If you have ever lived near the ocean, you know about tides. Like clockwork, the tide rolls in and out moving massive amounts of water from here to there and back again. This massive movement of water also happens to contain a huge amount of energy. If the power of the tides could be converted to usable energy, many think tidal energy would be the answer to many of the energy problems in the world.
There are two basic theories on how to convert tides into power. The first involves converting the power of the horizontal movement of the water into electricity. The second involves producing energy from the rise and drop of water levels. With our vast knowledge of hydroelectricity production with dams, converting moving water is currently the favored technology.
With hydropower, energy is produced by passing moving water through turbines which spin and create electricity. While this may seem an obvious way to go after tidal power, there are some inherent problems. First, tidal water moves much slower. Second, the energy in tides are spread across great areas, to wit, the energy in the amount of water that would pass through even a large pipe is relatively small. This technological quagmire has never been solved, but a new approach is gaining adherents.
One new approach incorporates the dam principals in hydroelectric production. The idea is to let water come in when the tide is rising and then prevent it from leaving when the tide goes out. Doors are used to cut off the water. The water is then diverted into pipes with turbines and you essentially have hydroelectric power.
There are a few problems with this approach. First, the tidal area is devastated because the natural cycle is interrupted. Second, the volume of moving water is reduced because the dam can't be built with a large enough opening to allow all water to enter. Third, the inherent corrosive nature of salt water leads too much higher maintenance costs or at least is forecast to do so.
The advantage of tidal energy is it is extremely reliable and predictable. Orbital issues involving the moon cause tides. Although the moon is slowly moving away from the Earth, the sun is expected to burn out before it gets very far away. Regardless, this means tides are highly predictable from both size and time aspects. In fact, you can go to any surf store and pick up a tide table.
The tidal energy platform has a lot of potential if technological issues can be overcome. To date, Japan and a few European countries are the only ones researching solutions.
