Drilling to the depth needed to get high enough temperatures for energy generation can be hard. Depending on how active the area is. Iceland, which has tons of heat close to the surface can do it with relative ease. But elsewhere you may have to be drilling far deeper through much harder rock to get there. In some locations you may have to drill down many km at 10s of meters per day through the hardest rocks. It could potentially take months to hit the right depth.
You also need materials to ensure that the well doesn't collapse on itself, and stuff like that as well. I would expect the hole itself should have an extremely long lifespan, but I don't really have much to back it up.
Its not for electric generation, but for Geo HVAC the ground loop itself has a 50 year warranty and quoted 150+ year lifespan. The house will probably be long gone before the loop would go bad.
The operators very very very very much require advanced skills. Don't confuse roughneck work with drilling engineers. Drilling engineers also aren't by any means the only advanced skillset required. It requires a large team of highly educated (postgraduate degrees usually required) and highly paid professionals.
The materials you're using when drilling are expensive. The steel casings that you're putting down the hole are specialized alloys. You're using very large amounts of expensive specialized fluids to fill the hole during drilling (drilling mud) that are relatively hazardous and need to be treated after use. You're going through large numbers of very expensive consumable parts (e.g. drill bits are _not_ cheap, and there are a lot of even more expensive consumables). A large amount of the equipment and consumables are custom built for the specific conditions you're working in. There are certainly cases where you can use things that are a bit more of a commodity, but deep and hot wells usually don't fall into that category. And yes, there are a ton of companies that specialize in making all of these things either en masse or custom built to order, but they're still expensive. You're also going to need to run logs (i.e. downhole measurements) using a wide variety of very expensive and very specialized tools.
It's not just a hole. You're also building a subsurface structure and collecting information about the subsurface.
Any well has a limited lifespan. Geothermal wells aren't that different from hydrocarbon wells in this sense. You're not actually able to extract heat from the bulk of the rock mass. Rocks are _very_ poor conductors of heat. So you're extracting heat from relatively tiny depth within the rock mass along the surface of a pore network. You're flowing water from one well (an injector) to another well (a producer). As that flows and temperatures and water chemistry change, various minerals precipitate out and block the pore throats. Even in cases where you can avoid those reactions, you eventually block different pores and fracture networks with debris. You can and do use techniques to restore that (aka "workovers"). However, they are expensive and have diminishing returns. And even if none of the before-mentioned things happen, you'll eventually hit diminishing returns on the temperature you can produce, as the heat can't migrate from the bulk of the rock to the water-rock interface very quickly.
Either way, eventually you drill new injectors and producers. The cycle you need to do that on varies quite a bit depending on the specifics of the project. In some cases, it's a couple years, in others it's a decade or two. Either way, you need continued redevelopment plans to continue production.
All of that is not a problem and is work as normal. I'm just trying to lay out what subsurface projects entail (be they geothermal, oil, methane, or even large scale water production). It doesn't mean geothermal is impractical or overly expensive (far from it). But it does mean that there are very large initial captial expenses and then periodic capital expenses needed at later dates to continue optimal operation.
An astronomer/geophysicist could answer better, but my understanding is nothing we could possibly do would change the planets temperature the tiniest fraction of a degree.
I also read somewhere that if the sun disappeared and the earth flew off into space, life would persist in the oceans for millions of years because it would take that long for them to freeze to the bottom.
This question is usually asked when conversations about geothermal come up here, and for good reason because it’s a valid question. The long and short of it is that the amount of thermal energy that humans would be able to realistically extract pales in comparison to the amount already lost to heat flux through the surface, the amount generated via radioactive decay and frictional forces from gravity/tidal sources and convection in the core. Some answers on a relevant stack exchange answer with more general calculations [0].
Edit: Off the top of my head, it’s estimated that total core heat is approximately 10^31 J, heat loss at a rate of 47TW, (forgive me for not carrying out the calculation completely or for sources on those numbers, they can be easily searched, I’m on mobile), so the orders of magnitude difference already are so vast it’s a rounding error in siginificant figures.
At the scales were talking about it's somewhere between Going to the beach and getting shot by a swimming dog carrying a gun in its mouth and the problems caused by doing flybys of Jupiter.
