With nearly three-quarters of the Earth's surface being covered by water, utilizing the world's oceans as a sustainable, renewable energy source makes perfect logical sense. Currently there are three main types of hydroelectric power that are being utilized and further researched for their potential to provide the word with emission-free, renewable energy.
1. Ocean Thermal Energy Conversion (OTEC)
From the ocean's floor to its surface, thermal differences occur. OTEC processes involve the use of heat exchangers. The most successful OTEC plants use what is called an open-cycle system. What this does is take in warm water and compress it. Since the laws of physics dictate that when pressure increases so does temperature, the result of compressing the water results in it boiling. As the steam escapes from the now boiling sea-water, it is directed through a pipe where it will power a turbine. As the water vapor cools and condenses, it is reintroduced to the ocean where it continues to cool. OTEC works well in areas of low latitudes (i.e. the tropics) since the water is already quite warm.
2. Wave Power
In response to the gravitational pull from the Moon, the ocean's waves are constant. This makes them a potentially powerful source of renewable energy. Although the researchers of the world have not yet established a working wave farm, there are definitive plans for such a venture.
The concept behind wave power is to harness the up and down motion of the crests and troughs of each wave cycle. This would be accomplished by setting a buoy in the water that is connected to an onshore turbine or generator. The mechanical energy would then be used to power a turbine. The extreme variability of waves, combined with surface winds, proves a formidable challenge to the development of wave power as a renewable energy source.
3. Tidal Power
Much like wave power, tidal power also makes use of vertical motion. However, instead of energy being stored from each wave, the changing water depths that occur with tides are the source. In order to store tidal energy, a barrage must be constructed across the expanse of a body of water such as an estuary. Much like a hydroelectric dam, a barrage is a series of compartments and locks through which the water flows. The barrages are designed such that they can control how much water is flowing through at one time, and therefore, how much potential energy is stored.
Non-emitting renewable energy sources are fast becoming a necessity. The use of such hydroelectric power systems is now yet widespread, and there are considerable obstacles that must be overcome. However, the cost associated with starting up these power plants is a major deterrent. Until these technologies are more widely used and can produce cost-effective energy, the world will continue to consume its ever- diminishing supply of fossil fuels.