- Welcome to Wednesday
Nite at the Lab.

I'm Liz Jesse, the
media specialist

for UW Science Outreach.

On behalf of Wisconsin
Alumni Association,

Wisconsin Public Television,
UW Madison Science Alliance,

UW Madison Biotech Center,

and UW Extension and
Cooperative Extension,

thanks for coming out to
Wednesday Nite at the Lab.

We do this every
Wednesday, 50 times a year.

Tonight, it is my pleasure
to introduce Andrea Hicks.

Andrea grew up in
Dearborn, Michigan,

which I just found out tonight
is right outside of Detroit.

I don't know Michigan
very well, apparently.

She completed her PhD
in civil engineering

at the University of
Illinois at Chicago

and then completed a postdoc

at the Institute
of Environmental
Science and Policy.

Her research at the
UW, and maybe beyond,

focuses on the
environmental, economic,

and social impacts
of new technologies

compared to conventional
counterparts.

So I kind of thought
of this like,

we don't use Keurig at home

because I know that
conventional brewing is better.

So maybe that's kind of
what she talks about.

Tonight, she's going
to be focusing,

and we're going to be
talking a little bit about

the history of artificial light

and how it relates
to sustainability

of today's emerging
lighting technologies.

So, here we go with
the LED paradox.

Please join me in
welcoming Andrea Hicks.

[audience applauding]

- Thank you for
that warm welcome.

Can everyone hear me?

Nods? Okay.

So, first, I'd like to
thank the organizers

of Wednesday Night at
the Lab for allowing me

this platform to
present some work,

and to thank all of
you for being here

to learn about the LED paradox.

So, a little bit about
what we'll go over tonight.

We'll look at what
is artificial light?

What's the history of
lighting in Chicago?

It's a major city
not so far from here.

It's a nice place to start.

Our consumption of light,

what technologies changes mean,

Jevons paradox, and
novel consumption.

So, what is artificial light?

This is the point
where everyone's like,

artificial light,
it's in this room.

We have it.

I'll point to it.

So, to take it a more
philosophical way,

it renders the
invisible visible.

It's safety.

It's traffic control signals.

I'm from civil engineering,

so I have to throw in
some examples like that.

It's street lights at night
that encourage people to walk.

It's productivity.

Without artificial light,

there would be no night
shift at hospitals.

There would be no
third shift at plants.

And it decouples us from
the patterns of the sun.

We're no longer
dependent on the sun

as our sole source of light.

And here's a quote
from Harold Platt,

who wrote The
Electric City in 1991,

and that centers on Chicago
and it's history of light.

We'll talk a little
bit about his book

to give some background context.

"But the bright
lights of the city

quickly became both
a status symbol

and a physical
manifestation of progress,

wealth, and amenities."

So, light isn't just light.

It's a symbol of progress.

If you think about a cartoon,

what happens when
someone has an idea?

They get the light bulb.

So it's more than
just illumination.

So, this is a timeline
of lighting in Chicago.

In 1878, Barrett demonstrated
Brush's arc lamp.

And within a decade, there
are almost 7,000 arc lamps

built and operated in
the city of Chicago

at an annual cost of
a million dollars,

which is a lot.

"And so the electric
suppliers..."

This is also from Platt's book.

"...faced a consumer
market with no bounds."

And this is a question that
will permeate our talk tonight.

What is saturation of light?

When do we have enough light?

How much light is
too much light?

But there were some
problems with this arc lamp.

It was a fire hazard.

It was big.

You couldn't use it in
a residential setting.

So, in 1880,

or 1879 depending,

Thomas Edison invented the first

marketable incandescent bulb.

And Chicagoans suddenly
had this choice,

what kind of light do I want?

Do I want electric light?

Do I want a kerosene lamp?

Do I want to go by the
old gas lighting standby?

And so these incandescent bulbs

were much safer than arc lamps,

and could be easily
scaled to residential use.

But really, electric lighting

was only for the
wealthy at first.

It wasn't for the
everyday person.

