Energy Resources and Electricity Generation
5 marks · NormalA city is deciding between building a tidal power station and a new gas-fired power station.
Describe the energy transfers that occur in generating electricity using a tidal scheme.
State two disadvantages of tidal power stations.
Explain one reason why a gas-fired power station can quickly respond to sudden demand, but a tidal power station cannot.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) Potential energy of water (due to tides) is transferred to kinetic energy as the tide moves water through turbines. This kinetic energy turns turbines, which are connected to generators to produce electricity.
(b) Few suitable locations; can harm wildlife habitats; changes tides in estuaries; not continuous—only available at times when tides move (any two).
(c) Gas stations can be turned on quickly at any time, but tidal power depends on natural tidal cycles, so it cannot operate on demand.
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Marking points
T1 (a) · 1 mark · Identifies potential energy of water (tide) to kinetic energy.
T2 (a) · 1 mark · Kinetic energy (water) drives turbine, then generator makes electricity.
D1 (b) · 1 mark · States a valid disadvantage (e.g. limited locations; damage to environment/habitats).
D2 (b) · 1 mark · States another different disadvantage (e.g. not continuous—dependent on tides).
G1 (c) · 1 mark · Mentions gas can start/stop at any time, tidal can’t respond to sudden demand because cycle is fixed.
Worked solution
a) In a tidal power station, gravitational potential energy of water at high tide is converted to kinetic energy as the water moves through turbines. This kinetic energy turns the turbines, which drive generators to produce electricity.
b) Disadvantages: (i) Few places are suitable for building tidal power stations. (ii) They can harm wildlife habitats and only produce power at certain times each day (when tides change).
c) Gas-fired power stations can be started and stopped rapidly to meet sudden increases in demand, whereas tidal power stations can only generate electricity when tides are moving—their operation cannot be controlled to match unexpected changes in demand.