The big issue with geothermal energy is that rock doesn't conduct heat very well. When you first bore a hole and pump some water down, it's easy to use the hot rocks to generate steam which can in turn drive a turbine, but doing so cools down the rock the water comes in contact with. Digging deeper, the rock starts out hotter, maybe it takes twice as long to exhaust the initial heat, but it's still going to happen in a matter of hours. Long term, a geothermal well can't extract heat faster than heat flows into the well from lower in the Earth. This heat flow rate is in the milliwatts per square meter range. Now with horizontal boring technology, a single drilling rig might be able to plumb a large area, but even if they got all the energy in a 10km radius, which is about 3 times what current technology is capable of, you're still looking at around 30 MW of thermal heat flux, which would at best produce about 20 MW of electricity. That's like 8 on shore windmills or a 100 acre solar plant. It's a little better given that the heat flow is continuous rather than intermittent, and multiple borehole locations can be connected by pipeline to a single generator station to keep capital costs down, but still this is not a lot of power.
For context, to provide the electricity demand for kansas would require about 35% of the total geothermal flux into kansas. New Jersey's electricity demand is 7 times higher than what its geothermal heat flux could provide. For the whole US, electricity consumption is about 75% of geothermal heat flux if you ignore variations like the yellowstone hotspot.
Geothermal certainly makes sense in certain locations where the heat flux is high and other power sources are problematic - for example iceland is probably the most ideal spot on earth. The technology for extracting geothermal power may also be useful for future efforts to control volcanism (though at this point such plans are highly speculative), so research is warranted. But it is unlikely to ever be more than a minor slice of the world's energy supply, and certainly anyone claiming to solve the issue by just digging deeper is selling snake oil.
Don't discount the actual energy stored in the rock or capacity factor. Granit has 790 J/kg per degree C and 1 cubic meter is ~2700 kg.
So cooling 10 cubic kilometres of rock by say 50C releases 790J * 2700 * 1,000,000,000 * 50 * 10 = 10^18J or 600MW of heat over 50 years. At 33% efficiency your talking 200 MW of electricity for 50 years assuming 100% capacity factor and ignoring how fast it recharges.
If it’s a backup for solar and wind at 50% capacity factor then you could double the power output or double the lifespan.
Same basic idea as a well. When you extract water from underground it gets to your borehole through lot’s of tiny cracks greatly increasing the surface area.
In some places you can tap into an underground very hot aquifer. In others with sufficient permeability need only need to supply your own cold water. Worst case you also need to crack the rock: https://en.wikipedia.org/wiki/Enhanced_geothermal_system
The heat still needs to travel horizontally from this rock to your borehole. A 30 cm diameter borehole drilled 20 km deep with the bottom 12 km being used for heat collection would give you 12000 m^2 of surface area and an average temperature gradient of 135 Kelvin, which at a heat flux rate of 7 W/m^2/K would only give you 13 MW thermal, or about 4.4 MW electric when the well is first drilled and about 3 MW after 50 years. Comparable to a single windmill. You can increase your surface area through more drilling and fracking, but that adds to cost and environmental concerns.
As a battery for storing heat energy generated by other methods though it's great.
Fracking with water (which is what geothermal would do) has pretty limited environmental concerns, and has enormous gains in increasing surface area and reach, so it almost certainly what we're going to end up doing. Iirc this is part of Quaise's plan: drill 20km down then frack the bottom to get a really big volume and surface area at those very high temperatures.
My guess would be that this is a poor choice for backup energy for similar reasons that nuclear is a bad choice: drilling deep is rather expensive, so geothermal costs are mostly capex. That means you want to run the power plant at max output as much as possible to maximize profits. To use it as a backup plant for renewables however you would need to leave it mostly idle. Depending on how much renewable energy you have available you need full backup only for a few days to a few weeks per year.
I'm thinking the reverse... since the thermal conductivity of rock is low, you can either have the well operating at a very low level continuously, or you can have bursts of much higher output for a few hours/days with the same drilled boreholes.
Obviously you will still have to pay the capex for the turbines and generators for whatever peak level you decide, but I'd guess they're a smallish chunk of the total budget. If you think energy prices will be more volatile in the future (more extreme climate means more peak-usage days, and more renewables means more days/hours with a shortfall in generation), then it makes sense to overbuild turbines so you can rake in the $$$'s in that 1-2 days per year when energy prices spike up 1000x.
Geothermal has serious issues if water flow is not kept constant - dissolved minerals in the borehole water are just waiting for an excuse to crystallize/precipitate, and it’s already an issue at most active running plants, even when run continuously. Silica crystallization on heat exchangers, for instance, is a constant maintenance cost.
Stopping the flow (and letting it cool in the pipes ) for any length of time or with any frequency could mean not being able to ever start it again.
You can’t really filter this stuff out - it’s things like dissolved magnesium, iron, silica, boron, arsenic, etc. at least not without making it uneconomic I believe. The link below references concentrations of 250g/L or more (though often most of that seems to be salt).
It isn’t generally particulate until it’s too late. It’s the nature of water contacting hot rock.
You’re saying we should pull heat out faster than it’s replenished, but what do we do in 50 years? Didn’t we learn our lesson from oil that we can’t just kick the can down the road?
