Various forms of hydrokinetic turbines

Sep 9, 2017   //   by admin   //   Knowledge Base  //  No Comments

Hydrokinetic turbines use the kinetic energy stored in flowing water to generate more usable forms of energy. In ancient times turbines have application only in small water bodies but with the advancement in technology they can extract energy from waves, tides and currents of oceans and sea. These have potential to provide sustainable and dependable source of energy and much potential for future energy needs.

There are various forms of hydro-kinetic turbines:-

1) Traditional turbines

2) Wave energy converters

3) Rotating devices

Traditional water turbines: –

Traditional water turbines like Kalpan turbines, Water wheels and Reverse Archimedes’ screw used diversions and reservoirs for power generation. It has applications in rural areas in small hydro power plants. A typical micro hydro power plant has an automatic controller operates the turbine inlet valve to maintain constant frequency when the load changes on the generator. The kinetic energy of water allows the turbines to move and then mechanical energy is then converted into usable forms. The turbine is connected to a generator which supplies power to utility grid.

 

Wave Energy Converters: –

These devices harness the surface energy of waves in to other useful forms of energy. The energy generated is function of density of water and the speed of flowing water. The wave energy converters can be further differentiated into the following types:-

  1. i) Attenuators: –

They are long and multi segmented structure which floats parallel to the direction of waves. The attenuator is positioned perpendicularly to incoming waves. Some devices tap only the vertical motion while others tap both vertical and horizontal motions. The device captures energy as the motion of the wave causes it to contract where they the fragments connect. The energy hence produced drives generators and pumps.

  1. ii) Point absorber: –

Point absorbers harnesses surface energy of waves coming from all directions in vertical motion. The energy of waves causes buoyant top portion to move in up and down direction. This movement of the top portion drives generators and produces electric current

iii) Oscillating wave surge converter: –

Oscillating wave surge converter extracts energy from wave surges (vertical motion) and the movement of water particles within them. . It uses the oscillation between flap and a fixed point. This movement creates a usable form of mechanical energy and produces current.

  1. iv) Oscillating water column: –

Oscillating water columns is a partially submerged hollow structure. Waves are then directed into the lower part the surface by a funnel like structure, forcing the water column to rise and fall. This piston like movement pressurizes and depressurizes water column inside the body and this pressure of movement of air is used to move the turbine which produces current.

  1. v) Overtopping device: –

It is a floating reservoir like structure. The device creates water level to rise to break into reservoir with a funnel shaped structure. The water is then returned back to the sea after passing through various water turbines which later on generate electricity.

  1. vi) Submerged pressure differential: –

These are located near shore and attached to the water bed. The motion of waves which causes waterlevel to rise and fall over the device. The alternating pressure of waves is utilised to generate electricity.

vii) Bulge wave: –

Bulge wave consists of a rubber tube filled with water, anchored to the waterbed heading into the waves. The water enters through the stern and the passing wave causes pressure variations along the length of the tube, creating a ‘bulge’. The energy created by the bulge can used to drive turbines at the bend and water is then returned back to the sea.

Rotating devices: –

Rotating devices are constructed within in the water body to capture kinetic energy of flowing water which allows turbine to rotate and hence generating power. It uses heaving and swaying of waves creating a rotational energy that turns the rotor or the turbine. Some of the rotating device have design like wind turbines and have horizontal axis while the more practical version of rotating devices have vertical axis which resembles egg beaters.

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