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Why does water flow?
 
 
 
 
 
The Sun's heat...
...evaporates water from lochs and oceans...
...to form clouds.
It falls back to Earth as rain or snow.
It flows through streams and rivers, over waterfalls and underground, eventually reaching the ocean again.
This is known as the water cycle.
 
 
 
 
 
 
 
 
 
 
 
What's so good about energy from water?
All water flowing from a higher level to a lower level contains energy
It is this energy contained in water as it flows downhill that we extract to make electricity
And because the water cycle is driven by the Sun, the energy we get from it is never going to run out – it is renewable
Many other forms of energy, such as oil, coal and gas, are in limited supply.
Plus they have to be burned to release energy and so contribute to climate change.
Did you know?
Renewable energies such as wind, waves and solar power already account for nearly 20% of the world's electricity supply.
 
This is why we are playing our part in increasing the amount of water energy ‐ hydropower ‐ we use
 
 
 
 
Of course, using water energy to make our lives easier is nothing new
The ancient Greeks used water wheels to grind flour over 2,000 years ago.
Did you know?
By the 19th century, there were more than 20,000 working mills in Britain. Their mechanical energy was also used for grinding flour, or in textile production.
 
Then, in 1831, along came one very bright spark...
Scientist Michael Faraday discovered how to convert mechanical energy into electricity
So our modern watermills ‐ or 'turbines' ‐ can be located in areas that have the best conditions, which could be a long way from where we need the energy to power our homes, schools and offices.
Did you know?
All power stations use Faraday's discovery as a basis for generating electricity.
 
 
 
 
 
 
 
 
Where do we build hydro‐electric schemes?
Where there's water falling through a great height
All hydro‐electric schemes make use of the fact that water flowing from a higher level to a lower level contains energy.
This difference in height is known as the 'head' of water ‐ the greater the head, the more energy there is.
Did you know?
The first hydro‐electric scheme was constructed in Scotland in 1891. Scottish hydro‐electric schemes now generate around 12% of the gross power consumed in the UK.
 
Some schemes make use of a natural drop in the height of water, e.g. over a waterfall.
Some take water from lochs high in the hills above them through underground tunnels, aqueducts or pipes.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
A common method is to build a dam
This raises the water level artificially by creating a reservoir
Storing water that has the potential to generate electricity is a bit like storing a large quantity of electricity - which is very difficult to do otherwise
Water from the reservoir is forced under pressure into a waterway (or pipe) known as a penstock.
From there, it is carried to a turbine, often located inside the dam structure.
Adjustable guide vanes encircling the turbine control the flow of water through it.
When they open, high-pressure water is directed onto the rotating part of the turbine, known as the runner.
The turbine runner consists of blades, a bit like the propeller on a ship. These spin rapidly as the water rushes past.
The turbine shaft turns a series of magnets inside an electric coil in the generator ‐ this, in line with Faraday’s principle, produces an electric current.
Hydro‐electric facts and figures
Hydro‐electric power stations are fast
Hydro‐electric power stations can be brought into operation in less than two minutes.
This means we are ready to power all the kettles that are switched on at half-time on match day.
Did you know?
In some hydro‐electric schemes in Scotland, water passing through the turbines may have already passed through four other power stations upstream - so that's recycling on top of renewability.
 
 
Huge volumes of water pass through them
At full load, 130,000 litres of water pass through the turbines at Pitlochry every second – that’s one very big water bottle!
Dams have to be strong to hold back all this water
The force on Pitlochry dam is 12,000 tonnes. But how much is that? Click play to see.
The force on the dam is equivalent to six space shuttles!
 
 
 
 
 
 
 
 
Reservoirs are a great way of storing large amounts of energy
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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Loch Tummel, which feeds Clunie Power Station, holds 30.25 billion litres of water - a lot of potential energy. How long do you think it would power this 2 kW kettle for?
The kettle would boil for an amazing 251 years!
 
 
 
 
 
 
 
 
 
 
 
 
 
Downstream, at the lower end of the lift, the fish are attracted by a flow of water into a pool.
A sluice gate closes behind the fish and the water flowing into the pool gradually rises to the top of the lift.
The fish rise up with the level of water and are free to swim on their way upstream.
What happens to the fish after you build a dam?
A dam stops the flow of water ‐ but, of course, it also blocks the way for fish
For some fish, such as salmon and sea trout, to be prevented from swimming back and forth to the sea would be a disaster
So the engineers got together and decided to give the fish a helping hand ‐ their very own fish lift
Another way to let the fish get past the dam is via a fish ladder ‐ this consists of a series of stepped pools, similar to a staircase, the water level in each 'step' being slightly higher than the one before.
Openings below the water level allow the fish to swim from one pool to the next and eventually to swim around the dam.
Did you know?
The fish ladder at Pitlochry in Perthshire consists of 34 pools and is 310 metres long. It even has three larger pools that allow the fish to rest during their ascent!
Did you know?
We carefully manage the flow of water on rivers where there are hydro‐electric schemes, by releasing a regulated water flow downstream of their dams.
 
 
 
 
 
 
As the fish continue on their journey, so does your electricity
The electricity generated at the hydro‐electric power plant is usually at a voltage of around 11,000 volts
This is stepped up to a massive 275,000 volts using a substation transformer at the hydro‐electric power plant.
Stay Safe
Because of the high voltages involved, substations are extremely dangerous places for the public to enter.
Voltage is the force that pushes electricity through a wire.
 
 
 
 
 
 
 
 
But at such a high voltage, it's much too powerful to be used in homes, schools and businesses
So after passing through a number of substations, it is stepped down again ‐ this time to 240 volts
The electricity now travels underground in cables laid throughout urban areas.
Stay safe
If there are any overhead lines nearby, you should be very careful if you are fishing, flying kites and model aircraft or putting up tents – electricity will pass through many objects that touch the lines, with a serious risk of injury to anyone holding the object.
 
 
 
A hydro-electric scheme like Glendoe is capapble of powering a city the size of Stirling
If you look at the labels on the plugs for your appliances, they will tell you what voltage they use.
 
 
 
 
 
Just think - what started out as a drop of rain now lights up your house
at the flick of a switch...
Did you know?
A whopping 90% of the energy used in washing clothes goes into heating the water ‐ you can save energy simply by reducing the temperature setting, or washing your clothes less often. Click here for some extra tips on saving energy.
And it isn't only lights that use electricity...now we've reached the end of our journey ‐ it's time to put the kettle on!
 
 
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