Two differences, first with the right technology any location works, you can even drill deeper at the same location. Second they refill, globally at a rate of 44TW which is a lot faster than oil.
While I think this first-principle analysis is helpful, I fear it may be holding Quaise to too high a standard; their goal (AFAICT) is not to provide 100% of the energy needs of anywhere; it's a huge win if coal's 10-20% contribution of total power generation (or even just a substantial fraction of that) can be in-place replaced with a geothermal generator. Maybe this tech won't be cost-effective in 50 years as solar continues to get cheaper, but as a transitional bridge technology it could be incredibly impactful in the 10-20 year timeframe.
Also, you didn't specify a depth for your calculation; won't the flux be higher the deeper you go (i.e. be proportional to the delta-T)? They are talking about going to 20km which as I understand it is WAY deeper than most geothermal systems contemplate. Their whole bet is predicated on the idea that with the gyrotron they can drill deeper since they don't need to mess with high-temp drill bits.
> Also, you didn't specify a depth for your calculation; won't the flux be higher the deeper you go (i.e. be proportional to the delta-T)? They are talking about going to 20km which as I understand it is WAY deeper than most geothermal systems contemplate. Their whole bet is predicated on the idea that with the gyrotron they can drill deeper since they don't need to mess with high-temp drill bits.
The depth doesn't matter at this scale. 20km deep the heat flux is about 0.3% higher. Things get complicated as you go down into the mantle, but at 20km you're still in the top part of the crust.
The only thing drilling deep does is increase your max temperature, which increases efficiency, but eventually you hit the same limit as with any other steam generating plant where you can only handle steam that is so hot and so high pressure. With current technology, that limits the efficiency percentage to the low 40s. Maybe with some technological improvements this can go up a bit, but the carnot efficiency of a heat engine where the water is heated to the point it will decompose is 87%, and there is no way you're even going to get near that in a real plant, so increasing efficiency isn't really going to make a huge difference.
> Maybe this tech won't be cost-effective in 50 years as solar continues to get cheaper
As we replace base load with less reliable sources we need to come up with some way of expressing a penalty for availability. Does it matter how cheap solar is if it isn’t available when we need it and storage is not practical?
From what I understand, most of the earth's mantle is not molten and you can only find molten rock, magma, in some specific places like mid-ocean rifts and volcanic hotspots. The mantle has convection currents, but those flow on geological timescales. The Earth's outer core is liquid, but that's almost three thousand kilometers below the surface.
Wikipedia says the Earth's crust is on average 15-20km thick. Soviets drilled 12km deep with 1980's tech. It's difficult for sure, but might be doable.
"Doable" is very different from "economically justifiable".
The thickness of the Earth's crust is strongly bimodal, making "average" meaningless: thinner under oceans, thicker on continents. Much thicker. Most of the planet is, of course, sea floor, so mostly thinner. But drilling the sea floor is unpleasant and expensive, and at the end, the hole is all the way down there.
Can I cool my house into the well during the summer? With surface heat abundant during the summer, I'd expect storing heat downstairs should make sense even if the efficiency of the underground reservoir is not exactly stellar.
That said, there's nothing saying that one can't use a heat pump to as a source of heat in the summer (which would also cool the house) in additional to other sources of thermal energy.
This works very well. The low heat conduction of rock also means that without going too deep you get to a temperature that is almost constant year round, so you can cool your house in summer and heat in winter so long as you're not dumping absurd amounts of heat.
> For context, to provide the electricity demand for kansas would require about 35% of the total geothermal flux into kansas. New Jersey's electricity demand is 7 times higher than what its geothermal heat flux could provide. For the whole US, electricity consumption is about 75% of geothermal heat flux if you ignore variations like the yellowstone hotspot.
It would be great if you can provide a bit more details on those assumptions. Thanks
(Electric energy use per year * 1 year) / (Area * 100 mW/m^2 * 60% thermal to electric conversion efficiency)
In reality electricity capacity needs to meet peak demand, not average demand, the heat flux in continental crust is more like 65 mW/m^2, and the thermal to electric conversion efficiency is going to be closer to 40%, so the situation is actually much worse for geothermal, but maybe with the right technological developments and implementation you could get better performance.
Bore hole open cycle loops probably wont be viable in areas that fracking is happening. Super hot steam mixed with methane doesn't sound like a good idea.
Furthermore! Maintaining a steam turbine is an operational expense not matched by any for wind or solar. There are reasons we are not drilling new regular geo wells.
Literally everything costs more than wind and solar. It is why nukes will soon be mothballed.
Iceland is over a volcanic hotspot where hot rock from deep in the mantle is physically rising up, so the heat conductivity of the rock doesn't matter as much. It's like the difference between standing in a pool of water and being sprayed by a hose.
That makes sense - thank you for helping me understand. If we drilled down low enough would convection in the mantel increase the availability of heat? I assume the issue is that that would be way too deep to dig, even with new tech like this?
Correct. The mantle is on average about 35km thick. Most (all?) oil wells are less than 5km deep, so this is roughly an order of magnitude deeper. The world's deepest borehole https://en.wikipedia.org/wiki/Kola_Superdeep_Borehole is 12km deep. But even before this, downhole temperatures reach 200C which apparently caused the rock to act like plastic, causing the drill stem to get stuck.
