Energy Resources and Electricity Generation
7 marks · NormalThe government of a country is deciding between building a geothermal power station and a gas-fired power station to supply electricity to a new city. The city is also encouraging the use of solar heating panels for domestic water heating.
Describe the main energy transfers involved in generating electricity using geothermal energy.
Explain one advantage and one disadvantage of using a gas-fired power station compared to geothermal power for the city.
Explain how a solar heating panel works to heat water for a house.
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(a) Thermal energy from hot rocks underground (geothermal energy) is transferred to water, producing steam that turns a turbine, which then turns a generator to produce electricity.
(b) Advantage: Gas-fired stations can be turned on and off quickly to meet changes in demand. Disadvantage: They produce greenhouse gases and use a non-renewable resource, unlike geothermal energy which is cleaner and renewable.
(c) A solar heating panel contains copper pipes and a black metal surface that absorbs heat from the Sun. Water flows through the pipes and is heated by the absorbed thermal energy. Insulation prevents heat loss, and the glass traps an air layer to keep the heat in.
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · States geothermal heat transfers thermal energy to steam to turn turbine.
A1 (a) · 1 mark · Describes conversion to electrical energy using a generator.
M2 (b) · 1 mark · Explains one valid advantage of gas-fired station vs geothermal.
A2 (b) · 1 mark · Explains one valid disadvantage (e.g., emissions, non-renewability) of gas station.
M3 (c) · 1 mark · Describes absorption of Sun's energy by black surface or copper.
M4 (c) · 1 mark · Mentions water flowing through pipes is heated.
A3 (c) · 1 mark · States at least one feature improving efficiency: insulation or glass trapping heat.
Worked solution
a) In a geothermal power station, thermal energy from hot rocks deep underground heats water. The steam produced rises and spins a turbine. The turbine turns a generator, converting kinetic energy into electrical energy.
b) One advantage of a gas-fired power station is that it can be started rapidly to meet peak demand, making it flexible. One disadvantage is that burning gas produces carbon dioxide (a greenhouse gas) and uses up a non-renewable fuel, whereas geothermal energy is renewable and cleaner.
c) A solar heating panel has a black-coated copper sheet attached to pipes filled with water. The black surface absorbs the Sun's thermal radiation; copper conducts the heat to the water in the pipes. Glass on top traps air, providing insulation and reducing heat loss, so water leaving the panel is hot.