You might want to look into just how much heat is contained within the Earth, how much escapes naturally every year, and how much is replaced by radioactive decay. Suffice it to say ..... no. There is no way that mankind can extract enough energy to make any real impact on the Earth's interior. The only potential issue here is closer to the surface, i.e. that injecting water into rock strata can trigger small quakes where there were none before (as we've found out via hydrofracking elsewhere).
Suffice it to say there are no easy solutions to the problem of baseload power. Expecting everyone to live in the dark is unrealistic. Expecting solar power to magically stop being inefficient and unworkable in most locations is unrealistic. Expecting the same of wind power likewise. So we're left with not a lot of good options, only less bad ones. That's life... and that's engineering. There are no perfect solutions... just ones you can live with.
We live above the skin, all the drilling we have ever done at depth has yet to pierce the skin through to the white apple interior.
Any "cooling" we do would be preemptively use the heat within the apple skin that is already slowly radiating outwards .. and the pinpricks, or tens of thousands of pinpricks we might make would not cause "widespread cooling of the apples interior".
At a planet scale no, but locally these geothermal plants can have an effect. Some Icelandic geysers for example have weakened or even stopped due to geothermal power plants in the area.
The US NPS has cited this as a reason for not installing geothermal generation near the Yellowstone hotspot. They don’t want to potentially impact Old Faithful.
> They require more capital investment than solar or wind projects: $3,000 to $6,000 per kilowatt, compared with $1,700 to $2,100 per kilowatt for wind and solar. (However, a geothermal plant will produce between two and four times as much electricity as a wind or solar plant of the same capacity.)
Capacity is the most they can produce at any given time. Solar only produces power during the day. Geothermal produces power 24 hours a day, without any regard for day or night. Therefore for the same “capacity” geothermal will produce more power per day because it produces for more hours a day at the same rate.
(This does not account for any complications such as the cost of that capacity or whether geothermal has other downtime to consider.)
The napkin math factor I use is to get the average power you need to divide solar and wind's name plate power by about 4. So to get the same amount of total yearly energy as a 1GW nuke plant that runs 24/7 you need 4GW of solar. Because solar produces about 6 hours of power per 24 hour day.
From a capital cost perspective this is not nice at all. Too be fair upside of solar/wind is solar and wind farms don't go down for a year and a half of unplanned maintenance like nuke plants sometimes do.
Grid PV in a good location is more like 30% capacity factor. They typically use 1 axis tracking to collect more power in morning and evening due to the demand curve.
Given the environment geothermalhydro is in and thus the equipment has to operate in, does it require more maintenance of the infrastructure? Presumably the steam would have different kinds of particles that could deposit accumulate and affect equipment (scaling)? Could be very manageable or could incur significant money to maintain. I don’t know, just asking.
You could use it for district heating of buildings in winter, but that's about it.
As the article mentions, you need to get above the phase transition between liquid and gas at high pressure (they mention 150c) to be able to reliably and quickly convert the thermal energy into kinetic, then into electrical inductance (gas expansion moving a turbine, moving a dynamo).
Maybe if you went into business making pot roast, you could cook meat low and slow, or set up massive dehydrators.
Running it under a shallow drying bed might make salt extraction from water evaporation faster, too.
Sadly, none of those things tend to be very close to mines.
That's not true at all. If any other liquids were more useful they would have been used long time ago, even in places where the cost is not of primary concern, such as nuclear submarines.
Nuclear submarines have no use for a working fluid that boils below 100 C. Indeed, they pressurize the water so that the boiling point is well above that point, because they have no difficulty heating water well above that.
Steam is used everywhere despite that it is quite corrosive, mainly because it is cheap.
You clearly don't know what you are talking about. Water steam is a perfect medium for turbines because of its favorable thermodynamic properties, mainly high specific heat allowing water steam to absorb large amount of thermal energy. Also water steam is not corrosive because water itself is not corrosive. It's the dissolved minerals making it corrosive and that's why water used for turbines is purified first.
Yet, steam turbines attached to nuke and coal plants spend 10-20% of their time offline, being overhauled mainly because of high-temperature/high-pressure steam's corrosiveness.
Cold distilled water is not corrosive. Superheated steam, howsoever pure, little resembles cold liquid water in any detail. Furthermore, hot water will pick up minerals from whatever it runs through.
