54:28,320 --> 00:54:29,440
That's kind of neat.

1302
00:54:29,440 --> 00:54:34,190
And so your T high is basically
that of generated by the sun.

1303
00:54:34,190 --> 00:54:36,430
And you T low is the ambient.

1304
00:54:36,430 --> 00:54:39,190
So typical mechanical
engineering there.

1305
00:54:39,190 --> 00:54:41,449
And you also have
solar power towers.

1306
00:54:41,449 --> 00:54:43,990
There's some work being done at
MIT in this as well with Alex

1307
00:54:43,990 --> 00:54:48,100
Slocum and others that are
using fields of mirrors

1308
00:54:48,100 --> 00:54:50,700
to concentrate the sunlight
into a tiny little spot,

1309
00:54:50,700 --> 00:54:52,685
right here, in a big tower.

1310
00:54:52,685 --> 00:54:54,810
Say, for example, that spot
right there, it's dark.

1311
00:54:54,810 --> 00:54:55,726
It's not in operation.

1312
00:54:55,726 --> 00:54:57,674
But if it were, the sun
would be concentrated

1313
00:54:57,674 --> 00:54:58,590
onto that little spot.

1314
00:54:58,590 --> 00:55:00,899
It'd be really, really
bright, indicative

1315
00:55:00,899 --> 00:55:02,690
of it's very high
temperature, on the order

1316
00:55:02,690 --> 00:55:05,350
of a couple thousand Kelvin.

1317
00:55:05,350 --> 00:55:08,660
And then the sunlight would
either be absorbed up here,

1318
00:55:08,660 --> 00:55:11,710
with some molten salt, or
reflected down underground

1319
00:55:11,710 --> 00:55:13,200
to a heat reservoir.

1320
00:55:13,200 --> 00:55:16,740
And that would be your T
high running your engine.

1321
00:55:16,740 --> 00:55:18,850
So your Carnot engine.

1322
00:55:18,850 --> 00:55:22,550
And then the T low would
be the ambient temperature.

1323
00:55:22,550 --> 00:55:23,890
Solar to heat.

1324
00:55:23,890 --> 00:55:26,470
This is really important
in developing countries.

1325
00:55:26,470 --> 00:55:29,850
Not to be overlooked, the very
simple, low tech conversion

1326
00:55:29,850 --> 00:55:31,770
of sunlight into heat.

1327
00:55:31,770 --> 00:55:33,190
You can heat water.

1328
00:55:33,190 --> 00:55:35,450
This is very, very
common on rooftops

1329
00:55:35,450 --> 00:55:37,630
all throughout the
sunbelt of the planet.

1330
00:55:37,630 --> 00:55:39,720
You'll see these on the
roof, painted in black.

1331
00:55:39,720 --> 00:55:45,490
They contain potable water,
typically used for either,

1332
00:55:45,490 --> 00:55:48,060
say, for example,
showers or kitchen use.

1333
00:55:48,060 --> 00:55:53,410
And the fancier
versions that are really

1334
00:55:53,410 --> 00:55:54,960
marvels of engineering.

1335
00:55:54,960 --> 00:55:57,260
These materials all
have to be coefficient

1336
00:55:57,260 --> 00:55:59,230
of thermal expansion matched.

1337
00:55:59,230 --> 00:56:01,290
As it heats up, the
glass tubing has

1338
00:56:01,290 --> 00:56:03,420
to match the expansion
of the metal around it.

1339
00:56:03,420 --> 00:56:04,920
So it is quite a
feat of engineering

1340
00:56:04,920 --> 00:56:07,000
that they make these so well.

1341
00:56:07,000 --> 00:56:08,500
There are a few
companies in Germany

1342
00:56:08,500 --> 00:56:12,210
that really pioneered
this effort right here.

1343
00:56:12,210 --> 00:56:16,550
Of course, you have tracking
versions, like solar ovens.

1344
00:56:16,550 --> 00:56:19,080
Not too common.

1345
00:56:19,080 --> 00:56:21,424
You typically find more still
in developing countries.

1346
00:56:21,424 --> 00:56:23,590
Unfortunately, you find a
lot of wood burning, which

1347
00:56:23,590 --> 00:56:27,680
isn't good for the cook,
which, unfortunately,

1348
00:56:27,680 --> 00:56:30,040
most often is female.

