The operational process of a hydroelectric power station
The diagram below shows how electricity is generated in a hydroelectric power station.
Summarise the information by selecting and reporting the main features, and make comparisons where relevant. Write at least 150 words.
- 1.River water enters high-level reservoir behind a dam
- 2.Daytime: Intake opens, water flows down to power station
- 3.Daytime: Water spins reversible turbines to operate generator
- 4.Daytime: Electricity is produced and sent to the national grid
- 5.Daytime: Water exits into low-level reservoir
- 6.Nighttime: Intake closes
- 7.Nighttime: Reversible turbines pump water from low-level back to high-level reservoir
Chart redrawn by BandLadder from the data in the original IELTS practice task. Many IELTS practice tasks come from the Cambridge IELTS series (Cambridge University Press & Assessment); all rights in the original tasks remain with their owners.
Band 8 sample answer
The provided diagram illustrates the operational cycle of a hydroelectric power station, highlighting the distinct processes that occur during the day and at night to generate electricity and maintain water levels.
Overall, the system functions as a closed-loop mechanism, utilising a high-level reservoir, a power station with reversible turbines, and a low-level reservoir. The process is defined by a clear shift in activity between daylight hours, when power is generated, and nighttime, when the system is replenished.
During the day, the intake from the high-level reservoir is open, allowing water to flow downwards towards the power station. This movement of water drives the reversible turbines, which in turn operate the generator to produce electricity for the national grid. After passing through the turbines, the water is discharged into the low-level reservoir.
Conversely, at night, the intake from the high-level reservoir is closed. The process reverses, as the turbines function as pumps to move water from the low-level reservoir back up to the high-level reservoir. This ensures that the station is prepared for the next cycle of electricity generation, demonstrating an efficient method of energy management.
185 words. Every figure in the answer comes from the chart above.
How to write about process diagrams
- Say how many stages there are and where the process starts and ends.
- Use the passive and sequencers: first, after this, once, finally.
- Keep every stage; a missing step costs task achievement.
- cyclical
- occurring in a repeating series of events
- closed-loop
- a system that operates in a self-contained cycle
- replenished
- filled up or restored to a previous level
- conversely
- introducing a statement that reverses the previous one
- discharged
- sent out or released from a contained area
- mechanism
- a system of parts working together in operation
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Frequently asked questions
What should the overview say?
The diagram illustrates a cyclical hydroelectric system that generates electricity during the day and recharges its water supply at night.
How long should an IELTS Task 1 answer be?
At least 150 words; 170 to 200 is the safe range. Spend about 20 minutes on it and leave 40 for Task 2, which carries twice the marks.
How do I describe process diagrams?
Say how many stages there are and where the process starts and ends. Use the passive and sequencers: first, after this, once, finally. Keep every stage; a missing step costs task achievement.
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