Many materials that are not especially corrosive as cold liquids behave quite differently at extreme pressure and temperature. Water has uncommon valuable thermodynamic properties, but not uniquely so; its chief virtue is that it is good enough and cheap.
OK, give me an example of one such liquid from your list of 'many' that has all the desired properties of water and doesn't have any undesired, such as being a poison. You can't because there aren't any.
Ideal thermodynamic efficiency is 1-Tcold/Thot in an absolute temperature scale. This means given a perfect mechanism to turn heat into work this is the upper bound of how much of the heat can be turned into useful work.
Say ambient air is 20 deg C, with your 90 deg C heat source then you get 1-293/363 which is about 20%. So it's not to say you can't get work out of this system, but it's not great compared to having something nice and not.
And even then, you can't push a turbine with a hot liquid so your energy extraction technique now gets complicated.
would it be possible to use a heat pump to increase the temperature to a more efficient range? Or would all of the efficiency gained be lost by operating the heat pump?
I have wondered about this as well... If your heat pump uses say 1kW, and they usually provide 4x-5x heat out, so say 5kW of heat out and your able to extract 50% of that as energy using say a turbine, you would get 2.5kW out? or maybe 1.5kW (subtracting the initial 1kW used to run it?) so maybe not great but maybe possible?
given perfect heat pumps/engines in that circumstance, you would get exactly as much energy out as you put in. Theoretically perfect heat engines are called 'reversable' for that reason: they give you the best possible exchange between heat and work. Said another way: heat pumps can give you 4-5x the heat out as work you put in precisely for the same reason you can't get much work out of that heat: the temperature increase is small. If you were to heat something up to a temperature where you could more efficiently extract work from it, it would require more energy to do so.
Yes you can use a heat pump, but that requires work to run. Think compressors and whatnot. So even with a perfectly efficient heat pump that limit still holds because you are using some of the energy gained from your new hot temperature to run the heat pump.
They tried experiments fracking into hot rock in australia and went bankrupt proving the concept. Bit of a shame. More money got pumped into CCS which is demonstrably bloody useless, works for gas well life extension but not sequestration
To clarify at least two companies circa 2003-2013 successfully proved Australian geothermal could generate power at the 1MW level via pilot plants .. and had no futher investment or interest to expand further.
Pulled out at the wrong time, the wellhead kit is probably buggered now. The qld government wasn't sufficiently keen, some say they make too much money from non renewable energy. Maybe times have changed now.
There are a lot of near-surface options for heating and cooling. They reduce electrical usage rather than generate it.
I worked on geo control systems for FL buildings. We'd pump water up from the aquifer, transfer heat from the building into it and dump it back. It starts getting cost effective above 10k or 15k sqft.
In northern states they do large closed loops wound over a large yard or field and buried just below the surface to capture daytime heat or pump heat into the earth. Basically a larger version of rooftop water heating.
There are a lot of variants of this but you get the idea.
My understanding is that, while you can do surface loops with enough area, its easier and less disruptive to just do vertical holes for ground loops. At least in Northern Virginia drill ~150ft of well per ton. At 400ft the wells maintain temperature a relatively consistent temperature year round year round.
Drilling down is best for retrofitting existing structures and built environments, but for new neighbourhood development trenching is super cheap since you have to disturb all that dirt anyway. Prep for roads and all the underground services means you have the ground open anyway, might as well run some coolant lines while you're down there.
District heating loops can be done almost for free with greenfield development and it should be highly incentivized to slash the energy required to heat and cool the new structures.
Make drilling cheaper. This would also help with water access. The biggest cost of small geothermal and water projects is always the drilling. Drill rig time is always a limiting factor.
We just recently got Geo HVAC, for our two units it was 800 total feet divided into 2 wells. And drilling was in the area of 25% of the total cost. 50% for the units themselves, and I guess 25% for the other parts, labor, and misc stuff.
While drilling is definitely a big chunk, all of it is so much more expensive than traditional air heat pumps that even without drilling it would still be at least 50% more expensive. Double without US Federal incentives.
I've been thinking one could add a water powered bit on the tip not unlike the tips they have on more traditional drill rigs. I think there is lots of room for improvement on this technique, lots of white space between this and a traditional rig.
