In hydroelectric power plants the potential energy of water due to its high location is converted into electrical energy. The total power generation capacity of the hydroelectric power plants depends on the head of water and volume of water flowing towards the water turbine.

The principle of hydropower

The principle behind the production of hydropower is simple; it uses the energy of flowing water. Many hydropower plants benefit from several storage schemes, and in some river systems a number of power stations are positioned in cascade one after the other, so that the water’s energy can be exploited several times before it finally flows out into the sea. Inside the power station, the water drives a turbine, whose mechanical energy is turned into electrical energy in the generator. Hydropower is a highly flexible energy source, since the water can be stored in the reservoirs until needed. Hydropower schemes without reservoirs are often called run-of-river.

Advantages of hydropower:

1. Power is usually continuously available on demand.
2. Given a reasonable head, it is a concentrated energy source.
3. The energy available is predictable.
4. No fuel and limited maintenance are required, so running costs are low (compared with diesel power) and in many cases imports are displaced to the benefit of the local economy.

5. It is a long-lasting and robust technology; systems can last for 50 years or more without major new investments.

    

Against these, the main shortcomings are:

1. It is a site specific technology and sites that are well suited to the harnessing of water power and are also close to a location where the power can be economically exploited are not very common.
2. There is always a maximum useful power output available from a given hydropower site, which limits the level of expansion of activities which make use of the power.
3. River flows often vary considerably with the seasons, especially where there are monsoon-type climates, and this can limit the firm power output to quite a small fraction of the possible peak output.

Lack of familiarity with the technology and how to apply it inhibits the exploitation of hydro resources in some areas.