History
Hydro Power has been available for centuries, originally powering flour and saw mills situated beside rivers, providing a cheap energy source in comparison to steam engines.
Hydro Generation has evolved over the years from small units available for individuals based on run of the river diversion schemes to mass generation schemes providing power to the public via large storage dams. With the increasing awareness of global warming caused by carbon emissions and environmental impacts of large dam systems, the return of small low environmental impact run of the river hydro schemes are now a days, more popular than ever.
Turbine Types
Hydro turbines consist of three main types, impulse turbines, reaction turbines and zero-head turbines.
Impulse turbines are typically high pressure low flow turbines and are either of the Pelton or Turgo design. These turbine provide a water jet at high velocity that impacts with the turbine runner, this energy impulse is converted to rotational torque by the turbine and is then used to drive a generator to provide electricity.
Reaction Turbines are typically low pressure high flow turbines and are either of the Francis, Kaplan or Crossflow turbine design. These turbines provide a turbine impeller sealed inline with the water flow and use blade hydrodynamics to create rotational lift to generate the torque used to drive the electric generators.
Zero-head turbines are relatively new and use the velocity of the water current to generate rotational power just like a wind turbine, however due to the higher density of water compared to air, the water versions can be much smaller that the wind types. These turbines use the Tyson, Gorlov, Dareius or airfoil designs converting kinetic energy and have much lower power capabilities that the potential energy conversion of traditional hydro turbines, but are suitable for applications were there may be lots of water flow but no fall in elevation. Such applications include irrigation channels and rivers.
Electrical Connections
Hydro power generation can be used in both grid connection situation and for stand alone applications. They can be provided with generators and alternators using 12/24/48VDC or 240/415/690VAC or as high voltage systems with 3.3/6.6/11kV generators and interface with medium voltage networks at 11/22/66kV using step up transformers.
Grid Connection is where the site has an electrical connection to the Network Service Provider and power can be used to reduce your electricity consumption or provide excess generation to be sold back to the Network Service Provider either via a Nett Metering arrangement or at Wholesale electricity prices on a contract arrangement or at the spot market rates.
Stand Alone Applications are where the site has no connection to the main grid and may be run in conjunction with a backup generation system such as a diesel generator, solar power system or battery bank. These systems are much more complex that a standard grid connected solution as the turbine must provide both frequency control via a governor and voltage control via and excitation controller. Thes design may also require the system to run multiple units in parallel and the complexity is then increased even further and special design considerations are required to provide system stability and plant automation as well as flow control to provide optimum system efficiency.