Band 8.5 IELTS Writing Task 1 Model Answer

Overall Band Score: 8.5 · Cambridge IELTS 14 · 2026-08-09

IELTS Writing Task 1 question

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.

Student answer (Band 8.5)

The diagram illustrates the process by which electricity is generated in a hydroelectric power station during both the daytime and nighttime.

Overall, the system operates as a continuous cycle in which water is released from a high-level reservoir during the day to generate electricity, while at night, the water is pumped back to the upper reservoir for reuse. The key components of the system are the dam, reversible turbines, generator, and two reservoirs.

During the daytime, water stored in the high-level reservoir is released through an intake and flows downhill towards the power station. As the water passes through the reversible turbines, they are activated and drive a generator, which produces electricity. The electricity is then transmitted through power lines to the national grid. After passing through the turbines, the water is discharged into the low-level reservoir.

At night, when electricity demand is lower, the process is reversed. The reversible turbines operate in the opposite direction and function as pumps, drawing water from the low-level reservoir and sending it uphill through the same channel. The water is consequently returned to the high-level reservoir, ready to be released again the following day.

Thus, the hydroelectric power station functions as a closed-loop system, repeatedly moving water between the two reservoirs while generating electricity during periods of demand.

AI examiner evaluation

Task Achievement / Task Response — Band 8.5

The response is excellent. You have clearly identified the main features of the hydroelectric power station, including the cyclical nature of the process and the distinction between daytime and nighttime operations. The overview is concise and effectively summarises the core mechanism. You have successfully highlighted the key components and described the movement of water between the high-level and low-level reservoirs. The information is accurate, well-selected, and logically presented, fully satisfying the requirements of the task. No significant information is omitted, and the comparison between the two phases is clear and well-developed.

Coherence and Cohesion — Band 8.5

The essay is logically organised with a clear progression of ideas. Each paragraph has a distinct focus: the introduction and overview, the daytime process, the nighttime process, and a concluding summary. Cohesive devices such as 'During the daytime', 'After passing through', 'At night', and 'consequently' are used effectively to guide the reader through the process. The paragraphing is logical, and the referencing is clear throughout. The flow of information is smooth, and the relationship between the different stages of the cycle is well-articulated, making the text very easy to follow.

Lexical Resource — Band 8.5

You demonstrate a wide and precise range of vocabulary appropriate for a technical description. Terms such as 'continuous cycle', 'reversible turbines', 'closed-loop system', and 'discharged' are used accurately and naturally. The vocabulary is sophisticated and contributes to the clarity of the explanation. There are no noticeable errors in word choice or collocation, and the language used is consistently formal and academic, which is ideal for this type of task. The control over technical terminology is impressive and enhances the overall quality of the response.

Grammatical Range and Accuracy — Band 8.5

The response exhibits a wide range of grammatical structures with full flexibility and accuracy. You have successfully employed complex sentence structures, such as 'The electricity is then transmitted through power lines to the national grid' and 'The reversible turbines operate in the opposite direction and function as pumps, drawing water from the low-level reservoir'. Punctuation is used correctly throughout, and there are no grammatical errors. The control over tense and voice is consistent, and the writing is error-free, reflecting a high level of grammatical competence.

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