How Does Geothermal Energy Work?

Video Transcript

"Hi, I'm Steve Jones, and I am going to explain, how geothermal energy works. Now, first of all, I have a diagram here of the earth, so you can't see it all, but this is the earth's crust, which is quite a thin layer, fifteen kilometers at the maximum, and then you've got the core, the very center, which is thought to be liquid, but nobody really knows, and this mantle, which is kind of semi-molten rock, it's rock about to melt,so you can imagine that this is very hot. It's a huge source of energy, and at the margin here, just between the mantle and the crust, you're going to have some very hot rock. Now, we're not talking about going very far down into this, but the maximum 5 or10 kilometers, the very maximum, but maybe it is only 1 kilometer. It depends where you are on the surface of the earth, and what the geological situation is there. What happens, is this hot rock here, is continually heated by the mantle, and therefore, if we push cold water down into this area, then the water that comes back up, if we create another up well, then whatever comes up, should be hot, because this here, will be a place, where the cold water comes in contact with hot rock. Normally, this rock is fractured, and this is done in a very simple way. You drill a very deep hole here, another very deep hole here, you put a charge of dynamite at the bottom of each, and you explode it, so the rock just becomes rubble, and the water can flow, from one to the other. You push the cold water down, under pressure, and out it comes, at this side, heated up. The temperature down here, may well be as high as a thousand celsius, so this is the way we actually use the water, to bring the energy to the surface. The big advantage of this energy of course, is because the earth is such a huge object, and there is so much heat within it, and all the time it is creating more heat, from nuclear processes within the earth, plus other things. This will remain as a source of heat, for millions and millions of years. It will take a long time for the heat to run out, so this is a very renewable form of energy."