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High Energy Society
Why do we care about
energy?
What is Energy

Energy is the ability to do work.
• Stuff that enables us to move an object




Faster movement needs more energy
Heavier object needs more energy
We measure energy in Joules (J)
It takes about 200 J to do one deep knee
bend
Other Units of Energy




1
1
1
1
Btu = 1055 Joule
calorie = 4.186 Joule
Calorie = 1000 calorie = 4186 J
kWh = 3,600,000 Joule
Energy and Power



POWER is the rate of using energy.
Something that is powerful uses a lot
of energy quickly.
 Power = Energy/Time
This is a Rate Equation
We measure power in watts (W)
Energy and Power

Doing deep knee bends at the rate of
one every 2 seconds uses energy at
the rate of 100 W.
Energy and Power


Doing deep knee bends at the rate of
one every 2 seconds uses energy at
the rate of 100 W.
It would take the same amount of
energy to do 10 deep knee bends in
20 min as it would in 20 sec, but by
doing them in 20 sec, you use
energy at a faster rate.
Energy and Power



Common unit of power is a kilowatt
(kW). 1 kW = 1000 W.
 Energy = Power x Time
Common Unit of Energy = kWh
(kilowatt-hour)
1 kWh is the amount of energy you
would use if you consume energy at
the rate of 1 kW for 1 hr. (10 people
doing deep knee bends for an hour.)
When you pay your electric bill the quantity
is “kWh”. What are you paying for?
0%
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I’m
B.
I’m paying for
energy
I’m paying for
how fast I use
energy
I’m
A.
Energy and Power


Because a watt is already a rate it is
incorrect to say “watts per hour” or
“watts per year”
1 hp = 746 W
Why do we care about energy?


Energy provides us with
Necessities
• Food, heat, shelter, water

Conveniences
• Dishwasher, automobile, entertainment

The more energy we have available
to us, the more comfortably we can
live
Why do we care about energy?


Energy use is strongly correlated to
standard of living (as measured by
GDP per capita.)
For most of history we could rely on
our own body or animals to do work.
This is a few hundred watts of power
at most.



Today in the US we consume energy
at a rate of 13 kW per person.
You may think of this as having 130
“energy servants” doing work for you
24/7.
Typically less wealthy nations have a
lot fewer “servants”
GDP vs. Energy Use
GDP vs. Energy Use
Trend is Linear
We are doing better on a GDP per
kWh basis.
Energy

End-use energy
• Energy actually consumed
• Cars, homes, factories, etc.

Primary energy
• Fuel energy or energy flow plus
transportation energy
Energy Use By Sector
Electric Utilities
40% (1/3)
Transportation
28% (1/3)
Industrial/Residential
And Commercial
32% (1/3)
Energy Source By Sector
Electric Utilities
Coal (46%)
Transportation
Petroleum (93%)
Industrial/Residential
And Commercial
Natural Gas(52%)
Where
does our
energy
come
from?
Approx
81% from
fossil fuel
Which of the following is NOT one of the
three basic energy sectors in America
1.
2.
3.
4.
Transportation
Electrical
Generation
Industrial
Residential and
Commercial
Heating
0%
1.
0%
2.
0%
3.
0%
4.
The primary energy sector that
uses coal is
1.
2.
3.
Electrical
Generation
Industrial
Residential and
Commercial
Transportation
0%
1.
0%
2.
0%
3.
The primary energy sector that
uses petroleum
1.
2.
3.
Transportation
Industrial
Residential and
Commercial
Electrical
Generation
0%
1.
0%
2.
0%
3.
Oil Supply and Demand
How Much Is There?

Proven Reserves:
• Resource that we know is there
• We can extract it at current prices with
current technology.

We can increase Proven Reserves by
1) Finding new reserves.
2) Improvements in technology
3) Changes in economic conditions

Unproven Reserves:
• We think that it is there based on
testing/experience
OR
• We know that it is there but it is too
expensive to extract with current
technology/economics.

Note: We never totally extract all of
the energy, it just gets too difficult to
get after a while.
How Long Will It Last ?

Simplest analysis is Rate Equation
• Straight-line model

If we know (or can guess) how much
we started with (Q) and we know
the rate we are using it (R) and how
much we have already used (Qu)
Time = (Q-Qu)/R
How Long Will It Last ?



Rate Equation doesn’t take changes
in use rate into account
How long = Amount remaining/Rate
Similar to Simple interest - Interest
on principle only


Poor approximation because it does
not take into account changes in rate
of use.
The demand for energy has been
constantly increasing so rate
equation time is probably too long
Exponential Change


Amount of change depends on
current amount.
Similar to Compound interest –
interest on principle + interest
Year
0
1
2
3
4
5
6
7
8
Amount
$1000
$1100
$1210
$1331
$1464
$1610
$1771
$1948
$2143
Interest
$100
$110
$121
$133
$146
$161
$177
$195
Total
$1100
$1210
$1331
$1464
$1610
$1771
$1948
$2143
Note: Money had just about doubled after 7 years.
If we had just added $100 per year (constant
rate) we would have only had $1700 after 7
years.
Doubling Time
In general, if our percentage growth
per unit time is P (%/unit time) then
the time for our initial quantity to
double is DT where:
DT=70%/P
Example: If P=10%/year then
DT = (70/10)years =7 years


Between 1960 and 1970, US energy
consumption grew by 45%
What is P in the doubling time
expression?
/y
r
0%
10
%
/y
r
0%
9%
0%
/y
r
0%
5%
D.
4.
C.
/y
r
B.
45%/yr
4.5%/yr
9%/yr
10%/yr
45
%
A.
How long would it take U.S. energy
use to double?
yr
0%
18
yr
0%
15
.5
0%
yr
0%
10
D.
yr
C.
5
B.
4.5 yr
10 yr
15.5 yr
18 yr
4.
A.



Between 1960 and 1970, US energy
consumption grew by 4.5%/yr. This
would mean energy use would double in
only 70/4.5 =15.5 years!
With constant rate if we double our
reserves, we double their expected life.
With exponential growth, doubling
reserves will only add a short amount of
time.
Obviously exponential growth in energy
demand CANNOT go on for very long.
If we start with $1000, approximately how
much money would we have in 14 years if it
gains interest at 10% per year?
1.
2.
3.
4.
$2000
$2400
$4000
$8000
0%
1.
0%
2.
0%
3.
0%
4.
Hubbert Analysis


Production of a natural resource
follows a bell-shaped curve with time
Initially applied to petroleum
production
Rationale

Based on finite amount of resource
Rationale


Based on finite amount of resource
Initially, development of a new
resource shows a period of rapid
growth. Easy access, addition of
infrastructure
Rationale



Based on finite amount of resource
Initially, development of a new
resource shows a period of rapid
growth. Easy access, addition of
infrastructure
As high quality, easy to find
resources are depleted, production
will peak and then decline.
Hubbert (1956)

Production will have a “Bell Shaped”
Curve.

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In the 1950’s, Hubbert predicted
that the US oil production would
peak in the 1970’s….It did.
Current models predict world oil
production will peak in 5-20 years
More when we get to each fossil fuel
source.