A well with 200C temperatures would yield more energy, but you're still limited by how fast heat energy can migrate towards the borehole, followed by transporting it for 12km without it cooling off.
A similar situation is apparently happening with the London tube, but in reverse. Heat from the trains is being absorbed by the rock underground, but it can't migrate away fast enough. As a result, the tube tunnels are heating up decade by decade, to the point where temperatures underground reach the mid-30s in summer. Eventually they will have to do something about it, but that probably won't happen until enough people get killed by heat exposure in a stuck train.
The writer Aleksey Tolstoy came up with the idea of the laser-like machine that melts the rock in 1920s (maybe also influenced by H.G.Walls), when his science fiction book was first published. In this book a genial engineer Garin creates a beam that can be used both in mining (he wants to get the gold from the mantle, so uses American VC funding to set up a mining operation in Pacific) and as a weapon (he also wants to rule the world, so he uses his machine to destroy German and American competitors).
Re-using coal plant grid infrastructure is a good idea. So good that it's regularly done today, with big energy consumers like data centres setting up in those areas to save money.
Battery systems and solar are other initiatives that are currently re-using the existing lines.
However, while it makes a nice hook for a story, I'm dubious of any energy system that relies on that minor cost saving in established grids to be viable.
Well, minor is a relative term, but regardless, my point is stronger the more the business case relies on this re-use.
Solar can win on price with entirely new builds against already depreciated Coal plants. If you can't beat that price, then you are at best a complement to solar, and sticking solar, battery or synchronous condensors in the old coal plants might make more sense instead.
See: Cost–benefit analysis of coal plant repurposing in developing countries
I’m generally curious after reading this, what effect does our molten core have on our ambient surface temperature? I can’t imagine much, but it can’t be nil, and I genuinely have no idea.
> The flow of heat from Earth's interior to the surface is estimated at 47±2 terawatts
And
> Despite its geological significance, Earth's interior heat contributes only 0.03% of Earth's total energy budget at the surface, which is dominated by 173,000 TW of incoming solar radiation
Thank you so much for the link, there is a lot in here that is genuinely fascinating!
For instance heat from the surface “thus penetrates only several tens of centimeters on the daily cycle and only several tens of meters on the annual cycle”
This is why ground source heat pumps are suprisingly effective. You're drawing on the yearly solar inflow to the ground, at a depth where the temperature is quite stable, due to accumulating and averaging over years.
My curiosity in using things like heat pumps is that what happens when you move too much of that heat energy away. The heat might be doing nothing but, it has been there for a long time. At what point is too much heat displaced to the surface and what is the outcome of that?
For them to actually work the energy needs to be replaced, flowing from the hot areas to the (relatively) cold areas, mostly coming from the sun.
If you have a small area and continually pump the heat out then you end up with the inside of a freezer, which uses the same tech for exactly that purpose, but also intentionally insulates to prevent the heat getting back in.
Thats for sure but, where does that energy come from? I would say it comes from the earths own rotation, would this infinitesimally slow the earth rotation?
Solar radiation, ultimately (wind heats air, air expands, that creates a pressure differential which ultimately caused wind).
Maybe you‘re thinking of tidal power plants? Tides are gravitationally caused, and as far as I know tapping into them infinitesimally changes Earth‘s rotation (and to some extent probably also Earths and the Moon‘s orbit).
Geothermal energy comes from a mixture of radioactive decay and from gravity pressuring the Earth's core into gradually solidifying over the course of billions of years.
I also read that Quaise value proposal is drilling a 20km deep hole but once you reach there, how do you transform that into usable energy? Push water to extract vapor?
I'm also curious how they would deal with rock deformation as it reaches the point of becoming less solid and more squishy. There would need to be a mechanism to maintain hole integrity post-drilling.
To your question, I'm wondering if they simply pump down water and extract resulting steam once it reaches the point of vaporization? The steam condensers and everything else are already built on-site for coal generation.
One difficulty would be handling any accumulated minerals that got into the steam loop from interaction with the rock in the hole. Unlike traditional closed-loop steam generator, an open system would pick up contaminants and eventually cause scaling.
Just curious, is this process performed in alternate phases (pump water, wait for the vapor ) or is it done at the same time with different pipes in the same hole?
Paging u/Animats, who had some interesting thoughts on a previous write-up of Quaise which had less info. I think he mentioned that gyrotrons had not been deployed for this use-case and that should make us skeptical because sticking one on the end of a multi-km long drill bit sounds Hard(tm).
An adviser of Quaise (an MIT research engineer) claims:
> “This will happen quickly once we solve the immediate engineering problems of transmitting a clean beam and having it operate at a high energy density without breakdown,” explains Woskov, who is not formally affiliated with Quaise but serves as an advisor. “It’ll go fast because the underlying technology, gyrotrons, are commercially available. You could place an order with a company and have a system delivered right now — granted, these beam sources have never been used 24/7, but they are engineered to be operational for long time periods. In five or six years, I think we’ll have a plant running if we solve these engineering problems. I’m very optimistic.”
Interested in what others think here. Seems overly optimistic to me.
It's a really elegant solution though if it works; the idea of boring a hole in an existing coal plant and repurposing the old steam turbine & transmission equipment sounds like it could really lower the cost.