But, at the same point,
there was this radical shift

in psychological perception
of interior lighting levels.

And this goes back
to our question

of how much light
is enough light?

How much light is
too much light?

So what had seemed
all right before

was dark, gloomy,
and depressing.

So already we're
craving more light,

because we have more light.

Now, in 1893,
Chicago's World Fair,

Chicago was dubbed
the city of light.

And, by 1912, about half of
Chicago's middle class families

had electricity in their
homes and electric light.

So, look at that quote again.

It's a status symbol.

It's progress, it's
wealth, it's amenities.

Light is more than
just illumination.

It means we're moving forward.

And some photos from
the World's Fair.

They're not great, but,
you know, early 1900s.

And it was amazing.

We had all of this light.

So, before we start to talk
about the actual consumption

of light, some
little background.

One unit I'll talk a lot
about today is a lumen,

and a lumen is an
international standards unit

for the measurement
of brightness.

And another way
to think about it,

it's the light of one
candle one foot away.

Although, I suspect most
people don't compare

their light bulbs
to candles at feet.

Maybe people do,
and that's okay.

And so it's a measure
of light output,

and it's a nice way
when we talk about

different efficiencies of
lighting to compare them.

About 800 lumens is about
a 60-watt incandescent,

which translates
into CFLs and LEDs.

So, this we're already
using our lumen.

This is teralumen hours per year

of light consumed in
the United Kingdom.

It's a study by
Tsao et al in 2010

that looks at the
consumption of light

over time and changes
in technology.

So here we are
transitioning from candles

to gas, to kerosene, and
eventually to electricity.

And the whole time we're
consuming more light.

Yes, the lines go up,
consuming more light.

And it's largely, this
work by Tsao et al,

was largely based
on some earlier work

by Fouquet and Pearson,

that looked at the
price of lighting.

So, how much per
million lumen hours?

We're using those lumens again.

So what's the cost of light,

as we transition over
time from gas light

to kerosene light
to electric light?

And the point is,
it's been going down,

over time in the UK
during this study,

which ends at about 2000.

I see people talking,
this is a good sign.

So okay, so we've
been using more light

and the cost of light
has been going down,

at least in the UK.

So, the Energy Information
Administration very recently

put together a chart
of energy consumption

in the United States
starting from 1776,

which is nice.

Usually you can't find data,
at least in engineering

when I'm looking for
something from the 1700s.

And, okay, so we
consume more energy.

This is in quadrillion
British thermal units.

And our energy
consumption broken down by

what we're consuming.

And over time, we've
transitioned from coal

to more toward natural gas
and petroleum products.

So, okay, the question is,

how much energy do we
use for artificial light?

Is it a lot?

Is it a little?

Would we even see
it on this graph?

So, when I started
studying this,

and the first data is
from maybe around 2001,

we were using 8.2 quadrillion
British thermal units

of electricity for lighting
in the United States.

So, if you take a look,

that is a little bit higher

than nuclear energy
consumption in 2015.

So, based on the
premise of this talk,

do you think it's
gone up or down?

Some up?

Shall we raise hands?

Who thinks it's gone up?

Okay.

Who thinks it's gone down?

- [Audience Member] Are
you asking input or output?

- Total energy consumption.

- [Audience Member] So
the energy input into it.

- Right.

And who doesn't know?

[audience chuckling]

That's okay.

So it's actually gone down,

which seems a little
counterintuitive
with a talk called,

The LED Paradox and
the Rebound Effect.

But, in 2010,

about 7.5 quadrillion
British thermal units

were devoted to
electricity for lighting,

and in 2013, 6.9 quads,

which comprised about 18% of
total US electricity usage.

So it's gone down.

Why are we talking about
energy rebound and the paradox?

We'll get there.

So, let's think a little
bit about efficiency.

And, here, we've got a
compact fluorescent lamp,

which was invented
or inspired in 1973

during the oil crisis,

and in 1974, made by an
engineer at General Electric.

And in the 1980s, CFLs were
introduced to the public.

So, who remembers that?

Okay.

