[HN Gopher] Deep geothermal energy is poised for a big breakout
___________________________________________________________________
Deep geothermal energy is poised for a big breakout
Author : shubhamjain
Score : 67 points
Date : 2020-10-21 18:02 UTC (4 hours ago)
(HTM) web link (www.vox.com)
(TXT) w3m dump (www.vox.com)
| rfrey wrote:
| For anybody who is interested in this stuff, I was the CTO of a
| Canadian geothermal company, and I became convinced that it was
| folly to dig 4km down to get hot water when we are surrounded by
| waste heat in large industrial plants that is largely untapped.
|
| By way of example, I was working on a geothermal plant in Alberta
| that would generate 5MW and cost $60 million (CDN) to build.
| Similar heat can be found everywhere at surface, especially in
| Alberta which has a heavy industrial base. Harnessing the heat
| from industrial sources is exactly the same as a geothermal
| plant: only the source of heat is different.
|
| For example, I scoped a project on a natural gas pipeline
| compressor station. It used a RB211 gas turbine to drive the
| compressor. Capturing the waste heat from the exhaust stack of
| that engine gave us 7MW of net generation, at a cost of $30
| million, and much lower operating expenses to boot.
|
| 58% of the energy we generate each year is lost, much of it
| (upwards of 20%) as industrial waste heat. That's terajoules of
| electrical generation potential globally, just from the easily
| captured stuff.
|
| It's not exactly like geothermal energy, because you have
| counterparty risk in that the cement factory (or whatever) might
| close. But the tech is identical to geothermal, and there's no
| exploration risk or digging expense.
| JoeAltmaier wrote:
| Sounds like low-hanging fruit. But not really scalable. A 7MW
| plant sounds OK for some applications. But a really big
| geothermal plant might compete with nuclear.
| rfrey wrote:
| It's a good point, but there are many grid experts who argue
| that smaller, distributed generation is more robust and
| reliable than larger, 500MW+ plants. Outside a few areas,
| most geothermal plants are quite small: I doubt we'll ever
| see one over 15MW in Canada, for example.
|
| A 7MW plant doesn't sound like much, but if you're cookie-
| cuttering 9 of them along a line, costs come way down since
| they're all essentially identical. I did some back-of-the-
| envelope calculations and if we did all the larger (over
| 15000hp) natural gas compressor stations in the US and
| Canada, we'd be looking at something like 42TWh per year of
| generation. That compares to 68 TWh for all deployed utility
| solar (2018 tho). That's just gas compressor stations, which
| are about 15% of the industrial heat generated in the US.
| rfrey wrote:
| Responding specifically to the competition with nuclear:
| you're absolutely correct: the Geysers geothermal complex
| (which is actually about 22 power plants) is about 1.6GW.
| That's easily the world's largest though: I don't think
| there's another one over a gigawatt anywhere. And you need
| really special conditions for that kind of power -
| specifically really hot geological conditions.
|
| The problem, as always, is that jerk Carnot and his limit.
| Most accessible geothermal fluid is <150C except in very
| geologically active areas. That puts a pretty hard limit on
| plant efficiency.
| foobarian wrote:
| Thinking about this with a software engineering hat on I am
| breaking out in cold sweat. You attach these waste heat
| generators to random other industrial machinery and now
| suddenly you can't do any maintenance or power cycling for fear
| of disrupting the power supply to whole regions. It also seems
| organizationally very complicated to have co-located hardware
| owned by completely unrelated organizations. I guess if it was
| all nationalized or belonged to one huge multinational it may
| be less of a concern.
| pjc50 wrote:
| 7MW is pretty small. _Any_ generation gear may trip off the
| grid at any moment; provided it doesn 't do so too frequently
| or in sync with other failure, this is not normally a
| problem.
|
| That's roughly the load of an electric train. Eurostar are
| 16MW.
|
| It's also the sort of problem that batteries providing grid
| stability services help a lot with.
| rfrey wrote:
| The engineering miracle of the electrical grid is exactly
| this sort of coordination. Think of this as being like solar
| energy - except it's generating 95% of the time rather than
| 25% of the time. That's considered baseload electrical, and
| although it's not awesome if a 10MW plant drops off the grid,
| the system is capable of handling it.