The article is quite skeptical of Quaise:
"While it is exciting to see the interest in geothermal, much of the effort leaves me skeptical.
Quaise is staffed heavily by former Schlumberger employees. Schlumberger is known for being too expensive and impractical in many of its business units for shale. It is on-brand that they are building a laser-like drilling technology! Quaise deserves credit for correctly identifying the challenges in geothermal economics and pursuing a path with a greater than zero chance of success. But many of their assumptions are off base. The large, bureaucratic companies you work with at Schlumberger often do things like limit trip speed to 500'/hr. One time tripping fast caused a blowout by swabbing the hole, so no rig contracted by the company can trip fast even if the blowout risk is low. Smaller companies are ripping out of the hole at 4000'/hr. Tripping in granite is like tripping in a cased hole. Most companies will push the speed to the physical limits of the crew and rig. And even at 50,000' depths, on-bottom drilling will dominate total time (assuming a high-temperature motor is available). Both PDC bits and motors suffer from the vibration drilling in hard rock causes. There is a decent chance that PDC and elastomer-free motor assemblies will see longer runs at deep depths because the rock is more ductile."
I have no background in energy at all, so I'm not qualified to comment on this at all. Just leaving it here as a counterpoint to the original article.
If I read this right, this is still the basic geothermal structure and idea but is really an improvement in drilling?
Geothermal seems to be limited by finding suitable places for it, which is generally where you only need to build fairly shallow wells. Building deep wells is expensive. If you can build deeper wells faster and cheaper then it opens it up to move areas.
Is that correct?
Better and cheaper drilling has way more applications thatn building geothermal wells. I mean we need to build tunnels all the time. Cheaper drilling probably has significant applications for the oil and gas industry too.
So if that's true, why the focus on geothermal? I mean I support research into renewables but it's a whole lot easier if, say, you can get the oil and gas industry to pay for your R&D, effectively.
My understanding is that geothermal energy production is still pretty low.
It's also worth noting that boiling water to steam and turning a turbine has inbuilt costs that you can't escape. There's only one power source that directly creates energy and that's solar. Additionally, solar has no moving parts (other than facing PV pannels towards the Sun, optionally).
Note the one of those limited, presently suitable areas in the US is Yellowstone: a geographically immense caldera. But if this tech proves cheap enough, as it may in time, we'll be able tap geothermal anywhere rather than pay to transport or transmit the energy. That's what's notable about the tech:
"Houde began his talk with a quote from the Department of Energy’s 2019 Geovision report, an analysis of the geothermal industry in the United States: 'Supercritical resources can be found everywhere on Earth by drilling deep enough…Drilling to this depth is financially prohibitive with existing technology…Economic production of supercritical resources will require the development of entirely new classes of drilling technologies and methods.'
> So if that's true, why the focus on geothermal? I mean I support research into renewables but it's a whole lot easier if, say, you can get the oil and gas industry to pay for your R&D, effectively.
I believe that is what they are doing, with initial projects being related to gas exploration, and using that to refine the technology.
I've been following Quaise for a while and I have never seen any mention of such a plan. Oil and gas is into vertical drilling and fracking, which these people have little use for so the applications aren't that similar really.
There are other geothermal startups doing more O&G-like drilling though.
Fantastic. Geothermal power has such potential. "The amount of heat within 10 000 meters of the earth's surface is estimated to contain 50 000 times more energy than all oil and gas resources worldwide." - The International Renewable Energy Agency
Always fascinated by all of these approaches. Though I still am fascinated, that all energy available to us is derived from gravity in one way or another.
>that all energy available to us is derived from gravity in one way or another.
How so? Our major energy source is oil, where the energy comes from sunlight. And light's energy is from the electromagnetic fundamental force, not gravity.
The sun. How did the sun form and why does it produce light? Gravity pulled some hydrogen into a ball, enough of it was there that gravity forced it to fuse.
Sure. Our energy is still derived from the photons released by the sun, even if the sun needed gravity to form. Gravity is necessary, but isn't the source of the energy.
And fusion happens through an interaction of the weak nuclear force. Finally, without the strong nuclear force there wouldn't even be hydrogen atoms for any of this to happen. All four are necessary, the energy we use comes from electromagnetism.
Can someone clarify the geochemistry for me? What happens to the rock vapor? Does it resolidify along the existing wall, or does it recondense into fine particulates, and are those particulates easier to remove than pieces of the solid rock itself?
Then, can somebody clarify the physics for me- how far away can the target be from the energy source of the gyro-tron?
I really don't love being negative all the time, but this project is going nowhere.
Boring rock in this way is a permanent "we're 5-10 years away research project."
They've coupled a never ending research project with the idea of "hey there's already some power lines here" which is the smallest of efficiency gains in the big picture.
There is, but I can't remember the link, haha. You just kinda learn things over the years. This one can be reached by clicking on the domain name of a linked article, so it's easy to remember how to get there.
MIT produces interesting engineering content. They've been a regular on the HN frontpage for as long as I've been coming here which is a pretty long time. Why would it be weird?
TANSTAAFL... If we tap the energy from the molten core, part of the system that both drives/stabilizes the rotation of the planet, and provides the magnet generating our solar radiation shield (van allen belts), then I think we can expect eventually to face rotation/stabilization degradation.