Maybe half a dozen people,
that's a good start.

And, but there
were some problems.

They were expensive.

They were about
$25-$35 per light bulb,

and that number
is a little fuzzy,

because they were
often subsidized

by the electrical utilities.

They're blue.

They failed early,

and they had inconsistent
light input, output.

Not well received.

So, as we talk about
lighting technologies,

let's talk a little bit
about how they work.

So in an incandescent,

which is sort of
what we think of

as the conventional technology,

an electric current runs through
the filament, heating it,

and then it starts to glow
and light is produced.

But what about a CFL?

So, in a CFL, it has this
curlicue shape, right?

And an electric current
goes through the argon

and a small amount
of mercury vapor,

which is stored in the curlicue.

That generates invisible
ultraviolet light

that excites a
fluorescent coating,

which is on the outside,
and produces light.

This is from the friendly
folks at Energy Star.

So, what about LEDs?

So, LEDs, or light
emitting diodes,

and we'll talk about how
they work in a second,

are considered an
enabling technology,

because they enable other
products and other technologies

that would not be
possible without them.

And this is a graph

from data mined from
the US patent database

on the percentage of light
emitting diode patents per year,

applications per year,

broken down by the
application's application.

So, what is the goal of this?

And you can see LEDs for
illumination are near the top.

And illumination is what
we primarily thought of

for what we do with light.

You light a candle
to have light.

You turn on an incandescent
light bulb to have light.

But with LEDs, we start
to have other options.

We have liquid crystal displays.

We have manufacturing,
communication,
military, medicine.

There's all, and novelties,
which we'll talk about later.

There's some exciting novelties.

And so they have all
of these properties.

They don't get really
hot, they're small.

You can enclose them,
and they can get wet.

And the first red LED
came about in 1961.

So they've been around,

but we're now just
starting to use them

for residential
lighting applications.

So, how do LEDs work?

And I enjoyed this.

This is from howstuffworks.com.

And forgive me if
you've spent time

studying quantum mechanics.

This is just a very
brief overview.

So, LEDs are semiconductors,

and current flows through the
diode, and the electrons move.

There's holes that
exist at a lower energy

and there's free electrons,

and when the electron moves
to a lower energy level,

it emits a photon,
which is light.

Very brief overview.

And that is,

this a red LED,

but it doesn't have
to be a red LED.

You have your semiconducting
material embedded in the lamp.

Okay, so we have LEDs.

They work a little
bit differently.

Does anyone have an LED?

At home?

[audience murmurs
responses]

Okay.

There's a few folks.

How about an LED
with you right now?

Okay, so there's
people with LEDs.

Are there people with
smartphones right now?

Okay.

So, these exist, we have them.

There are many in this
room at this moment.

So when we start to look
at the lighting market,

and this is from the US
Department of Energy in 2012

based on their 2010 data.

This is annual
electricity consumption

in terawatt hours per year,

broken down by sector.

And the focus today
will be residential.

And residential,

okay, so it's primarily,
in 2010, incandescents.

Do you think that's changed?

Maybe?

[audience responds]

So it has at some
people's houses for sure.

And other people's houses,
we'll talk about too.

But, overall, in 2010,

we used about 700 terawatt
hours of electricity

annually for lighting.

And although residential
isn't the biggest sector,

it's interesting
because you're starting

to deal with consumers and
their individual behaviors.

Do you think people demand
more light over time?

Maybe?

So, in 2001, the average number

of sockets per household was 43.

Do you think that's gone up?

- [Audience Member] Yeah.

So, as of 2010,
the average is 51.

And that's one way of
consuming more light,

that you have more light
bulbs in your house.

Now, there's been some
evolutions in technology too.

And this starts at 2011
and goes through 2016.

And we've got pictures
of an incandescent

and a CFL and an LED.

And these are residential
screw-in type replacements

with a lumen output
of about 800.

So, 60-watt bulb equivalents.

So we're comparing
apples to apples mostly.

So, in 2011,

an LED was $33.90,

which seems like a
lot for a light bulb.

