How does it work?

Hydro power works by using falling water to drive a turbine, which generates electricity. The amount of energy produced by a hydro power scheme depends on how far the water is falling and the flow rate (i.e. how much water is flowing past each second).

Micro hydro power systems usually have a water intake above a weir or dam. Some of the water flowing along a river is re-directed into the intake which screens for debris and fish to prevent them entering the turbine. From the intake water leads into a channel or pipe (called the penstock) where it falls down through one or more turbines. The water passing through the turbines, generates electricity and is returned to the river afterwards (see diagram to the left).

How much energy can it generate?

Hydro projects are generally categorised in terms of energy production as follows:

• Large hydro - Over 5MW (5000 kW)

• Small hydro - Under 5MW

• Micro hydro - Under 100kW

The amount of energy that can be generated from a hydro site is determined by two factors:

• The flow rate of the water

• The distance the water falls (called the head).

If correctly sited hydro power provides a fairly steady reliable renewable energy source as its output is only effected by seasonal changes in the river’s flow rate. Seasonal variation is an important factor, it would not usually be economic to have a hydro system offline in the summer months due to a lack of water.

Why is it important?

Small scale hydro power can provide clean, safe energy. Hydro power produces no pollution in operation and does not produce carbon dioxide so it does not contribute to climate change.

Large hydro-electric dams can provide very large quantities of energy but generally have serious environmental consequences such as flooding large areas of land and displacing populations. Micro Hydro (less than 100 kW) power systems are seen as a cleaner and safer alternative.

What does it look like?

The turbine and the majority of the machinery for small hydro power systems can be hidden in a small building by the side of the river. This may be designed in a traditional style to blend in with the surroundings.

Similarly pipes can be buried, reducing any visual impact that they might have.