Of course, eventually might be a million years from now. I remember climate change deniers saying that climate change might produce a visible effect by 2400, and by then we could fix it. Now look where we are with that.
There's also fracking. To tap the core we probably need to do deep drilling, with a lot of the problems that drilling for oil or fracking cause, except possibly magnified because of the depths we're talking about.
It is much easier, and safer, to tap solar energy. If we pour research into solar efficiency and house-scale batteries, we could provide all of the electricity needed for U.S. homes and have enough to sell to Canada and Mexico with only 16k sq miles (the size of Nellis AFB).
"A square mile, 5,280 feet times 5,280 feet equals 27,878,400 square feet. Divided by 15 sq.ft. per module, we can fit 1,858,560 modules per square mile. At 0.6266 kilowatt-hours per module per day, our square mile will deliver 1,164,574 kWh per day on average, or 425,069,510 kWh per year. Back to our goal of 4,000,000,000,000 kWh, divided by 425,069,510 kWh per year per square mile, it looks like we need about 9,410 square miles of surface to meet the electrical needs of the U.S. That’s a square area a bit less than 100 miles on a side. This is a bit over half of the approximate 16,000 square miles currently occupied by the Nevada Test Site and the surrounding Nellis Air Force Range." [1]
Just a nit: fracking problems aren't from the depth of the drilling. In fracking (hydraulic fracturing) they drill a hole then push high pressure fluid into the hole in such a way as to cause large volumes of rock to break apart. For something like this, you'd want the hole to be stable and not tear apart all the rock around it, like in a traditional well.
The electricity will eventually be turned into heat too. Since PV panels are pretty dark, in most places where you put them they will increase the amount of heat generated, because less light is reflected back to space.
It all gets turned into heat anyway. Whether at the solar panel or in the electrical transmission process, inverters, or the actual devices being powered.
Solar is much more limited by resources and manufacturing ability, likely would cost a lot more than this just in finished product, will take up a ton of land (very expensive), works much better in certain areas than others, plus the still unsolved problem of grid-scale storage for at night. You also need to still build the equipment to hook it up to power lines; if you can retrofit existing power plants into something that works 24/7, then that is a much better alternative.
I think the reality is we need a “yes and” approach, not a “no but”.
There is no possible way for humans to ever extract enough geothermal energy in any of our lifetimes, expanded out to 100,000 lifetimes, to ever affect the geothermal reserves of the earth. You are making things up to fit you argument that solar is better.
There was this idea going around that solar power would cause global warming, since a solar panel is typically warmer than whatever was there before it was installed. But the idea turns out to be bullshit, the warming effect is tiny compared to what the equivalent co2 from fossil fuels would cause.
> It is much easier, and safer, to tap solar energy. If we pour research into solar efficiency and house-scale batteries, we could provide all of the electricity needed for U.S. homes and have enough to sell to Canada and Mexico with only 16k sq miles (the size of Nellis AFB).
A million times this.
We have solutions at our hands, but we're not willing enough to use them
Hm. Annual PV module production in 2020 was ~180 GW [0]; peak power per 1m² is on the order of 200W, meaning roughly the equivalent of 1000 km² or ~386 sq. miles or thereabouts of PV modules.
Covering 16,000 sq. miles would take about 40 years of the entire global PV module production - a few years less if adjusted for production increase.
Doesn't sound very realistic to me, especially considering infrastructure, storage solutions(!!!), and maintenance/replacement have to be added on top of that.
I'm all for clean and sustainable power generation, but a little diversity (wind, nuclear, geothermal, biomass, tidal power, hydropower, etc.) seems to be more realistic and actually achievable.
I think geothermal can be part of a solution, as can solar, and nuclear, and wind, etc. We need all hands on deck here. I think you're not wrong to worry about cooling the interior of the Earth too much, but that's a much slower problem we would have plenty of time to adapt to. Millions of years is longer than humans have been a species. Given all the other very viable energy options out there, I don't see us overdoing it on the geothermal front. Global warming on the other hand is going to fuck us up over the next century.
One thing I would like to see happen is tap the energy at Yellowstone in a big way. We want to cool that down before it blows up in our faces.
For every few miles you drill the temperature rises by 370F. The closest we've ever come to drilling was with the Japanese scientific drilling ship Chikyu [1]. It had to stop because of extreme pressure collapsing the walls of the drilling hole after just 7km. Just putting it into perspective, the amount of heat trapped inside Earth is immense.
I've wondered as well about the effect of pumping all of that heat - energy - out of the core and into (effectively) space.
Best case, our use falls in the .003% mentioned in another thread of heat that contributes to warming the Earth's crust, and the surface is that .003% cooler.
The worst case, though, is we start slowing (maybe even stopping) the flows of molten rock as it's cooled down. I don't even have the beginnings of a background to comment - does anybody?
Global energy usage is 15TW. The earth's core currently dissipates 47TW through passive cooling. The core has a mass 528,000 times that of the atmosphere.
I don't think I even need to do the math on this, to demonstrate that our total energy usage is many orders of magnitude smaller than what would be required to cause the problem you're discussing.
Solar is great, and growing fast, but for fairly obvious reasons works better as part of a multifaceted solution than as a single source.