1349
00:56:30,040 --> 00:56:34,120
And so this illustrates some
of these societal questions

1350
00:56:34,120 --> 00:56:35,380
that solar involves.

1351
00:56:35,380 --> 00:56:37,110
It's not just the technology.

1352
00:56:37,110 --> 00:56:38,790
This involves gender equality.

1353
00:56:38,790 --> 00:56:40,870
This involves
societal development.

1354
00:56:40,870 --> 00:56:44,930
This is a much broader topic
than just the fundamentals

1355
00:56:44,930 --> 00:56:47,202
of the physics of how the
solar cell device works

1356
00:56:47,202 --> 00:56:48,910
or how sunlight is
converted into energy.

1357
00:56:48,910 --> 00:56:52,230
And that's why we have the
three segments of the course.

1358
00:56:52,230 --> 00:56:54,840
Lastly, solar to fuels.

1359
00:56:54,840 --> 00:56:57,910
The way I've traditionally
broken it down--

1360
00:56:57,910 --> 00:57:01,490
it's a little bit wishy washy--
is into enthalpy and entropy

1361
00:57:01,490 --> 00:57:03,120
in the sense that,
in enthalpy, you're

1362
00:57:03,120 --> 00:57:06,340
storing the sunlight in
bonds-- in chemical bonds.

1363
00:57:06,340 --> 00:57:09,150
The bonds are
forming-- more complex,

1364
00:57:09,150 --> 00:57:12,000
higher energy molecules
are being created.

1365
00:57:12,000 --> 00:57:15,510
So you're taking water and
splitting into the gases.

1366
00:57:15,510 --> 00:57:18,011
Or you're taking CO2 and
water and converting it

1367
00:57:18,011 --> 00:57:18,760
into hydrocarbons.

1368
00:57:21,270 --> 00:57:24,970
And those can be used
to store the fuel

1369
00:57:24,970 --> 00:57:28,140
and, ultimately, release it in
the form of burning the fuel.

1370
00:57:28,140 --> 00:57:30,130
So it's a closed loop cycle.

1371
00:57:30,130 --> 00:57:32,710
And what I refer to
as entropy, which

1372
00:57:32,710 --> 00:57:35,700
I get some flack from the
folks in chemistry for,

1373
00:57:35,700 --> 00:57:38,220
is the separation of phases,
in other words, desalination.

1374
00:57:38,220 --> 00:57:41,450
If you separate your
salts from your water,

1375
00:57:41,450 --> 00:57:44,530
then you're increasing
the energy of your system.

1376
00:57:44,530 --> 00:57:46,500
You're doing a
physical separation.

1377
00:57:46,500 --> 00:57:49,540
And it is a form
of energy storage.

1378
00:57:49,540 --> 00:57:53,540
So this right here is the
example of the renewable fuel

1379
00:57:53,540 --> 00:57:55,510
cycle where you
have sunlight coming

1380
00:57:55,510 --> 00:57:57,400
into your starting compounds.

1381
00:57:57,400 --> 00:57:59,162
Using some catalyst,
typically, you're

1382
00:57:59,162 --> 00:58:00,620
creating the
intermediate compound,

1383
00:58:00,620 --> 00:58:02,000
which is a solar fuel.

1384
00:58:02,000 --> 00:58:03,370
Then you burn your solar fuel.

1385
00:58:03,370 --> 00:58:04,828
Then you have your
final compounds.

1386
00:58:04,828 --> 00:58:06,467
In the ideal world, 5 equals 1.

1387
00:58:06,467 --> 00:58:08,550
The final compounds are
identical to the beginning

1388
00:58:08,550 --> 00:58:09,050
compounds.

1389
00:58:09,050 --> 00:58:12,510
And you have a closed loop
cycle, a renewable cycle.

1390
00:58:12,510 --> 00:58:14,500
And so a lot of work is
going on here at MIT.

1391
00:58:14,500 --> 00:58:16,333
This is a recent paper
we published together

1392
00:58:16,333 --> 00:58:17,700
with Dan Nocera.

1393
00:58:17,700 --> 00:58:20,710
His group is looking to
special types of catalysts.

1394
00:58:20,710 --> 00:58:22,030
Our group makes solar cells.

