Hydroelectric power stations generate electricity using the energy stored in the weight of water. Large volumes of water are retained using a dam. If this water then flows downwards, its energy is transferred to the turbines that begin to rotate. This rotational energy generates the electricity via the connected generators.
The advantage of hydroelectric power plants is that no greenhouse gases are created and any rubbish in the water is captured by screens in the plant and disposed of. In addition, the water in the river can be precisely regulated to prevent, for example, flooding. The disadvantages are that the construction of such large-scale power stations changes the natural balance of the river and fish, for example, can die in the turbines. There is also the danger that the dam bursts. Silting can also occur with large dams, which reduces the dam capacity.
In pumped storage power plants, the water is not stored at a higher level by blocking its natural course but is first of all pumped upwards to reservoirs where it is then released to generate energy. Although 25 per cent of the energy is lost, the double conversion of energy is still worthwhile from a commercial point of view. This is because the electricity prices are generally lower when there is surplus electricity but correspondingly higher during peak times as a result of the increased demand.