AFAIK they aren't planning to do any fracking, and it's not obvious that it is even possible at these depths. And the drilling is far less disruptive as it is given that it is done at atmospheric pressure (no drilling fluid).
As for your second point, batteries are not cheap. Nowhere near cheap. We need solutions not pipe dreams.
TANSTAAFL applies to batteries. There is no viable path known to produce multi-day batteries to cover everyone on the planet. Solar & wind is great. But we're not solving the climate crisis without baseload power generation and distribution. All hands on deck.
Firstly, the energy from geothermal is NOT from the core or even remotely that deep of an energy source. It is from potassium and other elements doing radioactive decay in the crust and upper mantle.
Nonetheless, it is worth putting some numbers to gain perspective:
1. World electricity demand was 24K terawatt hours in 2019 [1]
2. Mt St Helens volcano released 24 megatons of energy when it erupted [2]. That is 28 terawatt hours.
3. Thus, you would be adding 824 equivalent Mt St Helen eruptions a year in terms of additional energy extraction from the earth. Which sounds like a lot, but it really isn't for several reasons.
4. In particular, the earth is already radiating substantially than this amount of energy to the surface. "Because of the internal heat, the Earth's surface heat flow averages 82 mW/m2 which amounts to a total heat of about 42 million megawatts."[3]. That is 42 terawatts of continual energy loss from the crust/upper mantle to the surface. That is 16 times as much electricity as humanity uses -- and it is already be radiated to the surface.
My guess is that if we started extracting this from 20KM down and bringing that heat to the surface, then it would cause some increase in energy radiated to the surface, but it would also be concentrating that energy radiated to the surface at the location of the plant and potentially decreasing that energy from its slow radiation path to the surface through the rock above it.
Either way that potassium and uranium is going to decay. Either way, that heat will eventually make it to the surface and eventually be lost to space. The question is whether we can stand in the middle of that process and capture it for use. Our using of that heat and turning it into electricity -- ultimately still turns into heat and is radiated to space. It just is turned into heat when it is loses on the electricity transmission grid, when it is used to heat a house, when it is used to move a car, etc.
TANSTAAFL really doesn't intersect with the reality that stars burn and the earth decays whether we use the energy or not. Entropy comes for us all. We are just trying to be a step in the ultimate transition of all this energy to the heat death of the universe.
I have absolutely zero knowledge which would qualify me to talk about this topic. But based on what I know about our world and its ecosystems, I just can't imagine that drilling holes into earth and extracting it's heat can be a good idea when done in large scales.
I could imagine that this seems reasonably safe right now, only for us to find out that it's actually a horrible thing to do. As has happened lots of times before. This is just a gut feeling and I'm not anti or whatever, it just feels...weird to me.
No idea what the bad effects could be. Loss of internal heat, destabilization, sinkholes, loss of pressure, volcano eruptions back-firing through these holes. Admittedly, these examples sound like apocalypse movie scenarios. Which just validates my initial statement about me actually not knowing very much.
Could also be like deforestation. Trees do die just like that, without our intervention. This benefits the forest. A couple of humans can chop wood in said forest and it will not affect it too much. But if whole cities and countries suddenly have to get their wood from this forest, it will disappear very fast.
So maybe geothermal energy is not a risk when a couple of plants exist. But if humanity starts to rely on it too much and starts building geothermal plants like crazy, the damage could show. Maybe the damage only appears locally in the vicinity of these plants, which would still be worrying.
I just want to disclose again that I am just spit-balling here.
The well drilling using microwave lasers, generated using those gyrotrons, certainly sounds novel enough. It will need a R&D program to bring it up to a mature tech level.
The concept of reusing existing coal plants sounds clever.
Should we be concerned about cooling down the earth's core over the long term? I'd rather if we focus our efforts on renewables (basically anything that gets energy from sunlight - solar, wind, biomass)
Short answer: no. There's not enough time until our sun goes super nova in a few billion years to trickle cool the planet's core in any appreciable way by siphoning of really tiny amounts of energy.
What the article doesn’t address is the potential for earthquakes. I thought that was the limiting factor in a lot of deep geothermal drilling? Didn’t Iceland run into this?
It depends on the rock formation the project is targeting. If one targets a steam reservoir or a sedimentary rock formation, generaly things are ok (save for this one case in Germany where Earth started to rise [0]). In case you target hot (dry) rock that you need to fracture to increase the heat exchange surface, then more often than not you are going to induce seismicity. It's been well studied in Alsace and some small induced earthquake was felt in Strasbourg and attributed to nearby geothermal developments [1].
Perhaps you are thinking of fracking? In fracking they dig deep, horizontal wells and inject a water/sand mix into the well to fracture the rock. This method has resulted in measurable earthquakes.
I actually got really excited after reading the article, and the entire piece is about how "down to earth" (pun intended) the technology being developed here really is.
They are going to great lengths to make it compatible with the existing power grid (just replacing the heat source for current generators), re-utilizing abandoned mines and all.
So, would you care to elaborate why you think it would never materialize?
The article puts a lot of weight on the use of pre-existing technology in a new mode for making deep bore holes, and glosses over the engineering challenges that have yet to be solved ("transmitting a clean beam and having it operate at a high energy density without breakdown").
I'm not equipped to judge how difficult those problems will be to overcome in practice. Obviously this would be very cool if it bears out, but it's hard to tell if it will.
