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Hydroelectric energy

Hydroelectric energy

Cromford’s eighteenth century water wheel in England and China’s impressive Three Gorges Dam are subtly connected. Even though they hardly look similar, they’re in fact two crafts of the same human skill: harnessing energy from earth’s blue gold, water.

About hydroelectric energy

Water, humankind’s first power

Water is much more than the basis of life and an essential part of our food chain and hygiene but also, one of mankind’s first forays in harnessing energy through natural resources, hence, hydroelectric power. Based on the 2019 report by the International Renewable Energy Agency (IRENA), total capacity from the world’s hydroelectric power plant amounts to 1,172 GW: about 50% of total renewable power output.

Even if hydroelectric power is the dean of renewable power sources, this hasn’t stopped R&D from increasing its efficiency. Thanks to currently available technology, 90% of water is now transformed in electricity, delivering a three-fold increase in efficiency compared to traditional power sources.

A low carbon footprint and high efficiency are the factors that concur in delivering excellent performance: along the world’s biggest renewable power plants, the top five in this ranking are powered by water. 

History of hydroelectric energy

Water and energy. A two thousand year-old connection

First hydraulic wheels

A full century before the birth of Jesus, in Egypt’s Alexandria, rivers were moving hydraulic wheels that in turn propelled the millstones. The hydraulic wheels served as energy amplifies, proving a powerful yet simple technology harnessing moving water and transforming it in energy.

One energy, many uses

By the ninth century, water’s motive power helps mankind in fulfilling many different tasks: tanning hides and skins, grinding malts for beer, milling olives, sugar and pigments for dying. 

The era of mills

Medieval times saw two kinds of mills dotting its scenery. The “retricine” mill is a horizontally-mounted wheel harnessing the flow of moving water, while the “vitruvian” mill is vertically-mounted. 

Water meets industry

England’s Cromford Mill was the world’s first industrial water-powered cotton-spinning mill, representing a decisive first step in the expansion of production and commerce in the British Empire. 

The Francis turbine

The next evolutionary step was moving from the wheel to the hydraulic turbine, transforming water’s kinetic energy in mechanical energy which is in turn transformed in electricity. This invention was the brainchild of British engineer James B. Francis. His namesake turbine was the most used of its kind in hydroelectric power plants.

The dynamo sees the light

Italian engineer Antonio Pacinotti invents the dynamo, a device transforming mechanical energy in direct current. He was unable to patent his invention and in 1869, Zenobe Gramme patented a machinery of which Pacinotti’s device was a fundamental component.

Edison’s groundbreaking invention

At the International Electricity Exposition in Paris, American Thomas Edison showcased its “Edison system”, a device engineered to generate centralized electricity for lighting purposes in direct current. 

The first hydroelectric power plant

The world’s first hydroelectric power plant went online in the American town of Appleton, Wisconsin. 

Lights at La Scala

Giuseppe Colombo, engineer and trailblazer of industrial progress, opened continental Europe’s first power plant using the “Edison System”. Its power lighted up the iconic La Scala Opera House, to that day illuminated by gas lamps which posed a frequent hazard in closed environments.

Alternating current

Italian engineer Galileo Ferraris introduced the first engine and Alternate Current engine ever devised for industrial use. Alternate current proved to be the most reliable solution, allowing to reduce energy loss over long distance transmission. 

Water lights up Rome

The Acquoria hydroelectric power station went online. Located in Tivoli, a small city in the outskirts of Rome, it delivered energy to the Eternal City via the world’s first Alternate Current power grid.  

A new idea springs into action: the Kaplan turbine

Austrian professor Viktor Kaplan is the inventor of his namesake turbine. The turbine was engineered to harness small water jumps to the fullest, even as little as a few dozen meters, while also coping with substantial water flows.

An American record

The world’s biggest hydroelectric power station comes online in the United States. The Hoover Dam is a majestic piece of engineering that towers over the Colorado river, boasting an installed capacity of 1345 MW later upgraded to 2080 MW. Its title was later taken away a few years later by the Grand Coulee Dam on the Columbia river. 

Italy, the European leader in hydro

Construction works went underway on the Belluno hydroelectric power plant, becoming Europe’s biggest once fully operational. 

Water all the way

Hydroelectric power reaches a 65% share of total installed capacity.

The Chinese giant

Work is completed on the Three Gorges Dam over China’s Yangtze river. With a capacity of 22.5 GW, generating 98.8 TWh yearly, this mammoth project is by far the world’s most powerful power plant.

The Queen of renewables

Today, hydroelectric energy represents a 90% share of global renewable energy generation,  contributing to 17% of the world’s total installed capacity.

How hydroelectric energy works

Water and gravity, a perfect mix

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Hydroelectric power can count on two simple yet formidable allies: water and gravity. All types of hydroelectric power plants leverage on gravity to accelerate its flow and unleash the power carried by its kinetic energy.

In order to harness electricity from water, a reservoir is needed to store its potential energy, usually in the form of an artificial lake created by a dam located upstream.

A series of giant water mains allow water to forcefully cascade downstream, where the bulk of the power plant machinery is located. Thanks to the drop created by the water mains, water increases its speed until it makes the turbine blades spin, which in turn are mechanically connected to a generator. This is the moment for electricity to run through an alternator that lowers the intensity of the current while increasing its voltage to streamline its subsequent feeding in the power grid.

Hydroelectric basins

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Power plant

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Strong points of hydroelectric energy

Long-lasting and efficient energy

Flexibility and efficiency

Output from hydro power plants can be quickly adapted to suit new supply-based needs, while its kw/hour costs are very competitive. 


The service life of an hydroelectric power plant can potentially span a century: ample time to generate sustainable energy aplenty. 

Less CO2

Hydroelectric power plants are carbon neutral, representing a great advantage for both the environment and humankind’s wellbeing. 

Did you know?

A waterfall made from 24 million light bulbs

The name says it all: Niagara Falls. Located at the American-Canadian border, they’re one of the world’s most valued and visited natural landmarks. Far from being the tallest, what makes them so spectacular is the hugely vast waterfront and its impressive flow rate: roughly 168 thousand cubic meters a minute during an overflow. A natural resource with an extraordinary renewable power potential.

Works on an hydroelectric power plant started out by the end of the nineteenth century, carefully respecting the beauty and relevance of such an iconic natural landmark. Niagara Falls currently see two main power plants, namely, the Robert Moses Niagara Power Plant and the Lewiston Pump-Generating Plant. The whole hydroelectric complex generates energy worth roughly 2.4 million kilowatts. That’s enough energy to light up 24 million 100-watt light bulbs at once.

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