Why hasn’t tidal power taken off yet? © Alamy

Why hasn’t tidal power taken off yet?

Tidal power has good potential as a renewable energy source but there are currently a few barriers to its growth.

Although wave and tidal power have the potential to deliver 20 per cent of the UK’s electricity needs, we receive less than 3 per cent of our energy in this way. While other renewable energy sources, such as wind or solar, have seen rapid growth in recent years, tidal power lags behind.

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Tidal power uses underwater turbines to harness the phenomenal energy unleashed by rising and falling tides. Tidal farms typically use barrages or artificial lagoons to channel the flow of water, and newer types of turbines can be installed directly on the seafloor.

Unlike solar or wind power, which only generate electricity under the right weather conditions, tidal power can reliably be harnessed every day. The Moon’s gravitational pull ensures two daily powerful tides across the globe.

Despite their low carbon credentials, tidal farms can spell trouble for the local environment. Turbines can injure marine animals and barrages restrict the movement of migratory species. The electromagnetic fields and noise generated are also a concern, particularly for animals that use echolocation.

However, the large price tag accompanying new tidal farms can make them a tricky proposition for politicians. Of five proposed projects in the Severn Estuary shortlisted by the UK government in 2008, the cheapest came in at £2.3bn, and none were greenlit.

Why is tidal so expensive? Some costs are unavoidable. Tidal farms need to be durable enough to withstand the force of the tides and their large size entails a vast quantity of construction materials, particularly concrete.

But technology-related costs may fall: tidal power is still in its infancy and although expensive today, government support for tidal power may help costs tumble, following in the footsteps of offshore wind energy.

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Asked by: John Awbery, Reading

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