And if we go to 2013,
okay, we're at about $13,

and today we're at about $4.50.

And incandescents have
dropped a little bit.

There's some other factors at
play that we'll talk about.

And CFLs have dropped
a little bit too.

The energy consumption

has steadied for the
conventional incandescent,

and it's gone down
a bit for an LED,

going from 12 watts
to about eight.

There's also a huge difference

in the lifetimes of these bulbs.

So the lifetime
of an incandescent

is about 1,000 to 2,000 hours.

And a CFL?

About 8,000 to 12,000.

But an LED is about 25,000.

So, in theory, you
could have a light bulb

that lasts a really long time,

even if it costs a little more.

And it should be
more efficient to run

because it consumes less energy.

So then everyone
should buy them, right?

No? Maybe?

So, we talked a little
bit about the cost,

and this is a chart
looking at ownership cost.

So the ownership cost
is the purchase price

plus the use price
normalized over the lifetime.

And, in this case, this
is all in 2010 dollars.

And it looks at the
ownership cost of light

from 1800 to about 2011,

where we're
transitioning from fire,

which are things like
candles, kerosene lamps,

to incandescents, fluorescents,

high intensity discharge,
LEDs, and CFLs.

So the ownership cost
has been going down,

much like we saw
in that one chart

looking at the United Kingdom,

where they were transitioning
from gas and kerosene

to electricity.

And there's some other
factors at play also.

So, the Energy Independence
and Security Act of 2007,

who has heard of it?

Four people.

All right, we're doing well.

[audience laughing]

Who has heard somewhere on
television or the internet

about someone trying to
ban incandescent bulbs?

All right, we're talking
about the same thing.

So, the Energy Independence
and Security Act of 2007

took effect between
2012 and 2014.

And it's not a ban,
per se, on bulbs,

but it requires increasing
of the efficiency

of incandescents.

So, if you look, we've
got this EcoSmart box,

and it says it's a
better incandescent.

So it's formerly a
60-watt incandescent,

and what they mean is it
produces about 800 lumens.

But now it requires 43 watts,

so we've made an
efficiency gain.

You also start to see things

like the lighting
facts per bulb,

which, does this remind
anybody else of food labels?

[audience laughing]

That's why I'm like,
calories of brightness.

So I can tell by
looking at this,

the brightness is
about 800 lumens,

so it's a 60-watt
equivalent bulb.

And the energy used
is about 13 watts,

so it's probably a CFL.

Or it could be a
really early LED.

And they rate the lifetime,
and they say, okay,

I'll use this for
three hours a day,

and it will last for nine years.

So it's a way of
distilling information.

But here's the question,

when you heard about
the ban on bulbs,

did anyone start
ordering incandescents?

[audience laughing]

It's okay, two honest people.

All right.

So, this is David Brooks
of Just Bulbs in Manhattan.

And I got this from
the New York Times,

where he's commenting
that he has one customer

who's ordering thousands and
thousands of incandescents,

because she never wants
to be without them,

and to please not
tell her husband.

[audience laughing]

So, he'll be surprised
one day when he finds

their storage unit of
incandescent bulbs.

[audience laughing]

But, So we have
interesting behaviors

that come about too that,

I do not want a more
energy efficient bulb,

I'm going to use this
incandescent forever.

Okay.

That's part of
evolutions of technology.

So whenever I talk about CFLs,

the question of
mercury comes up.

Who here knows that
a CFL has mercury?

All right.

How much mercury do you think?

So, I see some people
saying a little bit.

So, it's about,

currently they have
about five milligrams

of mercury per bulb.

And, okay, is that a lot?

Is that a little?

Should we care?

There was one study that
came out several years ago,

where they said, okay,

so there's five milligrams
of mercury in the CFL,

but it's more efficient
than an incandescent.

So what if I look
at the life cycle

and I burn coal to
make my incandescent,

power my incandescent
throughout the lifetime?

Is that, how does the
mercury balance work out?

And if you move to the CFL even
though it has mercury in it,

you're saving mercury through
the gains in efficiency.

