An introduction to energy resources
An introduction to energy resources

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.

Free course

An introduction to energy resources

6.1 Concentrating energy

As far as human needs are concerned, there is a marked difference between 'dilute' and 'concentrated' energy. Water vapour in the atmosphere, for example, has considerable potential energy since a huge mass globally (about 13 × 1015 kg—Smith, 2005) is held high above the Earth's surface. But this potential energy represents a very dilute form of energy; falling rain could not turn a water wheel. It is only when energy can be 'concentrated' that it can be put to good use — in this case by rainfall accumulating in streams and rivers, or being stored in reservoirs at high elevations. The concentration can be expressed colloquially in terms of energy density, which is the amount of energy stored by a resource divided by the volume of the space that it occupies.

Some forms of energy are relatively difficult to concentrate, so have a low energy density, whereas others are easier to concentrate. The energy contained in moving air is rather difficult to concentrate; windmills and wind farms have to be sited where natural factors enhance wind speed and constancy. Solar power has a low energy density, so requires large collecting devices. The potential energy of rain is naturally concentrated and held in mountain lakes; we concentrate this energy artificially when rainwater is stored in a reservoir. This emphasises why fossil fuels are so valuable as they represent naturally concentrated forms of the solar energy that reached the Earth millions of years ago.

The ultimate form of concentrated energy is matter itself, in the form of nuclear energy.


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