For the purposes talked about in the linked article they're not really looking for new tech that lies between a traditional mining drill and a garden hose though - they're looking beyond the capabilities of traditional mining drill:
Commercial drilling doesn’t usually go much deeper than seven kilometers (four miles)—for cost reasons, it’s often even less than that—and many places that might benefit from geothermal aren’t hot enough at that depth to reach the 150 °C needed to generate electricity economically.
Reaching sufficient temperatures may mean going deeper, which would require new techniques and technologies that can withstand high heat and pressure.
Agreed: how? Drilling companies have been competing on price for a hundred years; anyone who came up with a significantly cheaper drilling system would be raking in the dough until everyone else caught up.
Drilling is supposed to get cheaper when it is done with microwaves instead of drill bits.
But the expense of maintaining the necessary steam turbine still makes it hard for geo to compete with wind and solar. This is also a major factor in the cost of operating a nuke plant, with similar effect on competitiveness. Really big steam turbines cost less to keep than a lot of small ones, but then you generally need to build two so you have a backup when one is down for maintenance.
In summary, a (dumb yet durable) metal waveguide+pipe stretches down, it emits microwaves to vaporize the rock face, and gas pumped down through it is released so that it exhausts back up along with the removed mass of rock-vapor/particles.
> [P]roducing the supercritical steam needed requires drilling to depths of 10 to 20 km [...] rock is capable of both producing superheated steam and destroying the microchips and seals required for directional drilling.
I was hopeful that all of the unused drilling capacity after the shale boom/bust would allow some of the know how and equipment to be reallocated to geothermal but the grid operators and markets are not offering the premium to firm capacity that is required for the longer lead time and increased capital requirements and increased risk in geothermal projects vs wind and solar which can be augmented with battery storage.
It’s going to suck though when we hit a weeklong stretch of cloudy still weather if there isn’t enough spare capacity from other sources to compensate for the missing wind and solar.
> if there isn’t enough spare capacity from other sources to compensate for the missing wind and solar
This seems like a problem Elon would gladly dabble in, pushing out a NACS firmware update or something as an emergency limiter. Maybe first responders get priority, like they do for mobile network congestion.
Or dirtier power remains on cold standby for unusual peaks. This would eventually be outlawed, I imagine.
Hydrogen is even better for longer-term storage (e.g. seasonal). Produce hydrogen via electrolysis from solar in the summer, then power things when it's cloudy + low sun angle in the winter. There are quite a few major hydrogen storage projects in progress that do exactly that, FWIW. E.g. https://www.energy.gov/lpo/advanced-clean-energy-storage (Disclaimer: My wife works on that project)
Batteries don't compete for long term storage. Losses are too high. Hydrogen is an excellent solution for longer term (weeks to months to years) storage.
I'm trying to imagine the apocalyptic scenario that'd have all of Texas windless and cloudy for a week? Nameplate values for Texas wind & solar will eventually be well above peak required: excess power can be sold for silly things like bitcoin, desalination, fabbing, etc.
And there is also night. And clouds. Texas is good for solar but December and January still have relatively high variance - for example, in December 13 solar produced only 19.3 GWh while it produced 103 GWh two weeks later on December 27.
Winter Storm Uri came pretty close to that. Very overcast every day. Pretty low wind compared to normal. I'm not blaming wind or solar for the failures; it was largely failures in gas production. But solar and wind output weren't close to their nameplate capacity.
Bitcoin sounds like the absolute worst thing to buy with excess electrical production. But desalination sounds like an excellent thing to buy. Silly is not the word I'd use.
The best thing to buy is just battery energy storage (or molten salt or hydro-pumped). Storage prices are falling even faster than the solar PV modules themselves, and there are dozens of huge factories being built every year, in the USA as well.
> The Drake Landing Solar Community (DLSC) is a planned community in Okotoks, Alberta, Canada, equipped with a central solar heating system and other energy efficient technologies.
> In 2012 the installation achieved a world record solar fraction of 97%; that is, providing that amount of the community's heating requirements with solar energy over a one-year time span.
> In 2015–2016 season the installation achieved a solar fraction of 100%. This was achieved by the borehole thermal storage system (BTES) finally reaching high temperature after years of charging, as well as improving control methods, operating pumps at lower speed most of the time, reducing extra energy need as well using weather forecasts to optimize transfer of heat between different storage tanks and loops. During some other years, auxiliary gas heaters are used for a small fraction of the year to provide heat to a district loop. The systems operate at coefficient of performance of 30.