So you're coming out ahead.

Now,

I've given talks similar
to this enough times,

that there are some good
anecdotes that come up.

Who here has heard
of Mercurochrome?

[audience laughing]

All right.

So, I was giving this talk once

and I always, almost always,
got attacked by someone

for the mercury content in
CFLs and they're terrible

and they're going to kill
us all and [muffled].

I was like, okay.

So that's what I was expecting.

And he comes up

and he starts telling
me that he doesn't think

the mercury is a big deal.

Okay.

Good, someone's finally
not attacking me over this.

And so then he tells me

about something
called Mercurochrome,

which, help me if I'm wrong,

is something at one point
we used to dab on cuts

to sort of clean
them and heal them?

I was like, oh, okay.

So then he proceeds to tell me

that similar to our
friend in New York

hoarding the light bulbs,

that he's hoarded Mercurochrome.

[audience laughing]

And he has boxes and
boxes full of this,

that he still uses it today,

mercury is not a big deal, and
then he pulls out a bottle.

I was like, okay,

I guess mercury isn't
a big deal to everyone.

And that's a really
great anecdote

to keep next time
I talk about this.

So, just a side note.

So one way to think about this,

and I alluded to
this a little bit

when I was talking about
the mercury in a CFL

versus if you burned coal for
the lifetime of incandescent.

So, something called
life cycle assessment.

Has anyone heard of it?

Okay, three or four
people in the back.

That's a good start.

So life cycle assessment
is a systematic tool

for looking at the
environmental impact

of a product or process
throughout its lifetime.

So you're breaking it down

into components
like raw materials.

What's the environmental
impact of my raw materials?

What is the environmental
impact of my manufacturing?

What about the use phase?

So in this case, when I
take the light bulb home,

I put it in the
socket, I turn it on.

And what about end of life?

What happens when it's done?

So there's some Coca-Cola
bottles on this slide,

and that's because the
first documented life cycle

assessment was actually done
by the Coca-Cola Company,

I believe in the 1960s.

And they were curious about
the energy consumption

for their packaging,

because energy means money.

And they wanted to know what
kind of packaging should I use?

What should I put my soda in?

Or I could say pop
because I'm from Michigan.

And so the study results
were never released,

but that's sort
of what we herald

as the first life
cycle assessment.

So, to put that in perspective,

we can look at one.

This is from the US
Department of Energy

for an incandescent light bulb.

And I've got the electricity
generation mix on the side,

because that's a
valid point in this.

And, okay, so you have your
materials and manufacturing,

it's a very small
part of the life cycle

environmental impact.

And the really big
part is the use phase.

So when you take your light
bulb home and you use it.

And on the bottom we've got
all of these categories.

So you see things
like global warming.

And global warming,

has anyone heard of an
environmental footprint?

Right, so these are
different units to do.

So global warming,

you're thinking about
carbon dioxide emissions.

Nitrification you're
worried about nitrogen.

And we like to look at a suite,

because you might find
that while something

is very good in one category,
it is very bad in another.

And you need to think about
the environmental trade-offs.

So, it's long been established

that the environmental impact
for incandescent lighting

is during the use phase.

So the question was,
what about these new,

more energy-efficient lights?

They're more energy efficient,

so they should have
less use phase impact,

but they require
more raw materials.

So how does this balance out?

So, we can look at a
compact fluorescent,

and the use phase
is still dominant.

Although, some phases
like non-carcinogenics,

we start to see more in
materials and manufacturing.

And the same is true when
we start to think about

light emitting diodes.

And in categories like
non-carcinogenics,

the bigger manufacturing
and materials cost

has to do with the heat syncs

that go into making
light emitting diodes.

But we're going to go back.

So we know the use
phase is dominant,

and we know the ownership
cost has been going down,

so it costs less to use these.

So, who's ever heard of
William Stanley Jevons?

All right, I got like
three or four people again.

So, he is an economist
from the 1800s,

and he was looking at coal.

