How is electricity generated from water?

Water has been used as a source of power for thousands of years. Written records dating back to 240BC make note of water mills being used to grind flour. This technology remained largely unchanged until the middle of the 18th century, when the water turbine was invented; when electricity was discovered in the 19th century, hydroelectric power was born. 

The principle of hydroelectric power is very simple; water is used to rotate a turbine, inside of which is a coil and a magnet. As the coil rotates around the magnet, current is generated. It should be noted that for the vast majority of electricity generation methods, the function of the turbine is the same – it rotates and generates electricity. The only thing that differs is how the turbine is spun; in the case of hydroelectric power, it is spun by waterpower from rivers (with a few exceptions). 

Hydroelectric power is regarded as a renewable energy source as the process produces no greenhouse gasses, and the water being used to power the turbine is returned to the environment after it has been used. According to the British Hydro Association, hydroelectric power accounts for 17% of the world’s electricity, and 70% of the world’s renewable power. China is the world leader in this with a vast number of giant hydropower dam projects in operation. In the UK specifically, hydropower accounts for around 30-40% of our renewable power. Most of this is in large hydro plants that take advantage of reservoirs and mountainous regions of the country to power their turbines, but with innovations such as the Archimedean screw it’s possible to create smaller-scale hydroelectric installations in smaller bodies of water, providing local power or even power to individual properties. 

There are other more specialised attempts to use water to generate electricity; these include tidal power systems, and wave power systems. Tidal power systems rely on tidal currents to turn turbines rather than the flow of a river, while wave power systems take energy out of waves to generate electricity. Though neither of these sources are widely used, they both hold promise as alternate ways to generate electricity from renewable and clean sources.