5 ms·

I had similar questions about the heat exchange over time affecting the earth's core temperature, but it looks like far smarter minds than me have done the calc

I had similar questions about the heat exchange over time affecting the earth's core temperature, but it looks like far smarter minds than me have done the calculations and dismissed that as nothing to be concerned about. But that then brings me to my next question - I am assuming that the plentiful supply of heat will be used to drive steam turbines in order to generate electricity? Will that mean that the actual limit may be the plentiful supply of clean water which can be converted to steam? That would still leave a lot of drought affected area unable to utilise geothermal energy, wouldn't it?

llukas 9y ago
You can pump water back after it condenses?
- cyberferret 9y ago
  Assuming you can scavenge 100% of super heated water. There is always going to be some loss factor. And if a geothermal installation is going to need several hundred million litres of water then an installation in an arid area will still be problematic. It also comes down to how that heat is harnessed - will they be channeling the latent heat up and using it to generate steam at the surface, or will they be pouring the water down into the interior and converting it to steam within the subterranean chambers and harnessing the resulting steam pressure coming back up etc.?
  - adrianN 9y ago
    After the water went through the turbine it's not superheated anymore. You probably have a condenser already to improve efficiency. I wouldn't be surprised if it's a completely closed loop anyway.
pjc50 9y ago
This is a general problem with steam-thermal plants of all kinds, unfortunately. You can recondense the water, but the easiest way of doing that is with .. more water. This is why nuclear plants are so often built on the coast.
taneq 9y ago
Well, you don't need clean water. You can use your distilled water in a closed loop and condense it using any old water. That's what the big towers on a nuclear power plant are for - they're cooling towers for the condensors. This could even increase rainfall (and thereby fresh water supply) if you have a source of brackish water nearby to use as cooling water, since a decent fraction of the cooling water evaporates.
- sandworm101 9y ago
  There is also some evidence that the big puffy white clouds that are produced reflect solar radiation, reducing net heat even if they are a little hotter than background.
- craftyguy 9y ago
  If I'm not mistaken, the condensers are cooled by water, hence the plumes of steam you see rising above nuclear power plants. So if you are using a similar technique with geothermal plants and are in an area where you cannot quickly radiate excess heat away, you'll still need a secondary, renewable, source of water... right?
  - mattnewton 9y ago
    Right but gp is arguing that water isn’t in competition with drinking water, you can use grey water, which should be easier to come by
leggomylibro 9y ago
There was an interesting article a little while ago about those sorts of challenges in a New Zealand town which started to 'use up' its volcanic activity through power generation and just good old runaway private use of the 'free' hot water: https://arstechnica.com/science/2017/10/plugging-in-to-a-volcano-geothermal-power-and-the-science-that-enables-it/ https://arstechnica.com/science/2017/10/plugging-in-to-a-vol...
- jgamman 9y ago
  yeah - you gotta manage the extraction. think of it as heat mining/fishing. you want a rate of extraction just less than the replenishment rate or else you screw up the reservoir.

llukas 9y ago

You can pump water back after it condenses?

cyberferret 9y ago
Assuming you can scavenge 100% of super heated water. There is always going to be some loss factor. And if a geothermal installation is going to need several hundred million litres of water then an installation in an arid area will still be problematic. It also comes down to how that heat is harnessed - will they be channeling the latent heat up and using it to generate steam at the surface, or will they be pouring the water down into the interior and converting it to steam within the subterranean chambers and harnessing the resulting steam pressure coming back up etc.?
- adrianN 9y ago
  After the water went through the turbine it's not superheated anymore. You probably have a condenser already to improve efficiency. I wouldn't be surprised if it's a completely closed loop anyway.

pjc50 9y ago

This is a general problem with steam-thermal plants of all kinds, unfortunately. You can recondense the water, but the easiest way of doing that is with .. more water. This is why nuclear plants are so often built on the coast.

taneq 9y ago

Well, you don't need clean water. You can use your distilled water in a closed loop and condense it using any old water. That's what the big towers on a nuclear power plant are for - they're cooling towers for the condensors. This could even increase rainfall (and thereby fresh water supply) if you have a source of brackish water nearby to use as cooling water, since a decent fraction of the cooling water evaporates.

sandworm101 9y ago
There is also some evidence that the big puffy white clouds that are produced reflect solar radiation, reducing net heat even if they are a little hotter than background.
craftyguy 9y ago
If I'm not mistaken, the condensers are cooled by water, hence the plumes of steam you see rising above nuclear power plants. So if you are using a similar technique with geothermal plants and are in an area where you cannot quickly radiate excess heat away, you'll still need a secondary, renewable, source of water... right?
- mattnewton 9y ago
  Right but gp is arguing that water isn’t in competition with drinking water, you can use grey water, which should be easier to come by

leggomylibro 9y ago

There was an interesting article a little while ago about those sorts of challenges in a New Zealand town which started to 'use up' its volcanic activity through power generation and just good old runaway private use of the 'free' hot water: https://arstechnica.com/science/2017/10/plugging-in-to-a-volcano-geothermal-power-and-the-science-that-enables-it/ https://arstechnica.com/science/2017/10/plugging-in-to-a-vol...

jgamman 9y ago
yeah - you gotta manage the extraction. think of it as heat mining/fishing. you want a rate of extraction just less than the replenishment rate or else you screw up the reservoir.