A wind turbine generates electricity. Some of the energy input to the turbine is wasted. Explain how the efficiency of the wind turbine can be calculated, and describe TWO ways in which the efficiency of the turbine could be increased.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A wind turbine converts kinetic energy from moving air into electrical energy. Engineers monitor the energy input and the useful energy output of the turbine. Not all of the input energy is transferred usefully — some is wasted as heat and sound.
Model answer (5 marks)
Efficiency = useful electrical energy output ÷ total mechanical energy input from the wind. It is expressed as a percentage and can never be greater than 100 % because of the conservation of energy.
To increase efficiency:
1. Lubricate the moving parts of the turbine. Lubrication reduces friction between the blades, shaft and gearbox, which lowers the amount of input energy lost as waste heat and therefore more energy is converted into electricity.
2. Add thermal insulation to the turbine structure. Insulation reduces heat loss to the surroundings, so less input energy is wasted as heat and the remaining energy can be used more effectively to generate electricity.
To increase efficiency:
1. Lubricate the moving parts of the turbine. Lubrication reduces friction between the blades, shaft and gearbox, which lowers the amount of input energy lost as waste heat and therefore more energy is converted into electricity.
2. Add thermal insulation to the turbine structure. Insulation reduces heat loss to the surroundings, so less input energy is wasted as heat and the remaining energy can be used more effectively to generate electricity.
Examiner tips
- State the definition of efficiency and the 100 % limit first. Then give two specific engineering improvements that reduce energy loss. Use the exact terms "lubrication" and "thermal insulation" as the mark scheme recognises them.
Common mistakes
- Writing efficiency as output ÷ input instead of input ÷ output. The correct ratio is useful output divided by total input. Failing to mention that efficiency cannot exceed 100 %. Giving generic answers such as "improve blade design" without linking to friction or heat loss.
Mark scheme (5 marks)
- Efficiency is the ratio of useful output energy to total input energy
- Efficiency can never exceed 1 (or 100%) due to conservation of energy
- Lubrication of moving parts reduces friction
- Lubrication reduces waste heat energy transferred to the surroundings, so more energy is usefully transferred as electricity
- Thermal insulation reduces the rate of heat loss to the surroundings / waste heat energy can be recycled and used as an input
Key terms in this question
Related
- All Edexcel A-Level Physics (9PH0) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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