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Water (Hydro, Tidal, Wave)
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Hydro power

Show me a map of Hydroelectric projects in the UK (as of end 2004)

Hydro power is produced when the kinetic energy of flowing water, is converted into electricity by a turbine connected to an electricity generator.

Hydropower can be exploited at various different scales. Large-scale is typically taken to mean more than 20 MW of grid-connected generating capacity and is usually associated with a dam and a storage reservoir. There are many large schemes in Scotland, which were built during the 1950’s. The potential for identifying new large-scale schemes is now more limited, not only because there are fewer commercially attractive sites still available, but also because of environmental constraints.

Schemes of less than 20 MW now offer a greater opportunity for providing a reliable, flexible, and cost-competitive power source with minimal environmental impacts. These small-scale schemes are making an increasing contribution towards new renewable energy installations in many regions of the world, especially in rural or remote regions where other conventional sources of power are less readily available. Small scale schemes can be associated with a dam and storage reservoir or can be located in a moving stream ("run of river").

Tidal Power

Tidal power can use either conventional or new technology to extract energy from a tidal stream. It is usually deployed in areas where there is a high tidal range. Typically a barrage with turbines is built across an estuary or a bay. As the tide ebbs and rises, it creates a height differential between the inner and outer walls of the barrage. Water can then flow through the turbines and drive generators. Some tidal barrages operate on both the rising and falling tide, but others, particularly estuarine barrages, are designed to operate purely on the falling tide.

It is also possible to make use of the tidal flow that occurs between headlands and islands or in and out of estuaries. It is this application that is the focus of much research and development, and new products for this purpose are now being commercialised. These “in-flow” tidal turbines can be arranged singly or in arrays, allowing a range of power outputs to be produced.

Wave Power

The power of the waves is readily visible on nearly every ocean shore in the world. There has been much research to harness the power of these waves, and various machines have now been developed. These fall broadly into three categories:

Machines which channel waves into constricted chambers. As the waves flow in and out of the chamber, they force air in and out of the chamber. These airflows are in turn channelled through a specialised turbine, which is used to drive a generator. This type of machine is principally designed for use on or near the shore, or for incorporation into breakwaters. Commercially, this kind of machine is the most advanced and is particularly advantageous when incorporated into coastal protection.

Fixed or semi-fixed machines which utilise the pressure differential in the water that occurs at a submerged point as the wave passes over that point. The pressure differential is used by a variety of means to cause a fluid to flow in a circuit, which is then used to drive a turbine and generator.

Machines which utilise their buoyancy to cause movement in a part of the device as it moves up and down in the wave. The movement is used either directly or indirectly to drive a generator.

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