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Can renewable energy sources power the world?
Can renewable energy sources power the world?

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4 Small-scale hydro

In the early days of electric power, generators with output ratings between a few kilowatts and a few megawatts were installed on streams or rivers, often using the dams and sluices of old watermills.

Activity 1 Plant output size

What plant output size do you think is now referred to as ‘small-scale’?


With continually rising demand for electricity, and the growth of national transmission networks, capacities of several hundred megawatts have become the norm for modern power stations, and plant outputs below about 10 MW are now referred to as small-scale.

In the industrialised countries, environmental issues have increasingly limited the potential for further major hydro development, whilst small-scale schemes, considered to produce fewer deleterious effects, have received growing encouragement. More recently, a market has begun to emerge for micro-hydro plants, generating a few tens of kilowatts for an isolated house or farm. Very small-scale plants are a practicable option for electricity in developing countries without extensive grid systems.

A World Energy Council survey in 2010 (WEC, 2010a) suggests that the global total small-scale (

You’ll now look at calculating the stored energy and power available in hydro schemes.