AltaRock Energy Melts Rock with Millimeter Waves for Geothermal Wells (2020) | Hacker News Reader

AltaRock Energy Melts Rock with Millimeter Waves for Geothermal Wells (2020)

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68 pointsrfreytag43 comments

As an RF engineer, this is a very creative application of mmW and I hope can be successful, but is not without very significant challenges which the company has made no claims to have solved. The issue is, mm-waves (and all high frequency RF really) are very sensitive to distance and losses. As a random example [1] gives some numbers for theoretical and precision machined waveguides in these frequencies. In the very best case we're talking about 0.03dB/cm loss. That means in the first meter of ideal waveguide you've lost half the power! And not just disappeared, you just dumped 0.5MW into the pipe itself, meaning it would likely melt within minutes. Meanwhile, their concept is to bore 20km into the earth.

The only way I could imagine this working is to lower the gyrotron itself down the borehole, but there's presumably tradeoffs of physical dimensions and output power that make it challenging. Again maybe not impossible, but there's no indication they've made fundamental advances in miniaturizing the source, or producing lossless waveguide.

Related, another interesting company I came across is Petra [2], who is doing something similar -- plasma/heat based non-contact drilling. But because they fracture the rock instead of vaporizing it, there's essentially gravel/sand leftover which is hard to evacuate from a deep vertical shaft, hence their focus on power/fiber trenches not geothermal.

[1] https://www.nrao.edu/meetings/isstt/papers/2012/2012151153.p...

[2] https://petra.cc/

For distance transmission at these frequencies, quasi optical systems are usually used. As you rightly point out, TE10 mode waveguide would be completely impractical.

See here for a good explanation of quasi optical transmission: https://www.bridge12.com/learn/what-are-quasi-optics/

I'm thinking about the opportunity cost and the longevity of a solid-state rock, exo-"microwave oven" vs. drill bits.

How is it going to displace molten rock after it is softened?

And, if it's too hot for drill bits, how is it any better for electronics, power conducting cables, and cooling apparatus?

It seems like hammer technology in search of nails like flying cars and battleship rail guns.

One thing I do know is conventional microwaves heat the bejesus out of the edges of silicon dioxide objects like glass containers and ceramic bowls far sooner and better than they do food. Perhaps they have a dipole moment similar enough to water that it's unavoidable and typically enclose tasty vittles from spilling and sloshing all over.

> But because they fracture the rock instead of vaporizing it, there's essentially gravel/sand leftover which is hard to evacuate from a deep vertical shaft, hence their focus on power/fiber trenches not geothermal.

Getting cuttings out of the borehole is a solved problem with present drilling technics used in the Oil & Gas industry or geothermal. The drilling fluidsbrings them back. One needs the drilling fluids (mud) to avoid the well to collapse, I guess Petra is staying clear of deep borehole drilling because they can't operate their technology with drilling mud present. Also the deeper you go, the smaller the hole and they may face miniaturizion issues too.

It seems pants on head crazy that a mere 20 feet or so below the ground it's a livable and pretty comfortable temperature year round, virtually worldwide. And yet we spend an enormous amount of money, time and energy heating and then cooling our living spaces by almost any other means possible. Yes, the occasional home has geothermal, but the fact that it's still the exception baffles me. Heck, if you have a well or even city water then you are already piping 55-degree fluid into your living space and a lot of the complicated work is already done.

I get that there are some tough engineering challenges involved, but as a species we don't seem all that interested in solving them relative to the effort we've put into many other endeavors.

I’d support some directed project to figuring out how to do geothermal at scale and most efficiently/effectively. Call it long term infrastructure investment.

My partner has an idea on how to conduct this process using our form of cheap energy. please send us you address at email morphle at ziggo dot nl

When you can just burn coal/gas/oil to heat and cool your house and say 'la la la' loud enough to not hear the environment dying around you, it really is the best option.

Emissions costs are a solution to that. Sadly, some countries are not part of these agreements.

