I wonder as well. The self-proclaimed world's largest spa, Therme Erding [1], is the result of an oil drilling attempt hitting a hot sulphur/fluoride spring instead at ~2.3km depth. Today, it powers the entire spa and close by communities with geothermal energy.
Just need a way to efficiently extract the heat from whatever depth and convert it to electricity by usual means.
It's really an almost surreal experience, with encrusted hot spring water pipes and steam everywhere in the district. Sometime you even need to be careful where you step to avoid to be scolded by steam coming up from the ground, likely due to overflow from the hot water boreholes flowing to the rainwater drainage system.
And it's not just the modern hot water boreholes they use to supply the hot spring baths & other users. One time we even saw a traffic code & couple sandbags placed on a random hillside next to the road, as there was steam escaping out of it. :D
I've had an idea that is probably impractical and/or impossible, but seems like it would be neat: Every house should have a super deep hole drilled in their back yard, and a small self-contained Stirling engine [1] generator lowered into it, with wires up to the house. Free electricity on a micro scale, 24/7. I'm sure the idea has been explored by people with a much better grasp of physics and engineering than myself. But we've done crazier things as humans - like covering half of the ground in asphalt and stringing wires point to point around the globe, so it doesn't seem unreasonable to me.
For any heat engine - including a stirling engine - you need a heat difference between the hot and cold side, ideally as big as possible. If you put the stirling engine at the bottom of the hot hole, the whole machine will be hot, there will be no difference in temperature and it will not run.
This also discounts stuff like the need for maintenance, that is hard to achieve at the bottom of a hot & likely very humid if not water filled borehole.
For that reason, most geothermal systems pump water down & then back up again (possibly using multiple wells) & have the heat engines at the surface, where they can be easily serviced & a good heat differential can be achieved, via air or water cooling.
This in the end, is generally an industrial operation though, not really something suitable for every single house. Still helps with maintenance, as you can provide energy for many houses & don't hat to maintain the geothermal power production equipment for each house separately.
Lots of potential uses indeed — also for travel, potential megastructures, and mining beyond the wildest hopes of asteroids but it's likely to be harder to get the stuff (gold, iron, etc) down there than it is to travel millions of kilometers out there through the void and radiations...
And yes, potentially much more heat than we'd know what to do with currently.
Interesting hard sci-fi (well, basic physics principles mostly) about it by Isaac Arthur: https://youtu.be/jZQP2oNDkAM
Disclaimer: absolutely not affiliated with the man but deeply hoping that such perspectives become maintream, normal expectations. Not holding my breath, but one hacker at a time, we'll get there!
Yes. The problem is that the thermal conductivity of rock isn't great, so it needs to be in a "hot" area and to have some kind of underground fracturing allowing water to spread out and heat up.
It must be easier to get environmental permits for geothermal since it has such a small footprint compared to wind and solar and won’t kill any birds, make noise, make pulsing light, etc.
Let me check Wikipedia for you: "The Earth's geothermal resources are theoretically more than adequate to supply humanity's energy needs, but only a very small fraction may be profitably exploited. Drilling and exploration for deep resources is very expensive. Forecasts for the future of geothermal power depend on assumptions about technology, energy prices, subsidies, plate boundary movement and interest rates."
When the article mentioned that the temperature was twice what they had expected, I wondered the exact same thing.
Could they cover the hole, pour water into it and use air pressure changes in the hole to generate electricity? There must be a way to make the hole air tight. I suspect that the rock near the bottom of the hole would already be air tight.
Also I never understood why steam engines release all the hot stream into the air? Doesn't that waste energy to let the hot steam out? Isn't it better to keep the heat trapped inside the system and generate electricity from the pressure only?
Isn't it better to keep the heat trapped inside the system and generate electricity from the pressure only?
Steam engines are old technology. They've been replaced by modern steam turbines, in which the steam is either cooled and recirculated, or used for other processes, or both.
