8 Energy production
8.1 Energy sources
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Date: ……………………………….
Efficiency 2
For this worksheet use g = 9.8 m s−2.
1
A pumped storage system using water has an output of 1.18 MW. If the water falls a total vertical distance of
275 m at a rate of 564 kg s−1, determine the overall efficiency of the system.
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2
A rectangular solar heating panel from a particular company is 1.2 m by 0.88 m and has an efficiency rating of
19%. Assuming that the average solar intensity at the roof of a particular house is 650 W m−2 and that a
minimum output of 3800 W is required for heating, how many panels are required?
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3
A rectangular water storage tank has dimensions 45 m × 65 m × 75 m. If the water falls 280 m vertically
through a turbine and has a density of 1.0 × 103 kg m−3, calculate the power generated by the system in
6.2 hours.
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4
The energy released in a nuclear reactor using uranium-235 is 180 MeV. The energy released by one atom of
carbon-12 during combustion is 4 eV. Calculate the ratio of energy density of uranium-235 to carbon-12. Take
the density of uranium-235 to be 1.9 × 104 kg m−3 and that of carbon-12 to be 1.0 × 103 kg m−3.
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5
The speed of the wind entering a wind turbine having 14 m long blades is 18 m s−1. If the density of air is 1.2
kg m−3 and the efficiency is 57%, calculate the power output of the wind turbine.
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8 Energy production
8.1 Energy sources
1
A wind farm generator produces 10.0 kW. The wind speed increases and its output increases to 90.0 kW.
Assuming the efficiency remained the same, by what factor did the wind speed increase?
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2
The intensity of incident solar radiation on a photovoltaic cell is 302 W m−2. If the area of the cell is 2.38 cm2
and its efficiency is 17.6%, calculate the power output.
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