Geothermal energy means heat that is extracted from the Earth’s interior and converted into energy. “Geo” means earth and “thermal” means heat.
It is an emerging technology that harnesses the heat from miles below the surface of the earth. If you didn’t know already, you drill down below a mile down under the surface, it starts to get warmer and warmer the lower you go. Think about volcanoes and hot springs, lava fountains – you get the idea? Like in Hawaii and Yellowstone natural park, you will see incredible amounts of heated material shooting out of holes in the ground.
Heavy Elements at the Earth’s Center
This naturally occurring heat is the stored heat in the center of the earth, it’s been there since the planet was first formed and it exists in absolutely vast quantities. If you go back to the formation of the earth billions of years ago it was a ball of superheated liquid and gasses that gradually cooled and became more solid, and was getting showered with meteorites which will have been transferring their heat and mass to the earth . The heavier elements like iron went to the center of the earth and with this the contraction, its gravitational shrinking was adding to the pressure and heat in the core.
As those heavy elements were sinking to the core the lighter elements that were rich in radioactivity were coming to the surface of the earth and concentrating themselves in the upper mantle in the crust. This natural radioactivity comes from elements such as uranium, thorium and potassium and they really concentrated in the rocks in the earth’s crust.
Heat from Radioactivity
If you look at the crust of the earth it’s only one percent of the total volume of the earth but has tremendous quantities of radioactive elements – these radioactive elements, if you know about radioactivity, in a radioactive element the nucleus is unstable so over time the nucleus will throw off lots of little particles and so the particles run right into one another and this creates heat. This natural radioactivity occurs in most of the rocks in the crust, it does not seem very much but it is there and is easily measured, and is stored in the rock – it has been there for hundreds of millions of years. The heat from this radioactivity, miles below the earth’s surface, is what we tap into to generate electricity…
Finding Locations to Drill
So, say, we want to be able to produce geothermal energy in a location where there are no volcanoes or hot springs available. How do we find the right locations to drill? It’s not obvious as the resources could be one two miles below the surface of the earth. What is needed is some kind of remote sensing technique for exploring for these hidden systems (which could be over a hundred kilometers square sometimes)
By using satellites that contain radar and sophisticated imaging systems what we can scan the surface for the telltale signs of geo thermal reservoirs miles below. If we can locate and identify places where the surface of the earth can be seen to actually flex (only maybe perhaps millimeters per year) that slight deformation below will give us the data needed to further explore an area that looks promising in more detail, and if confirmed do a test drill. When we see signs of the kind of cracks and fractures necessary for a geothermal plant then we would go in and then drill a well and tap into to all the hot fluids that are down there in this geothermal reservoir.
Converting Geothermal Energy to Electricity
The question is -how do you convert this thermal energy to electricity?
The way that we produce electricity is the same way as we do in natural gas or coal-fired or even nuclear power plants. They all produce electricity by heating water to create steam to drive turbines that power generators. When we bring high pressure hot water to the surface the pressure is reduced and the water boils or flashes to produce steam.
As it tries to expand we capture it in a restricted flash vessel and force it to travel through high-pressure nozzles so what happens is the steam shoots out of these nozzles at something like four hundred fifty miles per hour. The steam then hits turbine blades turning a generator and creates electricity through electromagnetic induction coils that rotate within a magnetic field, and that’s how we use geothermal heat should produce electricity.