My biggest question is whether this will be the next climate crisis. There have been recent articles about how the earth's geology is cooling faster than expected. There are questions around if our planet will become a dead planet as it cools. It seems like speeding this up could be an issue, especially given how little we know.
Total human energy consumption is 7.8e20 joules[0]. The heat content of the earth is 1e31 joules[1]. That is a difference of 100 billion times. Safe to say there is not going to be a problem for a very long time.
Yeah, but it looks like humans are doubling the amount of energy produced/consumed per year every 30-40 years.[0] If we say it takes 150 years to increase the amount of energy consumed by a factor of 10, then we'll be consuming 100 billion times more energy than we do today in well under 2,000 years.
Compared to a human life, that is a very long time. Compared to the time it's going to take for the sun to expand and swallow the earth (which others in the thread are doing), it really isn't.
Simple extrapolation is not always effective. "This problem came to a head when in 1894, The Times newspaper predicted… “In 50 years, every street in London will be buried under nine feet of manure.”" [0].
Geothermal heat provides less than 0.1% of the total heat of our planet. It is pretty much all just the sun. So as long as the output of the sun does not change much it won't be a problem (so will have to wait billions of years and even then sun will actually get bigger and hotter first before getting colder)
The planet is expected to still be mostly molten by the time the sun swallows it, so there is a huge margin. I think people underestimate just how much energy there is down there.
Won't Earth be engulfed in the first phase? If that's the case, Solar gasses will also drag down our orbital velocity and Earth will fall towards the core. So it won't be around for the second phase.
My understanding of the term vaporization means turning a solid into a vapor... so that implies there's nothing substantial left after vaporization that can't be otherwise removed simply through ventilation.
My understanding is they propose to excite the material with electromagnetic waves until it undergoes a phase shift, solid to liquid to gas.
So then they have superheated gaseous rock in the bottom of the bore hole, how do they get it out? Conservation of mass: it must go somewhere.
Ventilation isn't so simple. The gaseous rock will condense, then harden on the walls of the ventilation tube. Or, maybe it reacts with the materials of your down-hole equipment.
I've worked in oil and gas for years. It's possible the article is missing a bunch of details, but I'm extremely dubious of their idea.
First, how do they plan to address well control? As you drill down through the Earth, you drill through many layers of rock, some of which contain oil and gas in various quantities. Since the thousands of feet of rock above is heavy, they are under a lot of pressure, and will be happy to flow out through your borehole and up to the surface if you don't take measures to keep the formation under control. If they are allowed to do that, those flammable materials can easily ignite and cause a fire big enough to destroy your entire drilling apparatus and be very difficult to put out. Note that you don't necessarily need enough oil and gas to be commercially produceable to generate a disastrously bad blowout.
Oil wells address this by filling the borehole with drilling fluid at a specific density, which produces enough pressure at the bottom of the hole to counter formation pressure. Every well is also fitted with multiple blowout preventers to seal off the well in case of a sudden pressure increase from the formation, and also allow heaver weight fluid to be circulated in to get back under control. The wells are also drilled and cased in sections, so that there is never too large of an amount of borehole uncovered that needs to be kept under control.
So given all that, exactly where is this Gyrotron going to be? If it's at the surface, how are they planning to microwave through miles of drilling fluid and have enough energy at the bottom to cut more rock? If it's at depth, how is this Gyrotron going to survive the high temperatures there? High-end electronics are much more sensitive to extreme heat than drill bits are. Especially if you're pumping ~megawatts of energy through them to actually cut rock. Speaking of, how would we even get that much electric power down there? Oil and gas has spent many billions of dollars on this and has yet to find a good solution.
Also, how are they planning to keep this whole straight and judge depth? Holes thousands of feet down don't just stay straight, you have to actively keep them straight. The oilfield has plenty of ways to do this with conventional drilling hardware, how will their Gyrotron system manage it? And we also need to transport rock cuttings / fumes to the surface fast enough to support the drilling rate, how will they do that?
I'm also wondering about fluid flowrates. If they manage to drill down far enough to get to rock hot enough, how much fluid do they need to flow in order to get enough heat energy to the surface to operate these steam turbines? How big pipes do they need up and down to flow that rate? They also need to flow slow enough at depth to pick up lots of heat, and also fast enough through the mid and shallow depths to not lose all that heat to the local formation before it gets to the surface. For that matter, what's the heat flow rate from the magma into the rock at the depth they were drilling out - how much heat power can we really extract long-term with their setup? (I see jjk166 has addressed that, and that it is another serious issue).
Don't get me wrong, geothermal is a really nice solution, and I wish all the luck in the world to anyone working on using it more. I just don't see any technology here that address the real issues with getting large-scale energy from geothermal.
I think the idea is to use a traditional drilling technique to start the whole until they are past any gas pockets, then use the beams after that. The beam drilling doesn't require fluid, and the process itself creates a glass wall/lavatube on the side of the hole. They drill quite slowly relative to traditional drilling to evacuate the ash and fumes, but they don't need to replace the drill head so the overall process is faster.
