Hydropower

Hydropower, also known as water power or water energy, uses falling or fast-running water to make electricity or power machines. It changes the energy from moving water into power. Hydropower is a way to make sustainable energy and is mostly used to create electricity. It can also store energy in a system called pumped-storage hydroelectricity.

Hydropower is a good choice instead of fossil fuels because it does not make carbon dioxide or other harmful gases. It gives a steady supply of power. But it can have some problems for the environment and people, and it needs a good water source, like a river or high lake. Groups like the World Bank think hydropower is a way to help economic development without adding too much carbon to the air.

For a long time, people have used hydropower from watermills as a renewable energy source. They used it for irrigation and to run machines like mills for grinding grain, sawing wood, textile work, lifting things, and more. A trompe uses falling water to make compressed air, which can power other machines far away.

Calculating the amount of available power

Hydropower can be measured by two main things: how high the water falls and how much water is moving. The higher the fall and the more water, the more power can be made. Each bit of water can do work based on how high it falls.

To find out how much power water can create, we look at the flow of water, its weight, the height it falls, and how strong gravity pulls it. For example, a turbine that works well can make about 97 million watts of power if it has a lot of water flowing through it and a good height to drop from. People who run these power stations check how well their turbines work by comparing the electricity they make to what could theoretically be made from the moving water. They also think about things like how the water flows, the weather, and the exact height and location of the power station to make sure they get the most power possible. Some older power systems, like water wheels, can get power from moving water without needing a big height difference. But the amount of water can change a lot during different times of the year, so careful planning is needed to make sure there is enough power all the time. Dams can help by storing water.

Disadvantages and limitations

Main articles: Hydroelectricity § Disadvantages, and Renewable energy debate § Hydroelectricity

Hydropower has some disadvantages. If dams break, it can be dangerous for people and the land.

Dams and reservoirs can also harm nature. They can stop animals from moving up rivers and change the water temperature. Some fish and other water animals lose their homes because of this. Building dams can also cover up land, and people living near a dam may have to move. Sometimes important places for culture or religion cannot be used either.

Applications

Mechanical power

Watermills

Rail transport

Compressed air

See also: Trompe

When lots of water flows down, it can push air together without any moving parts. This happens when water falls and mixes with air bubbles. The air gets squeezed as it falls into a chamber below, and this compressed air can be used for different jobs. An old example was built near Cobalt, Ontario in 1910, which gave power to mines close by.

Electricity

Main article: Hydroelectricity

The biggest use of hydropower is to make electricity. It makes a lot of the world's electricity and gives power to many countries. In 2021, the world had a lot of hydropower ability, more than any other renewable energy.

Making electricity from water starts by turning the energy from water into electrical energy.

There are two main ways to make this electricity. One uses a dam with a lake behind it called a reservoir. The water stored there can be used anytime to make electricity. It flows through channels to spin a turbine connected to a generator, which makes electricity.

The other way is called a run-of-river plant. It controls the flow of water but does not store it in a lake. This needs a steady flow of water and cannot make power as reliably. The moving water itself is the main source of energy.

Both ways can cause problems. Building dams can bother people living nearby and need a lot of space. Dams and lakes can also harm areas downstream. Run-of-river plants are less efficient because they depend on how much water is flowing, which changes with the seasons.

Hydroelectric plants can be small or very large, enough to power whole countries. Since 2019, the five biggest power stations in the world have been hydroelectric dams.

Hydroelectricity can also store energy by moving water to a higher lake when there is less demand, and then letting it down to make power when needed.

Other ways to make electricity from water include using the movement of tides in oceans and rivers.

• A conventional dammed-hydro facility (hydroelectric dam) is the most common type of hydroelectric power generation.

• Chief Joseph Dam near Bridgeport, Washington, is a major run-of-the-river station without a sizeable reservoir.

• Micro hydro in Northwest Vietnam

• The upper reservoir and dam of the Ffestiniog Pumped Storage Scheme in Wales. The lower power station can generate 360 MW of electricity.

Rain power

Rain power is a cool idea where we use falling rainwater to make electricity. Scientists are looking for new ways to turn the energy from raindrops into power. One idea is to use special solar panels that work in both sunlight and rain.

Researchers have found that tiny devices can make a very small amount of electricity from each raindrop. While this is not enough to power a house, it could help run small sensors. Another way is to collect rainwater and use it to spin a tiny turbine, which can make enough energy to charge batteries. Students in Mexico built a system that uses rainwater running off rooftops to spin a small turbine and make electricity.

History

Ancient history

The basics of hydropower go back to the ancient Greek civilization. Waterwheels were used in China at the same time. We have records of water wheels and watermills from the ancient Near East as far back as the 4th century BC. Hydropower was used in places like Sumer and Babylonia with irrigation machines. The waterwheel was probably the first kind of water power.

In the Roman Empire, writers like Vitruvius wrote about water-powered mills as early as the first century BC. The Barbegal mill in France had 16 water wheels that could process grain. Roman waterwheels were also used to cut marble, like at the Hierapolis sawmill. These sawmills used a waterwheel to move saws.

In China during the Han dynasty (202 BC – 220 AD), water-powered tools were used. Some think they were powered by water scoops, while others think waterwheels were used. Ancient Indian texts from the 4th century BC mention machines that might have used water power, but this is not certain.

In the Islamic Empire, especially during the Islamic Golden Age and the Arab Agricultural Revolution (8th–13th centuries), hydropower was used a lot. They built many water-powered mills, including for making cloth, grinding grain, and processing paper. Engineers also used water turbines and built dams to help power these mills.

19th century

The first hydropower turbine was made in the 1800s by a French engineer named Benoît Fourneyron. This turbine was used at Niagara Falls in 1895 and is still working. In the early 1900s, an English engineer named William Armstrong built the first private electricity station in his home in Cragside, Northumberland, England.

As industries grew during the Industrial Revolution, water was an important energy source for many inventions, like Richard Arkwright’s water frame. Even after steam power became more common, water still powered smaller operations, such as bellows in furnaces and gristmills.

Improvements in technology led to better turbines. In 1848, James B. Francis created an efficient turbine design. Later, Lester Allan Pelton invented the Pelton wheel turbine, which worked well in places with high waterfalls like the Sierra Nevada.

20th century

The 1900s saw the building of very large dams to provide electricity over long distances. Countries built big hydropower projects. The United States built major dams like those at Niagara Falls and in the Sierra Nevada, inspiring similar projects around the world. During the Cold War, countries like the United States and the USSR helped build big dams in other parts of the world, such as the Three Gorges Dam and the Aswan High Dam.

While big dams were popular early on, opinions changed later in the 20th century. Smaller hydropower plants became more common again in the 1970s, supported by governments wanting more independent energy sources. By the 1990s, only about 18% of the world’s electricity came from hydropower. Other types of energy, like tidal power, also started to develop during this time.