I don't know about directly as a battery, but there is potential for energy storage. If you have geothermal HVAC at home, it can (sometimes) be use to heat water in a water heater. Dumping the extra heat into it. And I have heard stuff about using excess energy in the grid to put extra heat into home water tanks as well, so demand is reduced later. It is not getting converted back to electricity, but still a store for energy.
I don’t think thermodynamics lets that work. You can’t move heat from something cold to something hot so unless you are preheating your water to a temperature higher than your deep borehole rocks, all you’re doing is putting the first N joules of heat energy into the water you’re going to pump into your steam turbines using excess grid energy instead of geothermal energy.
Of course you can move heat from something hot to something cold, it’s called a heat pump. Though yeah I get what you meant. There are heat pumps that have entered production that are designed to generate the kind of industrial levels of heat required to heat the water to the level required to add heat to such reservoirs. Whether it makes sense, I can’t say. But it certainly makes sense for geothermal well used for district heating (not electricity). It’s already being done.
Funny thought: if you use a heat pump to store heat energy in summer to be used in winter.. and your reservoir can retain the heat efficiently (think the heavily insulated sand reservoir used in a project in Finland for instance)… could that make the battery effectively more than 100% efficient?
HVAC geo scales up. You could do a neighborhood utility and homes can heat/cool for the cost of air circ. You'll wind up with a novelty, an HOA that benefits every home (fees for for power/maint pumps).
A couple of generations ago, we had neighborhood sewage utilities all around here. Neighborhood geo seems less complex than that.
This was tried using money for 2010 olympics in Whistler BC as the athlete accommodation was sold as subsidized housing to local workers after the olympics.
The geothermal district heating project had many ongoing issues with repair costs being borne collectively by the new owners. Some saved $150/mo by removing it and switching to electric [0]
There are probably a dozen articles on the issues in that pique news paper spanning a decade. Lots of finger pointing between the parties responsible for the design, installation and maintenance. The Vocal group of owners got bailed out by the local government at one point but it didn’t resolve the ongoing issues.
Not to say the technology is hopeless, just in this instance it wasn’t done properly so maybe it isn’t as easy as people think.
There are some places (e.g. https://heet.org/geo/) that are looking at neighborhood "geothermal" - basically using ground temperature as a heat reservoir for heat pumps. They're getting buy-in from natural gas utilities, some of whom see it as a way to keep using their capital, rights of way, and expertise in digging holes in the ground (and maybe in billing folks, too) to keep making money as households convert to heat pumps.
As a layperson I was certainly impressed by the notion that enhanced geothermal could get us the last x% of firm energy needed for a stable grid once solar+wind+batteries have gone as far as they can go.
Another interesting tidbit is that you can actually use their system to store excess energy from, e.g., wind and solar.
Once we have plenty of solar and wind generation capacity built out, it will be time to start building out short-term storage. Until then, generating capacity is the best place to put capital. In time we will have tropical solar-powered ammonia synthesis, to ship to places that are in danger of draining short-term storage or are in polar night.
So, "as far as they can go" is meaningless. They can go the whole way.
I used to worry that might cool down the earth’s interior too quickly and regret it with mass geothermal.
But waste heat (not global warming from carbon, which is a separate and more pressing problem) will boil the oceans in a few hundred years on our current trajectory, and now I’m for cooling as much as possible however we can.
Wow. Have you got a source for that? Waste heat from human power generation and use, not from the Earth cooling? Boil as in bubbles of steam or just slightly evaporate a little? A few hundred as in < 1000 years? And current trajectory as in something like exponential growth which obviously won't happen? I'm sure some part of that makes the idea far less serious than it sounds.
It’s based on extrapolation of current trends, so I doubt it’ll actually happen. Besides, we’d all die before it got to that. But here are some sources that describe it:
Thanks. The video says in 400 years the surface temperature of Earth will be 100 degrees if we assume exponential growth of heat generation. So yea it's that clearly bad assumption of exponential growth that spoils it.
One possibility is further collapse of the price of other renewables.
If solar were nearly free (< $0.01/kWh, say) it could make sense to bank that energy as underground heat. The thermal time constant for hot rocks scales as the square of the linear dimensions of the rocks, and can easily reach many years even for relatively shallow systems (this is why geothermal works at all). Such a system would not need to drill as deeply as a natural geothermal system operating at the same temperature, and might be able to get much hotter than anything not drilling near a volcano.
