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

This free course is available to start right now. Review the full course description and key learning outcomes and create an account and enrol if you want a free statement of participation.

Free course

Can renewable energy power the world?

5.2 Hydropower resources – world, regional, national

As you saw in Week 1, almost a quarter of the 5.4 million EJ (1.5 billion TWh) of solar energy reaching the Earth’s atmosphere each year is consumed in the evaporation of water. Water vapour in the atmosphere therefore represents an enormous, constantly replaced, store of energy. Unfortunately most of it is not available to us.

When water vapour condenses into water, most of its stored energy is released into the atmosphere as heat, and ultimately re-radiated into space. But a tiny fraction, (about 200 000 TWh y−1), reaches the Earth as rain or snow, with roughly one fifth of this falling on hills and mountains, descending to sea level in the world’s streams and rivers. The 40 000 TWh y−1 of energy carried by this flowing water can be regarded as the world’s total hydro resource.

It is obviously not possible to build hydro plants on every river or stream, so the usable fraction of this flow will be significantly lower, and at the time of writing, the world’s technical hydro potential is estimated to be about 16 000 TWh y−1, (two-fifths of the above total resource).

But how much hydroelectricity is available at a cost competitive with power from other sources? One definition of this economic potential suggests that it is the fraction of the total resource that:

can be exploited within the limits of current technology under present and expected local economic conditions. The figures may or may not exclude economic potential that would be unacceptable for social or environmental reasons.

(WEC, 2010a)

Estimates of the economic potential for hydropower in different countries or regions are much less reliable than estimates of the total or technical potential. Here we consider only the total resource and the technical potential, leaving the economic aspects until Section 5.10.

We now move on to look at hydro resources from a regional point of view.

RENC_1

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 over 40 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, find out more about the types of qualifications we offer, including our entry level Access courses and Certificates.

Not ready for University study then browse over 900 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 prospectus