1395
00:58:22,030 --> 00:58:24,810
So we work together to make
these nifty little devices that

1396
00:58:24,810 --> 00:58:27,084
convert sunlight
into storable fuels.

1397
00:58:27,084 --> 00:58:29,000
What you see here are
little bundles coming up

1398
00:58:29,000 --> 00:58:32,790
from the water in which the
solar cell device is embedded.

1399
00:58:32,790 --> 00:58:34,350
The water is near pH neutral.

1400
00:58:34,350 --> 00:58:36,450
Then it's converting
that sunlight into gas,

1401
00:58:36,450 --> 00:58:40,491
into hydrogen and oxygen,
which can then be stored.

1402
00:58:40,491 --> 00:58:41,990
On one side of the
device, you could

1403
00:58:41,990 --> 00:58:44,200
be creating oxygen. On the other
side, hydrogen, for instance,

1404
00:58:44,200 --> 00:58:45,870
if you have a
physical separator,

1405
00:58:45,870 --> 00:58:48,642
you'd be able to store
that electricity.

1406
00:58:48,642 --> 00:58:50,475
This is an example-- a
very simple example--

1407
00:58:50,475 --> 00:58:52,360
of desalination driven by solar.

1408
00:58:52,360 --> 00:58:54,750
There are much fancier
examples, as well.

1409
00:58:54,750 --> 00:58:56,100
But that gives you an idea.

1410
00:58:56,100 --> 00:58:58,910
You have contaminated
or salty water.

1411
00:58:58,910 --> 00:59:00,690
And you're
evaporating the water.

1412
00:59:00,690 --> 00:59:03,120
It dribbles down into this
little collector over here,

1413
00:59:03,120 --> 00:59:05,660
and finally out into your
collecting pot, leaving

1414
00:59:05,660 --> 00:59:07,390
the salty, brine behind.

1415
00:59:10,070 --> 00:59:12,450
And then in the
broader perspective,

1416
00:59:12,450 --> 00:59:15,850
we have many other issues beside
just the conversion technology

1417
00:59:15,850 --> 00:59:16,760
itself.

1418
00:59:16,760 --> 00:59:19,610
We have how do we
use the electricity

1419
00:59:19,610 --> 00:59:22,150
and how do we store it.

1420
00:59:22,150 --> 00:59:25,930
Is the solar power generation
centralized and all the users

1421
00:59:25,930 --> 00:59:29,130
distributed, similar to
how we produce power today?

1422
00:59:29,130 --> 00:59:31,600
Do we have one big solar field
that's producing electricity

1423
00:59:31,600 --> 00:59:34,780
for all of Cambridge,
or do we have

1424
00:59:34,780 --> 00:59:37,860
the individual solar panels
in each of our houses

1425
00:59:37,860 --> 00:59:39,450
that are producing
the power locally,

1426
00:59:39,450 --> 00:59:40,360
and they're all interconnected?

1427
00:59:40,360 --> 00:59:42,443
In case a cloud goes over
one region of Cambridge,

1428
00:59:42,443 --> 00:59:43,600
there's still coverage.

1429
00:59:43,600 --> 00:59:45,080
That's a really big question.

1430
00:59:45,080 --> 00:59:47,850
And the economics are what's
driving this right now.

1431
00:59:47,850 --> 00:59:50,627
These large field
installations give you a sense.

1432
00:59:50,627 --> 00:59:51,710
This is a road right here.

1433
00:59:51,710 --> 00:59:53,168
These little green
specs are trees.

1434
00:59:53,168 --> 00:59:56,620
These are huge field
Installations of solar.

1435
00:59:56,620 --> 00:59:59,950
The economics are
driving it right now.

1436
00:59:59,950 --> 01:00:02,472
But there are opportunities
with commercial buildings.

1437
01:00:02,472 --> 01:00:04,680
This is the Moscone Center
in downtown San Francisco.

1438
01:00:04,680 --> 01:00:08,170
It's like the Heinz Convention
Center equivalent there.

1439
01:00:08,170 --> 01:00:11,570
This is an example of a
house in Rochester, New York.

1440
01:00:11,570 --> 01:00:15,680
That housing development in
Rancho Cordova in California.