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[ 2.1 ms ] story [ 185 ms ] threadDrilling deep holes is expensive, prices are unlikely to come down much. Steam generators are expensive too.
I'm sure the rigs are an expensive capital outlay, but do the operators require advanced skills?
Once a hole is drilled, does it have a limited lifespan, or is that investment something that can be hypothetically used for eternity?
You also need materials to ensure that the well doesn't collapse on itself, and stuff like that as well. I would expect the hole itself should have an extremely long lifespan, but I don't really have much to back it up.
Its not for electric generation, but for Geo HVAC the ground loop itself has a 50 year warranty and quoted 150+ year lifespan. The house will probably be long gone before the loop would go bad.
The materials you're using when drilling are expensive. The steel casings that you're putting down the hole are specialized alloys. You're using very large amounts of expensive specialized fluids to fill the hole during drilling (drilling mud) that are relatively hazardous and need to be treated after use. You're going through large numbers of very expensive consumable parts (e.g. drill bits are _not_ cheap, and there are a lot of even more expensive consumables). A large amount of the equipment and consumables are custom built for the specific conditions you're working in. There are certainly cases where you can use things that are a bit more of a commodity, but deep and hot wells usually don't fall into that category. And yes, there are a ton of companies that specialize in making all of these things either en masse or custom built to order, but they're still expensive. You're also going to need to run logs (i.e. downhole measurements) using a wide variety of very expensive and very specialized tools.
It's not just a hole. You're also building a subsurface structure and collecting information about the subsurface.
Any well has a limited lifespan. Geothermal wells aren't that different from hydrocarbon wells in this sense. You're not actually able to extract heat from the bulk of the rock mass. Rocks are _very_ poor conductors of heat. So you're extracting heat from relatively tiny depth within the rock mass along the surface of a pore network. You're flowing water from one well (an injector) to another well (a producer). As that flows and temperatures and water chemistry change, various minerals precipitate out and block the pore throats. Even in cases where you can avoid those reactions, you eventually block different pores and fracture networks with debris. You can and do use techniques to restore that (aka "workovers"). However, they are expensive and have diminishing returns. And even if none of the before-mentioned things happen, you'll eventually hit diminishing returns on the temperature you can produce, as the heat can't migrate from the bulk of the rock to the water-rock interface very quickly.
Either way, eventually you drill new injectors and producers. The cycle you need to do that on varies quite a bit depending on the specifics of the project. In some cases, it's a couple years, in others it's a decade or two. Either way, you need continued redevelopment plans to continue production.
All of that is not a problem and is work as normal. I'm just trying to lay out what subsurface projects entail (be they geothermal, oil, methane, or even large scale water production). It doesn't mean geothermal is impractical or overly expensive (far from it). But it does mean that there are very large initial captial expenses and then periodic capital expenses needed at later dates to continue optimal operation.
I also read somewhere that if the sun disappeared and the earth flew off into space, life would persist in the oceans for millions of years because it would take that long for them to freeze to the bottom.
Edit: Off the top of my head, it’s estimated that total core heat is approximately 10^31 J, heat loss at a rate of 47TW, (forgive me for not carrying out the calculation completely or for sources on those numbers, they can be easily searched, I’m on mobile), so the orders of magnitude difference already are so vast it’s a rounding error in siginificant figures.
[0] https://earthscience.stackexchange.com/questions/2302/can-th...
https://what-if.xkcd.com/146/
You might want to look into just how much heat is contained within the Earth, how much escapes naturally every year, and how much is replaced by radioactive decay. Suffice it to say ..... no. There is no way that mankind can extract enough energy to make any real impact on the Earth's interior. The only potential issue here is closer to the surface, i.e. that injecting water into rock strata can trigger small quakes where there were none before (as we've found out via hydrofracking elsewhere).
Suffice it to say there are no easy solutions to the problem of baseload power. Expecting everyone to live in the dark is unrealistic. Expecting solar power to magically stop being inefficient and unworkable in most locations is unrealistic. Expecting the same of wind power likewise. So we're left with not a lot of good options, only less bad ones. That's life... and that's engineering. There are no perfect solutions... just ones you can live with.
