The problem is getting geothermal energy where you want to. So far, no one has ever drilled to the mantle. The main problem with the conventional drilling approach is that the drillbits require too much torque. The proposed solution is to use high pressure water jets to drill into the Earth's crust by carving out small pellets one at a time then pushing them up to the surface with water pressure. The water jet technology could be borrowed from conventional water cutting machines that use garnet in the water, but instead use sand. This way, you should be able to reach the mantle in a nice water cooled torque-free manner. Oh, and one thing that I forgot to explain is that somebody needs to figure out the exact shape of the drill bit with the water jets on it.-- elvatoedwardo, May 10 2004 A study comparing abrasive jet, water jet, and diamond drilling http://216.239.39.1...22&hl=en&lr=lang_enThey like the water jet for small diameter fast penetration [ldischler, Oct 04 2004] Does anybody care to calculate how much water pressure it would take to force the dirt up and out of a hole, say, 100 meters deep?-- 5th Earth, May 10 2004 Without water resistance it takes 0 psi because the earth's gravitational field is conservative.-- elvatoedwardo, May 10 2004 The pressure required to lift the dirt will be something above the static head in the hole (i.e. at 100 metres you will require something a bit above 10 bar pressure), with the additional to account for frictional losses and so you get the required water flowrate through your nozzle.
Water flowrate required to lift the dirt is the other important parameter, and will be a function of particle diameter, relative densities of particle and fluid (water), and the hole diameter. Too low and the dirt will stay at the bottom.
It's an idea that might work, but I can't see it being more efficient than conventional drilling. (-)-- suctionpad, May 11 2004 If you haven't noticed, nobody has ever drilled through the mantle yet. This is because it takes too much torque. That is the WHOLE point to this idea, which is to get past that hurdle.-- elvatoedwardo, May 11 2004 Give the hole a large diameter (5-6ft clearance?) so you can put in extra pumps or other equipment to lift the dirt out. Also allows service people to get down there if something really gets stuck.-- kbecker, May 11 2004 As with any means of power transmission, there are power losses when fluid flows through hoses. I don't have a feel for what they would be under the high pressures used by water jet cutting. Would this require really long high pressure hoses or would the high pressure pump be down in the hole requiring power to be transmitted down there in some other way?
How much abrasive media would be pumped down the hole? Would it need to be extracted somehow?-- half, May 11 2004 Perhaps you could install a hydraulic motor that is hooked up to a high pressure pump inside of the drill bit so that it would step up the pressure. The main question still on my mind is: what shape of pellets would you want to scoop out?-- elvatoedwardo, May 12 2004 [Zanzibar] It’s simple, really. If your wastewater column is at 15,000 psi at the bottom because it’s 30,000 feet high, your cutting water has also gained that same amount of pressure for the same reason. So it’s at 1000 atmospheres plus the pump pressure at the surface. The bigger problem is getting rid of the rock chips that are normally flushed out with drilling mud.-- ldischler, May 12 2004 Here is another way to picture it: If you can just get the water and the pellets back out, perhaps by jet-pumps along the way, then at 30,000ft deep you'd have 885atm or 13,000psi of extra pressure to cut with.
At first glance, it would seem unfeasable for a 300ft high tree to grow because it would take at least 130psi for the water to reach the top branches.-- elvatoedwardo, May 12 2004 I think that the pursuit of non-polluting energy is a very worthwhile goal; a lot more useful than trying to make your farts smell good.-- elvatoedwardo, May 12 2004 i thought Tucks were supposed provide relief from a certain malady, not be it.-- xx, May 12 2004 random, halfbakery