| whatshisface wrote:
| The factory turning off will cut out its own power
| consumption, which will never be greater than the power
| you're getting back out.
| TeMPOraL wrote:
| > _You attach these waste heat generators to random other
| industrial machinery and now suddenly you can 't do any
| maintenance or power cycling for fear of disrupting the power
| supply to whole regions._
|
| It's not that you can't. But you have to _coordinate_ with
| another party, particularly if you 're generating large
| amounts of energy this way. But the grid is evolving towards
| increased storage to accommodate renewables, so this will
| mitigate the impact of shutting generation down to run
| maintenance on the heat source.
|
| But if we don't want to couple random industrial plants to
| the supply side of the power grid, I wonder if we couldn't be
| using this with some self-contained carbon recapture devices.
| Heat -> power -> less CO2 in the air. If that kind of tech
| will ever be workable, that is.
|
| All this to say, when I put my software engineering hat on,
| I'm starting to get sick thinking of _all that capacity being
| wasted_.
| dundarious wrote:
| I'm ignorant on the topic, but seems more like a great cost-
| & carbon-reduction technology for the industrial plants,
| rather than a power generation technology for the masses. For
| what it is, it sounds great though.
| rfrey wrote:
| It never meets economic hurdle rates for industrials on
| their own, which is why we're building them as independent
| power plants. We _prefer_ to sell the electricity back to
| the host facility, but we often sell into the grid.
| pfdietz wrote:
| Waste heat is one of the markets Climeon is going after.
| They've had success in exploiting waste heat on ships, for
| example.
|
| https://climeon.com/
| rfrey wrote:
| They're a great, innovative company. They're mostly focused
| on smaller stuff - 150kW and below, although I think they did
| some larger bespoke projects earlier.
|
| For larger stuff my favourite company is Exergy
| (www.exergy.it). They resurrected a format of turbine - a
| radial outflow configuration - that lost to axial turbines in
| the early 1900s, recognizing that it had special advantages
| when used with organic fluids rather than steam.
| trhway wrote:
| > It used a RB211 gas turbine to drive the compressor.
| Capturing the waste heat from the exhaust stack of that engine
| gave us 7MW of net generation, at a cost of $30 million, and
| much lower operating expenses to boot.
|
| the main issue here is actually such a low efficiency turbine -
| an efficient one wouldn't have such an easy capturable exhaust
| heat to start with. One can understand that a gas turbine on a
| plane for example has weight limits so you can't tack on
| additional turbine stages, etc. to increase efficiency, yet for
| ground based it would only be about increased capital costs of
| such a turbine - so that means that running inefficient turbine
| is cheaper, i.e. the energy/fuel is still very cheap.
| epistasis wrote:
| I'm surprised that the waste heat is enough to drive a turbine
| and generate electricity! How much waste heat is that hot?
| Combined cycle natural gas turbines already do this. Natural
| gas combustion drives a turbine, then the "waste heat" drives a
| steam cycle. Even though that steam cycle is less than 50%
| efficient, I'm guess the wasted heat there can't be used,
| right?
|
| How high of a COP would it take to make a heat pump a feasible
| way to make lower temperature waste heat a source? Or is this
| where the thermodynamics breaks down?
| floatrock wrote:
| Yeah, it's unclear whether those 5 and 7MW figures quoted are
| electricity production or just heat energy.
|
| Not to imply that "just heat energy" is useless --
| https://en.wikipedia.org/wiki/District_heating is the term
| for using waste industrial heat to heat up homes in the
| surrounding areas. More common in Europe and Canada than the
| US I believe.
|
| Cogeneration is when the concept is used specifically by
| electricity plants. It's used mostly in places that have need
| to generate their own electricity and heating like college
| and hospital campuses -- by harvesting the waste heat for
| another localized purpose, it becomes cheaper than relying
| solely on the grid.
| rfrey wrote:
| A gas turbine has about 25-30MW thermal in the exhaust
| gasses, typical is gas at 480C and 90kg/s. At those
| temperatures we can convert that to electricity at about
| 20% efficiency. We lose about a megawatt in parasitic load
| such as pumps.
