Energy sources can be divided into two main groups: non-renewable and renewable. Non-renewable sources like coal, oil, and natural gas are limited and will eventually run out, though they are widely used today. Renewable sources like hydro, solar, wind, geothermal, and tidal are practically inexhaustible but many are still in the research phase and not yet widely used at a large scale. Both non-renewable and renewable sources have advantages but also problems regarding their environmental impacts, costs, and issues around development and infrastructure needs.

1. Energy sources
Unit 4

2. • Energy sources:
• Natural sources to produce energy for domestic purposes, industries and
transport.
• The control, production and distribution of the energy sources has become a
major strategic factor.
• Can be divided in two groups:
• Depending on economic importance: Traditional or alternative.
• Depending on whether or not they will run out: Renewable or non-renewable.

3. Non-renewable energy sources
• Limited resources and may run out.
• Coal:
• Rock fossil fuel.
• Use: Was the force of the industrial revolution. Nowadays, it’s in
decline, it is used as fuel for thermal energy production.
• Problems: Is pollutant and expensive to mine.
• Oil:
• Fossil fuel with a high calorific value.
• Use: Highly valued energy resource for transport, heating and
chemical industry.
• Problems: Is pollutant, and non-renewable. The most widely
used resource. Worries about the remaining reserves.

4. • Natural gas:
• Production associated with petroleum.
• Use: fuel for heating and electricity production.
• Problems: Despite it is less polluting than oil or coal it’s a non renewable source of energy.
• Nuclear energy:
• Enriched uranium used as fuel in nuclear reactors.
• Use: Electricity generation.
• Problems: Safety of nuclear plants is in discussion and it generates radioactive waste very
harmful for people and environment.

5. Renewable energy sources
• Sources that are practically inexhaustible. Include Sun,
water, wind. Most of them are still in the research
phase. Big companies prefer to exploit the traditional
ones.
• Hydro power:
• Use the source of water stored in reservoirs to generate
electricity.
• It’s not polluting but the construction of reservoirs
leads to environmental impacts.
• Solar:
• Use the radiation of sun to generate energy: electricity
or heat.
• Two types:
• Photovoltaic: Solar panels made form silicon that
generates electricity form sunlight.
• Thermal: which captures the sun’s heat. This heat is used
directly or converted into mechanical energy and in turn
electricity, known as concentrated solar power.
• Problems: It’s expensive and depends on the amount of
sun radiation over a place.

7. • Wind energy:
• Obtained by harnessing the force of the wind. Non polluting energy.
• Use: Production of electricity.
• Problems: alter the landscape, noise pollution, danger for bird wildlife.

8. • Geothermal energy:
• Uses the heat from inside the earth to produce electricity or heating.
• Reduced to areas with intense volcanic activity or thermal waters.
• Tidal energy:
• Uses the movements of seawater caused by tides, waves and currents.
• Is still in research phase.