Hydropower

Hydropower, also known as water power or water energy, is the use of falling or fast-running water to produce electricity or to power machines. This is done by converting the gravitational potential or kinetic energy of a water source into power. Hydropower is a method of sustainable energy production and is mainly used for hydroelectric power generation. It can also be part of an energy storage system called pumped-storage hydroelectricity.

Hydropower is an attractive alternative to fossil fuels because it does not directly produce carbon dioxide or other atmospheric pollutants, and it provides a relatively consistent source of power. However, it has some economic, sociological, and environmental downsides and needs a strong source of water, such as a river or elevated lake. International institutions like the World Bank see hydropower as a low-carbon way to support economic development.

Since ancient times, hydropower from watermills has been used as a renewable energy source for irrigation and operating mechanical devices, such as gristmills, sawmills, textile mills, trip hammers, dock cranes, domestic lifts, and ore mills. A trompe, which produces compressed air from falling water, is sometimes used to power other machinery from a distance.

Calculating the amount of available power

Hydropower can be measured by looking at 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, but they can also change the environment where they are built.

Disadvantages and limitations

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

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

Dams and reservoirs can also harm nature. They can stop animals from moving up rivers, change the water temperature, and reduce the amount of oxygen in the water. Some fish and other water animals lose their homes because of this. Building dams also covers up land, which can release gases that warm the planet. People living near where a dam is built may have to move, and sometimes important places for culture or religion cannot be used.

Applications

Mechanical power

Watermills

Rail transport

Compressed air

See also: Trompe

When there is a lot of water flowing down, it can create air that is pressed 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 tasks. An old example of this was built near Cobalt, Ontario in 1910, which provided power for nearby mines.

Electricity

Main article: Hydroelectricity

The biggest use of hydropower is to make electricity. It creates about 15% of all the world's electricity and gives more than half the power to over 35 countries. In 2021, the world had almost 1400 GW of hydropower ability, more than any other renewable energy type.

Making electricity from water starts by turning the energy from water either because of its height or because it is moving 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 constant flow of water and cannot make power as reliably. The moving water itself is the main source of energy.

Both ways have some problems. Building dams can bother people living nearby and take up a lot of space that others may want. 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. More rain means more electricity, but less rain means less.

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 an exciting idea where we use falling rainwater to make electricity. Scientists are studying 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 even built a system that uses rainwater running off rooftops to spin a small turbine and make electricity.

History

Ancient history

Evidence shows that the basics of hydropower go back to ancient Greek civilization. Waterwheels also appeared in China around the same time. We find records of water wheels and watermills from the ancient Near East as far back as the 4th century BC. Hydropower was even used in places like Sumer and Babylonia with irrigation machines. The waterwheel was likely the first form of water power.

In the Roman Empire, writers like Vitruvius described water-powered mills as early as the first century BC. The Barbegal mill in what is now France had 16 water wheels that could process up to 28 tons of grain each day. Roman waterwheels were also used to cut marble, like at the Hierapolis sawmill from the late 3rd century AD. These sawmills used a waterwheel to move two saws through a system of rods.

In China during the Han dynasty (202 BC – 220 AD), water-powered tools like trip hammers and bellows were used. Some believe these were powered by water scoops, while others think waterwheels were used instead. Ancient Indian texts from the 4th century BC mention machines that might have used water power, but this is still debated among historians.

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

19th century

The first hydropower turbine was developed in the 1800s by a French engineer named Benoît Fourneyron. This turbine was used in a plant at Niagara Falls in 1895 and is still working today. 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, so did the need for power. Water was a key 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 a highly 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 competed to build the biggest and best 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.