1441
01:00:15,680 --> 01:00:17,890
So you have examples of
residential installations

1442
01:00:17,890 --> 01:00:18,890
as well.

1443
01:00:18,890 --> 01:00:20,820
Are we just going to let
economics drive this?

1444
01:00:20,820 --> 01:00:22,570
Is there going to be
some policy involved?

1445
01:00:22,570 --> 01:00:25,730
Is there a smarter way to
do it, not only from a cost

1446
01:00:25,730 --> 01:00:29,090
perspective, but from a societal
perspective or an energy grid

1447
01:00:29,090 --> 01:00:30,750
robustness point of view?

1448
01:00:30,750 --> 01:00:32,330
What are the right choices here?

1449
01:00:32,330 --> 01:00:34,950
There's a lot of open questions
right now in the field.

1450
01:00:34,950 --> 01:00:37,130
And what about energy storage?

1451
01:00:37,130 --> 01:00:40,540
Are we going to store it in
terms of batteries and fuel?

1452
01:00:40,540 --> 01:00:42,080
Centralized storage?

1453
01:00:42,080 --> 01:00:44,740
Are we just going dump it into
the grid and be free riders?

1454
01:00:44,740 --> 01:00:46,360
Let the grid handle it, somehow.

1455
01:00:46,360 --> 01:00:49,190
Hope that the grid a stable
enough that when a lot of solar

1456
01:00:49,190 --> 01:00:51,450
is being produced and when
no solar is being produced,

1457
01:00:51,450 --> 01:00:53,760
it'll just be able
to accommodate.

1458
01:00:53,760 --> 01:00:56,316
I guess the resistance in the
turbines of the fossil fuel

1459
01:00:56,316 --> 01:00:57,940
plants will either
increase or decrease

1460
01:00:57,940 --> 01:01:00,619
depending on how much energy
we're pumping into the grid.

1461
01:01:00,619 --> 01:01:03,160
And so at the end of the day,
we have this very complex space

1462
01:01:03,160 --> 01:01:04,740
of conversion technologies.

1463
01:01:04,740 --> 01:01:07,790
The solar electricity,
solar to heat, and so forth.

1464
01:01:07,790 --> 01:01:11,530
And the system itself, whether
we have centralized generation

1465
01:01:11,530 --> 01:01:13,171
of electricity
distributed generation,

1466
01:01:13,171 --> 01:01:15,420
and whether the storage is
centralized or distributed,

1467
01:01:15,420 --> 01:01:17,980
whether you have storage inside
of our house on the inverter,

1468
01:01:17,980 --> 01:01:19,830
let's say, or in the
basement, or rather

1469
01:01:19,830 --> 01:01:22,750
the storage is some
centralized storage

1470
01:01:22,750 --> 01:01:24,750
facility in the
center of Cambridge

1471
01:01:24,750 --> 01:01:27,130
that serves as a buffer.

1472
01:01:27,130 --> 01:01:30,220
And we have all of
this space to play in.

1473
01:01:30,220 --> 01:01:32,670
We're going to be focusing
on solar to electricity.

1474
01:01:32,670 --> 01:01:34,980
So we'll be focusing on
these two columns right here.

1475
01:01:34,980 --> 01:01:37,440
And specifically,
the technologies

1476
01:01:37,440 --> 01:01:41,500
during the first two thirds, and
then, the broader, system level

1477
01:01:41,500 --> 01:01:43,380
impacts in the
third of the course.

1478
01:01:43,380 --> 01:01:45,910
So that puts it
all in perspective,

1479
01:01:45,910 --> 01:01:48,590
I'm not going to get
too much into this.

1480
01:01:48,590 --> 01:01:51,820
I'm just going to say one
quick word about CO2, energy,

1481
01:01:51,820 --> 01:01:53,850
and climate change.

1482
01:01:53,850 --> 01:01:56,360
You hear a lot of
talk about, at least

1483
01:01:56,360 --> 01:02:01,330
from the political sector, that
scientists are, shall we say,

1484
01:02:01,330 --> 01:02:04,630
in a lot of debate whether
climate change exists or not.

1485
01:02:04,630 --> 01:02:06,720
That is patently false.

