Question

2. The total energy consumption of Hong Kong in year 2008 was 285,430 TJ. Assume the daily rate of solar energy received in Hong Kong is 10 kWh/m2 and that a solar PV panel has an efficiency of 10% in converting sunlight to electricity.
(a) Calculate the land area that is required for solar panels if Hong Kong uses sunlight as its only energy source to support the year 2008 energy consumption. (4 points)
(b) Compare against the total land area in Hong Kong, what percentage of land will the solar panels take up? (2 points)
(c) Even during the night we still need electricity and given that we can only rely on solar energy, what can Hong Kong do to ensure electricity made from solar energy is available 24 hours a day (i.e. both during the day and night)? Explain your answer. (8 points)

Answer 1

Ans- Given- Total energy consumption of Hong Kong in year 2008 = 285,430 TJ.

=7.92 X1010kWh.

-The daily rate of solar energy received in Hong Kong =10 kWh/m2.

-A solar PV panel efficiency =10%.

Now,the solar energy received in Hong Kong in 1 year = 365 X 10 kWh/m2= 3650 kWh/m2.

The energy converted into electrical energy=0.10 X 3650 = 365 kWh/m2.

(We know that area of hong kong= 1,106 km²=1106X106m2.)

The area required to produce 7.92 X1010kWh electrical energy= 7.92 X1010kWh/365 kWh=0.021 X1010m2.

Ans-a) The land area that is required for solar panels if Hong Kong uses sunlight as its only energy source to support the year 2008 energy consumption = 0.021 X1010m2.

Ans-b)The percentage of land will the solar panels take up=(solar panel area/total land area )X100=(0.021 X1010m2/1106X106m2)X100=0.189.

Ans-c) Yes,it is true that during night we need electricity and a solar panel field can produce electricity only during the day hours when the light is falling on them,to solve this problem we have to install a power storage batteries which can store the extra power that is being generated by the solar panels and it can be use as backups during the night.These energy produced by the solar panels can not only be stored in the form of batteries but can also be stored as various potential and kinetics energy form.

Note that the energy that we have calculated in the above problem is for both day as well as night requirement.So extra energy calculate can be stored in the form of batteries and can be utilized at night,But you should also remember that the efficiency of storing energy in batteries is plays an important role in calculating energy consumption.

Hope you have understood the answer.

Best wishes!