| colechristensen wrote:
| You won't be able to take waste heat economically from a
| power plant, they're generally designed to capture more and
| more heat until diminishing returns take over.
|
| There are a lot of other industrial processes though that
| don't do any heat capturing.
|
| Something left out though is that you might have lower
| capital costs but if you try tacking a power plant on
| somebody else's factory, they're going to want a cut.
|
| Efficiency is dictated by temperature differences, you get a
| bigger cut for less investment when the temperature
| difference between heat source and environment is largest.
| brundolf wrote:
| What if you just sold the equipment (+ setup services) to
| the plants directly? They could turn around and reuse the
| recovered energy themselves, or sell it on down the line,
| but there would be no coordination/mixed-incentives
| problem.
| rfrey wrote:
| Yup, we offer about 10% of electricity revenues back to the
| plant in exchange for the heat.
| DoingIsLearning wrote:
| Would this have similar seismic risk as fracking? Applying high
| pressure water injections into bedrock?
| barney54 wrote:
| In some locations there have been concerns about geothermal and
| induced earthquakes.
| http://www.seismo.ethz.ch/en/knowledge/things-to-know/geothe...
| allannienhuis wrote:
| Only some of the geothermal tech requires injection of fluids
| along the lines of Fracking. The article suggests for those
| cases the risks are lower, due to the different pressures and
| fluids required. Other techniques (closed-loop systems) don't
| require it at all (but do require advanced drilling tech).
| X6S1x6Okd1st wrote:
| I'm surprised that we're already generating almost half as much
| energy as all the decay energy in the core.
|
| It did not take long for the human race to start being a major
| force on the planet after we started agriculture.
| pfdietz wrote:
| It's not clear there's much decay energy in the core. That
| would depend on whether uranium, thorium, or potassium would
| dissolve in high pressure liquid iron-nickel.
|
| Uranium and thorium are highly concentrated in the Earth's
| crust, btw, relative to the rest of the Earth.
| mrfusion wrote:
| With the advances the boring company is making I wonder if we
| could just point one straight down (or at an angle) and cheaply
| make geothermal.
| yxhuvud wrote:
| I suggest you read the article.
| ginko wrote:
| If you would use the heat from earth's core to run power plants,
| presumably by leading in water and running a steam turbine,
| wouldn't that eventually heat up the atmosphere since you pump
| out the heat in the core faster than it would naturally?
| dmitriy_ko wrote:
| No. There's always heat coming to earth and radiating back to
| space. Amount of greenhouse gases in the atmosphere determine
| equilibrium temperature. Adding heat doesn't change equilibrium
| temperature.
| trophycase wrote:
| No offense but I have a hard time believing this. Isn't
| pumping heat from the center of the earth to the atmosphere
| more or less the same as having a larger amount of incoming
| solar energy? And certainly it would be hard to argue that
| more energy from the sun wouldn't heat the planet. Wouldn't
| the equilibrium temperature be both a function of energy in
| and radiation rate (which is also a function of temperature?)
| CorrectHorseBat wrote:
| No
|
| > Wouldn't the equilibrium temperature be both a function
| of energy in and radiation rate (which is also a function
| of temperature?)
|
| Exactly, and since we're not changing the energy in (that
| energy is going to reach us whether we pump it up or not),
| and thus the equilibrium does not change.
|
| Where else can all that generated energy go other than up?
| rwcarlsen wrote:
| But it would otherwise go "up" at a slower rate - so heat
| adding more slowly but over longer. Pumping heat up is
| effectively compressing this time horizon - resulting in
| a difference in rate of heat added. Now if that
| geothermal energy was replacing nuclear or fossil fuel
| use, then it might be a wash. But as soon as that energy
| replaces hydro, wind, or solar (which don't add new heat
| to the atmosphere - just use heat already there) - then
| we would increase the rate of heat energy being added to
| the atmosphere.
| simonh wrote:
| It's no different than generating heat in the surface
| environment any other way, such as in a nuclear reactor or by
| burning coal or gass.
|
| Waste heat radiates into space fairly readily, especially at
| night, so at the rate we currently use energy it's not a
| significant factor compared to the incredible amount of heat
| that radiates down on us from the sun.
