TYPES HYDROPOWER
Dams
The most common type of hydroelectric power plant uses a dam on a river to store water in a reservoir. Water released from the reservoir flows through a turbine, spinning it, which in turn activates a generator to produce electricity. But hydroelectric power doesn't necessarily require a large dam. Some hydroelectric power plants just use a small canal to channel the river water through a turbine.
Another type of hydroelectric power plant - called a pumped storage plant - can even store power. The power is sent from a power grid into the electric generators. The generators then spin the turbines backward, which causes the turbines to pump water from a river or lower reservoir to an upper reservoir, where the power is stored. To use the power, the water is released from the upper reservoir back down into the river or lower reservoir. This spins the turbines forward, activating the generators to produce electricity.
TIDAL ENERGY
Unlike in wind turbines, the blades in tidal energy devices move a lot slower because of the high density of the medium (water). However, they carry a lot of power.
Tidal barrages
One type of tidal energy system uses a structure similar to a dam called a barrage. The barrage is installed across an inlet of an ocean bay or lagoon that forms a tidal basin. Sluice gates on the barrage control water levels and flow rates to allow the tidal basin to fill on the incoming high tides and to empty through an electricity turbine system on the outgoing ebb tide. A two-way tidal power system generates electricity from both the incoming and outgoing tides.
A potential disadvantage of tidal power is the effect a tidal station can have on plants and animals in estuaries of the tidal basin. Tidal barrages can change the tidal level in the basin and increase turbidity (the amount of matter in suspension in the water). They can also affect navigation and recreation.
Several tidal power barrages operate around the world. The Sihwa Lake Tidal Power Station in South Korea has the largest electricity generation capacity at 254 Megawatts (MW). The oldest operating tidal power plant is in La Rance, France, with 240 MW of electricity generation capacity. The next largest tidal power plant is in Annapolis Royal in Nova Scotia, Canada, with 20 MW of electricity generation capacity. China, Russia, and South Korea all have smaller tidal power plants.
The United States does not have any tidal power plants, and it only has a few sites where tidal energy could be economical to produce. France, England, Canada, and Russia have much more potential to use tidal power.
Tidal turbines
Tidal turbines look similar to wind turbines. They can be placed on the sea bed where there is strong tidal flow. Because water is about 800 times denser than air, tidal turbines have to be much sturdier and heavier than wind turbines. Tidal turbines are more expensive to build than wind turbines, but capture more energy with the same size blades. Strangford Lough, Scotland, and Uldolmok, South Korea, both have 1.5 MW tidal turbines. A tidal turbine project is under development in the East River of New York. Another project with up to 400 MW of electricity generation capacity is under development in northern Scotland.
Tidal fences
A tidal fence is a type of tidal power system that has vertical axis turbines mounted in a fence or row placed on the sea bed, similar to tidal turbines. Water passing through the turbines generates electricity. As of the end of 2016, no tidal fence projects are currently operating.
Wave energy (WE) harnesses the kinetic energy in the up-and-down movement (waves) of water in the ocean. The waves are caused by wind action, and wind action is caused by the sun heating the surface of the waters, generating air pressure. This means as long as there is the sun, there will be wind and waves, even though its intensity may vary.
Wave energy locations are best where there are strong winds traveling over very long distances. This makes places like the west coast of UK a great point, because of the winds over the Atlantic.
Wave Energy is captured by devices called Wave Energy Devices. There are several types of Wave Energy Conversion devices including the following:
A. Point Absorber: This floating structure moves up and down and in all directions. With some conversion mechanisms inside it, power is converted and stored in a hub at the base.
B. The Attenuator: This floating device also rides the waves, flapping like the wings of a bird, a movement caused by the pounding waves. The kinetic energy in the movement is converted into energy and stored.
C. The Oscillating Wave Surge Converter: This device extracts energy from the waves of the water. It is installed below the water surface, but the current is strong enough to cause it to oscillate.
Some tidal converters work just like the wind turbines. Kinetic energy from the spinning of the blades, caused by the currents is tapped with the help of some converters inside of the spinning structures to generate electricity.
Examples of tidal energy converters include the Horizontal Axis Turbine, Vertical Axis Turbine and the Oscillating Hydrofoil.