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GCSE Questions: Energy Sources

Q25. The diagram shows a house with a solar power system.

The solar cells on the roof generate electricity for the household.

When the electricity generated by the solar cells is not needed, the energy is stored in a large battery.

(a) The solar cells on the roof of the house always face in the same direction. Explain one disadvantage caused by the solar cells only facing in one direction.

In order to obtain maximum conversion of solar energy to electricity the sun's rays would need to shine at right angles to the surface of the solar panel.

The Sun changes position in the sky during the day (and over the year). Therefore fixed solar cells aren't always pointed directly at the Sun and therefore don't always receive the maximum intensity of solar radiation. It would be better to have them track the Sun's movement through the sky.

[2 marks]

(b) The mean current from the solar cells to the battery is 3.5 A.

Calculate the charge that flows from the solar cells to the battery in one hour.

1 h = 60 x 60 s

t = 3600 s

I = Q/t

3.5 A = 3.5 C/s

Total charge = 3.5 x 3600

Q = 12,600 C

 

[3 marks]

(c) At one time in the day, the total power input to the solar cells was 7500 W.

Given that the efficiency of the solar cells was 0.16, calculate the useful power output of the solar cells.

efficiency = useful power output/total power input

useful power output = efficiency x total power input

= 0.16 x 7500

= 1200 W

[4 marks]

(d) The wasted energy that is not usefully transferred by the solar cells is dissipated.

Choose from the phrases below what best describes what happens to energy that has been dissipated.

The energy becomes less useful.
The energy is destroyed.  
The energy is used to generate electricity.  

[1 mark]

(e) Choose from the reasons below which one best describes why is it unlikely that all the UK's electricity needs could be met by solar power systems

A very large area would need to be covered with solar cells.
Solar power is a non-renewable energy resource.  
The efficiency of solar cells is too high.  

[1 mark]

(Total 11 marks)