And he said when the efficiency
of coal usage increases,

we're actually using more coal,

which was this big
revolutionary idea at the time.

And some people would say
it's revolutionary today.

If it's more efficient,
how are we consuming more?

So who thinks we do?

Discounting the
title of this talk,

of energy efficiency
and the rebound effect.

So, there was a
study out of MIT,

that looked at
multiple industries

over multiple time periods
and geographic scales.

And they said,
okay, we can look at

the annual average
change in efficiency.

So that's your delta E over E.

And we can look at the
change in consumption.

And if the change in consumption

is more than the
change in efficiency,

we're going to out-consume
our benefits of efficiency.

So, if you look at
the last column,

with delta Q over Q
and delta E over E,

all of the numbers
are bigger than one,

which means that over the
time scales they looked at,

we out-consumed all the
benefits of efficiency

from a consumption standpoint.

And they qualified this though.

They said in the short-term,

you might see savings
because increased consumption

hasn't caught up with your
increases in efficiency.

But on the long-term,

we haven't seen this in
any of these industries.

And they took a large
spread of things

like passenger air travel,
motor vehicles, refrigeration.

So, one question would be,
how do you consume more light?

Do we buy more lights?

So, suddenly the cost of
lighting has gone down,

I'll buy more?

I buy brighter lights.

This goes back to when
we were talking about

electric lighting in Chicago,

where they were saying what
had once seemed adequate

for indoor lighting,

suddenly seemed dim and dark
and hopeless and depressing.

So let's have more light
because we can have more light,

and we think we need more light.

You could leave the
lights on longer.

Maybe you never turn
off your lights then,

because they're efficient.

It's an extreme example,

but it's possible.

And the more times I've
given a talk like this,

someone will say, no,
I would never ever ever

leave my lights
on longer, never.

And then they'll
start telling me that,

you know, I bought this LED.

I'm like, great,
you bought an LED.

And I decided to
put in on my garage,

and now I leave it on all night,

because it's so cheap to run.

Okay.

Well, that goes back to our
safety, to what is light.

And there's some
utility of light

that you can't really
measure for lumens per watt.

It's what is safety,
what is security?

So, there, this is
results from a study

that looked at how long do
people leave their lights on.

And this is a national survey

that looked at five or six
major metropolitan areas.

So there's a spread.

The average is 8.9 hours
per day plus or minus 5.1.

Okay.

And the most commonly
occurring value was six.

However, if you look,
there are people

who leave their lights
on one hour per day,

and people who leave their
lights on 24 hours per day.

So, looking at this, I would say

the population is heterogeneous.

And I get nods.

So, they're different.

And we can look at questions.

This is a slightly older study.

So, what's the highest price
you would pay for an LED?

And at the time of the
study, an LED was $33.99.

And most people said
they would pay about $17.

Does anyone remember
what we're at now?

Right, about $4.50.

So, in theory, based on this,

we should see people
buying a lot more LEDs.

But populations
are heterogeneous,

people interpret
things differently.

And this was a really
interesting question
from the survey,

where we asked, we
framed the same question

three different
ways, essentially.

And we called it light bulb A,

light bulb B, and light bulb C.

So A is an incandescent, B
is a CFL, and C is an LED.

So, we framed asking people,

so it costs so many dollars

and it lasts for so many hours,

what would you pick?

And then we asked
the same question,

it costs so much

and it would cost you
this much to run per year,

which would you pick?

And then we also said, okay,

it costs this much to purchase,

and for the same amount of money

you could drive so
many miles per year,

which would you pick?

So across all three,
about half the respondents

said they would pick
option B, the CFL,

and they didn't
know it was a CFL.

I'm sure if they Googled it,

they would have
known it was the CFL.

But you see this movement
between question 18,

and then when you look
at question 19 and 20 of,

LED versus incandescent.

So there's some interesting
issues of perception

of what is efficient,
what should I buy,

how should we word things.

So, how should we model this?

Has anyone heard of
an agent-based model?

Maybe a social
scientist out there?

So, agent-based modeling

has roots in the
social sciences.

