First Lecture Powerpoint Notes by liuhongmeiyes

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```									Physics 162                                                   Winter 2007

The Big Picture

    We use a heck of a lot of energy
 primitive society used < 100 W of power per person

 our modern society burns 10,000 W per person

 surely not in our homes! Where is this energy going?

    Energy availability has enabled us to focus on higher-level
issues as a society
 art

 Science

 entertainment

 home shopping network

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Physics 162                                                 Winter 2007

Once upon a time…
    Long ago, almost all of our energy came from food
(delivering muscle power), and almost all our energy went
into securing food for ourselves
    Enter the work animal, supplementing our muscle power and
enabling larger-scale agriculture
    Later we burned wood to run boilers, trains
    150 years ago, muscular effort and firewood provided most of
our energy—and today this is less than 1% of the story
    Today, more energy goes into growing/harvesting food than
comes out of food! (is this bad news for biodiesel??)

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Physics 162                                                                    Winter 2007

The Global Energy Scene
   Global energy production is about 400 QBtu/yr
 a QBtu is a quadrillion Btu, or 1015 Btu

 so about 41020 J per year

   U.S. share is about one fourth of this (100 QBtu or 1020 J)

   1020 J/yr = 31012 W (do the calculation!)
 divided by 300 million people (3108) = 104 W per
person (10 kW, as stated above)

We’ll talk about units next week. 1 Btu is the energy required to raise 1 pound of water by
1oF. There are about 1000 Joules (J) in a Btu. A Watt (W) is a measure of power, or energy
per unit time, and 1 W = 1 J/s. A 100 W light bulb uses 100 J of energy each second.

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Physics 162                                                                                                                                  Winter 2007

The Great Energy Disparity
30,000
Switzerland
Gross Domestic Product (GDP): \$ per capita

Sweden
Japan
Iceland      Norway

Germany                      United States
Italy           U.K.
Belgium

10,000

Many countries in the world lie in this quarter-circle!!

1989 data; Reproduced from
Poland                                             Fig. 1.3, Ristinen and Kraushaar
Cuba
India
0                     10              20                   30                40               50                 60
Energy equivalent barrels of oil per capita per year
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Physics 162                                      Winter 2007

Now on a Logarithmic Scale

• More Countries

• Fills in the gaps

• 1971 data

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Physics 162                                                        Winter 2007

A note on graphs: log vs. linear
    Many graphs in the book are on logarithmic scales
    This condenses wide-ranging information into a compact
area
    Pay attention, because you could warp your intuition if you
don’t appreciate the scale
    Log scales work in factors of ten
    A given vertical span represents a constant ratio (e.g., factor
of ten, factor of two, etc.)
    An exponential increase looks like a straight line on a logarithmic
scale

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Physics 162                                                                                     Winter 2007

Example Plots

Exponential plot is curved on linear scale, and straight on a logarithmic scale

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Physics 162                                                                       Winter 2007

Aside: Exponential Growth and the Rule of 70 (or 72)
If some quantity, the price of oil say, increases by 10% per year, how many years does it
take for the price to double?

10 years x 10%/year = 100% = doubled price: correct???

No, because the increase compounds (as in your savings account or, maybe more
appropriately for today’s college student, on your credit card)

Say the price of oil is \$50/barrel this year and it increases by 10%/year. Prices in
following years:

0    \$50
1    \$55
2    \$60.50                                 Rule of 70 (or 72):
3    \$66.55
4    \$73.21                Doubling time = 70 years/annual % growth rate
5    \$80.53
6    \$88.58
7    \$97.44
8    \$107.18
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Physics 162                                 Winter 2007

Evolution of Energy Sources

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Physics 162                                               Winter 2007

U.S. Consumption in 1996
Source         Amount          QBtu    Percent   1018 Joules

Coal           1.00109 tons   20.99   22.3%     22.1

Natural Gas    21.91012 ft3   22.59   24.1%     23.8

Petroleum      6.14109 bbl    35.72   38.1%     37.7

Nuclear        681109 kWh     7.17    7.6%      7.56

Renewables     695109 kWh     7.39    7.9%      7.80

Total                          93.81   100.0%    99.0

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Physics 162                                                                                        Winter 2007

The Fall of the Work Animal
     Used to rely completely on animals
for transportation
     Trains entered the picture in the
mid-1800s

Average Horsepower/person in the US
     Cars entered the scene in a big way                                                   automotive
around 1920
     World has never been the same
Nonautomotive
     Work animal fell off the map around                                                          inanimate

1940
     Today automotive is over 95% of
the story

work animal

Year

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Physics 162                                                Winter 2007

How much does this cost us?
   Presently in the US we use the energy equivalent of ~60
barrels/year/person

60 barrels/yr x 42 gallons/barrel x \$2.80/gallon = \$7056/year
= \$19.30/day
    Total spent in US = \$7056/year * 290,000,000 ~ \$2T
~ 20% of US GDP

   This does not include the economic and social costs of ongoing
instability in oil-producing regions of the world . . .

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Physics 162   U.S. Consumption vs. Production Winter 2007

policy change

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Physics 162                             Winter 2007

Where is our energy produced, and of what flavor?

