Of all the sources of renewable alternative energy available, the most popular currently being ethanol, one often overlooked is tidal energy. Tides involve the massive movement of water that occurs everyday throughout the world, raising lowering water levels on any coast at any time. Even in larger lakes like lake Superior, and rivers that are close enough to the sea, the daily movement of tides are highly noticeable to the point where they are part of the daily forecast.
So why not harness the energy of these massive water movements? As a form of hydropower, tidal energy is more reliable than either wind energy or solar power considering its predictability. There are three main ways to harness this energy, the first being a barrage system in which the entrance to a tidal estuary is damned and energy is collected from the daily rise and fall of the water level. However, these barrages and be costly and as with any dammed project, suffer from a myriad of environmental issues that follow any damming project.
The second are tidal lagoons, which operate much like barrages except that they can be self-contained structures that do not completely damn off an estuary, costing less and causing less environmental damage. The third system, and by far the best environmentally speaking, is a tidal stream system, which works in much the same way as a windmill, except that it is underwater. There is no damming and the system can also continuously supply energy, which barrages cannot.
As of yet Tidal Stream systems are being looked into for most major tidal power projects at sights with strong thermal or natural high-velocity currents including the coasts of Canada and the Straight of Gibraltar. Other theories of tidal power include vortex induced vibrations along the ocean floor.
While at present only nations or state bordering a major tidal body of water have to potential ability to profit off this technology, it is certainly worth investigating, especially as methods like tidal stream systems and vortex induced vibrations continue to develop, which unlike most hydropower dam projects, do not impede the natural lives of surrounding plant and animal life, which is always a consideration when developing eco-friendly technologies.