Can Geothermal power make up for declining fossil fuels?
Preface. Geothermal power plants are cost justified only in places where volcanic or tectonic activity brings heat close to the surface, mainly in “ring of fire” nations and volcanic hot spots like Hawaii. Even then drilling can only be done where the rocks below are fractured in certain ways with particular chemistries. A great deal of heat needs to be fairly close to the surface as well, since drilling deeply is quite expensive.
The reasons drilling is so difficult and expensive are:
- You have to remove all the rock you’ve cut from the hole which gets harder and harder as the hole gets deeper
- Drilling erodes the drill bit and pipe so you have to keep replacing them
- Drilling heats the rock up, so it has to be cooled down to keep the equipment from getting damaged
- The deeper you go, the hotter it gets, and the more expensive the drilling equipment gets using special metallurgy
- the fluids wreak havoc on boreholes by destroying their liners and concrete plugs, and are very corrosive, it’s scary stuff (Oberhaus 2020)
- Pipes have to be thick and heavy to survive pumping pressures, about 40-50 pounds per foot. A deep well might have a million pounds of piping. Just its own weight can break it if not well made, and at some point it’s hard to find hoisting equipment with enough power to lift it
- If the rocks aren’t stable, the hole may collapse
- There are often pressurized fluids that want to flow up the hole that can cause a dangerous blowout
- Some deep rock leaches toxic or radioactive materials, which increases costs to dispose of them and can make the drilling equipment hazards to touch
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