That's around 170 trillion years if I did the math right.
We live above the skin, all the drilling we have ever done at depth has yet to pierce the skin through to the white apple interior.
Any "cooling" we do would be preemptively use the heat within the apple skin that is already slowly radiating outwards .. and the pinpricks, or tens of thousands of pinpricks we might make would not cause "widespread cooling of the apples interior".
See: (actual geoscientists): https://www.ga.gov.au/ausgeonews/ausgeonews201306/geothermal...
The US NPS has cited this as a reason for not installing geothermal generation near the Yellowstone hotspot. They don’t want to potentially impact Old Faithful.
Solar/wind: 1.7k - 2.1k / kW → N
Geothermal: 3k - 6k / kW → 2N - 4N
Looks like an investment no-brainer.
(This does not account for any complications such as the cost of that capacity or whether geothermal has other downtime to consider.)
From a capital cost perspective this is not nice at all. Too be fair upside of solar/wind is solar and wind farms don't go down for a year and a half of unplanned maintenance like nuke plants sometimes do.
Ex: 32.8% https://en.wikipedia.org/wiki/Solar_Star
Always wondered whether we can use it for energy….
As the article mentions, you need to get above the phase transition between liquid and gas at high pressure (they mention 150c) to be able to reliably and quickly convert the thermal energy into kinetic, then into electrical inductance (gas expansion moving a turbine, moving a dynamo).
Maybe if you went into business making pot roast, you could cook meat low and slow, or set up massive dehydrators.
Running it under a shallow drying bed might make salt extraction from water evaporation faster, too.
Sadly, none of those things tend to be very close to mines.
Problem is that mature turbines are designed for steam. Turbines for other fluids cannot approach their market volume.
Steam is used everywhere despite that it is quite corrosive, mainly because it is cheap.
Cold distilled water is not corrosive. Superheated steam, howsoever pure, little resembles cold liquid water in any detail. Furthermore, hot water will pick up minerals from whatever it runs through.
Many materials that are not especially corrosive as cold liquids behave quite differently at extreme pressure and temperature. Water has uncommon valuable thermodynamic properties, but not uniquely so; its chief virtue is that it is good enough and cheap.
Gas turbines are common when power to weight is more important than cost.
I use to scoff, but turkey sous vided is yummy
Say ambient air is 20 deg C, with your 90 deg C heat source then you get 1-293/363 which is about 20%. So it's not to say you can't get work out of this system, but it's not great compared to having something nice and not.
And even then, you can't push a turbine with a hot liquid so your energy extraction technique now gets complicated.
Geodynamics writes off Cooper Basin geothermal assets https://reneweconomy.com.au/geodynamics-writes-cooper-basin-...
Petratherm Ltd: https://www.energymining.sa.gov.au/__data/assets/pdf_file/00...
(now doing other exploration: https://www.petratherm.com.au/projects-overview/)
To quote GeoScience Australia (2013):
What's happened to geothermal? Simple in concept—complex in application : https://www.ga.gov.au/ausgeonews/ausgeonews201306/geothermal...I worked on geo control systems for FL buildings. We'd pump water up from the aquifer, transfer heat from the building into it and dump it back. It starts getting cost effective above 10k or 15k sqft.
In northern states they do large closed loops wound over a large yard or field and buried just below the surface to capture daytime heat or pump heat into the earth. Basically a larger version of rooftop water heating.
There are a lot of variants of this but you get the idea.
District heating loops can be done almost for free with greenfield development and it should be highly incentivized to slash the energy required to heat and cool the new structures.
While drilling is definitely a big chunk, all of it is so much more expensive than traditional air heat pumps that even without drilling it would still be at least 50% more expensive. Double without US Federal incentives.
How?
https://youtu.be/3pOSzBgB8WU?si=kCyDZA0GkKMFAzNH
Could easily be improved upon, seems workable
Not so great once the pressure increases or granite|schist layer intercede.
I was just mentioning that something I've been thinking of was similar.
But the expense of maintaining the necessary steam turbine still makes it hard for geo to compete with wind and solar. This is also a major factor in the cost of operating a nuke plant, with similar effect on competitiveness. Really big steam turbines cost less to keep than a lot of small ones, but then you generally need to build two so you have a backup when one is down for maintenance.
