Geothermal is not an easy solution. Just drilling deep enough doesn't begin to address the environmental and engineering issues involve. Perhaps these issues will be resolved. I hope so.
Err...care to explain? I was under the impression that the only engineering issue with deep geothermal was precisely to drill deep enough.
Once you've done that, the rest is pretty straightforward: boil water to run a turbine. Actually I'm 100% sure people are talking about converting coal plants in place with deep geothermal.
Also,you put back the water you pump up, so it's literally a closed loop. What environmental issues are you talking about? The mud?
Drilling that deep is not easy. Directional drilling equipment is very expensive, and heat + pressure take a toll very quickly on such equipment. Directionality is important as boreholes are rarely straight an it is entirely possible to drill a borehole in a U shape accidentally. Drilling requires high pressure pumps to clear the face of the drill bit, and the cut material must be returned out of hole. That's one hell of a compressor or mud pump. Below a certain depth rock behaviour changes from brittle deformation toward more plastic (and explosive) deformation, to eventually plastic deformation entirely. Groundwater pressures can collapse holes. Deformation can collapse holes. The rock grinds back at drilling gear. Equipment can become stuck and difficult to dislodge. Holes eventually collapse and partially close on their own, requiring casing of the hole. To case, drill a section, retrieve gear from down hole, slide casing in, replace Drilling gear, repeat for each length of casing. It can be quite different per hole, and per rig setup. Some rig setups permit casing in place (this is more a drillers specialist area than my own).
Then, there's the issue of keeping the hole open long term. Hydrothermal activity tends to dissolve minerals in water. Minerals tend to crystallise out inside boreholes and pipes over time, like hard water in water pipes in rural areas, constricting flow.
What is being proposed is difficult and requires an extreme amount of maintenance through its life cycle.
While all that is true the original article concerns using high intensity microwaves to drill, with an unbalanced purge gas. One of the advantages of this is the potential to create a glass casement as you drill. I'm not in the industry but it's a neat paper and your comment reads like you're simply unfamiliar with what they're proposing, ambitious as it is.
MIT has verified the basics concepts at lower power levels. So while there's still uncertainty and risk here, it's wrong to say it's totally untested. It's trying to make the jump from lab demonstration to commercial viability, which is exactly what you'd expect a research project like this to be doing.
The jump from lab demonstration to commercial viability is exactly the place where almost every tech trick fails.
So there is no need to pay this thing any attention. Geothermal under ideal conditions is not competitive. Steam turbines have operating costs solar and wind do not.
This is the same reason nukes are a dead end, and D-T fusion besides. It doesn't matter how cheap your heat source is if you need to pay for operating a steam turbine to get any power out. Solar and wind provide high-grade energy directly, so are impossible to compete with anywhere they work.
There are uses for direct heat piped underground to heat buildings, but you don't need to bore to 10km, or even 3km, to get enough heat for that.
When something hard is under pressure, it can bend or deform, or it can break or shatter.
Imagine a hammer striking a sheet of metal and the metal denting. For a brief moment, the pressure and heat of the hammer strike causes the metal to deform. Conversely, if the hammer hit something like a sheet of glass, it would shatter.
Plastic in this sense is not like Tupperware plastic at room temperature, but plastic heated when it is first being molded into shape.
Explosive deformation is again like the hammer hitting a sheet of glass- if the glass were already under pressure, breaking it would relieve the pressure causing shards to fly everywhere.
Rock at the surface is relatively cold and under little pressure- it is hard, but brittle, and simply breaks. As you get deeper, it is under more pressure and as it breaks, that pressure can get relieved unpredictably (fault lines cause formerly stable walls of already drilled hole to collapse).
With even more depth comes more pressure but also more heat, which relaxes the crystalline structure of the rock. It can start deforming rather than breaking. Drill bits become less effective as the rock flows around it rather than getting broken up and pumped away.
Edit: if you haven't watched videos of hydrologic presses destroying things on YouTube, you see something like this in reverse; sometimes things can deform a bit, but eventually explode under pressure. The most surprising to be to watch was a deck of playing cards literally shatter.
I was mostly thinking about the corrosive power of water when it is extremely hot and contains dissolved minerals as this water will. I doubt very much that you could actually reuse the water. Protecting the equipment, disposing the heat, obtaining make up water, and doing something with the brine are major problems.
I'm not saying that it can not be done. It probably can, but I feel that the article was a little naive.
I suppose that I should say something about injecting high pressure water into the earth. At this depth you are interacting with tectonic forces. High pressure water can unlock existing forces resulting in earthquakes in a manner similar to the quakes triggered by fracking.
In summary, there is a cost for everything. There are few, if any, silver bullets capable of solving major problems.
They’re likely referencing something like this [1]. The “fracking earthquakes” have stemmed lazy disposal of well wastewater. Wells can take millions of gallons of water; ideally we’d be treating reusing that water.
"At any one geothermal field, however, the temperature of the geothermal reservoir or the fluid levels/fluid pressure in the reservoir may decrease over time as fluids are produced and energy is extracted. Produced fluids can be re-injected to maintain pressures, although this may further cool down the reservoir if care is not taken. Over time, it is commonly necessary to drill additional wells in order to maintain energy production as temperatures and/or reservoir fluid pressures decline."
"It ain't what you don't know that gets you, it's the things you think you know that just ain't so."
Usually credited to Josh Billings.
It is, e.g., what turned the Iraq invasion into a national disaster. What was wasted on invading Iraq, to no purpose, could have paid, instead, for the entire transition to wind and solar, decades sooner.
Numerous billionaires minted off the fiasco would not now be actively undermining democratic institutions.
I remember when cold fusion was discovered in the 1980s. Everyone was very excited - clean, cheap, unlimited power. The environmentalists were horrified.
It (cold fusion) was complete bollocks as you say.
Actually, if you think back, the hole in the ozone layer was captivating environmentalists and so was acid rain. Remember the photos of Scandinavian forests of fir trees stripped of their leaves? Remember the moratorium and then ban on CFCs (Chloro fluoro err thingies) and how the Arctic was errr fixed?
Our cars used to run on leaded petrol. I can still remember the odd yellow coloured verges of the A303 (UK, SW England). If you were headed west to go on holiday to Devon or Cornwall, you would see quite a few laybys with a stall flogging strawberries. Mmmm mildly lead flavoured!
Yum!
Nowadays we have rather odd weather to deal with and a massively reduced biodiversity.
I also remember nuclear fusion and being told by some chaps at the JET in Oxon that NF is about 25 years away. I also had the joke about NF being 25 years off explained to me in around 1998.
NF is still roughly 25 years away but actually I think it really is, give (or don't bother to take) say 25 years.
The physicists weren't excited. They pointed out that if Pons and Fleischman had been making enough DD fusion to boil water, they'd have been killed by the neutrons.
The internet of the time consisted of NNTP newsgroups. There was a lot of talk about it by a lot of people, and a lot of opinions and claims of expertise. Filtering out what was true wasn't that easy.
I am not a nuclear physicist and nobody I knew at the time was, either, though personally I thought it was one of those too-good-to-be-true things, and sure enough, it was.
My larger point, however, was that there was a lot of pushback from environmentalists who, when faced with a solution to the energy problem, looked for a way to stop it.
