An introduction to sustainable energy
An introduction to sustainable energy

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 sustainable energy

3 Present energy sources and sustainability

What are the principal energy sources at present, and how sustainable are they?

About 80 per cent of the world's energy is currently supplied by fossil fuels such as coal, oil and gas. Present estimates suggest that, at current consumption rates, there are over 200-years' worth of coal left, 60-years' of gas, and 40-years' of oil. Fossil fuels are hydrocarbons, and their combustion releases carbon dioxide into the atmosphere, one of the main causes of the human-induced greenhouse effect.

Nuclear energy is a fairly new technology which currently provides nearly 7 per cent of our primary energy requirements. It is based on harnessing the very large quantities of energy that are released when the nuclei of certain atoms, such as uranium-235, are induced to split or fission. Estimates suggest that there is sufficient fuel for many decades or even centuries, depending on use rates, but there are major concerns regarding safety and the disposal of nuclear waste products.

The combustion of biofuels such as wood or other biomass material gives us bioenergy. To be sustainable, the forests that provide traditional wood fuel need to be re-planted at the same rate as they are cut down. The incomplete combustion of wood can also release a mixture of greenhouse gases with a greater overall global warming effect than can be offset by the CO2 absorbed by growing replacement trees. Modern bioenergy power plants burn straw and forestry wastes.

Hydroelectricity is the power from flowing water, a source which has been used by humanity for many centuries. In 2000, it contributed over 17 per cent of world electricity. Its original source is the sun; water evaporated from oceans falls as rain or snow into rivers, where its flow can be harnessed using water wheels or turbines. Larger installations can have adverse environmental effects, but smaller projects may have little, if any, impact


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