In summary, a (dumb yet durable) metal waveguide+pipe stretches down, it emits microwaves to vaporize the rock face, and gas pumped down through it is released so that it exhausts back up along with the removed mass of rock-vapor/particles.
> [P]roducing the supercritical steam needed requires drilling to depths of 10 to 20 km [...] rock is capable of both producing superheated steam and destroying the microchips and seals required for directional drilling.
[0] https://jpt.spe.org/microwave-drilling-sounds-like-science-f...
https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu...
It’s going to suck though when we hit a weeklong stretch of cloudy still weather if there isn’t enough spare capacity from other sources to compensate for the missing wind and solar.
This seems like a problem Elon would gladly dabble in, pushing out a NACS firmware update or something as an emergency limiter. Maybe first responders get priority, like they do for mobile network congestion.
Or dirtier power remains on cold standby for unusual peaks. This would eventually be outlawed, I imagine.
Batteries are better bet.
Batteries don't compete for long term storage. Losses are too high. Hydrogen is an excellent solution for longer term (weeks to months to years) storage.
So really you're the one being disingenuous.
Coal is not natural gas
> The Drake Landing Solar Community (DLSC) is a planned community in Okotoks, Alberta, Canada, equipped with a central solar heating system and other energy efficient technologies.
> In 2012 the installation achieved a world record solar fraction of 97%; that is, providing that amount of the community's heating requirements with solar energy over a one-year time span.
> In 2015–2016 season the installation achieved a solar fraction of 100%. This was achieved by the borehole thermal storage system (BTES) finally reaching high temperature after years of charging, as well as improving control methods, operating pumps at lower speed most of the time, reducing extra energy need as well using weather forecasts to optimize transfer of heat between different storage tanks and loops. During some other years, auxiliary gas heaters are used for a small fraction of the year to provide heat to a district loop. The systems operate at coefficient of performance of 30.
https://www.dlsc.ca
https://www.sciencedirect.com/topics/engineering/drake-landi...
http://proceedings.ises.org/paper/swc2017/swc2017-0033-Mesqu...
Funny thought: if you use a heat pump to store heat energy in summer to be used in winter.. and your reservoir can retain the heat efficiently (think the heavily insulated sand reservoir used in a project in Finland for instance)… could that make the battery effectively more than 100% efficient?
A couple of generations ago, we had neighborhood sewage utilities all around here. Neighborhood geo seems less complex than that.
0: https://www.piquenewsmagazine.com/opinion/letter-to-the-edit...
Not to say the technology is hopeless, just in this instance it wasn’t done properly so maybe it isn’t as easy as people think.
https://www.volts.wtf/p/enhanced-geothermal-power-is-finally
As a layperson I was certainly impressed by the notion that enhanced geothermal could get us the last x% of firm energy needed for a stable grid once solar+wind+batteries have gone as far as they can go.
Another interesting tidbit is that you can actually use their system to store excess energy from, e.g., wind and solar.
So, "as far as they can go" is meaningless. They can go the whole way.
But waste heat (not global warming from carbon, which is a separate and more pressing problem) will boil the oceans in a few hundred years on our current trajectory, and now I’m for cooling as much as possible however we can.
How does this work?
[0] https://www.usgs.gov/observatories/yvo/news/why-cant-we-dril...
Could We Stop Yellowstone From Erupting with a Giant Geothermal Power Plant? - https://www.construction-physics.com/p/could-we-stop-yellows...
https://news.ycombinator.com/item?id=35703906 213 points | 8 months ago | 174 comments
https://news.ycombinator.com/item?id=38596622 141 points | 23 days ago | 137 comments
https://www.youtube.com/watch?v=9vRtA7STvH4 (commentary from Sabrine Hossenfelder, highly recommended)
https://www.nature.com/articles/s41567-022-01652-6.epdf
https://dothemath.ucsd.edu/2011/07/can-economic-growth-last/
If solar were nearly free (< $0.01/kWh, say) it could make sense to bank that energy as underground heat. The thermal time constant for hot rocks scales as the square of the linear dimensions of the rocks, and can easily reach many years even for relatively shallow systems (this is why geothermal works at all). Such a system would not need to drill as deeply as a natural geothermal system operating at the same temperature, and might be able to get much hotter than anything not drilling near a volcano.