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

Start this free course now. Just create an account and sign in. Enrol and complete the course for a free statement of participation or digital badge if available.

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 (<10 MW) hydro capacity at the end of 2009 was about 60 GW. This is about 6% of the world’s total hydro capacity: a proportion that seems to have remained much the same for several decades. In the UK small scale hydro produced over 1 TWh for the first time in 2016, about 23% of total hydroelectric production. (BEIS, 2017)

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

Take your learning further

Making the decision to study can be a big step, which is why you'll want a trusted University. The Open University has 50 years’ experience delivering flexible learning and 170,000 students are studying with us right now. Take a look at all Open University courses.

If you are new to University-level study, we offer two introductory routes to our qualifications. You could either choose to start with an Access module, or a module which allows you to count your previous learning towards an Open University qualification. Read our guide on Where to take your learning next for more information.

Not ready for formal University study? Then browse over 1000 free courses on OpenLearn and sign up to our newsletter to hear about new free courses as they are released.

Every year, thousands of students decide to study with The Open University. With over 120 qualifications, we’ve got the right course for you.

Request an Open University prospectus371