Hydro – Kinetic Energy

Oct 31, 2012   //   by admin   //   Knowledge Base  //  No Comments

Hydro – Kinetic Energy

Water bodies have been a clean source of renewable energy since olden times. The history of harnessing water power is very old. It was first used by Greeks to grind wheat by using water power generated by moving water over water wheels in eighteenth century. The word Hydro means water and kinetic means moving so we can define, Hydro- Kinetic Energy as the energy derived from moving water over a turbine or wheel. It is a very eco-friendly and clean form of energy since there is no emission of greenhouse gases.

Traditional hydro- power systems used diversions created by dams or water reservoirs. While the new and advanced technology doesn’t require these. Instead of impoundments and diversion, these harness energy in currents, surfaces waves and tides.  These devices are still under development and commercialization .There is one thing common between both of the two technologies i.e. underwater turbines. Both of them use horizontal or vertical axis turbine which helps rotor to turn generator.  The energy generated is function of density of water and the speed of flowing water. Unlike solar energy and wind energy these have more capacity to generate power as water has more density then air. For generation of power hydro-kinetic devices need a minimum current and depth. As water flows through a turbine or other device, the kinetic energy of the flowing river, tidal fluctuations, or waves is converted into electricity by the device. The minimum current required for operation is generally 2-4 knots while the ideal currents are 5-7knot. Depth of water body is a very important factor in the total energy that can be generated as we need sufficient water level so that device can be submerged into it. The Hydro – kinetic devices can mainly categorise into two types:-

–       Wave Energy converters

–       Rotating devices

Wave energy converters– It utilises the motion between two bodies i.e. Displacer and Reactors. They transfer energy on the basis of changing or fluctuating waves. There are further four common types of WEC’s:-

1) Oscillating water column:  The waves enter into the collector through the lower side of the collector which partially inside the water, which causes the water level inside the collector to rise and fall. This change in water level acts as a piston for the system, as it drives air that is trapped in the device above the water into a turbine, producing electricity by a coupled generator.

2) Point Absorber: The energy is generated from waves coming from all directions with a central point which forces the water body to move the turbine. There are many possible arrangements of this system. For e.g. Hose Pump point absorber which utilises vertical motion of waves to generate electricity.

3) Attenuator: These are long & combined floating arrangements which are aligned parallel to the wave direction and generate electricity by the waves.

4) Over- topping device: It is a device with reservoirs which is  filled by incoming waves to level above the average surrounding ocean. The water is then released, and gravity causes it to fall back toward the ocean surface. The energy of the falling water is used to turn turbines.

Rotating Devices: – Rotating devices capture the kinetic energy stored with in a flow of water as it passes across a rotor. The rotor turns with the current, creating rotational energy that is converted into electricity by a generator. Rotational devices are very similar to wind turbines in concept. These are more commonly used in rivers and streams.

There are many benefits of using hydro –kinetic energy.

1) It is a clean and renewable form of energy.

2) There is greenhouse emission during construction or operation.

3) There’s no initial or afterwards flooding due to hydro- kinetic power systems.

4) These can be set-up with a low investment.

5) Unlike conventional sources of dams and reservoirs these do not affect livelihood of local communities. As they are setup mostly underwater these doesn’t require relocation of peoples.

6) These avoid impacts on wildlife that are associated with conventional hydropower projects.

7) There is no noise pollution.

8) These have competitive cost per kWh compared to other renewable sources of energy.

9) There is no requirement of much labour force.

10) These have minimal infrastructure, they arrive pre-assembled and can be quickly installed.

Despite of the above benefits hydro-kinetic still needs development and proper supply of these especially the regulatory process. The regulatory process for both dams and hydrokinetic devices is the same, which makes difficult to obtain a license to deploy hydro-kinetic devices. There is no conflict over permitting issues for deployment which makes the field – test difficult. Without a proper license or permission and field test investors and sponsors usually hesitate to fundraise these projects.

For a proper deployment, there is need of change in existing regulatory process. Proper funding for research and development should be made available. The discussion and cooperation among public and private bodies should be encouraged. With proper framework and development hydro-kinetic energy has a wide scope of its role as renewable source of energy. With proper utilisation of available water resources will be a clean and sustainable solution to our dependency on fossil fuels.

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