4 popular types of turbines you should know

Water power achieves its greatest usefulness when it is converted into electricity. The conversion is made possible by electrical generators that are able to transform a waterwheel's rotary motion into electric current. Here are four types of turbines you should know.

• The turbine accepts water through a rectangular orifice and then passes it through a barrel-shaped runner in such a way that the water strikes the ring of blades on the runner two times.
• It is simple enough for someone with a home machine shop to make and it can match the performance of other turbines whose fabrication requires a considerably greater level of technology.
• They work well over a wide range of water flow, are relatively free from problems caused by silt and flotsam and jetsam and are not affected by cavitation.
• To improve efficiency, the turbine's rectangular orifice can be partitioned and parts of it closed off completely during periods of low water flow.

• These turbines are most effective at relatively low heads.
• The propeller is completely submerged and is impelled more by the dead weight of the water than by the water's velocity.
• To overcome this limitation, large hydroelectric installations employ several turbines in tandem, shutting down one or more whenever the flow lessens.
• Others use Kaplan turbines, which have automatically adjustable blades that compensate for any change in the water flow.

• Francis turbines can be used over a wide range of heads that are measured at one metre (three feet) or more.
• As with a propeller turbine, the runner is immersed in the head water, which is guided onto the blades of the runner by a ring of adjustable vanes.
• The Francis turbine is highly efficient at its optimum flow but easily damaged by grit and cavitation.
• It is often used in large hydroelectric stations and is relatively expensive.

• Operates best with heads of 16 metres (50 feet) or more.
• The high-velocity jet of water that results from such heads spins the bladed runner up to generator speed without the need of additional gearing.
• A Pelton turbine will operate efficiently on a head of 50 metres (160 feet) with a flow as little as 0.2 litres per second.
• Though the search for a high head restricts installations to hilly or mountainous locations, very little flow is required to run a small Pelton turbine, in some cases no more than the water which issues from a modest spring on a head as low as five metres (18 feet).
• Depending on the location, waterways might dry up or freeze over during parts of the year, so care must be taken to select a water source that will provide year-round power. Impulse turbines have been improved so that the jet is oriented at an angle to the blades.

Turbines are useful energy sources, used to power lighting, heating, television, computers, refrigerators, washing machines, vacuum cleaners and small appliances. This brief look at four common turbines should help you better understand the roles and benefits of using a turbine.