Hydro electric is energy from running water which humans harness using dams and a generator. The first use of water to generate electricity was in 1882, and nowadays there are many hydro-electric power stations, providing around 19% of the world's electricity.
To use it, a dam is built to trap water, usually in a valley where there is an existing lake. Water is allowed to flow through tunnels called penstocks in the dam, to turn turbines and then drive generators. The dam has to be most thick at the bottom because the pressure of the water is so much greater. (See pressure in liquids)
This method works well because gravitational potential energy is stored in the water above the dam. Because the water is very high, it will arrive at the turbines at a high speed and cause them to spin. A generator(s) is attached to these turbines and is also forced to spin - producing electricity. The water then flows away down the river as normal. In New Zealand, this way of making renewable energy counts for more than half the country’s energy because New Zealand is so mountainous. This is also the same for Switzerland. Even though the dams are very expensive to build, the costs can be shared with the flood controls, as they are also used for that.
This method is possibly the most reliable way of making renewable energy. Also, unlike solar, which only works when it is sunny, or wind, which needs wind, hydro electric works throughout the year, unless there is a drought.
- The energy is free, except for building the dams.
- It is probably the most reliable ways of creating electricity.
- Electricity can be generated at all times.
- No pollution is created.
- If there are peak times, then water can be stored in the reservoir and released at these times
- Hydro-electric power stations can get to full power very quickly.
- The dams are very expensive.
- It is hard to find a suitable site, where residents and the environment around is happy
- The water quality downstream is worsened.
- Upstream there will be flooding causing damage to the environment living there.