Energy Resources and Electricity Generation
7 marks · NormalA village uses two main sources for its electricity supply: a local river is used for hydroelectric power, and a diesel generator provides backup power when needed. Many houses also have solar heating panels for water heating.
Describe the energy transfers that occur when generating electricity using the local hydroelectric power station.
Give one environmental disadvantage of using the diesel generator.
Suggest one reason why the diesel generator is only used as a backup and not as the main supplier.
Explain how the design of a solar heating panel makes it efficient at heating water. Refer to specific features.
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) Gravitational potential energy of stored water is converted to kinetic energy as water flows down, which turns a turbine (kinetic to mechanical energy), spinning a generator to produce electrical energy.
(b) Burning diesel releases pollutants, including CO2 and other gases, causing air pollution and contributing to global warming.
(c) It is more expensive to run and produces more pollution than hydroelectric power.
(d) Solar heating panels use a matt black copper surface to absorb maximum heat from the Sun (good absorber), glass covers trap an air layer for insulation, and copper pipes are excellent conductors to transfer heat efficiently to the water. Thermal insulation reduces heat loss to the surroundings, making the panel more efficient.
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Identifies GPE to KE and KE to turning turbine/generator.
A1 (a) · 1 mark · Correctly states the production of electrical energy from spinning generator.
B1 (b) · 1 mark · States a valid environmental disadvantage for diesel generator.
B2 (c) · 1 mark · Gives a valid reason (cost or pollution) for backup use.
M2 (d) · 1 mark · Mentions black surface or copper for good absorption/conduction.
M3 (d) · 1 mark · Mentions insulation (glass/air layer/insulating backing) for preventing heat loss.
A2 (d) · 1 mark · Links features to efficient heating (e.g., absorbing/retaining heat, efficient transfer to water).
Worked solution
a) Water is stored at a height in a reservoir; its gravitational potential energy is converted to kinetic energy as it flows down. The moving water turns a turbine converting kinetic to mechanical energy, which spins a generator, producing electricity.
b) Burning diesel releases carbon dioxide and other pollutants, contributing to air pollution and global warming.
c) Diesel is used only as a backup because it is costly to run and produces more pollution compared to the clean, renewable hydroelectric station.
d) A matt black copper surface absorbs more of the Sun’s heat. Glass cover with trapped air acts as insulation, while copper pipes conduct heat efficiently to the water. Insulation on the back and edges reduces heat loss, making the system more efficient in heating water.