The diagram shows how electricity is generated in a hydroelectric.. (Task 1 Process Diagram Band 9)

You should spend about 20 minutes on this task.

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.

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Model Answer 1 (Band 9)

The diagram elucidates the process of electricity generation at a hydroelectric power station, underscoring the continuous cycle of water between a high-level reservoir and a lower one, facilitated by a dam and power station apparatus.

An overview of the system reveals that the operation hinges on the diurnal cycle, with water intake from the river occurring during the day, and the nocturnal reversal of water flow, from the low-level reservoir back to the high-level one. This cyclical process is critical in the generation and regulation of electricity.

During the day, water is channeled from the high-level reservoir through the dam to the power station. The flow of water is directed onto the reversible turbines, which in turn, operate the generator to produce electricity. This electricity is then transmitted via power lines to the national grid. The intake for this process is open during the day and closed at night to ensure a regulated flow of water.

Conversely, at night, the turbines' function is inverted; they utilize surplus electricity from the national grid to pump water from the low-level reservoir back to the high-level reservoir. This ingenious use of reversible turbines underscores the station's efficiency in managing water resources for continuous electricity generation. Notably, the flow of water back to the high-level reservoir only occurs at night, preparing the system for the next cycle of electricity production.

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Model Answer 2 (Band 9)

The provided schematic offers an in-depth view into the sequence of operations by which a hydroelectric power station generates electricity.

Central to the diagram are two reservoirs positioned at different elevations, connected by a power station that houses reversible turbines and a generator. The process is characterized by its reliance on the natural cycle of day and night, which dictates the direction of water flow and the activity of electricity generation or water pumping.

By day, the station engages in electricity production. Water is allowed to flow from the high-level reservoir, passing through the turbines, stimulating the generator to produce electricity that is then dispatched to the national grid. The intake from the river to the high-level reservoir is open, facilitating this process.

At night, the operation is reversed; the turbines are employed to pump water from the low-level reservoir back up to the high-level one using excess energy from the grid. This ensures that the high-level reservoir maintains sufficient water volume to continue electricity generation in the next cycle. The intake from the river remains closed during this time, emphasizing the station's efficient use of water. The careful management of this cycle allows for consistent electricity supply and resource conservation, illustrating the sophistication of modern hydroelectric power stations.

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Model Answer 3 (Band 8)

The provided diagram showcases the process of electricity production in a hydroelectric power station, which is initiated by the flow of water from the river into a high-level reservoir and ends with the transmission of electricity to the national grid.

During the day, water flows down the river to reach a high-level water storage facility that features a dam. The water then passes through the intake of the dam, after which it moves towards the hydropower station. The turbines at the hydropower station are activated, and the water turns them to generate power that is subsequently supplied to the National Grid. Finally, the water is stored in a low-level reservoir at the end of the daytime.

The night operation begins by reversing the turbines and pumping the water from the low-level reservoir. This water is then directed towards the dam and transported to the high-level reservoir. It is important to note that the intake to the dam remains closed, ensuring that all the water is retained in the high-level reservoir.

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Model Answer 4 (Band 8)

The provided illustration depicts the process of generating power in a hydroelectric power plant. The power generation process involves releasing water from a dam during the day, which is then pumped back at night. The overall process is both innovative and environmentally friendly.

The process can be divided into two main stages - the daytime and night-time stages. The daytime stage involves the production of electricity from the river and the storage of water in a reservoir. The river water is channelled into a high-level reservoir, which is backed by a dam and an intake area leading to the power station. During the day, the intake area is open, and the water flows into the power station turbines to generate electricity. The generated electricity is then transmitted to the national grid via power lines, while the excess water is stored in a low-level reservoir.

During the night-time stage, the water stored in the low-level reservoir is pumped back to the power station using turbines, and then it is transported to the high-level reservoir, which is closed during the night. The river water is stored at the upper level and flows down to start the cycle again.

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Model Answer 5 (Band 7)

The provided diagram illustrates the process of electricity generation in a hydroelectric power station, which can be broadly divided into day and night stages. The day stage involves the production of electricity from the river and the storage of water in a reservoir, while the night stage involves the return of water to the initial reservoir and the river.

The initial stage of the process involves the river water being channelled into a high-level reservoir, which is backed up by a dam. There is an intake area leading to the power station that is open during the day and closed at night. During the day, water flows through the power station turbines, generating electricity that is transmitted to the national grid via power lines. Excess water continues to a low-level reservoir.

The reversible turbines used in the day stage allow the power station to pump water from the low-level reservoir back into the high-level reservoir for use the next day. During the night stage, the water stored in the low-level reservoir is returned to the initial reservoir and the river, ensuring that the cycle can be repeated the following day.

Model Answer 6 (Band 7)

The image shows how electricity is generated at a hydroelectric energy facility.

Overall, the mechanism consists of a cycle where water is moved by gravitational force during the day from a high-level storage to a lower-level reservoir and returned to the first reservoir by a pump during the night.

To explain, the river ends into a high-level reservoir storing water behind a dam. There is an intake connecting this reservoir to a generator located in a lower altitude. During the day, the intake opens and allows water to flow from the high-level reservoir through a pipe to reach the generator. Then, the electricity is produced in the generator and is transmitted to national grid by power lines from the power station.

To continue the cycle, the water that has reached the generator during the day is moved and stored in a low level reservoir. During the night, this stored water will be pumped back the whole route into the high-level repository. However, the intake in high-level reservoir is closed during the night to prevent the backward shift of water from high-level reservoir and to facilitate the cycle to be completed.

Model Answer 7 (Band 6.5)

The presented diagram outlines the process of hydroelectricity generation in a power plant, which is cyclical and comprises four main stages: storing water high, using the water to generate electricity, storing water low, and pumping the water back uphill for reuse.

Initially, the dam stores the river water behind it in the upper reservoir, which has an intake at the bottom. During the daytime, the intake is open, allowing water to flow through. The water moves downhill into the lower reservoir, passing through the turbines, which turn their blades to generate mechanical energy. The spinning turbines drive the generator, which converts the mechanical power into electricity. The electricity is then transmitted to the national grid through power lines.

During the night, when the demand for electricity is low, the turbines switch to pump mode and pump the water kept in the lower reservoir back to the upper reservoir for reuse. This ensures that the plant is ready to generate electricity during the daytime, without the need for additional water supply.

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