Transcript talk1

Weaving Climate Change Concepts
Into
High School Science Teaching
PCCE Convention – Edmonton
October 16-17, 2012
Brian Martin – The King’s University
College
Contexts for Good Science Teaching
• Good science teaching provides conceptual hooks
that connect a student’s lived world with the world
of scientific ideas
• Climate Change Science is a complex subject that
reaches into virtually every part of the science
curriculum – this is a natural and fruitful area in
which to create these “hooks”
• Climate Change represents one of humanities
greatest challenges and developing climate change
literacy in students and the general population is a
critical need
Five Sample “Lessons”
Idea
Concept(s)
Suggested Curricular
Links
What is the mass of the
atmosphere
Force, Pressure
Science 10
Phys 20 – Unit B
Chem 20 – Unit B
How does the burning of CO2
change the atmosphere?
Stoichiometry
Chem 20 – Unit D
Acidification of the Oceans
Solutions, PH
Chem 30 – Unit D
The Physics of Wind Power
Conservation of Momentum and
Energy, Power
Chem 20 – Unit C
Phys 30 – Unit A
Photovoltaic Energy
Energy and Power
Science 10
Phys 20 – Unit C
(1) Mass of the Atmosphere
Basic Facts:
•Atmospheric pressure 100 kPa
•1 Pa = 1N/m2
•Radius of Earth 6.38 X 106m
Every square m of the Earth’s
surface supports 104 kg of air
SA  4 R 2
What is the mass
of a column of air
1m2 at the base
which exerts a
force of 100 kN ?
Mass  4 R 2 (10 4 kg / m 2 )
 4 (6.38  10 6 m )2 (10 4 kg / m 2 )
 5  1018 kg
Ans: mg = 100 000 N
m = 104 kg
How many molecules are there in the
atmosphere?
Basic Facts:
•Atmospheric is mostly N2 and O2
•“molar mass” approximately 30
g/mol
•Mass of atmosphere 5 X 1018 kg
Number of mols 
mass of atmosphere
molar mass
5  1021 g

 1.7  1020 mol
30 g / mol
(2) How Much CO2 in ppm Does a
Barrel of Oil Produce? Basic Facts:
1 barrel releases 425 kg of CO2; in moles this is
425 kg
 104 mol
0.044 kg / mol
•Carbon-based fuel releases 3.15
times its mass in CO2
•Mass of a barrel of oil is about
135 kg or
•1 barrel releases 425 kg CO2
•CO2 has a molar mass of 44g/mol
Since the atmosphere contains 1.7 X 1020 mol
one barrel will release
104
17

6

10
1.7  1020
This is the fraction of CO2 relative to the entire atmosphere – multiply by 1
million to get the parts-per-million or ppm. So, 1 barrel releases an additional
6  1011 ppm
Is the observed increase in CO2 “natural” or
Basic Facts:
…
(30  109 bbl/a)(6  1011 ppm/bbl )
 1.8 ppm/a
•1 barrel of oil releases 6 X 10-11
ppm of new CO2 into the
atmosphere
•30 billion barrels of oil are
consumed annually
Slope = 1.8 pm/a
46 ppm
25a
Basic Facts:
A Bit Closer to home…
what is the annual Carbon footprint of the
Alberta Oil Sands in ppm?

•Fort Mac produces 1.5 million
barrels of oil per day
•Annual Carbon footprint is 40
million tonnes of carbon dioxide
•1 barrel of oil releases 6 X 10-11
ppm of new CO2 into the
atmosphere
40 Mt CO2
 9.4  107 bbl
425 kg / bbl
(9.4  107 bbl/a)(6  1011 ppm/bbl )
 0.006 ppm/a
…but – that’s not the end of the story!
Components of Fossil Fuel Emissions
Le Quéré et al. 2009, Nature Geoscience
How about Coal-Generated Power?
Basic Facts:
•The Sundance Coal-fired Power
Generation Plant on Lake
Wabamum produces 2126 MW
•Annual Carbon footprint is 17.5
million tonnes of carbon dioxide
The Sundance plant produces roughly 17.5/40 times as much CO2
as The Alberta Oil Sands
In other words – Sundance adds
(17.5 / 40)(0.006 ppm/a)= 0.003 ppm/a
(or about “half-a-Fort Mac”)
Let’s Re-run the Numbers…
Basic Facts:
•CO2 sources by percent:
•Coal 40%
•Oil 36%
•Natural Gas 20%
•Other 4%
If the burning of oil accounts for only 36% of
the total CO2 loading then the total
(anthropogenic) loading is …
1.8 ppm / a
 5 ppm / a
0.36
So – where is the rest going?
(3) Ocean Acidification
• The ocean buffers atmospheric
CO2
• The ocean’s pH has dropped from
8.20 to about 8.05 since the
industrial revolution
D pH is only 0.15 – why Worry?
pH   log10[H3O  ]
so

