Hydro power is the process of changing the kinetic energy of flowing water in a river into electrical power that we can use.
A dam is built where there is a natural lake or a big river in a valley. The dam is used to hold the water and create pressure so that the water can produce more electrical power. There is gravitational potential energy stored in the water and this energy is used to turn generators and create electricity. These turbines are within tunnels in the dam wall. Electrical generators are turned by these massive turbines and create electricity. Water flows through these tunnels with great pressure and is used to turn these turbines. The water has immense pressure due to the great height at which is kept in the dam. If there is a greater volume of water or there is a very large difference between the water level and where it flows out than you can get more power out of the water as it has greater potential energy. This difference in height of the water is called the head. The generator contains 2 main parts: the rotor and the stator. The rotator is the part which rotates and the wire has a huge magnet inside of it; and the stator is the part which is covered in copper. The electrical current is created when the rotor spins around the copper wire on the stator. This is the charge which is then used as electricity.
It is renewable because the process takes nothing away from the environment and therefore nothing needs to be replenished. The water stays in the water cycle and can keep producing energy endlessly.
Hydro power is also utilised by large scale companies as a private use. Many large mining companies or aluminium manufacturers use vast amounts of electrical so rather than buying from the state they can generate their own power by using hydro power generation.
In South Africa we have many possible hydro electric plant site possibilities. The US department of energy estimates that there about 6000 to 8000 suitable areas for hydro electric generation. The main areas would be in the Eastern Cape and KwaZulu-Natal regions. Many of these plants would be under 100 mega watt, but all these together would ensure a greater sustainable future for South Africa. We do already have a 1000 megawatt Pumped-Storage Facility in the Drakensberg but there are still many opportunities for more small scale plants.
Hydro power generation works well in mountainous countries as the water can be stored at very high pressures. The dam wall increases with width as you go down towards the base this is because the water pressure gets greater as depth increases.