Geothermal steam turbines typically use a heat exchanger and release the original steam, as geothermal steam tends to be very corrosive.
> Also I never understood why steam engines release all the hot stream into the air?
They don't. All practical steam engines have condensers that recover most of the water and as much of the heat as current technology and the laws of thermodynamics allow.
Yes, but not at a viable cost. Drilling is extraordinarily expensive and complicated.
There's the added issue that rock's thermal conductivity is low, and any thermal borehole would have a limited effective lifespan as it reduced the temperature of adjacent material.
Geothermal energy is a viable and widely tapped energy resource, where it's available. In almost all such locations, it's been substantially exploited, with two notable exceptions: the African Rift Valley (mostly in Kenya), and the Yellowstone supervolcano, a national park in the US.
Substantial developments exist in California (The Geysers), Hawaii, Iceland, Japan, the Philippines, New Zeland, and quite probably elsewhere. 1GW+ plants are possible, comparable with the largest practical thermal and nuclear power plants (generally 1-4 GW, though multiple plants or reactors may be co-located). Worldwide capacity as of 2015 is about 12.5 GW.
The two principle variants are standard and enhanced geothermal. A standard plant utilises naturally-occurring steam, and is far less expensive to develop. "Enhanced geothermal" involves boreholes and often water injection to provide power generation.
I'd followed the case of one such project in Australia, the Geodynamics Habanero project. I'd first read of that in 2014 through a grossly misleading and fatuously optimistic report which struck me as both odd and curiously fact-free. Digging showed that in reality the project was running years late, at 1/50th originally-planned capacity, well over budget, and with significant technical challenges.
Even had the project gone as initially scoped, the wells would have had a useful life of about 20-40 years, after which all available useful thermal energy would have been extracted, and would have to be replenished over ... long time, possibly centuries or more. There's a reason the Earth's interior remains molten -- rock is a very good insulator.
I'm not an opponent of geothermal power -- where appropriate it's highly useful, dependable, safe, and proven. In Africa it stands to make a tremendous difference, where even a small plant would make a tremendous increase in the availability (and probably reliability) of electricity. I'd encourage consideration of developing even such normally off-limits natural park resources such as Yellowstone (specifically excluded from a USGS geothermal resource survey I'd checked on some years back).
But enhanced development through borehole-based wells looks like a very long shot.
neuronic|6 years ago
Just need a way to efficiently extract the heat from whatever depth and convert it to electricity by usual means.
[1] https://en.wikipedia.org/wiki/Therme_Erding
m4rtink|6 years ago
https://en.wikipedia.org/wiki/Beppu
It's really an almost surreal experience, with encrusted hot spring water pipes and steam everywhere in the district. Sometime you even need to be careful where you step to avoid to be scolded by steam coming up from the ground, likely due to overflow from the hot water boreholes flowing to the rainwater drainage system.
And it's not just the modern hot water boreholes they use to supply the hot spring baths & other users. One time we even saw a traffic code & couple sandbags placed on a random hillside next to the road, as there was steam escaping out of it. :D
russellbeattie|6 years ago
1. https://en.m.wikipedia.org/wiki/Stirling_engine
m4rtink|6 years ago
This also discounts stuff like the need for maintenance, that is hard to achieve at the bottom of a hot & likely very humid if not water filled borehole.
For that reason, most geothermal systems pump water down & then back up again (possibly using multiple wells) & have the heat engines at the surface, where they can be easily serviced & a good heat differential can be achieved, via air or water cooling.
This in the end, is generally an industrial operation though, not really something suitable for every single house. Still helps with maintenance, as you can provide energy for many houses & don't hat to maintain the geothermal power production equipment for each house separately.
K0SM0S|6 years ago
And yes, potentially much more heat than we'd know what to do with currently.
