Hydropower, or power from falling water, has been used for thousands of years- but it’s only now that we use it to create electricity.
In the past people used falling water to turn a waterwheel to grind their grain. The first house in the world to be powered by hydroelectricity was Cragside House, in Northumberland, England, in 1878. which is quite close to Shotton Hall
Hydropower was not used on an industrial scale until the 20th century because hydroelectric power plants needed to be located on a water source. This meant that until the technology used to transmit electricity over long distances was developed, hydro energy could not be used on a big scale.
The biggest dam in the world is the Three Gorges Dam in China. When this is fully functioning it will produce 22,500 MW (megawatts).
How does it work?
A dam is built in order to store water. Water in both lakes and rivers can be dammed. These dams are thicker at the bottom than the top, because the deeper the water, the higher the pressure.
The trapped water flows through a pipe, or penstock, then turns the blades in a turbine by pushing on them. This spins a generator. The electricity is created in the generator by using powerful magnets and coils of wire. When the coils are spun quickly inside the magnets, they produce electricity.
The pipe, or penstock, will be angled downwards to give the water a change in height. This means the water will arrive at the turbines at high pressure, so that it has more energy we can use. After flowing past the turbines, the water flows downriver as normal.
Although hydro energy from dams can produce a great deal of electricity, and there are many suitable sites around the world, hydroelectric dams are very expensive to build. However, as water is free, the hydroelectric power station can produce a great deal of power very cheaply once the dam is built.
Advantages
- Hydro energy produces no waste or pollution
- Once the dam is built, the energy is practically free
- Hydropower is much more reliable than solar, wind or wave power
- Water can be stored (pumped storage) to manage peaks in demand
Disadvantages
- Dams can have large environmental impacts on the plant and animal life in that area by affecting their natural habitats, for example obstructing fish migration
- Dams are very expensive to build
- Building large dams can cause flooding upstream, causing problems for animals that used to live there
- Finding a suitable site can be difficult
- If the country is experiencing a drought, the rivers may provide less power or even dry up
Hydro energy from dams in the UK
There are many hydroelectric power stations in the UK, varying widely in size. For example, Laggan Dam is located on the River Spean in the Scottish Highlands.
Though this dam is not a direct source of hydroelectric power, the water from the dam is sent to a different loch through three miles of tunnel. From here the water flows to a facility for the generation of electric power near Fort William.
Pumped storage reservoirs provide a place to store energy until it's needed.
There are fluctuations in demand for electricity throughout the day. For example when a popular TV programme finishes, many people go and put the kettle on, causing a peak in demand for electrical power.
When electricity is suddenly demanded, we need a way of producing power which can go from producing no power to full power immediately, and keep generating power for half an hour or so until other power stations can catch up with the demand for energy. This is why pumped storage reservoirs are so useful.
How does it work?
A pumped storage plant has two separate reservoirs, an upper and a lower one. When electricity is in low demand, for example at night, water is pumped into the upper reservoir.
When there is a sudden demand for power, giant taps known as the headgates are opened.
This allows water from the upper reservoir to flow through pipes, powering a turbine, into the lower reservoir.
The movement of the turbine turns a generator which creates electricity. The electricity is created in the generator by using powerful magnets and coils of wire. When the coils are spun quickly inside the magnets, they produce electricity.
Water exiting from the pipe flows into the lower reservoir rather than re-entering a river and flowing downstream. At night, the water in the lower reservoir can be pumped back up into the upper reservoir to be used again.
In terms of how pumped storage and dammed water generate electricity, the methods are the same. The difference is that in pumped storage, the water is continually reused, whereas in hydroelectric dams, the water which generates electricity continues flowing downriver after use.
Advantages
- Pumped storage is a way we can generate electricity instantly and quickly
- No pollution or waste is created
- There is little effect on the landscape, as typically pumped storage plants are made from existing lakes in mountains
Disadvantages
- Expensive to build
- Once the pumped storage plant is used, it cannot be used again until the water is pumped back to the upper reservoir
Pumped storage in the UK
Most pumped storage plants are located in Scotland, except the largest of all, Dinorwig, which is in North Wales. Dinorwig, built in 1984, produces 1,728 MW (megawatts). This is enough electricity to power nearly 7 million desktop computers. Dinorwig has the fastest "response time" of any pumped storage plant in the world - it can provide 1320 MW in 12 seconds.