1.10 Renewable energy resources and trends
9 exam questions worth 28 marks. Write your answer, open the mark scheme, then give yourself the marks you earned. Your answers are saved on this device.
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Which renewable resource is not affected by the weather?
Choose one answer.
Correct Not quite: the answer is Geothermal
Mark scheme
D: geothermal
Model answer
Geothermal (D).
Explain why wind turbines are not a reliable source of electricity.
Mark scheme
wind speed varies / sometimes there is no wind (1); so electricity cannot be supplied on demand (1)
Model answer
Wind speed changes and sometimes there is no wind, so a wind turbine cannot always supply electricity when it is needed.
Describe how a hydroelectric power station generates electricity.
Mark scheme
water stored in a reservoir at height (1); falls / flows through a turbine (1); turbine turns a generator (1)
Model answer
Water stored high up in a reservoir flows down through a turbine. The turbine turns a generator, which produces electricity.
Give two environmental effects of building a tidal barrage across an estuary.
Mark scheme
any two from: affects habitats / wildlife of the estuary; changes the flow of water / tides; spoils the view; affects shipping / fishing; mud flats lost for birds
Model answer
It changes the habitat of wildlife in the estuary, and it can affect boats and fishing.
Use the bar chart: describe how the percentage of UK electricity from coal changed from 2000 to 2020, and suggest one reason for the change.
Mark scheme
fell from about 32% to about 2% (1); coal produces carbon dioxide / coal power stations were closed / concern about climate change (1); replaced by renewables / gas (1)
Model answer
The percentage from coal fell from about 32% to about 2%. This is because coal releases a lot of carbon dioxide, so power stations were closed and replaced by renewables and gas.
Evaluate the use of solar cells and gas-fired power stations to supply electricity to a town. Use ideas about reliability, cost and the environment.
Mark scheme
Level 3 (5-6 marks): a balanced evaluation with reference to reliability, cost and environment for both resources, and a justified conclusion. Level 2 (3-4 marks): comparison of at least two factors for at least one resource, with some reasoning. Level 1 (1-2 marks): simple statements, with no comparison. Indicative content: solar only works in daylight, weaker when cloudy / gas is available all the time and can respond to demand; solar has no fuel costs but cells are expensive to install / gas needs fuel; solar produces no carbon dioxide in use / gas releases carbon dioxide (climate change); a mix of the two with energy storage could be used.
Model answer
Gas is reliable and can be started up quickly to meet demand, but it is non-renewable, costs money for fuel and releases carbon dioxide, which contributes to climate change. Solar cells have no fuel costs and release no carbon dioxide when working, but they only work in daylight and give less in cloudy weather, so they are not always reliable and need a lot of land. The best answer for a town is to use both: solar to reduce emissions in the day, with gas (or stored energy) to cover the night and cloudy days.
A wind farm has 15 turbines, each rated at 2.0 MW. On average the turbines produce 30% of their maximum power. Calculate the average power output of the wind farm.
Mark scheme
maximum power = 15 × 2.0 = 30 MW (1); 0.30 × 30 (1); 9.0 MW (1)
Model answer
Maximum power = 15 × 2.0 = 30 MW. Average power = 0.30 × 30 = 9.0 MW.
Describe how pumped storage is used to store energy and then supply electricity when demand is high.
Mark scheme
spare electricity at times of low demand is used to pump water uphill to a reservoir (1); energy is stored in the gravitational potential store of the water (1); when demand is high the water is released to flow downhill (1); it turns turbines and generators to produce electricity (1)
Model answer
At times of low demand, spare electricity pumps water to a high reservoir, where the energy is stored in the gravitational potential store of the water. When demand is high, the water is released to flow down through turbines, which turn generators and produce electricity.
A town on the north coast of Scotland wants to build a renewable power station. Compare the use of wind power and solar power for this location.
Mark scheme
wind: the area is windy so wind turbines should work for much of the time (1); solar: short daylight / less sunshine in winter so a low output (1); both depend on the weather so are not reliable all the time / need back-up or storage (1); wind turbines affect the view / harm birds; solar cells need a large area (1)
Model answer
Wind power is likely to be better, since the north of Scotland is windy, whereas solar power would give a low output because there is little daylight in winter. Both depend on the weather, so they need back-up or energy storage, and each has an effect on the environment.
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