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.

Hydroelectric power station

The diagram illustrates the process of producing electricity in a hydroelectric power station.

Overall, the system is cyclical and operates on a daily rhythm. Water stored in an upper reservoir flows downhill during the day to generate electricity, while at night, when demand is lower, the process is reversed, with water being pumped back for reuse.

In the first stage, river water is collected behind a dam and stored in an upper reservoir. During the daytime, an intake at the base of the dam is opened, allowing water to pass through. As the water flows downward, it turns turbines located in a power station. These turbines convert the kinetic energy of flowing water into mechanical energy, which is subsequently used to drive a generator. The generator then transforms this mechanical power into electricity, which is transmitted to the national grid through power lines.

At night, when electricity consumption falls, the system works in reverse. The turbines function as pumps, transporting water from the lower reservoir back into the upper reservoir. This enables the cycle to be repeated the following day.

In summary, hydroelectricity generation relies on a renewable cycle in which water movement is harnessed to produce power during peak hours and recycled during off-peak hours.

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Vocabulary Bank for Process Diagrams (Task 1 Academic)

Here’s a specialized dictionary of words and phrases that you can use when describing processes or cycles:

🔄 Describing Processes / Stages

• Begin with / commence with → The process begins with water being stored in a reservoir.
• Subsequently / afterwards → Subsequently, the water flows through turbines.
• Followed by → This stage is followed by the generation of electricity.
• Next / then → The next step involves pumping water back uphill.
• Finally / ultimately → Ultimately, electricity is supplied to the grid.
• In the final stage → In the final stage, water is recycled.

⚡ Energy & Conversion Words

• Kinetic energy → energy of movement
• Mechanical energy → energy produced by machines/turbines
• Convert / transform / generate → Turbines convert kinetic energy into mechanical power.
• Transmit / deliver / supply → Electricity is transmitted to households.
• Harness → The system harnesses the power of flowing water.

💧 Water & Flow Descriptions

• Reservoir / storage / basin → Water is kept in the upper reservoir.
• Flow / pass through / channelled → Water is channelled through turbines.
• Downstream / downhill → Water flows downhill into the lower reservoir.
• Recycled / reused → Water is recycled during off-peak hours.
• Pump / transport back → Water is pumped into the upper reservoir.

📝 Linking & Cohesion (for Cyclical Diagrams)

• On a daily basis / during the day / at night → During the day, the turbines generate electricity.
• When demand is high / low → At night, when demand is low, water is pumped back.
• This cycle repeats / the cycle continues → This cycle repeats every 24 hours.
• Renewable process → Hydroelectric power is a renewable process.