What are Water Turbines?

James Doehring

Water turbines are used to extract energy from moving water, typically for production of hydroelectricity. They operate by forcing water past slanted blades, which spin the turbines. Water turbines can be mechanically attached to machinery or to an electric generator. Steam turbines use gaseous steam, rather than liquid water, to operate.

The Hoover Dam has 17 main water turbines.
The Hoover Dam has 17 main water turbines.

The precursor to water turbines was the water wheel, which was used for thousands of years. A water wheel is oriented vertically with only a small portion submerged beneath the water at any given time. This type of wheel relies on the horizontal momentum of water in a river to turn. For this to work, the wheel must have ridges or buckets to catch the water. The same principle is used in the paddle wheel of a steamboat.

The principle of water turbines is used in the paddle wheels of steamboats.
The principle of water turbines is used in the paddle wheels of steamboats.

Water turbines, however, operate in a different way, with the blades arranged in a way analogous to those of a windmill. Fluid flows through a windmill rather than past it. The same design is used for water turbines, though the shape of the blades is optimized for water instead of air.

The water turbine began to be used extensively during the 19th century. Before electricity was available, factories were powered mechanically. Water turbines were attached to machinery in much the same way a car’s engine is attached to its wheels. An engine can continue revolving while a transmission distributes power to the wheels by making or breaking a mechanical connection. In a similar way, a factory can be powered without involving electricity.

In recent times, water turbines have been used in hydroelectric power plants. These plants typically involve a dam with a significant difference in water level between sides. The plant extracts the gravitational potential energy stored in the higher water by forcing it to flow through water turbines; in other words, as the water falls from the high level to the low level, it pushes on a water turbine’s blades and spins the turbine. Rotational energy is converted to electricity with an electric generator. In 2008, hydroelectricity accounted for the majority of renewable energy produced worldwide.

Steam turbines, on the other hand, harness energy from steam instead of liquid water. They are used extensively in other types of power plants. In fact, the steam turbine is the primary method of converting thermal energy into kinetic energy in large-scale applications. Whether the heat in a power plant comes from coal combustion or nuclear fission, it is used to boil water and produce steam. The high-pressure steam is then diverted to flow through a turbine, causing it to spin rapidly and turn an electrical generator.

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