Fearless Icelanders to Drill Into Magma Chamber
Added 2024-01-24 17:00:15 +0000 UTC[This is a transcript with links to references.]
I don’t like places where hot stuff bubbles out of the ground, but Icelanders have no such issues. They’re now almost ready to start a new experiment that will drill right into a magma chamber. How do they know that this will not accidentally create a volcano? Let’s have a look.
Iceland is an island in the Northern Atlantic Ocean that sits right atop the Mid Atlantic Ridge. That’s where the North American and Eurasian tectonic plates rub. Those two plates are moving away from each other at a pace of approximately 2 centimetres per year. As the plates move apart, hot, molten rock – called magma -- can rise to the top. This is why Iceland sees frequent volcano eruptions and on occasion gets a new island, like this one which was born in 1963.
Not so surprisingly, Iceland has the largest per capita production of geothermal energy, which covers an amazing 66 percent of the country’s primary energy needs.
They also really like drilling deep holes to see what they’ll find. And boy have they found stuff.
Their most ambitious plan was the Iceland Deep Drilling Project. In their first attempt, in 2009, they tried to drill to a depth of 4 point 5 kilometres near Reykjavik, well above where they thought a magma reservoir was. However, just beyond 2 kilometres they drilled into an unexpected upper part of the magma chamber. The magma plugged the lowest 20 metres of the hole and damaged the drill. Aggressive gases began bubbling up that also damaged the surface equipment. Eventually the main valve failed, and the well was shut down.
They drilled a second hole in 2014 and encountered the same problem: The drill tapped onto a magma chamber where they didn’t expect it, and acidic gases wrecked the equipment.
You may wonder why they go to these troubles. The reason is as so often, physics.
You see, usually geothermal power plants work by piping water through hot layers underground. This heats up the water, which creates pressure which can then be used to drive a turbine and create electricity.
But water, or any substance really, has a limited capacity for how much energy it can transport, called the “enthalpy”. And the enthalpy of water makes a sudden jump at about 374 degrees Celsius. I understand that very well because at that temperature I would also jump.
If it gets even hotter the water is neither a liquid nor a gas but both. The phase is called “supercritical”. This may sound a bit obscure, but you can witness supercriticality yourself in my YouTube comments.
The amazing thing is now that supercritical water can carry several times more energy per mass, and the conversion to electric energy becomes more efficient. This means if you can build a geothermal plant with a reservoir hot enough so that the water becomes supercritical, that’ll suddenly dramatically increase the power production, by some estimates up to a factor 10. Supercritical water is kind of the holy grail of geothermal energy.
There have been a few attempts at supercritical wells in the past, notably in Italy and the United States. But they all ran into some sort of trouble. Either they blew up or they collapsed or both. And this is what the Icelanders were trying to do with their deep drilling, creating a supercritical well.
You might think that hitting upon magma and wrecking their equipment would have discouraged them, but not so. Yes, they had these nasty gasses and their drill got stuck in the magma, but it’s not like they accidentally created a volcano. Basically they concluded it wasn’t as bad as they thought it’d be.
So they’re doing it again, but this time on purpose. It’s called the Krafla Magma Testbed. They want to drill two new holes each about 2 kilometres deep, first nearby and then into the magma chamber that they know to be there.
The drilling for the first borehole is supposed to start by 2026. It will not drill right into the magma, but just close to the chamber to measure temperature and pressure. They also want to bring up samples from down there. The second new borehole will then actually drill into the magma chamber to test the possibility for a supercritical geothermal power plant.
Isn’t this kind of dangerous. Yes, it is. But. They know from the earlier drilling that while the magma chamber is under pressure, the pressure isn’t high enough to accidentally create a volcano. At least not unless the conditions down there have dramatically changed in the past 10 years. Honestly, I wouldn’t go anywhere near the thing.
The project has both scientific and technological purposes. They want to study the magma and what it’s doing under the earth when it’s not bubbling to the surface. According to the project’s website the purpose of this endeavour is an “Exploration into the utilization of super-hot, magma, geothermal energy and fluids” that “will revolutionize our energy landscape.” Yes, and a bit of magma might even revolutionize your landscape.
According to the website New Civil Engineer, the project management’s now seeking funding of 79 million pound for the first stage, so if you have few million to spare, maybe they’ll send you a fresh magma sample in return.
Geothermal energy is a rather obvious source of energy. The energy that’s contained in the deeper layers of Earth is staggering. Geoscientists have estimate that the total energy reserves in the upper 10 kilometres of Earth’s crust would be enough to power the entire world population for several hundred million years.
That sounds amazing, but the problem is that in most places finding hot spots underground is difficult. And drilling into them is not only difficult but also expensive, really expensive. It’s also not irrelevant to note that it isn’t so uncommon that the gases which are released from underground during the operation of a power plant contain carbon dioxide.
