Small Scale Hydro Power
What is Small Scale Hydro?
Harnessing the power of water represents one of the oldest renewable energies in the history of mankind; firstly to irrigate land and to power mills for more than 2,000 years, but more recently to generate electricity also. Therefore it is a mature and proven technology.Small scale hydro power, often called micro hydro, is a system that converts the energy of flowing water into electricity, usually having an output of 100 kW or less. Micro hydro systems differ from larger scale hydro power in that they utilise much lower quantities of flowing water during operation, generating less electricity as a consequence.
Although the tides and waves are both forms of hydro (water) power, only land based schemes will be presented in this booklet, i.e. those that use streams or rivers.
Common types of Small Scale Hydro
Small scale hydro systems are often defined in two general ways; storage schemes or run-of-river schemes. The former includes damming a whole stream or river to hold back a large volume of water, which is then released through a turbine, while the latter uses a weir to modify the flow of a stream or river and divert some of the flowing water to a turbine.
They can be stand-alone systems in which a load is powered directly or via a battery bank, or be grid connected in which excess electricity production can be sold to the grid.
They can also be defined as low-, medium- or high-head depending on the height from which the water falls. The head and flow rate of the stream define the turbine type necessary: low head need propeller or Kaplan turbines; medium head crossflow or Francis; and high head Pelton (impulse) turbines.
How does Small Scale Hydro Work?
In order for hydro power to work, water flowing from a high point to a lower point must be diverted through a turbine.
Water from a river, stream or weir/dam enters the intake and is diverted to the penstock. This then channels the water to a turbine located in the powerhouse. The pressure and flow of water cause the turbine to rotate and hence drive the generator. The water then exits through an outflow pipe, or tailrace, to recombine with the water course.
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