Fossil energy sources

​Millions of years ago, before dinosaurs were around, there were many strange looking plants and animals. When they died their remains were left behind and started to decompose. Over time, wind and rain caused the remains to be covered by layers of sand, salt, rock and water. As more layers appeared the remains were slowly compressed. Parts of the plant remains were replaced by sulphur from deep underground.

Leaving behind a dark rocky substance, coal. The remains of marine plants and animals turned to a thick oily liquid, oil. Others became packets of natural gas like methane. ​The energy from the plants and animals were stored in these deposits like energy fossils. Coal, oil and natural gas are all fossil fuels. When humans discovered that the chemical energy stored in these fuels, they dug up the coal, pumped out the oil, and extracted the natural gases.

Burning fossil fuels releases large amounts of thermal energy. Fossil fuel power plants harvest this energy and turn it into electrical energy. Then more fossil fuels must be dug up. The process begins again. Fossil fuels took millions of years to form so eventually deposits will run dry.

They are non-renewable energy sources. ​When fossil fuels are burned they release harmful gases like sulfur dioxide and nitrogen oxides. They also release lots of carbon dioxide which adds to global warming. Some power plants add in a filter that captures some of the harmful things that burning fuel releases. It stops them from being released into the air. This is called a capture system.

Burning fossil fuels also releases black residue called soot. Overtime soot builds up on surfaces like the pipe where the smoke comes out of the exhaust stack. The exhaust stack must be cleaned to stop it from getting blocked. ​This power plant uses natural gas. It burns gas in order to produce thermal energy. The thermal energy heats water in pipes above turning it into steam.

The steam powers a turbine and generator, which produces electrical current. But thermal energy is a messy kind of energy. It conducts outwards in all directions, so much is lost.  Only about one third of the chemical energy in the gas will be turned into electrical energy. The other two thirds are lost as heat. Coal and oil power plants work on the same principle as natural gas power plants. ​Technology is getting better however.

Newer natural gas power plants make use of two turbines instead of just one. The hot gas powers one, and the steam powers the other one. There are two cycles. This way the power plant turns two thirds of the chemical energy from the gas into electrical energy. Only one third is lost as excess heat.

It's more energy efficient. Fossil fuels may be harmful to the environment and limited in supply, but they produce a lot more energy than most renewable energy sources. Globally, fossil fuel power plants generate just over 65% of the world's electricity. We will have to find alternatives in the future though, because we won't have fossil fuels forever, unless we don't mind waiting a few million years for more fossil fuels to form.