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The word hydro comes from a Greek word meaning water. The energy from water has been harnessed to produce electricity since long. It is the first renewable energy source to be tapped essentially to produce electricity.

Hydro power currently suffices one fifth of the global electricity supply, also improving the electrical system reliability and stability throughout the world. It also substantially avoids the green house gas emissions, thus complimenting the measures taken towards the climate change issues.

Hydro projects below a specified capacity are known as small hydro. The definition of small hydro differs from country to country, depending on the resources available and the prevalent national perspective. The small hydro atlas shows that the largest of the projects (30 MW) is in US and Canada. Small hydro power has emerged as one of the least cost options of harnessing green energy amongst all the renewable energy technologies.

According to the power generated, small hydro power is classified into small, mini/micro and pico hydro. In India, it is being classified as follows.

Small hydro - 2 MW - 30 MW
Mini - 100 kW - 2 MW
Micro - 10 kW - 100 kW
Mico hydro - 1 kW - 10 kW

Projects with the range of 100 kW and above feed power into the grid. They are commercial by nature. Projects below 100 kW are mostly off grid options being harnessed for rural village electrification. They come under the social sector.

Hydro Power

The basics of power from water is the result of conversion of potential energy (the water body at a certain height which is known as the "Head") to kinetic energy (a flow which is known as "Discharge" down the pipe) which is transferred to the buckets in the turbine (mechanical energy). It is the prime mover for the generator (electrical energy) which produces electricity.

Essentially power from a small hydro potential site is derived from two parameters, head and discharge .

Where "head" is the vertical height from which the potential energy of water is converted into electricity after the fall and discharge is the flow rate of the water in the stream/river.

Power (kW) = H * Q * Y

H = Head in m(meter)
Q = Discharge in m3/sec (cumecs) Y = Specific weight of water, being the product of mass and acceleration due to gravity (9.81 kN/m3).

An altimeter is used for head measurement and various methods are used for discharge measurement based on the site conditions. Limited civil works is carried out for the development of the site for small hydro power. To maintain the power quality controllers and electrical equipments is used.

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