Hydro power is a renewable energy source with a huge amount of potential. Not only is hydroelectricity already providing close to twenty percent of the world's energy (projects in Canada and China - such as the Three Gorges Dam, for instance - have been incredibly successful) but it is also a growing field. Research is currently being carried out in the areas of wave and tidal barrage power to determine the feasibility of the technologies, and old hydroelectricity techniques are constantly being improved.
In countries or regions where there is significant rainfall the incorporation of hydroelectricity into the power generation portfolio is relatively straightforward - all it requires is a steady flow or large store of water. Coastal areas too are potential targets for hydro-power technology - wherever there are large tidal changes or fast currents force and energy can be harnessed. It is little surprise that the huge potential of water-generated energy is being investigated in such depth; after all human beings have historically relied upon water to mill, to irrigate, and since the industrial revolution to create power and electricity. It is fitting that in the hunt for renewable energy sources we return to a technology that has been around for thousands of years.
There are several different methods for generating electricity through the use of water. The two techniques that are most relied upon are the reservoir and run-of-the-river generation methods. Reservoir hydroelectricity uses the force of a large body of water being released through a small spill-way to push a turbine which in turn converts the energy into electricity. Whilst some of these types of dams or reservoirs release the water directly into a stream or river below, pumped-storage hydroelectricity uses two dams (one lower than the other) to contain the water released and thus recirculate it back into the higher dam. This provides a reliable and consistent source of energy regardless of rainfall.
The other popular form of hydroelectricity generation is what is known as 'run-of-the-river' and involves the steady flow of a river or spillway to turn a turbine. Both of the techniques mentioned are suitable for microgeneration projects as well as commercial and industrial-scale supply.
The other form of hydroelectricity generation, that which harnesses the power of the ocean, is a relatively new field of science and is for the most part still in the experimental phase. There are several different forms of ocean-powered hydroelectricity, including tidal barrage, wave and tidal stream power. Each system relies on the flow of the tides: barrage technology makes use of the shifting force of large bodies of water whilst the tidal stream system uses incoming and outgoing tides to turn turbines.
Wave power, meanwhile, utilizes the rise and fall of waves to generate mechanical energy. Though in their infancy, these technologies are being thoroughly investigated and are beginning to be installed in locations around the world.