Tidal Power: A Lecture

Transcript

Lecturer: Today I want to talk about tidal energy, a form of renewable power that gets far less attention than wind and solar.

Lecturer: Let me begin with the basics. Tides are caused mainly by the pull of the moon on the oceans, with a smaller effect from the sun. This gives tidal energy one great advantage over wind and solar power: it is extremely predictable. Engineers can say when the tide will be high or low years in advance.

Lecturer: There are two main ways of using the tides. The first is the tidal barrage. This is a wall built across an estuary, with gates and turbines inside it. Water flows in as the tide rises and out as it falls, turning the turbines both ways. The first large barrage was built at La Rance, in France, and it opened in 1966. It is still producing electricity today.

Lecturer: So why aren't there barrages everywhere? The main problem is cost. A barrage needs a huge amount of concrete and takes years to build. There is also an environmental problem. A barrage changes the movement of water in the estuary, and that can harm birds that feed on the mud when the tide goes out.

Lecturer: The second method is the tidal stream turbine. These work rather like underwater wind turbines. Instead of air, they use the flow of the sea, and they are fixed to the sea floor. They cost less to build than a barrage and do far less damage to the surroundings. But they need a fast current to work well, and that means they can only be placed in a few locations around the coast.

Lecturer: To summarise, tidal power is reliable and predictable, but it is expensive and not available everywhere. In the next session we will look at how engineers compare the cost of different renewable sources.