> Yes, the occasional home has geothermal

The use of the word geothermal like that feels like a silly marketing thing to me. The "geothermal" you are referring to here, is just a ground source heat pump. A ground source heat pump is drawing heat from the ground, exploiting the huge (but not unlimited) thermal mass of the soil. That thermal mass is the same reason it has a stable temperature year round.

Ground source heat pumps do not use geothermal energy, i.e. the 25–30 °C/km heat gradient of the Earth. AltaRock is actually trying to use geothermal energy. These are two very different concepts, so we should avoid conflating them, and use different words to refer to them.

I agree the term is technically incorrect but it's still used as such in the building/architecture industry AFAIK.

It's possible for an entire industry to engage in fraud. We need not assist though.

As a guy with poor understanding of construction techniques I sure as hell agree. Looked into it for my farm. I can’t build much underground due to a very high water table.

I'd say the overwhelming population of the earth does not want to live underground like a worm. The first level down might be OK for some if they still had access to natural sunlight, but everyone further down, especially to the depths that we would need to move tower blocks underground, would have a miserable existence.

We don't need to put the living space underground in order to leverage the thermal mass for heating or cooling.

That's easy to say, but nobody is stoping you or anyone else that thinks that way from building yourselves a home deep underground. There's no real engineering challenge, we know how to dig very big, very deep pits, the problem is the costs are astronomical relative to conventional housing. Not to mention the huge energy cost and thus carbon footprint of that kind of construction.

It's conceivable those costs might be reduced, maybe the Boring Company will find a solution, but the fact is it involves moving an awful lot of very heavy material.

Leveraging thermal energy != living underground, there are lots of ways to exchange the thermal energy without needing to dig a living space, etc.

https://dandelionenergy.com/ is one company trying to scale this.

In general, Americans don't want to pay a huge cost upfront for some efficiency gains. Especially since traditionally fossil energy was cheap.

Also look at heat pump clothes dryers. They're a win in that you don't need a vent (and associated vent cleaning), but they cost more upfront.

Hopefully these are areas where the government can provide low interest rate loans upfront, since they are investments that pay for themselves over time.

> Also look at heat pump clothes dryers

I live in a country that loves heatpumps, just about every home has one, but heat pump dryers have a bad rep. While they are energy efficient they are very slow to dry clothes, about 2 hours longer than a resistance electric dryer for a small-medium load (1.5 hours vs 3.5 hours).

>>Also look at heat pump clothes dryers. They're a win in that you don't need a vent (and associated vent cleaning), but they cost more upfront.

They don't really work at low ambient temperatures, so as someone who can only have a dryer in an unheated garage, that's not an option sadly.

I was 14 and living in Cleveland, Ohio in 1973. My dad had our house converted from oil heat to a ground source heat pump, with resistance heat backup.

Our water well was 220’ deep.

It seemed to work fine.

Things leak. It sounds like it should be easy to fix, but it really isn't. Not at scale, for a competitive price.

There was a fad to build homes into the sides of hills. It turns out if you want to do this, you have to do a significant amount of engineering and work if you don't want to have all your furnishings, electronics, books, and clothes to be ruined. I'm sure people will have examples where it has worked, but there are at least as many where it has not worked.

Similar for ground loop heat exchangers. It seems like it should be cheap and easy to put a pipe down and tap into that thermal mass, but it's just not cost competitive. It's not even a matter of externalities really - you can get better results by building with better insulation and more efficient heat pumps for the added cost.

Things like this can work if it's a community investment, but that's challenging to coordinate. It sounds like it shouldn't be, but it is.

Not really true. My house is built into the side of a hill. We just bulldozed and dug and put good drainage around the foundation, inside and out.

Pretty even temperature year-round. The floors are never, ever cold. HVAC costs around $90/month and it gets from -30 to 104 around here.

Never had one tiny ounce of water problems, not in 30 years.

I'm curious if you were involved with the construction/original owner. Do you know how many layers of moisture protection were added?

I am the original owner.

There was tar put around all parts of the cement walls underground. Then gravel and sand, then dirt.