Interesting hard sci-fi (well, basic physics principles mostly) about it by Isaac Arthur: https://youtu.be/jZQP2oNDkAM
Disclaimer: absolutely not affiliated with the man but deeply hoping that such perspectives become maintream, normal expectations. Not holding my breath, but one hacker at a time, we'll get there!
pjc50|6 years ago
An example: https://www.cnbc.com/2018/11/06/drilling-to-start-at-the-uks...
Not quite there yet: https://www.uniteddownsgeothermal.co.uk/future-programme
In both construction time and cost it's a bit meh compared to wind/solar, its only advantage is dispatchability.
generatorguy|6 years ago
205guy|6 years ago
https://en.wikipedia.org/wiki/Geothermal_energy
cryptica|6 years ago
Could they cover the hole, pour water into it and use air pressure changes in the hole to generate electricity? There must be a way to make the hole air tight. I suspect that the rock near the bottom of the hole would already be air tight.
Also I never understood why steam engines release all the hot stream into the air? Doesn't that waste energy to let the hot steam out? Isn't it better to keep the heat trapped inside the system and generate electricity from the pressure only?
technothrasher|6 years ago
Steam engines are old technology. They've been replaced by modern steam turbines, in which the steam is either cooled and recirculated, or used for other processes, or both.
Geothermal steam turbines typically use a heat exchanger and release the original steam, as geothermal steam tends to be very corrosive.
Turing_Machine|6 years ago
They don't. All practical steam engines have condensers that recover most of the water and as much of the heat as current technology and the laws of thermodynamics allow.
sp332|6 years ago
If you want a single project at a huge scale, check out https://news.ycombinator.com/item?id=15596350
dredmorbius|6 years ago
There's the added issue that rock's thermal conductivity is low, and any thermal borehole would have a limited effective lifespan as it reduced the temperature of adjacent material.
Geothermal energy is a viable and widely tapped energy resource, where it's available. In almost all such locations, it's been substantially exploited, with two notable exceptions: the African Rift Valley (mostly in Kenya), and the Yellowstone supervolcano, a national park in the US.
Substantial developments exist in California (The Geysers), Hawaii, Iceland, Japan, the Philippines, New Zeland, and quite probably elsewhere. 1GW+ plants are possible, comparable with the largest practical thermal and nuclear power plants (generally 1-4 GW, though multiple plants or reactors may be co-located). Worldwide capacity as of 2015 is about 12.5 GW.
The two principle variants are standard and enhanced geothermal. A standard plant utilises naturally-occurring steam, and is far less expensive to develop. "Enhanced geothermal" involves boreholes and often water injection to provide power generation.
I'd followed the case of one such project in Australia, the Geodynamics Habanero project. I'd first read of that in 2014 through a grossly misleading and fatuously optimistic report which struck me as both odd and curiously fact-free. Digging showed that in reality the project was running years late, at 1/50th originally-planned capacity, well over budget, and with significant technical challenges.
https://old.reddit.com/r/dredmorbius/comments/1wpa90/how_not...
Checking now, it appears the firm plugged the remaining wells in 2015 and cancelled the project.
http://www.thinkgeoenergy.com/geodynamics-plugging-wells-and...
Even had the project gone as initially scoped, the wells would have had a useful life of about 20-40 years, after which all available useful thermal energy would have been extracted, and would have to be replenished over ... long time, possibly centuries or more. There's a reason the Earth's interior remains molten -- rock is a very good insulator.
I'm not an opponent of geothermal power -- where appropriate it's highly useful, dependable, safe, and proven. In Africa it stands to make a tremendous difference, where even a small plant would make a tremendous increase in the availability (and probably reliability) of electricity. I'd encourage consideration of developing even such normally off-limits natural park resources such as Yellowstone (specifically excluded from a USGS geothermal resource survey I'd checked on some years back).
But enhanced development through borehole-based wells looks like a very long shot.
Wikipedia's treatment of geothermal is good:
https://en.wikipedia.org/wiki/Geothermal_power