1486
01:02:06,720 --> 01:02:11,799
The majority of
scientists, upwards of 96%,

1487
01:02:11,799 --> 01:02:13,340
believe that there
is strong evidence

1488
01:02:13,340 --> 01:02:17,310
to support the fact that human
energy consumption, especially

1489
01:02:17,310 --> 01:02:19,560
the high CO2 intensity of
our energy consumption,

1490
01:02:19,560 --> 01:02:21,896
is driving some form
of climate change.

1491
01:02:21,896 --> 01:02:24,270
What the magnitude is and what
the impact is-- obviously,

1492
01:02:24,270 --> 01:02:26,070
that is still under discussion.

1493
01:02:26,070 --> 01:02:28,580
But the reality
that our emission

1494
01:02:28,580 --> 01:02:31,180
of energy-- our emission of
CO2 as a result of energy

1495
01:02:31,180 --> 01:02:34,140
use, our fossil fuel energy use,
is driving some form of climate

1496
01:02:34,140 --> 01:02:37,850
change that there is widespread
consensus among the established

1497
01:02:37,850 --> 01:02:39,240
scientists in the field.

1498
01:02:39,240 --> 01:02:41,740
Now if you want to do some back
of the envelope calculations

1499
01:02:41,740 --> 01:02:45,040
just to convince yourself
that we, tiny, puny, little

1500
01:02:45,040 --> 01:02:47,690
human beings are having
an impact on our world,

1501
01:02:47,690 --> 01:02:48,930
do this for me.

1502
01:02:48,930 --> 01:02:51,810
Take the total energy
consumption rate.

1503
01:02:51,810 --> 01:02:53,270
This is the energy burn rate.

1504
01:02:53,270 --> 01:02:56,550
So it's the average
power-- average

1505
01:02:56,550 --> 01:02:58,760
rate of electricity use.

1506
01:02:58,760 --> 01:03:05,800
Look at just the fossil
fuel based energy sources.

1507
01:03:05,800 --> 01:03:09,640
Or if you prefer, take
the average CO2 intensity

1508
01:03:09,640 --> 01:03:14,770
of our energy mix, which
somewhere around 600 or maybe

1509
01:03:14,770 --> 01:03:17,680
800 grams of CO2
per kilowatt hour.

1510
01:03:17,680 --> 01:03:22,120
And then look at that
amount of CO2 emitted.

1511
01:03:22,120 --> 01:03:25,610
You can calculate how much
CO2 is emitted per unit time

1512
01:03:25,610 --> 01:03:28,280
from our energy mix knowing the
carbon intensity of our energy

1513
01:03:28,280 --> 01:03:29,240
mix.

1514
01:03:29,240 --> 01:03:31,370
Then do a quick back of
the envelope calculation.

1515
01:03:31,370 --> 01:03:34,170
Assume that our atmosphere
is 30 kilometers thick.

1516
01:03:34,170 --> 01:03:36,652
It's a generous assumption.

1517
01:03:36,652 --> 01:03:38,860
The density of the atmosphere
dwindles pretty quickly

1518
01:03:38,860 --> 01:03:39,800
above 10 kilometers.

1519
01:03:39,800 --> 01:03:41,750
But assume it's 30
kilometers thick.

1520
01:03:41,750 --> 01:03:44,070
And then dissolve
all of that carbon

1521
01:03:44,070 --> 01:03:46,070
that we're creating
from this energy mix

1522
01:03:46,070 --> 01:03:48,565
into that thin shell
surrounding our earth.

1523
01:03:48,565 --> 01:03:52,660
Our earth is on the order of
6,370 kilometers in radius.

1524
01:03:52,660 --> 01:03:55,884
And it's only 30 kilometers
thick, the atmosphere.

1525
01:03:55,884 --> 01:03:58,300
That's why those beautiful
photos from the space missions,

1526
01:03:58,300 --> 01:04:01,110
when you see that thin
blue shell on the planet,

1527
01:04:01,110 --> 01:04:02,880
right-- that's the atmosphere.

1528
01:04:02,880 --> 01:04:04,460
It's really, really thin.

1529
01:04:04,460 --> 01:04:07,900
Just do a quick carbon
density analysis.

1530
01:04:07,900 --> 01:04:12,100
And you'll see that we're adding
hi tens of parts per million

1531
01:04:12,100 --> 01:04:14,572
of CO2 to the atmosphere.