(  pH )
[H3O ]  10
• At [8.20] H3O+ concentration is 6.31 × 10-9 mol L-1
• At [8.05] H3O+ concentration is 8.91 × 10-9 mol L-1
• This represents a 41% increase in hydronium
ions – the ocean is being acidified
(4) The Physics of Wind Power
• How much power can a 100 m
diameter windmill produce?
• Estimate the size of a wind farm
capable of producing the power
output of the Sundance
thermoelectric plant (2100 MW)
Energy from the wind
• A packet of air of mass ‘m’ moving
with velocity ‘v’ has energy given
as
1
Ek  mv 2
2
m   Av Dt   A1v1Dt   A2v2Dt
1
Ek   Av Dtv 2
2
1
P   Av 3   Av 2 Dv
2
Energy and power
scale with the CUBE
of wind velocity!
The total energy available is the
difference between the energy of the
incident air packet and the exiting air
packet – Power that can be extracted is
expressed as:
Peffective
1
 P   Av(v12  v22 )
2
Note the crucial role of the incident and exit wind
velocity – we want to find the “sweet spot” – what is the
maximum value for Peffective?
Force and Power on a Windmill
• A variation on Newton’s 2nd Law
Dv
m
F  ma  m

Dv
Dt
Dt
 Av Dt
F 
Dv   Av Dv
Dt
P  Fv   Av 2Dv
• Combine the two differently derived
expressions for P
1
 Av(v12  v22 )   Av 2 Dv
2
1 2
(v1  v22 )  v Dv  v(v1  v2 )
2
This is known as Betz’s Law (circa 1920) and
leads to a remarkable result – the velocity
across the rotor of the windmill is
(v1  v2 )
v 
2
Insert this into the power equation to get…
(v1  v2 ) 2
1
P  A
(v1  v22 )
2
2
Let x = v1/v2 to get…
1
3
2
P   Av1 (1  x)(1  x )
4
1
1
1
3
P   Av1 (1  )(1  )
4
3
9
16 1

(  Av13 ) or
27 2
1
3
 C p  Av1
2
Cp is the power coefficient for a wind turbine and the
ratio 16/27 = 0.59 represents the maximum possible power
that can be extracted. More typically wind turbines achieve
80% of this or 0.47
Example – Enercon101 Wind Generator
Optimal wind speed is
around 10 m/s
Cp = 0.47 so
1
(0.48)(1.2kg/m3 ) (50m)2 (10m/s)3
2
 2400 kW
P 
How Many?
• To produce 2100 MW you will need…
n
2100 MW
 875 units
2.4 MW/unit
• “Rule of thumb” – generator spacing is 7 times the diameter
of the rotor or (0.1km)(7) = 0.7km
• Place in a grid 30 units X 30 units = 21 km X 21 km
• Cost? A 2008 figure commonly used is 1.3 million/MW so a
2100 MW wind farm would cost approximately $275 million
• From the TransAlta web site… “A 53-megawatt uprate to
Sundance 5 was completed in 2009 at a cost of $75 million.”
(5) Photovoltaic Energy
• By how much can I hope to
reduce my annual CO2 footprint
if I install 12, 235 W solar panels
on the roof of my house?
• How does the cost of electricity
produced by a PV panel
compare with current costs
@12 c/kWh?
kW = 1000 W is a power unit
kWh = 1000 W × 3600 s = 3.6 MJ
which is an energy unit
My Annual Electricity Use
• Total electrical energy
consumption 2011 was 10 MWh
• Under bright sunlight each panel
averages 140 W (averaged over
the year)
• Edmonton receives on average
2300 h bright sunshine per year
E  (12 panels)(140 W )(2300 h)
 3.86 MWh
I can offset about 40% of
my (electrical) CO2
footprint
Cost of Solar Energy
• Total cash outlay for system =
$15000
• Warranty period = 25 years;
estimated lifetime > 40 years
• Assume an average annual
energy production of 3.6 MWh
Net Cost  ($15000/25 a)  $600a-1
so...
$600a-1
 17 c/kWh
3600 kWh
But the cost of
sunlight won’t go up!