Hacker News Reader

Comment by ccozan | Hacker News Reader

I wonder why not investment goes into tapping the geotermal potential. Is like having a free reactor ( since both work on transferring heat to water -> steam )

View on HN

Most geothermal installations are near tectonic plate boundaries and require drilling only a few hundred metres or less. Being able to go down further would open up the possibility of using geothermal power in other regions, but it's very expensive.

Educated guess: it's very hard.

A pipe that long would be subject to break down every time the earth moves a bit. Fixing said leak would requires stopping the use of the pipe completely.

As 300 C is not that a huge temperature, the energy to pump the water may also cost a lot compare to the energy you get out of it.

I'm not saying we should not try, but it seems a great challenge. And we don't have the motivation of creating an atomic bomb to drive it.

With only a very tenous grasp on the basics of fluid mechanics and thermodynamics, I'd suspect it is simply a lot more cost effective to drive a significantly larger volume of water through a significantly shallower (hence, lower temperature - but cheaper to drill, maintain and force water through) well to reap the same amount of energy.

Assuming reasonable heat exchange efficiencies, you'd do as well with 1000m^3/hour at a 20 degree differential as you would with 100m^3/hour at a 200 degree differential.

Or am I missing something?

Yes, but if you can turn the water into steam you don't have to pump it back as much. So you leverage gravity in, density out. I have no idea if that evens out though.

City of Espoo is testing, 6+ km hole for energy, google for "Otaniemi drill hole" for more information.

Reply on news.ycombinator.com