Reaction hydro turbines
Reaction hydro turbines are the most commonly used turbines around the world. As their name suggests, they are not powered from a direct impulse or push, rather a reactive force.
Reaction turbines absorb the water’s energy as it passes through, lowering the pressure in the process.
To be effective, the turbines must be made to contain huge volumes of water pressure.
Reaction turbines are more commonly seen in areas with low and medium head applications.
Below are the most universally known types of reaction turbines:
The Francis hydro turbine is the most used form of hydropower in the world and is primarily installed for electricity generation.
Developed by James Francis, it can reach between 83 and 1000 revolutions per minute (RPM), depending on its size, which ranges from 10-750 megawatts (MW).
This evolution of the Francis hydro turbine was developed by Viktor Kaplan in 1913. It varies in one significant way though, with propeller-like adjustable blades.
While it can last for a number of years, this innovation leads to an expensive design, manufacture and installation.
This, like the Francis model, is still widely used today and is best suited for water with a high flow rate.
Its output is slightly smaller than the Francis at 5-120 MW, with the turbine reaching speeds between 79 and 429 RPM.
The Tyson hydro turbine is installed right in the centre of flowing water and for that reason doesn’t need a casement.
This is where the flowing water is most powerful, taking in more kinetic energy. The Tyson can also be easily relocated.
The Gorlov hydro system is quite a recent development in the hydro world. It won the Thomas Edison patent award in 2001, and was invented by Professor Alexander Gorlov.
The Gorlov is a spin-off of the Darrieus wind turbine – and has the same features as the vertical axis wind system.
Impulse hydro turbines
Impulse turbines are used in high speed water areas, where a huge momentum will cause the blades to turn.
The turbine is powered by a high velocity of water, as the jet hits the curved blades and changes flow direction.
Many turbines use technology of both reaction and impulse designs, but some, like the Pelton turbine, are exclusively impulse.
Invented by Lester Pelton in the 1970s, the Pelton hydro turbine remains one of the most efficient hydro energy designs.
This is because water leaves the product at a much slower speed, meaning most of the energy has been transferred.
However, some variations are not as energy efficient, with water leaving at a greater speed.
The Pelton design can come in all shapes and sizes, with the largest stretching to 200MW and the smallest just inches in width.
The Turgo hydro turbine is fantastic at achieving energy efficiency, and peaks at 87%. This modification of the Pelton turbine is much cheaper to make, making it extremely popular when low cost factors highly.
The Turgo is designed for medium head water levels, while handling a greater flow with its higher speed.
Radial and axis flow are the two most common types of hydro turbine design, but the Crossover opts for a different approach.
The water travels transversely across the blades and enters the system twice, increasing the energy efficiency.
The machine itself is lower speed than other impulse turbines, and it’s suitable for locations with low head but large levels of water flow.
Inventor Feu Jonval introduced this hydro turbine to France in 1843. This form of impulse turbine directs the flow of water onto curved blades after it’s descended through a fixed guide vane.
Jonval took ideas from other European mathematicians and engineers to create his design, especially the tried and tested innovation of curved blades.
The curved blades improved the turbines effectiveness and tripled its efficiency over the more common waterwheel.
Reverse overshot waterwheel
This Roman technology is scarcely seen around the world now, with its main use being in mines.
Its function is to remove water from lower levels of underground works.
Archemides’ screw turbine
Just like the reverse overshot, the Archemides’ screw is not very common. Historically, it was a way to move water from deep irrigation trenches.