Weaving Climate Change Concepts Into

High School Science Teaching

Weaving Climate Change Concepts Into

High School Science Teaching

PCCE Convention – EdmontonOctober 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

LinksWhat is the mass of the atmosphere

Force, Pressure Science 10Phys 20 – Unit BChem 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 CPhys 30 – Unit A

Photovoltaic Energy Energy and Power Science 10Phys 20 – Unit C

(1) Mass of the Atmosphere

What is the mass of a column of air 1m2 at the base which exerts a force of 100 kN ?

Ans: mg = 100 000 Nm = 104 kg

Every square m of the Earth’s surface supports 104 kg of air

2

2 4 2

6 2 4 2

18

4

4 (10 / )

4 (6.38 10 ) (10 / )

5 10

SA R

Mass R kg m

m kg m

kg

How many molecules are there in the atmosphere?

21205 10

30 /1.7 10

mass of atmosphereNumber of mols

molar massg

g molmol

(2) How Much CO2 in ppm Does a Barrel of Oil Produce?1 barrel releases 425 kg of CO2; in moles this is

Since the atmosphere contains 1.7 X 1020 mol one barrel will release

kgmol

kg mol4425

100.044 /

417

20

106 10

1.7 10

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

ppm116 10

Is the observed increase in CO2 “natural” or …

bbl/a ppm/bbl

ppm/a

9 11(30 10 )(6 10 )

1.8

Slope = 1.8 pm/a

46 ppm

25a

A Bit Closer to home…what is the annual Carbon footprint of the Alberta Oil Sands in ppm?

Mt CObbl

kg bbl7240

9.4 10425 /

bbl/a ppm/bbl

ppm/a

7 11(9.4 10 )(6 10 )

0.006

…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?

The Sundance plant produces roughly 17.5/40 times as much CO2 as The Alberta Oil Sands

In other words – Sundance adds

ppm/a)= 0.003 ppm/a(17.5 / 40)(0.006

(or about “half-a-Fort Mac”)

Let’s Re-run the Numbers…

If the burning of oil accounts for only 36% of the total CO2 loading then the total (anthropogenic) loading is …

1.8 /5 /

0.36

ppm appm a

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

pH is only 0.15 – why Worry?

• 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

pH

pH H O

so

H O

10 3

( )3

log [ ]

[ ] 10

(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

kE mv212

m Av t A v t A v t1 1 2 2

kE Av tv212

P Av Av v3 212

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:

effectiveP P Av v v2 21 2

1( )

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

• Combine the two differently derived expressions for P

v mF ma m v

t tAv t

F v Av vt

P Fv Av v2

Av v v Av v

v v v v v v v

2 2 21 2

2 21 2 1 2

1( )

21( ) ( )

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

v vv 1 2( )

2

Insert this into the power equation to get…

v vP A v v2 21 2

1 2

( )1( )

2 2

Let x = v1/v2 to get…

P Av x x3 21

1(1 )(1 )

4

p

P Av

Av or

C Av

31

31

31

1 1 1(1 )(1 )

4 3 916 1

( )27 212

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/sCp = 0.47 so

P kg/m m m/s

kW

3 2 31(0.48)(1.2 ) (50 ) (10 )

22400

How Many?

• To produce 2100 MW you will need…

• “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.”

MWn units

MW/unit2100

8752.4

(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 panels W h

MWh

(12 )(140 )(2300 )

3.86

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

-1

-1

Net Cost $15000/25 a a

so

$600a17 c/kWh

3600 kWh

( ) $600

...

But the cost of sunlight won’t go up!