# If temperatures are higher deep underground why can't we generate energy this way? **URL:** \ **Category:** Factual Questions\ **Created:** [August 1, 2003, 2:35am UTC](https://boards.straightdope.com/t/if-temperatures-are-higher-deep-underground-why-cant-we-generate-energy-this-way/192275 "2003-08-01T02:35:02Z")\ **Posts on this page:** 8\ **Page:** 2
**Author:** ![Grey](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Grey](https://boards.straightdope.com/u/Grey)\ **Post date:** [August 1, 2003, 5:01pm UTC](https://boards.straightdope.com/t/if-temperatures-are-higher-deep-underground-why-cant-we-generate-energy-this-way/192275/21 "2003-08-01T17:01:44Z")
What if we took existing mines as our hole in the ground? They are serviceable, accessible and some of the South African ones require massive cooling equipment to prevent their workers from being cooked, so they may be hot enough. You could use the ambient temperature and not the rock itself to draw heat from. The issue then is getting the working fluid to a place where it can be condensed and cycled back through without loosing too much efficiency. Hmmmm. ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [August 1, 2003, 5:29pm UTC](https://boards.straightdope.com/t/if-temperatures-are-higher-deep-underground-why-cant-we-generate-energy-this-way/192275/22 "2003-08-01T17:29:15Z")
> [@](#): > > \*Originally posted by RM Mentock \* > \*\*You still have to dig the whole, and heat doesn’t conduct through the rock all that well, so you’d use a lot of energy getting there, then suck out the available heat quickly–and there wouldn’t be that much of it to compensate. > > A lot of the geothermal applications depend upon convection rather than conduction. Advances in technology may change the picture. \*\* I see. So beyond the construction cost issues, if we pull the heat out of the surrounding soil or air to do work and essentially cool the area down, the rate at which it will re-heat would be quite slow in getting back up to useful temperatures that we can generate energy with. Is this it? ---
**Author:** ![Sofa\_King](https://avatars.discourse-cdn.com/v4/letter/s/58956e/32.png) [@Sofa\_King](https://boards.straightdope.com/u/Sofa_King)\ **Post date:** [August 1, 2003, 5:45pm UTC](https://boards.straightdope.com/t/if-temperatures-are-higher-deep-underground-why-cant-we-generate-energy-this-way/192275/23 "2003-08-01T17:45:39Z")
Can’t you generate some electricity by utilizing the [Seebeck effect](http://www.xyroth-enterprises.co.uk/seebeck.htm)? Seems like you could do it without moving parts. ---
**Author:** ![prisoner6655321](https://avatars.discourse-cdn.com/v4/letter/p/5f8ce5/32.png) [@prisoner6655321](https://boards.straightdope.com/u/prisoner6655321)\ **Post date:** [August 1, 2003, 5:46pm UTC](https://boards.straightdope.com/t/if-temperatures-are-higher-deep-underground-why-cant-we-generate-energy-this-way/192275/24 "2003-08-01T17:46:01Z")
Yes. Geothermal energy, though exciting, is not a viable alternative energy resource. Even locations that utilize naturally occuring geothermal resources, like The Geysers in California, have witnessed a significant decrease in energy output, due to man’s involvement. I wrote a paper on this in College. Imagine in 50 years old faithful not being so faithful. There was a church that wanted to tap geothermal resources just outside Yellowstone. That would have devastated the geysers in the Park. What the OP is talking about, using the ambient temperature of the rock, could generate electricity. Enough for a reasonable sized home. But the energy output would be short lived. ---
**Author:** ![MEBuckner](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mebuckner/32/2896_2.png) [@MEBuckner](https://boards.straightdope.com/u/MEBuckner)\ **Post date:** [August 1, 2003, 5:51pm UTC](https://boards.straightdope.com/t/if-temperatures-are-higher-deep-underground-why-cant-we-generate-energy-this-way/192275/25 "2003-08-01T17:51:45Z")
A Japanese company which specializes in [Ocean Thermal Energy Conversion](http://www.xenesys.com/english/otec.html) systems is apparently [trying to make something like the idea in the OP work](http://www.xenesys.com/english/stec.html). ---
**Author:** ![prisoner6655321](https://avatars.discourse-cdn.com/v4/letter/p/5f8ce5/32.png) [@prisoner6655321](https://boards.straightdope.com/u/prisoner6655321)\ **Post date:** [August 1, 2003, 10:55pm UTC](https://boards.straightdope.com/t/if-temperatures-are-higher-deep-underground-why-cant-we-generate-energy-this-way/192275/26 "2003-08-01T22:55:45Z")
Whoops. That “Yes” was in response to this: > [@](#): > > \*Originally posted by **astro** > I see. So beyond the construction cost issues, if we pull the heat out of the surrounding soil or air to do work and essentially cool the area down, the rate at which it will re-heat would be quite slow in getting back up to useful temperatures that we can generate energy with. Is this it? ---
**Author:** ![Rhum\_Runner](https://avatars.discourse-cdn.com/v4/letter/r/2bfe46/32.png) [@Rhum\_Runner](https://boards.straightdope.com/u/Rhum_Runner)\ **Post date:** [August 2, 2003, 3:04am UTC](https://boards.straightdope.com/t/if-temperatures-are-higher-deep-underground-why-cant-we-generate-energy-this-way/192275/27 "2003-08-02T03:04:06Z")
Also, don’t forget there would be a massive energy investment in digging the hole to begin with. Think of all the energy required simply to move the drill bits up and down as you dig, the man power to constantly be adding/taking off pipes from the drill etc. ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [August 2, 2003, 3:41am UTC](https://boards.straightdope.com/t/if-temperatures-are-higher-deep-underground-why-cant-we-generate-energy-this-way/192275/28 "2003-08-02T03:41:39Z")
Like I said earlier, you end up creating a cool spot underground… pity that it is too dangerous to tap the phenomenal energy of an active volcano unless anybody knows a safe method? I noticed a link to a Japanese OTEC company earlier on . Now that is a technology that seems promising- heavy on initial investment tho’. [Previous page](https://boards.straightdope.com/t/if-temperatures-are-higher-deep-underground-why-cant-we-generate-energy-this-way/192275.md?page=1)