Geothermal System Is A Real Gold Mine

What do you get when Pacific Northwest National Laboratories takes over what was once the largest and deepest gold mine in North America? The answer might be enough energy to power 10,000,000 homes. The enhanced geothermal systems project includes the lab and several partners from academia and industry and aims to test sending fluids down boreholes so the Earth can heat them up. Hot fluids, of course, can easily create electricity.

At 4,100 feet underground, the old mine is not very convenient to get to. However, modern technology means that the equipment is largely automated so workers can carry out experiments from home using a computer or even a phone. The system itself is 7 feet long by 7 feet wide and 30 feet long. It was assembled above ground, tested, and then split into 4×4 sections for transportation deep below the surface.

The work tunnel is airconditioned, although once you go down for your shift at 6:30AM, you don’t get to go back up until 6:30PM so working from home is a definite advantage.

Some researchers on the project hosted a “deep talk” (we see what they did there) recently and you can see the video, below.

Paradoxically, you can get heat from the earth or you can dump heat into the earth. Great way to cool your next gaming rig.

57 thoughts on “Geothermal System Is A Real Gold Mine

        1. I’ve heard quotes from 20-40 years, but that’s just loose memory.

          Interesting question: could you recharge the heat by dumping in excess electricity from elsewhere, and from adjacent solar collectors? Normally you would have terrible round-trip efficiency, but if you ran heat pumps for whatever they’re worth, you can in theory approach unity.

          The ideal coefficient of power for a heat pump is the inverse of the Carnot heat engine efficiency over the same temperature differential. In the non-ideal world, you can take the heat from a field of solar thermal collectors and use electricity to pump that up to however many hundreds of degrees you need, then pipe it down to the earth to store it for later.

          1. Brilliant idea to use the Earth as a “heat battery” so to speak. I share the concern that a planet-wide system could siphon off enough heat to affect Earth’s magnetic field. Your solution here but offset this by quite a large margin. The idea of tapping into the Earth’s core in some way shape or form kind of makes me think of what happened to the Planet Krypton. Lol

      1. Is that you? But actually geothermal is quite localized, however the further you dig down the hotter it gets but for the first 300+ ft it will be cooler in summer and hotter in winter underground

      1. Just to be clear, are you advocating for a nuclear war or other mass casualty event in order to reduce the population so that we need to generate less electricity? This would seem to miss the point…

        1. Hahaha. There’s some evidence pointing at education as good tool to reduce human population. Basically, it refers to people who are more educated having less kids than people who don’t. I would be up for that one, rather than a nuclear war.

  1. The popular-press “enough power for xxx homes”, generally assumes about a kilowatt per home. So “… to power 10,000,000 homes” will produce (it’s inferred) 10 GW of electricity.

    10 GW from horribly inefficient low-grade geothermal heat. You do very well to convert even 10% of that low grade heat input into electricity, so it requires transferring 100 GW of heat to make 10 GW of electricity.

    You can use that heat for (e.g.) district heating or desalination or something, but that’s a LOT of heat to get rid of. Where are you going to dump it? Certainly not a river. This is South Dakota. Dumping this amount of power into even its biggest river, the great Missouri, will raise the river temperature 40 degrees C. Or, in SD, that would be 72 F.

    Dump it into cooling towers? It will evaporate 10 tons of water per second. In terms a resident can relate to, that’s 700 acre-feet per day.

    1. Geo becomes much more efficient when it goes deep enough to produce super high pressure steam. Ideally that’s the way to go if drilling can reach the extreme depths needed in a cost efficient manner. We have endless power below our feet and from the sun. Between the two we don’t need any other sources of energy. Unfortunately currently tech makes both pretty inefficient. Solar panels only convert 21 or 22% of the energy that hits them. Give it a few years and quantum computers will help solve these problems and many more.

      1. Better solar panels do exist – multi layer stacks efficient at different wavelengths so you do get more out of them – but ultimately it doesn’t matter what percentage of the theoretical maximum you get if you can’t afford to deploy them, or as long as you have space to deploy more of them – cover ever building in something like 5% efficent panels and your city is probably entirely self powering – there is just so much surface area.

        (note that isn’t actually a sane idea as making that amount of solar panels to deploy them in sub-optimal locations only makes economic sense if they are very cheap and ‘green’ sense if you are able to build them with very green energy and materials so their time to pay back the creation costs becomes sane – my real point is there is a great deal of surface area to harvest energy from, so a cheap enough panel doing 20% is actually very adequate, just keeps chugging along giving you power for decade after decade with little maintenance – the same is largely true of geothermal and hydro, though they also have a bit of geographic restriction)

        1. > only makes economic sense if they are very cheap

          And installation is done by very cheap labor. Already module prices are less than 40% of total system cost for solar power, so no matter how cheap you make them you will probably never have it less than half the price from today’s.

