# Physics

(a) CO2 emissions C from a nation’s energy system can be expressed as:

C = Population x Energy consumption per person x CO2 emissions per unit of energy consumption.

Initially, total emissions are 600 million tonnes of CO2 per year. If, over a 50-year period, population doubles, energy consumption per person is reduced by 30% by means of energy efficiency and CO2 emissions per unit of energy consumption are reduced by 20% by renewable energy, what is C at the end of the 50-year period?
[Hint: If you try to guess the answer, you will be wrong. It may help to write out the equation in algebraic symbols.]

(b) (i) Jim and Jane’s house has a rooftop solar photovoltaic system with conversion efficiency 20% and surface area of collectors equal to 16 m2. It generates its rated power of 2 kW at noon on a clear day in summer. A neighbour decides to install a photovoltaic system with the same power generation. However, the neighbour chooses a cheaper system with conversion efficiency only 10%. Assuming that both roofs face the same direction, what surface area of collectors will the neighbour need?

(ii) Over a period of 12 months, Jim and Jane’s PV system generates 2.628 MWh of electricity. What is its capacity factor for the year?

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1. a) Consider per person C consumption.

C=K (.7)(.8) so a .56 factor per person

But population doubles, so 1.12 increase, or a 12 percent increase in emissions.

b. Let I be the energy density coming in.
Jim has .2I to generate 2Kwatts
Neighbor gets .1I, to get 2Kw her will need 2*16m^2

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