Drainage was put around the base outside the wall, and underneath the floor. It ran out the front of the hill, 10 yards from the house. It's never significantly flowed.

There's a 4" structural foam (the blue stuff) pad under the poured cement floor, nominally to insulate the floor but some moisture protection too I imagine.

Under that, sand then gravel, a couple feet worth total.

That's what I remember.

Thanks for the follow up. It sounds like you built in the 90s? The houses I was talking about were in the 60s-80s.

I think it's possible to build houses like yours, and I think it's possible for them to be economically feasible at scale, but it takes more early investment and competence, and that extra X% is hard for people to justify.

I think about how people will look for a feature list because quality is hard to determine.

90's

It ran out the front of the hill, 10 yards from the house.

This is key. Your house is not "a mere 20 feet below the ground" as thread parent suggested, it's in the side of a hill. This works fine if done correctly, and lots of builders have the experience to do that. It would be difficult to find anyone experienced at the construction of living spaces below 20 feet of soil. Those who do so as amateurs, like that criminal Beckwitt, generally have poor results.

tbh i don't know if anything could replace having windows for me. i have felt measurable changes in my mental state from living in places with few small windows and places with lots of large ones.

(i have also lived in places like houston where "some engineering challenges" become pretty absurdly difficult)

What do you mean? 10 degrees C is pretty comfortable?

True, but the same could be said for decently designed and built houses customized for the environment it's in. Go down the average residential street nearly anywhere in the USA and you are likely to see the same designs for homes built in the same decade despite a huge range in weather/temps.

Sad thing it's not particularly hard to make a radically more efficient home. One that will pay off many times over during the life of the house. However it costs the builder more, and saves money for the buyer. That disconnect means houses are built as cheap as zoning allows.

I've seen houses designed for below freezing weather that can be heated with 100 watts! The tricks weren't particularly expensive. Great insulation (of course), which of course can cause stale air and even unhealthy air. But then they engineered in the healthy amount of air from outside, but then had a energy recovery system where the exhausted air would heat/cool the incoming air so you could get a high flow with minimal energy losses. It's getting to the point where resistive heat, the crudest of heaters, is used despite being 3-4x less efficient than a heat pump. But the house is so efficient that the electricity used is minimal.

So no need to move 100 tons of rock, worry about leaks, safety issues, put up with worse windows/lighting, and where to put the 100 tons of rock, etc. Just use more insulation and a bit of smarts on energy efficient air handling.

mmWave geothermal is exciting because it can in theory allow for geothermal baseload power anywhere, not just places that have near surface volcanic heat like Iceland.

Big questions remain about it's technical and economic viability though.

So far I think they have only demonstrated melting a hole through a couple meters of rock, and as with all such things, the levelized cost is what matters in the end.

AltaRock has gone a bit quiet, but the technology is still progressing at pace. Here is a more recent article about Quaise (a spinoff from AltaRock).

They’re still in lab testing, but they’re having promising results and aim to start field testing next year.

https://news.mit.edu/2022/quaise-energy-geothermal-0628

"Project partners say they hope to start drilling in real-world test sites before the grant period ends in September 2022."

OK, what happened?

This is a more recent article (8/22) about this company and it’s affiliate

https://www.newscientist.com/article/mg25533992-500-millimet...

Could this be used for tunneling too?

Boring is in a different vertical.

how much can you do in 7 years? 2016 = https://www.youtube.com/watch?v=9qaOIyb2TWE

"AltaRock estimates that just 0.1 percent of the planet's heat content could supply humanity's total energy needs for 2 million years."

Ummm.. What?

one secret the fossil fuel companies don't want you to know!

There's a lot of heat down there, and more is continually being generated through radioactive decay and tidal forces.

I'm curious about the average radioscopic output of the entire Earth vs. the moon slowing the Earth down (several 10^12 W). I guess we would need temperature data at deeper depths than we have available.

Is this depleting heat away from the core or is this (more of) a rounding error in the core nuclear reaction to radiation process?

Reply on news.ycombinator.com