The diagram below shows the production of electricity using a system called Ocean Thermal Energy Conversion (OTEC).

Write a report for a university lecturer describing the information below.

Write at least 150 words.

How Ocean Thermal Energy Conversion (OTEC) works
Source: Daily Telegraph - 8th Jan 2008

Model answer

(150 words) The diagram illustrates how the Ocean Thermal Energy Conversion system produces electricity and drinking water. As regards its structure, the system includes an evacuated evaporation chamber and a condensing chamber which are linked together by two tubes.

In one stage, warm seawater at the surface of the ocean is led into the evaporation chamber where it boils to produce steam. The steam then moves upwards to turn a turbine to produce electricity. Leftover salt from the evaporation process sinks down and is discharged into the ocean.

In another stage, the steam which has finished powering the turbine goes downwards into the condensing chamber which is built approximately 1,000 metres under the sea. Inside the chamber, the water vapour then condenses into drinking water under the effect of the cold seawater (roughly 5 degrees Celsius) which flows around the chamber. This is where one cycle completes and a new cycle starts.