1532
01:04:14,572 --> 01:04:17,030
And then you look at the total
CO2 in the atmosphere, which

1533
01:04:17,030 --> 01:04:19,240
is in the order of
400 parts per million,

1534
01:04:19,240 --> 01:04:22,940
and you'll see that we're adding
an appreciable amount, just

1535
01:04:22,940 --> 01:04:25,206
given the carbon intensity
of our energy mix

1536
01:04:25,206 --> 01:04:27,330
and the total volume of
atmosphere into which we're

1537
01:04:27,330 --> 01:04:29,270
dumping that carbon.

1538
01:04:29,270 --> 01:04:31,080
And so the question
of whether or not

1539
01:04:31,080 --> 01:04:33,480
we are adding carbon to
the atmosphere, I think,

1540
01:04:33,480 --> 01:04:35,597
is indisputable, based
on some quick back

1541
01:04:35,597 --> 01:04:37,430
of the envelope
calculations and, of course,

1542
01:04:37,430 --> 01:04:39,170
the more in-depth models.

1543
01:04:39,170 --> 01:04:42,390
The only place where you can
have some wiggle room to argue

1544
01:04:42,390 --> 01:04:45,600
is whether or not CO2 actually
influences the climate.

1545
01:04:45,600 --> 01:04:47,540
And for that, there
are a number of studies

1546
01:04:47,540 --> 01:04:49,580
discussing that point.

1547
01:04:49,580 --> 01:04:54,340
I would refer you, specifically,
to these here, published

1548
01:04:54,340 --> 01:04:57,580
in Science in 2005, that
discuss historical correlations

1549
01:04:57,580 --> 01:05:00,660
over the last 600,000
years, correlating CO2

1550
01:05:00,660 --> 01:05:05,110
and mean global temperatures
based on oxygen isotope

1551
01:05:05,110 --> 01:05:08,900
ratios containing gas bubbles,
for example, in ice cores.

1552
01:05:08,900 --> 01:05:11,510
So I would say if you're
arguing whether or not

1553
01:05:11,510 --> 01:05:14,120
we're having an influence
on our atmosphere,

1554
01:05:14,120 --> 01:05:17,560
I would say that is a
difficult position to take.

1555
01:05:17,560 --> 01:05:20,409
The only room that I would
give you some room to maneuver

1556
01:05:20,409 --> 01:05:21,950
would be if you
said, well, you know,

1557
01:05:21,950 --> 01:05:24,440
CO2 really isn't that
bad in the atmosphere,

1558
01:05:24,440 --> 01:05:26,205
despite what our
infrared absorption data

1559
01:05:26,205 --> 01:05:27,580
seems to indicate,
that it really

1560
01:05:27,580 --> 01:05:31,220
does absorb infrared
light and reemit it.

1561
01:05:31,220 --> 01:05:34,800
So that's what I have to
say about the climate, which

1562
01:05:34,800 --> 01:05:37,592
is a huge motivator for a lot
of people taking the course.

1563
01:05:37,592 --> 01:05:39,800
And you're welcome to talk
about that in more detail,

1564
01:05:39,800 --> 01:05:42,420
but I'd really love to keep
this focus on the technology,

1565
01:05:42,420 --> 01:05:43,390
by and large.

1566
01:05:43,390 --> 01:05:46,590
And for that, I'd like to hand
out these background assessment

1567
01:05:46,590 --> 01:05:48,550
quizzes for each of you.

1568
01:05:48,550 --> 01:05:52,160
Please take a few moments to
fill these out-- just pass them

1569
01:05:52,160 --> 01:05:55,130
back-- so we can learn
more about your interests.

1570
01:05:55,130 --> 01:05:58,110
And what I'll also
do is pass around

1571
01:05:58,110 --> 01:06:00,140
this little solar
module, right here,

1572
01:06:00,140 --> 01:06:03,470
so you can get a sense of what
a small little solar cell looks

1573
01:06:03,470 --> 01:06:04,760
like up close and personal.

1574
01:06:04,760 --> 01:06:06,890
Once you're done, feel
free to come up and take

1575
01:06:06,890 --> 01:06:09,205
a look at the solar module,
right here, as well.

1576
01:06:09,205 --> 01:06:11,040
And thanks.