Practice Tests
IELTS Reading (AC) Task 1 #96

A. Among the array of renewable energy sources, tidal power stands out for its unique reliability. While solar and wind energy depend on variable weather conditions, the power generated from the rise and fall of ocean tides is remarkably predictable, governed by the consistent gravitational pull of the moon. This ancient form of energy, harnessed for centuries in rudimentary ways, is now being re-examined with modern technology, offering a potent, if geographically limited, alternative to fossil fuels.

B. The concept of utilising tidal forces is far from new. As early as the Roman era, and more extensively during the Middle Ages, coastal communities constructed tide mills. These structures, often built across tidal estuaries, featured a large basin that would fill with water during high tide. As the tide receded, the trapped water was channelled through a sluice gate, turning a water wheel to power machinery for grinding grain. The Eling Tide Mill in the United Kingdom, for instance, has been in operation for over 900 years, a testament to the enduring principles of this technology.

C. The modern incarnation of the tide mill is the tidal barrage. This method involves constructing a large dam-like structure across a river estuary or bay with a significant tidal range—the difference in height between high and low tide. During the incoming high tide, gates in the barrage open to allow water to fill the basin. At high tide, these gates are closed, creating a difference in water level. The stored water is then released through turbines embedded in the barrage as the tide ebbs, generating substantial amounts of electricity. The La Rance Tidal Power Station in France, operational since 1966, remains a prime example of this large-scale approach.

D. Recognising the significant environmental impact and high construction costs associated with barrages, engineers have developed alternative methods. One of the most promising is the tidal stream generator. Functioning much like an underwater wind turbine, these devices are submerged in areas with strong tidal currents. The moving water turns the blades of the turbine, which in turn drives a generator. This approach has a considerably smaller ecological footprint, as it does not require damming an entire estuary and allows marine life to move more freely, representing an innovative step towards more sustainable tidal energy extraction.

E. Despite its predictability and potential, the widespread adoption of tidal power faces several formidable obstacles. The initial capital investment required for construction is exceptionally high, and suitable sites with the necessary tidal range are scarce globally. Furthermore, concerns persist regarding the ecological consequences, including the potential disruption to marine habitats and changes in sediment flow. Consequently, while tidal power is unlikely to become a universal solution, it is increasingly viewed as a valuable component within a diverse portfolio of renewable energy technologies, particularly for coastal regions blessed with powerful tides.