When Green Energy is Blue Energy: Power From the Sea
Feeling a Tidal Pull: Using The Energy of the Tides
Tidal power can be thought of as a cross between ocean current and wave power—it’s similar to current power in the sheer amount of water in motion, but similar to wave power in that it is a periodic flow with some variability, rather than a constant, unidirectional stream. If you live near the coast or have visited the beach, you’re familiar with tides. But what you may not be familiar with is the jaw-dropping power and scale of tides in areas where the right geography channels and focuses them. For example, the River Severn in the United Kingdom has the second-highest tidal range in the world (the difference between the high and low tides is 15 meters!), exceeded only by Canada’s Bay of Fundy. Billions of tons of water can be funneled through areas like these each day, representing an enormous potential energy source.
There are two different ways to harness tidal power. The more ambitious is with a barrage (a “wall” obstructing the tide) or man-made lagoon. In these schemes, barriers would be built across all or a part of a bay or river. As the tide moves in and out, it flows past turbines in the barrage or lagoon wall, generating electricity. At present, there are only three functional barrage power plants—one in Canada, at the Bay of Fundy (very small scale, compared to what could be done there), one in France on the Rance River, and one in Russia.