Still sounds rather dubious. I dunno about this whole thing about the beam creating a protective glass wall, but I'll give them a pass on that. Also on how they'd actually evacuate all the fluid and how they'd extract ash and fumes without it. The most critical part sounds like heat. It's very hot down there, and we're also presumably running megawatts of electrical power for this beam, which all goes to more heat. Ambient temps at those depths may be over 300 F / 150C, and that's before we pump in megawatts of extra heat with no way to extract it.
I helped design and operate lots of oilfield electronics for those depths and temperatures. MTBF for the most hardened electronics we could get our hands on at temps over 150C was in the neighborhood of 200 hours max. Drilling slowly with much more sophisticated and unproven electronics, I expect they'll be dropping like flies if they ever work at all. And that's with extremely generous assumptions on the heat loads. MTBF of electronics drops exponentially as temperature goes up.
Problem with traditional drilling is that your drill has to contact with hot rocks. With gyrotron, it doesn't have to. If you pump lot's of water down to your electronics, it can be used to cool electronics, then gyrotron, then be dumped outside head where it flashes into steam (thanks to megawatts of energy that is melting rocks already) and helps to evacuate ash while also cooling it and preventing recondensation on walls of already drilled tube. Walls will still be glassy because they were just melted.
That doesn't sound practical at all. It doesn't matter if you have direct contact or not, everything down there is that hot, so you're gonna be that hot. Existing oilwells already flow fluid through at a fairly high flowrate - high enough that eroding parts is a concern - and it's not enough to get the temperature down much. You're gonna need something a lot better than "just pump some water though" to cool things down enough to get the MTBF back up. And that's before accounting for how much heat this rock melting microwave laser thing plus it's power transmission lines is adding to the environment.
The plan seems to be to have the gyrotron that generates the drilling beam on the surface, so the electronics don't have to withstand any heat at all. The "only" need to manage to get a beam that's clean enough that it reaches 20km into the ground.
Curiously, the other people who responded all think it'll be downhole. Anyways, this does make the device heat practical to handle, but now you have to figure out how you're going to get the vaporized rock out and shoot your microwave laser thing through 20km of rock vapors. And we're also presuming you can keep 20km of borehole exposed to atmospheric pressure with only this supposedly glass wall thing preventing formation fluids from flooding the borehole. If that cracks anywhere and floods it with high pressure hydrocarbons, maybe you could seal it up before all of your surface hardware gets blown up, but what do you do next? Oil wells have procedures for how to circulate heavier fluid back in to get the well back under control, but I have no idea how you fix a failed glass wall thing.
That's nice. But there's an even easier, cleaner and even mobile source of "free" energy - plus, it's fully open-sourced (no patents, fees, limitations, etc.): https://www.KryonEngine.org
Even if you're right, it's clearly impossible for the point to get an interesting discussion on HN. It immediately turns into an off topic flamewar. Therefore, please stop.
Fascinating. In the most basic of philosophies, extracting conserved energy from our planet doesn't really fix the problem. Even in the best case the unintended and unknown consequences will destroy any predictions as to how something like this plays out. But as far as band-aids go this one sounds like it could us a whole lot more time...
> This will happen quickly once we solve the immediate engineering problems of transmitting a clean beam and having it operate at a high energy density without breakdown
> [...] In five or six years, I think we’ll have a plant running if we solve these engineering problems. I’m very optimistic.
If only a few engineering problems have to be solved to make it work, then it will be ready in no time. It's not like those engineering problems are hard to solve or anything. That's why fusion works so great, cheap batteries are wide-spread and everyone has 100% effective solar-panels.
While your sarcasm is noted, it's important to also note that engineering problems would never be solved until someone is allocating the necessary resources to solve them. I'm not a huge fan of gross theoretical speculation as being a savior for humanity, but I very much appreciate an innovator's optimism that redirecting known technologies to a novel application will result in benefits to humanity.
Optimism is difficult to generate and easy to snuff out. We should be less inclined, as a society, to default to apathy.
That is fair. I recently watched "We Were Apollo" and was struck by how incredibly audacious a manned moon landing really was in 1960. That sort of positive thinking is what we really need for fixing the climate crisis and elevating humanity beyond constant resource conflicts.
It's worth remembering that national pride (and the beating that pride took when the Soviet Union beat us to space) is what drove the US to make such fast progress.
That national pride does not exist as a driving force for addressing climate change. We, in many ways, don't even have a national consensus on the need to address climate change.
Don't get me wrong, I'm rooting for them and all others trying to make such solutions happen. I just hate these handwavy breakthrough-like press releases which get published 100 times a day.
Perfectly valid reaction, and one I personally share. It's a delicate balance to support innovative minds and ideas while simultaneously insulating oneself from baseless corporate marketing hype.
For context, to provide the electricity demand for kansas would require about 35% of the total geothermal flux into kansas. New Jersey's electricity demand is 7 times higher than what its geothermal heat flux could provide. For the whole US, electricity consumption is about 75% of geothermal heat flux if you ignore variations like the yellowstone hotspot.
Geothermal certainly makes sense in certain locations where the heat flux is high and other power sources are problematic - for example iceland is probably the most ideal spot on earth. The technology for extracting geothermal power may also be useful for future efforts to control volcanism (though at this point such plans are highly speculative), so research is warranted. But it is unlikely to ever be more than a minor slice of the world's energy supply, and certainly anyone claiming to solve the issue by just digging deeper is selling snake oil.