And it's a method commonly
used to model individuals.

And it's really good at that,

and it's been used to
model things like fish,

geese flying in a V,
sheep, and people.

But there's more, those
are just a few examples.

And the idea is you have
all these individuals

following some set of rules,

seeking to maximize some
utility, and what do they do.

So there's this question of,

could we apply this to lighting?

What do people do

if they can pick energy
efficient lighting?

So the result is this nice
chart for an agent-based model,

where you've got some population

that we informed
with our survey data,

and if their bulb is burned out,

they go and buy
a new light bulb.

Okay, that's a good assumption.

If it burns out,
I'll buy a new one.

They use some probabilistic
utility to decide

which light bulb
based on the fact

they're a heterogeneous
population.

So, different people
value things differently.

And then, if their
bulb is more efficient,

they have this question of,
do they consumer more light?

And I was informed
with the survey data

that some people will
consume more light.

And the question of how much,

is sort of this interesting
tipping point we looked at.

So okay, we've got
some sort of model.

What do we know about the
data we put in the model?

So, one question on the survey
that went to this model,

was your environmental
mindfulness,

or your environmental attitude.

How environmentally friendly
do you think you are?

Do you care?

And this is looking at

statistically
significant correlations,

for people who thought they
were extremely mindful.

And, okay, so they
want to save energy.

They're concerned about
environmental friendliness

of what they buy.

They apparently were
not that interested

in the quality of light,

or how long their
light bulbs lasted,

which I thought was interesting

because you would worry about,
well I'm throwing it out.

In the survey, more
than 50% of the people

threw them out and
did not recycle.

Then we have our
average mindfulness.

They're actually worried about
the lifetime of the bulb.

So it's just interesting
to think about

the heterogeneity
of the population.

And, okay, so one way
you can think about

making these agents in a model,

is they were trying,

how would they
pick a light bulb?

So, in order to use a
probabilistic utility,

the question was, what do
you think is most important,

when you pick a light bulb?

Because we all go
and buy a light bulb

and we think about this
internally, maybe not formally.

But there's trade-offs.

And so 36% of the respondents

thought saving money as a result

of increased efficiency
was most important.

Only 12% ranked environmental
friendliness as the first.

So yet again we have
a spread of data.

We also said, would you
use more if you adopted

a more energy
efficient light bulb?

Which is crude and
surveys are never perfect.

Every time I talk about
something like this,

people tell me surveys
are never perfect.

And I say yes,
they're not, I know.

So about 50% said they
would use more light.

And we said, okay, well,
how would we use more light?

So, of that, 33% would leave
current lights on longer,

31% would purchase more lights.

And you could do both.

So, we have this model.

We have some scenarios,

predicated on the rebound
effect or Jevons' paradox.

The idea that people
will consume more.

So there's scenarios
with varying degrees of,

if you consume more, how much
more light would you consume?

Because the question
is, when are you

going to erode the savings
gained by efficiency?

So it varies from no rebound,

and we have some
spontaneous adoption

where people say I don't care

that my light bulb's
not burned out.

This LED is so cool, I
must go buy one right now,

which happens.

We're all guilty of that
sometimes with some things.

To scenario eight, which
is extreme rebound.

If you buy a more
energy efficient bulb

and you're that 50%
of the population,

you will leave your lights on
75% longer and buy 75% more.

So, the results aren't
that surprising.

We have our average annual
household light consumption

in mega lumen hours.

So, in the extreme scenarios,

the respondent, you
consume a lot more light.

You'd expect this.

So the question was really,

what does energy
consumption look like?

And in the extreme scenarios,
you consume a lot more energy,

more energy than you
were consuming initially.

So, what does this mean?

So, this is comparing
with some data

from the US
Department of Energy.

In their earlier studies,

they didn't consider
the rebound effect,

but they did consider a 1.75%
annual growth in lit spaces,

due to bigger houses and
expansion of lit spaces.

So, this is comparing
their data, the US DOE,

with the non-extreme
rebound scenarios.

