Water turbine facts for kids
A water turbine is a spinning machine that gets energy from moving water. Think of it like a windmill, but for water instead of wind!
Water turbines were first developed in the 1800s. Back then, they were used to power factories and machines. Today, they are mostly used to make electric power. They use a clean and renewable energy source, which means they don't pollute the air and the water keeps flowing.
Contents
History of Water Turbines
From Water Wheels to Turbines
For thousands of years, people used Water wheels to power things. Water wheels are big wheels that turn when water flows over or under them. But they had a problem: they were very big, and they couldn't use a lot of water or a very tall drop of water.
Over about 100 years, during the Industrial Revolution, water wheels slowly changed into modern turbines. Scientists and engineers used new ideas and materials to make them better.
The word "turbine" was created by a French engineer named Claude Bourdin in the early 1800s. It comes from a Latin word meaning "whirling" or "spinning." The big difference between old water wheels and new turbines is that turbines use a "swirl" motion of the water. This swirl helps the water push the turbine's spinning part, called a rotor, with more force. This made turbines much smaller and faster than water wheels, and they could use much more water from higher drops.
Important Inventors and Their Turbines
- In the mid-1700s, Johann Andreas Segner made a simple water turbine that spun horizontally. It was a first step towards modern turbines and is still used for small power projects today.
- In 1820, Jean-Victor Poncelet designed a turbine where water flowed inwards.
- In 1826, Benoît Fourneyron created an outward-flow turbine that was quite good at making power (about 80% efficient).
- In 1844, Uriah A. Boyden improved Fourneyron's design.
- In 1849, James B. Francis made a huge improvement to the inward-flow turbine, making it over 90% efficient! He also created ways to design these machines. The Francis turbine, named after him, is considered the first modern water turbine. It's still the most common type used around the world.
- Around 1913, Viktor Kaplan invented the Kaplan turbine. This propeller-like turbine was a big step forward because it could make power from much smaller drops of water.
A New Way to Use Water Power
Most early water machines, including water wheels, were "reaction" machines. This means they used the water's pressure to create power. These turbines needed to be fully enclosed or submerged in water.
But in 1866, an inventor named Samuel Knight came up with a new idea. He was inspired by the powerful water jets used in gold mining. Knight created a wheel with special buckets that caught the energy of a free jet of water. This jet was created by letting water fall from a great height through a pipe. This type of turbine is called an "impulse" turbine.
- In 1879, Lester Allan Pelton improved Knight's design by creating a "double bucket" that sent the water out to the sides, making it even more efficient. This is known as the Pelton wheel.
- Around 1895, William Doble made the Pelton bucket even better by making it elliptical with a cut in the middle. This is the modern Pelton turbine, which can be up to 92% efficient.
Later, other impulse turbines like the Turgo turbine and Crossflow turbine were developed.
How Water Turbines Work
Water turbines work by directing flowing water onto their blades. This pushes the blades, making the turbine spin. As the turbine spins, the force from the water creates work, turning the water's energy into useful power.
Water turbines are split into two main types:
Reaction Turbines
Reaction turbines get their energy from water that changes pressure as it moves through the turbine. They must be completely enclosed to hold the water pressure, or they must be fully underwater.
Most water turbines used today are reaction turbines. They are best for places where the water doesn't fall from a very high place (low to medium "head").
Impulse Turbines
Impulse turbines work by changing the velocity (speed) of a water jet. A powerful jet of water pushes the turbine's curved blades, making the water reverse direction. This change in the water's movement creates a force that spins the turbine.
Before the water hits the turbine blades, its pressure (which is like stored energy) is turned into kinetic energy (energy of motion) by a special nozzle. This nozzle focuses the water into a strong jet. With impulse turbines, the water pressure doesn't change at the blades, so the turbine doesn't need a special housing to contain pressure.
Impulse turbines are usually used where water falls from very high places (very high "head").
How Much Power?
The amount of power a water turbine can make depends on a few things:
- How efficient the turbine is.
- The density of water (how much it weighs).
- The force of gravity.