          1. Most buildings get (re)skinned in some cladding or something eventually anyway – so I didn’t consider the labor as extra cost – its not much changed from normal renovation work costs, and like normal cladding type jobs solar would be put up/modified once every few decades.

          2. It’s still extra work out of specialized labor to install solar panels anywhere. You’ve got the cost of wiring, inverters, potentially batteries, certifications, inspections.

            You also have to account for recurring maintenance cost at around 2-3% installed cost per year.

          3. Fitting solar doesn’t need much specialized labor at all, its pretty trivial as a tasks go, and any serious construction work cladding with insulation foams or solar will have the team of real hard hat type safety inspectors to go along with it – scaffolding specialists etc. Its nothing out of the ordinary there.

            Its not like you are suddenly paying for the university professor salary over normal builder rates for the bulk of the workforce. Its very much the same job to the comparable not solar alternatives I assumed you would be doing as basic maintenance anyway in this fictional scenario – nothing is majorly different to the costs of your basic roof repair etc – same people, doing the same jobs of erecting scaffolds, and working in harness on the rooftops – so if you were to have this fictional everything solar city the costs in labor while substantial are pretty consistent with the labor costs that the cycle of building maintenance dictates today – with perhaps a meaningful extra cost when the ‘window’ cleaners go round – though with how much bigger each job would get the rates would likely go down fairly significantly – the cleaners are not spending half as much time or money in transit and setup between each job, and probably won’t have as much downtime without a job they have to charge for…

          4. People often under-estimate how demanding a job actually is, until they get the “fly-by-night” contractor installing bathroom tiles with crazy glue, and the “friendly neighborhood electrician” who knows just enough about the job to be dangerous. It’s obvious to you what the green and yellow wire is supposed to be doing, but for someone who’s just seen someone else do it, it’s not that simple.

            You can burn your house down with shoddy electrical installations, and solar panels are not an exception as you’re dealing with high voltages and currents coming out of a large array.

          5. When you are dealing with cladding a city tower, housing association suburb etc you have extra qualifications and lots of cost involved no matter what – as its a ‘real’ above board scrutinized job not the brickie putting a garden wall, or cowboy builder a foolish individual homeowner could get in to save a few quid, at least ’till the insurance refuses to pay out…

            The price differential really won’t be meaningful, especially when you realize that its something you do to a building maybe once or twice after its built if that – the cost differential initially isn’t high, and then over the lifespan of the building, even if you assume the building gets zero benefit from the generated electric – frankly a stupid thought, its working out at a few pennies extra per year, take the assumption they get something out of the local power generation and that extra cost, even if it was massive would end up just delaying the point of pure profit a little longer.

          6. It’s worse than that.

            First: Most roofs aren’t built to hold the weight of solar panels.

            Second: Trades are not equal. Some are populated with 100% ‘hard working’* morons (e.g. roofing, painting, flat ‘crete).

            Many plumbers treat electricians as ‘wizards’. Which is crazy, they are still 99% cookbookers.

            If you ask a roofer to do electrical work, you have nobody but yourself to blame when the house burns.

            * they claim ‘hard working’, can’t confirm.
            My proudest moment as a pot grower…A union painter asked for something weaker. Couldn’t do his job on Trainwreck. That’s strong smoke! Modern ‘Trainwreck’ isn’t the same.

      1. You don’t know where ‘acre’ comes from? The “Kings acre” for taxes is 1 furlong along a road or furrow’s length as in plowing a field that can be plowed in one day and is 1/10 furlong wide. A strip of land 40 × 4 rods (660 × 66 feet). IIRC it is how taxes were collected. Furlongs were marked with stones along roads and thus became the measure used in friendly horse racing and eventually a measure of velocity in all physics problems that involve fortnights.

        700 acres-feet is a pond that is about 1600 meters across and looses 1 ft of water a day to evaporation or drain. Is isn’t a huge amount compared to typical irrigation, particularly in rice country like Sacramento, California.

    2. Closed-cycle systems can eliminate waste-water, and reduce damage to the ecosystem. Additionally, multi-stage thermal conversion (while each system has less than 40% efficiency independently) can improve overall conversion efficiency from earth to line.

      Although these systems come at a higher investment and maintenance cost, they offer lower operating costs and ultimately allow for higher productivity of the plant.

      1. Cooling tower water usage is not “waste water”, and you can’t eliminate it (*). The whole purpose is to dump the exhaust heat somewhere. In this case it’s into latent heat of evaporation, saving heating up huge water bodies at the expense of making clouds downwind.

        Multi-stage plants only work when you have huge temperature differences, with each stage tuned to its temperature range, like a gas turbine followed by a steam turbine. It’s not applicable here, with low temperature differentials. Carnot’s law still rules.

        (*) the exception that proves the rule is dry cooling “towers” that save water but require a very high exhaust temperature to operate. Works fine for a coal burner (like ESKOM operates), not usable in geo applications because the low-side temperature is so high. Not even really usable in nuclear plants (though I’m sure there’s an exception somewhere).

