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Weaving Climate Change Concepts Into High School Science Teaching

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### (1) Mass of the Atmosphere

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

- Atmospheric pressure 100 kPa
- 1 Pa = 1N/m2
- Radius of Earth 6.38 X 106m

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

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

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

(2) How Much CO2 in ppm Does a Barrel of Oil Produce?

- Basic Facts:
- 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 hasa molar mass of 44g/mol

1 barrel releases 425 kg of CO2; in moles this isSince the atmosphere contains 1.7 X 1020 mol one barrel will release

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

Is the observed increase in CO2 “natural” or …

- Basic Facts:
- 1 barrel of oil releases 6 X 10-11ppm of new CO2 into the atmosphere
- 30 billion barrels of oil are consumed annually

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?

- Basic Facts:
- 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 10-11ppm of new CO2 into the atmosphere

…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

(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 …

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?

- 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

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:

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

This is known as Betz’s Law (circa 1920) and leads to a remarkable result – the velocity across the rotor of the windmill is

Insert this into the power equation to get…

Let x = v1/v2 to get…

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

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.”

(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

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

But the cost of

sunlight won’t go up!

And there are a lot more…

- Compare CO2 footprints of Methane and Coal
- Look at Isotopic Mass Ratios and Ice-cores
- Look at Carbonate-biCarbonate speciation
- Greenhouse gas heating through collisional de-excitation
- Declining sea ice and slope
- IR spectroscopy and spectral windows
- etc

Resources…

- www.kcvs.ca
- www.explainingclimatechange.ca
- Using Climate Change to Creat Rich Contexts for Physics and Chemistry Education. Brian Martin and Peter Mahaffy

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