2.2 ELECTRICITY PRODUCTION 23 Fossil fuels as a source of energy were discovered during the Industrial Revolution; since then, they have been fundamental for the development of industry and technology. How did the greenhouse effect get its name? Coal Oil FOSSIL FUELS How is electricity generated? Electricity is produced in power stations by big generators that convert mechanical energy into electrical energy. The mechanical energy needed to start the generator can be provided by different means: fossil fuels, bioenergy, water, wind, the sun, or radioactive materials. Fossil fuels Natural gas, oil, and coal are called fossil fuels because they formed millions of years ago from the fossilised remains of plants and animals. In power stations, fossil fuels are burned to produce heat, which is used to heat water and transform it into steam. The force of the steam is used to spin turbines connected to a generator, which starts turning, converting the mechanical energy into electricity, which is then distributed to users through a power grid. Advantages of fossil fuels Most of the energy in the world is produced using fossil fuels; the main reasons for this are: Natural Gas high energy-efficiency: a small quantity of fossil fuels can produce a big amount of energy; accessibility and availability: they do not depend on weather conditions or geographical locations; they do not need any previous treatment to be used. Disadvantages of fossil fuels Producing electricity using fossil fuels, however, has some negative consequences on the environment: burning fossil fuels releases carbon and other greenhouse gases which are responsible for air pollution, the greenhouse effect , and climate change; fossil fuels are non-renewable energy sources; this means that their supply is limited, and they are estimated to run out in a short time; as they are found underground, fossil fuels have to be extracted from the soil; some methods for extracting fossil fuels are dangerous and harmful to local wildlife. For these reasons, over the last decades, scientific and technological research has been working on clean and renewable sources of energy to provide a more sustainable alternative. Light from the sun 29.4% Reflected coal: carbone greenhouse: serra oil: petrolio remains: resti to run out: esaurirsi soil: suolo to spin: ruotare steam: vapore 66 ELECTRICITY Long-wave radiant energy from the Earth 23.2% Absorbed 54.4% Reaches the surface 85.9% Earth Radiated back to the surface