Tidal Energy is another type of renewable energy resource that utilises large amounts of energy within the oceans tides to generate electricity. As we all know from our science lessons, tides are caused by the gravitational forces upon the earth of the sun and the moon, which varies due to their elliptical orbits around the earth. These gravitational forces cause our seas and oceans to rise and fall in a continuous and predictable cycle as vast quantities of water circulate around the earth. The result is that coastal areas have two high tides and two low tides within slightly more than a 24 hours cycle.
The earliest known exploitation of tidal energy was used by tidal mills, which were created by building a barrage across the mouth of a river estuary. Sea water was trapped in a tidal basin on the rising tide and released at low tide through a low-head waterwheel, providing power for everything from turning a stone mill to grind corn, sawing lumber to operating the bellows and hammers in ironworks etc.
Today, the rising incoming and falling outgoing tides are used to generate electricity, in much the same manner as hydroelectric power plants with the technology required to convert tides potential energy into electricity is very similar to the technology used for traditional hydroelectric power. Tidal barrages for electricity generation use large low-head turbines which can operate for a greater fraction of the day. But building dams and fences across tidal estuaries is an expensive process, therefore the best tidal sites are those that exist where a tidal bay has a narrower opening, thus reducing the length of the dam required.
Electricity is generated by the force of the sea water flowing both into and out of a tidal bay through a water turbine, turning an electric generator to produce electricity. Because there are two high and two low tides each day, electrical generation from tidal power plants can be predicted years in advance, unlike wind energy, and is characterized by periods of maximum generation every twelve hours, with no electricity generation at the six-hour mark in between the high tides.
Another tidal energy design that uses the currents created by the ebb and flow of the tides is Tidal Stream Generation. Tidal stream generation is very similar in principle to wind power generation except this time water currents flow across a turbines rotor blades which rotates the turbine, much like how wind currents turn the blades for wind power turbines. In fact, tidal stream generation areas on the sea bed can look just like underwater wind farms and in areas where the coastal currents are strong, a suitable tidal stream turbine can generate as much free tidal energy as a wind turbine at the same speed and almost four times the size.
Tidal energy has many advantages compared to other forms of renewable energy with its main advantage being that it is predictable, which means power generation is predictable too, unlike wind or solar energy and being located underwater, tidal turbines produce no emissions or noise. However, like many other forms of renewable energy, tidal energy also has its disadvantages such as its inflexible generation times dependent upon the tides and the fact that it operates in the hostile conditions of the open oceans and seas which can be a stormy and violent environment, resulting in the tidal turbines being destroyed by the very energy they were designed to capture.
Tidal energy is a renewable source of electricity that does not result in the emission of gases responsible for global warming or acid rain, which are associated with fossil fuel-generated electricity. Use of tidal energy could also decrease the need for nuclear power. Changing tidal flows by damming a bay or an estuary or locating large turbine generators onto the seabed could, however, result in negative impacts on aquatic and shoreline ecosystems, as well as on navigation and recreation.
Tidal energy requires a large capital investment in dams, turbines and support ships, but once a "tidal energy" plant is built the energy it generates is essentially free with the system being relatively inexpensive to run.
To learn more about "Tidal Energy", or to explore the advantages and disadvantages of using Tidal Energy as an alternative energy resource, visit http://eversity.co/elearning/tidal_energy.aspx
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