So, in the study we
found that, okay,

we can predict that energy
consumption for light

will drop a lot.

And then eventually
it'll inch back up,

which is what the paper
by [muffled] out of MIT,

that looked at all
the sectors, said.

Unless we come up
with something new,

or we come up with a policy,

we're eventually
going to out-consume.

So this brings up an
interesting question

called the saturation of light.

So what is the limit for light?

Is it constant daylight?

Everywhere, all the
time, outside even?

Is it light of a
certain brightness?

Does the saturation
for light in a room

change depending on
who's designing it?

So we don't know.

And there was a
paper a few years ago

by Tsao et al, that said,

it was a controversial paper.

They got lots of comments.

That said using a
Cobb-Douglas framework,

we don't think we've
reached saturation of light

anywhere in the world.

Okay.

So, going on that,
there's this question of,

what is saturation of light?

What does it look like?

But there's this
question because LEDs

are an enabling technology.

So what if we start
using light and lighting,

for things we never have before?

Or what if we start
using bigger things

we haven't thought of?

So this is looking at
television screens.

So the new flat screens
commonly have LEDs or all LEDs.

TV screens are getting bigger.

In 2015,

52% of television sales

were between 40 and 49 inches,

and 20% was greater
than 49 inches.

So, it's an enabling technology,

we can make bigger televisions.

We're consuming in
ways we hadn't thought.

What about this?

Does anyone recognize this?

So, County Stadium

and circa 1950s, I believe.

So this is a scoreboard.

And County Stadium
no longer exists.

But does the scoreboard in
Miller Park look like this?

No.

So, okay, this might
have had some light,

but it's not some brightly
lit television display.

And here we go.

This is a scoreboard
at Miller Park.

And we've got this black
and orange lighting.

And what about today?

We seem to have
caught Clay Matthews.

So we're using light in ways

we wouldn't have
thought to in the past.

If you would ask
someone in the 1950s,

is this the scoreboard
of the future,

I don't know that
they would have known.

So it's hard to come up
with a saturation for light

and a limit, if we have all
these new ways to use it.

And another example is a book.

So, Silent Spring
by Rachel Carson,

a very famous book credited
with the environmental movement,

talking about the
dangers of chemicals,

which isn't really
a topic of this.

But, okay, is this the only
way to read books today?

No.

All right.

So this is the first Kindle

in, I believe, 2007.

So only 11 years ago.

And both of these are not
backlit, you need light,

but light comes from
external sources,

like for illumination
in the room.

But then we go to something
like the Kindle Fire,

which you can buy today,

or many people probably
bought on Prime Day yesterday.

And you still need light,

but you've got this
backlit screen.

So we're using light in new ways

that we haven't
thought of before.

And I mentioned

that LED is an enabling
technology and novelties.

So we're using ways,

we're lighting things that we
wouldn't have lit before also.

So we've got LED screens,

but how about some pretend
candles that change color?

Or light-up glasses?

Or rope lighting,
which, on the way in,

someone told me they
bought for their garage.

Or what about a light-up shower?

You can buy it with an LED.

And light-up balloons

and snuggly children's
nightlights that don't get hot.

So, it's hard to come up
with this saturation of light

if we have all of these new

enabled technologies
coming about.

So just to think about
conclusions a little bit.

Historically, artificial
light has been about

more than just illumination.

It's progress.

It's wealth.

It's a status symbol.

And there's a potential
to save energy,

if we adopt energy efficient
technology for a while.

But eventually they either
need to come up with a policy,

or we need to come up with
a more efficient technology,

if we're considering
the rebound effect.

What is the saturation of light?

That's a good question.

It depends what we're
coming up with next.

And there are many
novel uses of light,

from children's toys
to light-up showers,

which I don't have.

But, maybe someone does and
that'd be very exciting.

So, with that, I need to thank

the University of
Illinois Institute

for Environmental
Science and Policy,

and the Civil and Environmental
Engineering Department,

here at the University
of Wisconsin, Madison.

And I enjoy this for questions.

[audience applauding]