Geothermal Energy, how does it work?


What is it?

Geothermal energy relates to the thermal energy that is generated and stored within the Earth. It is also defined as the type of energy that determines the temperature of matter. This heat amazingly comes from the very beginning of the Earth, as well as the radioactive decay of materials. It is uncertain which one generates the most heat, but it has been proposed that they account for roughly the same amount. The heat reaches the surface through a ‘continuous conduction of geothermal energy’. The temperature of the core can reach over 4000 °C!

Another attractive feature of geothermal energy is the fact that it is a renewable, low carbon energy source. In areas where these stations can be built they offer an incredible opportunity to generate heat and electricity without pollution the atmosphere with harmful emissions. 

Of course, this is a very basic explanation, but this is essentially the foundation of how geothermal energy works.


How does it generate electricity?

When it comes to generating electricity with geothermal energy, it is much the same as most power plants. The energy source is burnt to boil water and create steam. The steam rotates turbines and those turbines are connected to a generator that produces electricity.

The main difference is that you do not burn any fuel. Reservoirs of hot water found just a few miles below the earths surface are utilised to create this steam. There are, of course, different forms of geothermal energy and there are three forms that are utilised to generate electricity.



These types of geothermal plants are typically found near young volcanoes surrounding the Pacific Ocean. Steam is separated from water with the use of cyclone separators which goes on to turn the turbines etc. The water in this plant is not heated and can therefore be reused and reheated as it is returned to the reservoir.

Thermal Energy

This type of geothermal plant is largely used for heating and not the production of electricity. This is due to the difference in heat. A thermal energy plant uses heat pumps to extract energy from shallow sources that are around 10–20 °C. Whereas, liquid-dominated energy sources usually exceed heats of 200°C!

It has been known for some geothermal electrical plants to use co-generation to produce heat and electricity. Though using this type of geothermal is more cost effective for heating. Iceland are currently the world leader in thermal energy plants. Around 92.5% of their homes are heated with geothermal methods.

Enhanced geothermal

Enhanced geothermal systems (EGS) are an interesting type of plant. They take advantage of wells that are heated by the temperature of the earth. These wells are injected with water that will be heated and pumped back up. This is oddly enough very similar to a technique used for extracting oil and gas. Though this technique does not use toxic chemicals and is considered to be environmentally safe.


A brief history of geothermal energy

Geothermal energy has been used as early as the Palaeolithic times. Although this was simply hot springs used as baths. The next known use of geothermal energy was in the Qin Dynasty in the 3rd century BC. Then came the Romans in Bath, taking advantage of the hot springs for public baths and underfloor heating. The first ever building to use geothermal as their primary heat source was Hot Lake Hotel in Union County, Oregon. Around the same time greenhouses in Italy and Iceland were being heated with geothermal energy. Then in 1930 Charlie Lieb designed the ‘downhole heat exchanger’ to heat his home. Around 13 years later most homes in Iceland were heated with geothermal energy. Then in 1960 the first successful geothermal power plant began operation in The Geysers, California. Which leads us to today!

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