On average, carbon dioxide emissions are low for the currently existing power plants. Though there are some examples in Turkey where geothermal plants actually emit more Carbon Dioxide than a typical gas power plant. However, how much they would emit with deeper drilling or new extraction techniques, nobody knows.
What all of this means is that geothermal energy is a good solution, in some places, and we can almost certainly get more out of it than we presently do. But in most places it’s difficult and expensive is extremely unlikely to ever become our global main energy supply. And I for one am grateful for it. Because I don’t like hot stuff bubbling out of the ground…
Comments
As a mechanical engineer who spent my first years after university working on geothermal power (including designing in 1983 one of the early water reinjection systems - prior to the 1980s reinjection was viewed as risky in terms of possible quenching of production steam wells), I have to point out a couple of bloopers in this item: 1) "usually geothermal power plants work by piping water through hot layers underground. This heats up the water ...."? No, usually they work by extracting steam from a natural reservoir (which may be wet, i.e. saturated, or less-commonly dry, i.e. superheated steam). Yes, there is an extraction pipe as part of the production well, but the notion that water is piped back for re-heating after passing out of the turbine condenser gives a very misleading idea of the hardware that drives the economics of geothermal power. Reinjection is nowadays used for a couple of reasons - avoiding discharge of heavy metals into rivers (which used to be the practice) and avoiding depletion of the underground water table by replenishing it. But this is done in a much less controlled way than any imagined "piping". The return path to the production well is by natural permeability of the underground geology. As mentioned above, this needs to consider the possibility of quenching the steam wells, but done carefully, it can avoid this, while helping improve the long-term sustainability of the steam-producing wells. I note that the article Sabine cites (https://www.vox.com/energy-and-environment/2020/10/21/21515461/renewable-energy-geothermal-egs-ags-supercritical) explains "Enhanced Geothermal Systems", which are similar in concept to the practice of reinjection, but with the important difference that the claim that "in a nutshell ... EGS ... makes its own reservoir" is very optimistic. The British tried this in the 1980s (calling it "hot dry rock" geothermal) but found that very little of the water pumped underground could be recovered as steam. I grant that modern directional drilling and enclosed piping systems (at considerable expense) may improve that, but a careful read of this article makes it clear that this is futuristic stuff, not usual geothermal energy. For example, they say that "the engineering challenges remain daunting, especially as the targets get deeper and drier." 2) "supercritical water can carry several times more energy per mass, and the conversion to electric energy becomes more efficient. This means if you can build a geothermal plant with a reservoir hot enough so that the water becomes supercritical, that’ll suddenly dramatically increase the power production, by some estimates up to a factor 10." No - the specific heat (kJ/kgK) of supercritical water at 22 MPa and 374 C is several times more than regular water, but the specific enthalpy (kJ/kg) only increases by about a factor of two. More informatively than talking about ratios, the specific enthalpy of water at that temperature increases by about 2000 kJ/kg (from 1500 to about 3500 kJ/kg), which is similar to the rise when water boils due to latent heat of steam, reflecting the fact that the supercritical point marks a phase change of sorts. Higher temperatures mean that the conversion to electricity should get more efficient, but by nowhere near a factor of 10. A factor of 1.5 would be more like it. I guess what will improve is the pipe size to bring the water back to the surface, since the density of supercritical water is of the order of 100 times that of steam. (So the kJ/m^3 will go up dramatically, not the kJ/kg). But against that is the need for much longer pipes with much thicker walls to take the pressure. So I would urge caution about the real applicability of the science that the Icelanders are doing. And finally (at the risk of repeating my earlier posts) I would point out that the solar resource hitting the Earth 24/365 for the next billion years or so is about 130,000 TW. I note with mild amusement that the article gives as a: "Fun fact: The molten core of the Earth, about 4,000 miles down, is roughly as hot as the surface of the sun, over 6,000°C, or 10,800°F. That’s why the geothermal energy industry is fond of calling it “the sun beneath our feet.” The heat is continuously replenished by the decay of naturally occurring radioactive elements, at a flow rate of roughly 30 terawatts, almost double all human energy consumption." Hmmm - a 30 TW underground resource that needs expensive practices developed by the fossil fuel industry (and also emits non-trivial amounts of CO2), or a 130,000 TW resource that is inherently net-zero and well-proven to be converted through direct solar, wind, hydro and biomass technologies??
2024-01-26 21:42:34 +0000 UTCIn desert regions and the supply upstream, closed systems may be needed. Similarly, I hear that Lake Powell might convert the construction diversion tunnels to Archimedes generators.
2024-01-25 06:04:24 +0000 UTCWhile on the topic, for those who can access the Nature article below, it describes an on demand geothermal plant where you inject the water in the rock to heat it up when needed. https://www.nature.com/articles/d41586-024-00127-3 Trouble is that water is not always easy to come by. There are lots of hot spots in the Western US but water is scarce and the aquifers are draining at an alarming pace.
Rad Antonov
2024-01-25 01:24:47 +0000 UTC
