How Does Hydroelectric Power Work

Water has been used to power man-made mechanisms for hundreds of years, mostly in food production in the form of a mill wheel to grind corn.

However, using the kinetic energy of water probably became a reality earlier than you thought. In 1878, inventor Lord Armstrong lit his home in Northumberland using only the power of a nearby waterfall. It’s not until the latter half of the 20th Century that we began to take advantage of the massive potential of hydroelectric power.

Intriguingly, both the dirty and environmentally unfriendly coal power plants and clean, green hydro-power use almost identical technology to generate power. Central to a coal-fired plant is a turbine: coal is burned to produce heat energy, which is used to boil water into steam, which then drives a turbine. Hydroelectric power removes the coal and steam elements and instead, flowing water turns the blades of each turbine.

By damming a river next to a drop in elevation and releasing a controlled flow (and creating a large body of water behind the dam called a reservoir), you can effectively harness the Earth’s gravity as an energy source. It’s based on the principles discovered by physicist Michael Faraday: when a magnet moves past a conductor, it creates electricity. When the water flowing through a hydroelectric turbine turns the blades it rotates a shaft attached to a large disk called a rotor at the opposite end. The rotor is made up of loops of wire with current circulating through them, wound around stacks of magnetic steel. When active, the turbine propeller turns the rotor past the conductors located in the static part of the turbine, known as the stator.

Modern technology in even a single large turbine (which can weigh thousands of tons) can generate an enormous amount of power, but the cost-effectiveness of building the dam as well as the environmental and economic impact of flooding the area behind it can prohibit such ventures.

Biggest Dam – The Three Gorges Dam

Location: Yangtze River, China

Size: It’s 2,335 metres long, 101 metres wide and 115 metres at its thickest point. It took 15 years, approximately GBP 25 billion and nearly 14 million tons of cement and materials to construct it.

Fascinating fact: 34 turbines, weighing in at 6,000 tons each, generate 22,500 megawatts for an annual output of 60.7 terawatt hours per year in 2009. It is the world’s largest electricity-generating plant of any kind.

Tallest Dam – Nurek Dam

Location: Vakhsh River, Tajikistan

Size: The Nurek dam is an earth fill dam completed in 1980 when the Soviet Union had control of Tajikistan. At 300 metres it is the world’s tallest dam, though the Rogun Dam has a taller proposed height for when it is eventually completed.

Fascinating fact: A comparatively modest nine hydroelectric turbines have a total power output of three gigawatts, but amazingly, since 1994 this has been enough to supply 98 per cent of the nation’s total electricity needs.