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Physics 162                                                  Winter 2007

Lessons
    Our energy use is completely dominated by fossil fuels, with
only about 15% coming from nuclear and hydroelectric
 hydroelectric is the only truly renewable resource of the two

    Part of our enormous appetite is due to the expanse of our
country: transportation is important
    Space heating is also an issue in a country where detached
houses are the rule
    Any industrial society (at our current scale) is going to have a
large demand for energy
    Our use of energy is more efficient than it could be!
Conservation measures since the 1970’s have allowed energy
usage to increase more slowly than the growth of the GDP.

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Physics 162                                                                                        Winter 2007

Thanks to a lifestyle invented by your grandparents and
perfected by your parents generation, we live in a
special time and place…
                    We use almost 100 times the average amount used by the world ( per
person)
                    This phase has only lasted for the last century or so
                    Most of our resources come from fossil fuels presently, and this has a short,
finite lifetime and using it comes with potentially serious environmental
consequences.
Fossil fuel usage

Reproduced from Fig. 1.2,
Ristinen and Kraushaar

0      500    1000    1500    2000     2500   3000       3500         4000
year
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Physics 162                                                            Winter 2007

Global Energy: Where Does it Come From?
Source                 1018 Joules/yr      Percent of Total
Petroleum*                              158                   40.0
Coal*                                   92                    23.2
Natural Gas*                            89                    22.5
Hydroelectric*                         28.7                   7.2
Nuclear Energy                          26                    6.6
Biomass (burning)*                      1.6                   0.4
Geothermal                              0.5                   0.13
Wind*                                  0.13                   0.03
Solar Direct*                          0.03                  0.008
Sun Abs. by Earth*                   2,000,000       then radiated away

* Ultimately derived from our sun                    Courtesy David Bodansky (UW)

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Physics 162                                                     Winter 2007

Gas costs less than Perrier ! What’s going
on here?
    We spend about \$19/day, or \$7000/yr per person on energy
in the U.S.

 saves us much more than 20% of our time (labor-saving
devices, transportation, etc.)
    But we’re running through our fossil fuel resources at a
phenomenal rate
 let’s see if this lasts even another hundred years!

    The ‘third world’ is increasing its use of energy resources as it
    Our world will see a profound change in the next century as
we adjust to a world without gasoline
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Physics 162                                                    Winter 2007

Still fuzzy on the concept of energy?
    Don’t worry—we’ll cover that in great detail in the coming
weeks
    Energy is defined as the capacity to do work
    But what is work?
 we’ll get to this shortly

    At some level, I* don’t know what energy is: why there is
such a thing, why it’s conserved, where it all came from, etc.
 these are deep and interesting questions that some
physicists try to understand

Any questions???

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Physics 162                                                            Winter 2007

How about a question to work on right now?

The Toyota Prius, one of the early and increasingly popular hybrid vehicles, has a
base list price of about \$22,000 in 2006, about \$4000 of which pays for the
electric motor, batteries, second drive train, etc. The feds say the average
mileage is about 47 mpg. An approximately comparable non-hybrid Toyota
called the Matrix averages about 33 mpg. Assume a Prius with a regular
internal combustion engine would get the mileage of a Matrix.

With gas costing about \$3.00/gallon, how many miles would you have to drive
before the savings on gasoline make up for the \$4000 you had to pay to buy a
hybrid?

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Physics 162                                                           Winter 2007

To drive one mile with the Prius costs

\$3/gal = \$0.064/mile
47 miles/gal

To drive one mile with the Matrix costs

\$3/gal = \$0.091/mile
33 miles/gal

Every mile drive we save \$0.091 - \$0.064 = \$0.027/mile on gas. To save \$4000 we
need to drive
\$4000/(\$0.027/mile) ~ 148,000 miles

At 12,000 miles/year, that’s over 12 years. So, each year we recoup about \$300-400
of the initial \$4000 investment.
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Physics 162                                                                   Winter 2007

But wait, it’s worse than that . . .
The Prius has two drive trains and a battery pack. Maintenance costs will likely be
higher than for a conventional engine. There is not very good data on that yet.

The lifetime of the NiH battery pack itself is an issue. Toyota now offers an 8-year
warranty on the battery, with a current (dealer) replacement cost of about \$3000.
This should be included in the maintenance costs, too. At a rate of \$300-
400/year, that will consume most of the savings from higher gas mileage.

It’s possible that a current model hybrid will never actually pay for itself - that it is
impossible to recoup the initial investment plus ongoing maintenance costs.
Toyota knows this and is trying to bring the cost of hybrid technology down.
Market forces and economy of scale will make this happen (some).

Federal subsidies also change the equation by lessening the burden on individuals by
spreading the cost across all taxpayers. Is this a good investment?

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Physics 162                                                              Winter 2007

But what about CO2 emissions and Global Warming?
Hybrids make us feel good - very environmentally conscious - since they emit fewer
greenhouse gases. But the cost of any modern contrivance is heavily dependent on
the cost of energy: our lifestyle is very energy intensive. Since a hybrid costs more,
it must take more energy to produce than a regular internal combustion engine.
How many miles must one drive before this ‘environmental cost’ is recouped?

I don’t think the data exist to answer this question very accurately: it depends on
what fraction of the extra \$4000 was spent on energy. If 25% of the added cost
were energy, then you need to drive about 40,000 miles before the Prius become
really ‘green’.

It’s not really clear what all needs to be included. Should we include some fraction
of the energy used by Toyota employees to get to work every day? It’s a tough
question.

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