Question: How does Geothermal power work?

  1. Hi Caton,

    The middle of earth is about 5500 degrees Celsius. It is so hot because of residual heat left over from the formation of the earth, but mostly due to radioactive decay of minerals.

    This heat toward the centre of the earth means there is going to be a heat gradient between the surface and the core. Areas near edges of tectonic plates, or mid plate volcanic zones, are areas where this internal heat reaches the surface in much greater intensity.

    So how to use it? What we can do is by putting pipes down into these zones where there is hot earth, we can pump water down there which is subsequently heated by the surrounding rocks. If the water is heated to a greater than boiling, thus creating steam, we can use that to power a steam generator.

    If the water does not get above boiling, we can also use the sub-boiling water to heat a fluid with a lower boiling point, which can then drive the steam generators.

    Generators are the things that actually create the electricity.


  2. There is also geothermal cooling. A project I’m working on requires a building packed with computers and electronics in the Western Australian outback. The computers generate a lot of heat and with air conditioning it takes a lot of energy to dump that heat into the air outside the building when the air can be 40+ degrees. We will be sinking bores to bring water to the surface which might be warm, but is cooler than 40 degrees. In this case, it is easier to dump heat to the water and carry it away from the building. This substantially reduces energy usage, which means you don’t have to generate the power to run the air conditioning in the first place.


  3. It is sometimes called hot rock power but otherwise Dustin and Steven have covered it nicely.


  4. Nicely answered by Dustin and Steven.
    Caton, I’ll just add something to what Dustin has said.
    Geothermal energy is thermal energy that is generated and stored in the Earth, and most of this energy (~80%) comes from radioactive mineral decay, with ~20% of it coming from the original formation of the planet (20%). Using geothermal power is considered to be a sustainable and renewable source of energy because the amount of heat that would be taken/used is small compared to the total amount stored/produced within the Earth. The areas near techtonic plate boundaries used to be where the use of geothermal power was limited to in the past, but technological advances have meant that it isn’t so restricted any more. Apparently geothermal electricity generation is used in about 24 countries now, and around 70 countries use geothermal heating.



  1. I thought you said middle earth. LOL (middle earth is from the lord of the rings)


  2. Thanks for your great answers everyone!