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.
Weaving Climate Change Concepts
High School Science Teaching
PCCE Convention – Edmonton
October 16-17, 2012
Brian Martin – The King’s University College
(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 ?
Every square m of the Earth’s surface supports 104 kg of air
Ans: mg = 100 000 N
m = 104 kg
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
Slope = 1.8 pm/a
…but – that’s not the end of the story!
Components of Fossil Fuel Emissions
Le Quéré et al. 2009, Nature Geoscience
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”)
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?
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?
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
Optimal wind speed is
around 10 m/s
Cp = 0.47 so
kW = 1000 W is a power unit
kWh = 1000 W × 3600 s = 3.6 MJ which is an energy unit
I can offset about 40% of my (electrical) CO2 footprint
But the cost of
sunlight won’t go up!