# GCSE Questions: Energy Sources

Q2. Electricity can be generated using various energy sources.

(a) Give one advantage and one disadvantage of using nuclear power stations rather than gas-fired power stations to generate electricity.

 Advantages a nuclear power station produces no (or very little amounts of) greenhouse gases (or carbon dioxide) so it doesn't contribute to global warming, whereas gas-fired power stations do contribute to global warming. a nuclear power station produces no acid rain (or sulphur dioxide), whereas a gas-fired power station does. A simple reference to 'less atmospheric pollution' or stating that it produces 'no harmful gases' was considered insufficient to get you a mark. Mention specific gases! high(er) energy density in fuel therefore less fuel deliveries are needed one nuclear power station produces as much power as several gas power stations. Saying nuclear power stations can supply 'a lot of or more energy' was insufficient to get you a mark. using nuclear power saves using reserves of fossil fuels or gas as they are non-renewable and will run out. Disadvantages Nuclear power stations produce (long term) radioactive (or nuclear) waste or the waste produced is toxic accidents at nuclear power stations may have far reaching or longer term consequences than accidents at gas-powered stations Nuclear power stations have much high(er) decommissioning costs and/or high(er) building costs Nuclear power stations have long(er) start up times and are difficult to adjust to changes in energy demand.

[2 marks]

(b)

(i) A single wind turbine has a maximum power output of 2.0 MW.

The wind turbine operated continuously at maximum power for 6 hours.

Calculate the energy output of the wind turbine in kilowatt-hours.

2.0 MW = 2 000 000 W = 2 000 kW

Energy output = Power x time

= 2 000 x 6 = 12 000 kW h

[3 marks]

(ii) Why, on average, do wind turbines operate at maximum power output for only 30% of the time?

Any idea of unreliability of the wind got you a mark. Simply refering to the weather alone was insufficient to get you a mark - state the obvious!

The strength of the wind is unreliable/variable and you only get maximum power when the wind speed is high.

The turbine has to shut down if the wind is too strong.

[1 mark only]

(c) An on-shore wind farm is made up of many individual wind turbines. They are connected to the National Grid using underground power cables.

Give one advantage of using underground power cables rather than overhead power cables.

Any one from:

cannot be seen

no hazard to (low flying) aircraft / helicopters

unlikely to be damaged or affected by (severe) weather ('unlikely to be damaged' on its own was considered insufficient and no mark was awarded)

reduced shock hazard - 'safer' was considered insufficient

[1 mark]

(Total 7 marks)