Small-scale hydro power is one of the most cost-effective and reliable energy technologies to be considered for providing totally clean electricity generation. Small hydro is in most cases 'run-of-river' and it’s generally below 5MW.
How it Works
A duct is built to divert river water, usually in a valley close to a lake. Water flows through to turn turbines and thus drive generators.
Hydro-electric power stations can produce a great deal of power very cheaply (rainfall is the ultimate free fuel for the power plant and it is also generally more reliable than wind, solar or wave power), with absolutely no waste or pollution.
In case of dam-base plants, water can also be stored above the dam ready to cope with peaks in demand and therefore reservoir-based hydro-electric power stations can increase to full power very quickly and electricity can be generated constantly.
Many dams are used for flood control or irrigation, so building costs can be shared.
Sites include mountainous locations where there are fast-flowing mountain streams and lowland areas with wide rivers. With a barrage development, the turbines are constructed as part of the weir or immediately adjacent to it, so that almost no approach canal or pipe-work is required. However, finding a suitable site can be difficult.
The power available in a body of water depends on: the amount of water flowing per second, the flow rate, the height through which the water falls, the head and the force of gravity. The actual electrical power output of a scheme will depend on how efficiently it converts the power of the water into electrical power. A typical micro or mini-hydro scheme will be constructed from a variety of components:
- An intake, often incorporated into a weir, to divert the flow from the water course
- A penstock pipe to convey the water from the intake - must be of sufficient diameter to minimize 'head-loss'
- A powerhouse, in which the turbine and generator-set convert the power of the water into electricity
- An outflow through which the water is released back to the river or stream
- Underground cables or overhead lines to transmit the electricity
its point of use
Environmental Aspects of using the Technology
With proper management, ecological effects are negligible. Small-scale hydro power has many environmental benefits:
- It is quiet and visually unobtrusive
- It displaces generation by fossil-fuels or nuclear power, thereby reducing the Earth's pollution. However, without careful planning and management, water quality and quantity downstream can be affected, which can have an impact on plant life.