| snowwrestler wrote:
| Heat flux from inside the Earth is limited by the surface area
| of the Earth. Adding a geothermal plant essentially increases
| the available surface area, which would increase the flux.
|
| However, it would be a very small increase to a very small
| source of heat. Underground heat in total is only about 0.03%
| of total energy budget at the surface.
| mrfusion wrote:
| I believe it would be small potato's compared to the daily
| solar insolation the earth receives.
| mensetmanusman wrote:
| This is covering deep geothermal, trying to get into the huge
| heat source from radioactive decay in the earth's core.
|
| This is not covering back-yard geothermal for home
| cooling/heating.
|
| I had no idea such a small amount of the earth's heat could be
| harvested to satisfy all of humanity's energy need (assuming
| humanity doesn't start doing stupid things when we have access to
| unlimited energy...)
| dang wrote:
| Ok, we've deepened the title above.
| rfrey wrote:
| In industry we usually refer to "geothermal" as heat from
| radioactive decay, and "geoexchange" from the backyard stuff,
| where the source is solar heating.
|
| You're not wrong, that just seems to be the way we get around
| constant disambiguation. I was the CTO for a Canadian
| geothermal company.
| cwal37 wrote:
| We also just called it ground source when I briefly worked in
| the field. Although, in my experience, even though someone
| shells out $$$ for a "ground source heat pump" in their yard,
| it won't stop them from telling everyone they have
| geothermal.
| ggm wrote:
| I want to believe in GeoThermal. A recent experiment in Australia
| went bad, this really saddened me because the underlying model
| clearly works (Iceland, NZ) but something about the combination
| of drill, frack, extract and process to energy just didn't work
| out, nor did the post experiment remediation (IIRC)
|
| I also believe, that we actually deplete both deep heat, and deep
| coolth. Deep heat, you have to keep expanding the deep heat
| extraction zone or create pumped states in a wider area somehow,
| Coolth: London underground was lovely and airconditioner cool, it
| now has 100+ years of soaked in heat and is significantly hotter
| than it used to be.
| AtlasBarfed wrote:
| Well, assuming we can drill very deep, I would think the
| supervolcano calderas have massive amounts of energy that we
| could exploit and ... possibly ... avoid future extinction-level-
| event eruptions.
|
| I also wonder how deep would be sufficient to "dump" nuclear
| waste. I would think once you get to a sufficiently viscous
| level, heavy-element nuclear waste would slowly descend into the
| core.
|
| What could go wrong?
| allannienhuis wrote:
| I expect the amount of heat one could extract would be
| absolutely negligible compared the the amount of heat in a
| supervolcano caldera, so I doubt there would be any affect at
| all.
| Valgrim wrote:
| If I read the article correctly, Geothermal energy extraction
| involve pumping cold water in and hot water out. If I wanted to
| put nuclear waste somewhere underground, it would probably be
| very far away from the place I pump water from.
| eppp wrote:
| Would probably be ok to just use for heat transfer.
| jws wrote:
| People have pondered cooling Yellowstone's magma chamber by
| surrounding it with geothermal wells.+ The result would be 5GW
| (for comparison that is 1/6th of California's needs) of clean
| energy at about $0.10/kWH for thousands of years and a
| significantly reduced chance of a supervolcano eruption event
| killing millions of people.
|
| It might alter or stop the geysers though, so it isn't going to
| go anywhere.
|
| [+] https://www.bbc.com/future/article/20170817-nasas-
| ambitious-...
| AnimalMuppet wrote:
| Why do volcanoes erupt? Because pressure builds up that is
| stronger than a weak/thin spot in the crust can take. If we
| drill a hole then the strength of the crust at the hole is...
| zero. Doing that in the neighborhood of a supervolcano might
| not be wise...
| rfrey wrote:
| Geothermal has a problem in that the capital to build a plant is
| much higher (2-3x) that of a combined cycle natural gas power
| plant. Even though the fuel is free, in order to make the
| economics work you have to project power prices out 50 years.
| Usually when we scope power plants the proformas only go out 15
| years.
|
| And by "make the economics work" I'm not talking about excessive
| returns. I'm talking about a <10% rate of return, getting the
| investment back in 10-14 years.
___________________________________________________________________
(page generated 2020-10-21 23:00 UTC)