Hydro-electric power is electricity produced by the movement of fresh water from rivers and lakes. Gravity causes water to flow downwards and this downward motion of water contains kinetic energy, that can be converted into mechanical energy, and then from mechanical energy into electrical energy in hydro-electric power stations. ("Hydro" comes from the Greek word hydra, meaning water). At a good site hydro-electricity can generate very cost effective electricity.

History and Development

The conversion of kinetic energy into mechanical energy is not a new idea. As far back as 2000 years ago wooden waterwheels were used to convert kinetic energy into mechanical energy. The exact origin of water wheels is not known, but the earliest reference to their use comes from ancient Greece.

However, it was much later, in 1882 in the United States, that the first hydro-electric plant was built. This plant made use of a fast flowing river as its source. Some years later, dams were constructed to create artificial water storage areas at the most convenient locations. These dams also controlled the water flow rate to the power station turbines.

How Hydro-Electric Power  Stations Operate

The amount of electrical energy that can be generated from a water source depends primarily on two things: the distance the water has to fall and the quantity of water flowing. Hydro-electric power stations are therefore situated where they can take advantage of the greatest fall of a large quantity of water- at the bottom of a deep and steep-sided valley or gorge, or near the base of a dam.

Unlike conventional coal-fired power stations, which take hours to start up, hydro-electric power stations can begin generating electricity very quickly. This makes them particularly useful for responding to sudden increases in demand for electricity by customers ("peak demand").

Hydro-stations need only a small staff to operate and maintain them, and as no fuel is needed, fuel prices are not a problem. Also, a hydro-electric power scheme uses a renewable source of energy that does not pollute the environment. However, the construction of dams to enable hydro-electric generation may cause significant environmental damage.

Originally, hydro-electric power stations were of a small size and were set up at waterfalls in the vicinity of towns because it was not possible at that time, to transmit electrical energy over great distances. The main reason why there has been large-scale use of hydro-electric power is because it can now be transmitted inexpensively over hundreds of kilometers to where it is required, making hydro-power economically viable. Transmission over long distances is carried out by means of high voltage, overhead power lines called transmission lines. The electricity can be transmitted as either AC or DC.