- The "head" (how high the water falls).
- The "flow rate" (how much water flows per second).
Pumped Storage
Some water turbines can do double duty! They are designed for Pumped storage hydroelectricity. This means they can act like a pump to push water uphill into a reservoir when electricity is cheap (like at night). Then, when electricity is needed most (during the day), they can reverse and act as a turbine, letting the water flow downhill to make power. Deriaz or Francis turbines are often used for this.
Efficiency
Big, modern water turbines are very efficient. They can turn more than 90% of the water's energy into mechanical energy.
Types of Water Turbines
Here are some common types of water turbines:
Reaction Turbines:
- Francis
- Kaplan, Propeller, Bulb, Tube, Straflo
- Tyson
- Water wheel (though less efficient than modern turbines)
Impulse Turbines:
- Pelton
- Turgo
- Michell-Banki (also known as the Crossflow or Ossberger turbine)
Designing and Using Turbines
Choosing the right turbine mostly depends on how high the water falls (the "head"), and less on how much water is flowing.
- Impulse turbines are usually for very high drops of water.
- Reaction turbines are for lower drops of water.
- Kaplan turbines are great because they can work well even if the amount of water flowing changes a lot.
Smaller turbines might have horizontal shafts (spinning sideways). Very large Francis and Kaplan turbines usually have vertical shafts (spinning upright). This helps them use the water's height better and makes it easier to connect to the generator. Pelton wheels can be either vertical or horizontal.
Typical Heights for Turbines
Here are the typical "head" (height of water drop) ranges for different turbines:
Taking Care of Turbines
Water turbines are built to last for many decades with very little care needed for their main parts. They usually only need a big check-up every few years. During these check-ups, workers remove, inspect, and fix any worn parts, especially those that touch the water.
Common problems include:
- Cavitation pitting: Tiny bubbles in the water can burst and chip away at the metal.
- Fatigue cracking: Small cracks can form from the constant stress.
- Abrasion: Dirt or sand in the water can wear down the parts.
Damaged steel parts are fixed by welding, often using stainless steel. The worn areas are cut out or ground down, then new metal is welded back to make the part like new.
Other parts that need checking include bearings (which help parts spin smoothly), seals, cooling systems, and all surfaces.
Impact on the Environment
Water turbines have both good and bad effects on the environment.
Good Impacts: They are one of the cleanest ways to make power. They don't burn fossil fuels (like coal or gas), so they don't produce smoke, ash, or harmful gases like carbon monoxide. They also don't create nuclear waste. Since they use a renewable energy source (moving water), they can operate for many decades and provide a lot of the world's electricity.
Bad Impacts: Historically, there have been some negative effects. The spinning blades or gates of water turbines can harm fish and stop them from migrating (moving up and down rivers). This can disrupt the natural balance of rivers and affect people who rely on fishing. For example, American Indian tribes in the Pacific Northwest relied on salmon fishing, but many dams destroyed their way of life.
However, things have improved! Since the late 1900s, engineers have found ways to build hydropower systems that guide fish and other creatures away from the turbine intakes without much harm or loss of power. In the United States, it's now against the law to block fish migration, so dam builders must include fish ladders to help fish move past the dams.
Related pages
Images for kids
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A Kaplan turbine and electrical generator cut-away view.
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A Francis turbine runner, rated at nearly one million hp, being installed at the Grand Coulee Dam.
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A chart showing where different water turbines are used.
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A Francis turbine at the end of its life, showing damage from water.
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The spinning part (rotor) of a small water turbine.
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The building of a Ganz water Turbo Generator in Budapest in 1886.
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A Roman turbine mill at Chemtou, Tunisia.
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A propeller-type runner rated 28,000 hp (21 MW).
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A drawing from Pelton's original patent (October 1880).
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Different types of water turbine runners. From left to right: Pelton wheel, two types of Francis turbine, and Kaplan turbine.
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Walchensee Hydroelectric Power Station in Bavaria, Germany, has been working since 1924.
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See also
In Spanish: Turbina hidráulica para niños