      2. “Less than 40%” for a stage is a tall order. You need something around 400 C steam temperatures to even approach that. Practical geothermal systems are more like 10% efficient over a stage.

        1. And with the low temperature differential in geo, you only get that one 10% stage.

          A combined turbine plant will approach 40% in the gas turbine, then recover almost 40% (of the remaining 60%) in a steam turbine. The combination turns about 60% of the input heat into shaft power to the alternators, and that’s about the very best you can do, even with an extremely hot input.
          In a cogen facility, you could use the waste heat for district heating, though at the cost of reducing the steam turbine efficiency and output power.

          1. > 40% in the gas turbine, then recover almost 40% (of the remaining 60%) in a steam turbine.

            Steam turbines are limited by materials to about 625 C steam temperature, and that caps the thermal efficiency at around 42%. In theory you could go up to about 800 C before water starts to break down into oxygen and hydrogen, but it’s just too expensive to make a steam boiler or a turbine that would handle it.

            A combined turbine makes use of the fact that the actual fuel combustion temperature is between 1200-1500 C so you may turn a relatively inefficient Brayton cycle turbine for the first part down to 625 C exhaust temperatures.

            It’s a bit non-intuitive if you’re thinking about stacking heat engines one after the other, but here the steam turbine inlet temperature is more or less fixed by the maximum steam temperature. Even though the steam turbine is second, it gets 42% of the energy out first, and the gas turbine extracts about 37% of the remaining 58% which brings the absolute combined efficiency up to 64% for the best units out there.

            Confusing enough?

            For combined heat and power, you take the heat out from the middle of the two stages, from the steam boiler before the steam turbine, or sometimes from the middle of the steam turbine right before the temperature drops below boiling. It can’t be extracted all the way from the condenser because it would be just 30-40 C and that’s not hot enough.

    3. California and Nevada have a drout problem not enough water and power problem. This would be a solution to their problems. Create distilled water plant and another company that can use heat water as it cools to make their product’s as a cooling grid to return water back to Lake Reservoir minimize what is released in air changing climate. Solutions sometimes needs the right location to make best posable out come.

    4. The heat makes steam, the steam drives a turbine that makes electricity. Then it is recycled again. This is the only renewable energy that works 24 hours per day, 365 days per year. Just because you don’t understand how it works does not mean it is bad.

    5. It’s actually much more feasible and efficient than you’re making it out to be. You’re not limited by the temp of the source water. You’re just pulling BTUs of heat out. I built a geothermal system that pulled enough BTUs out of pond water (+/-50 deg) to heat a 2500 sf house in winter using a very high efficiency water to water heat pump, proven technology, been around for many years.

      1. You think you can up total system efficiency by raising your hot side temp with a heat pump?

        Do heat pumps run for free? Do you think the heat pump will cost more or less to run than the gain in generation efficiency?

        You are suggesting obfuscated perpetual motion.

        We obey the laws of physics on this web site!

    6. > generally assumes about a kilowatt per home

      “Powers a home” has various definitions. At minimum access level, you’re talking about 250-500 kWh a year (IEA). That’s just 29-57 Watts which can be achieved by something like 300-600 Wp of solar panels and a bunch of car batteries on average. It is probably not quite enough to run a fridge, but a room light or two, a cellphone charger and occasionally a television. At this access level, your power consumption is going to be very inefficient because you need converters and inverters, batteries at low DC voltages, which waste much of it.

      If you limit the amount to 1 kW for an entire household of four, you need to go to Mexico, Mongolia, Panama, or Mauritius to get by with that little. On the other end of the spectrum is Iceland with 5.9 kW per person because they just got free geothermal power everywhere. Norway is another spendthrift with 2.9 kW per person because they have ample hydroelectric power and oil.

      The United States is moderate at 1.3 kW per person. Germany is basically half of that, but only because they use natural gas for so many household appliances thanks to the ridiculously expensive electricity surcharges by the “Energiewende” . Hence the geopolitical reliance on Russia.

  2. This facility is a research plant. It will not be producing power for millions of homes. The state it’s in doesn’t have a million people, total.

    People are doing research there with plans to deploy a number of power plants in many different places at around 5 MWe capacity each.

    Presumably the ultimate hope is to be able to build thousands of such plants around the US.

    1. Makes sense. I was misled by the first two sentences in the article which, if read too literally, implies that the gold mine site being studied itself would be the source of ‘energy’ (power) for 10 M homes. The linked article is much more clear about it.

  3. What are the environmental concerns with this? If Fracking is bad, how is injecting water into the sub surface any better? Running pipes and loops, that makes sense, but just pushing water down into the rock will have consequences. This can’t deploy everywhere and if you think the Nimby crowd dislikes windfarms, they’re going to seriously dislike this. One earthquake caused by the geothermal plant and the neighbors will balk at construction of any more units.

    1. I figure using holes already there from oil extraction would mitigate that issue. Lots of transferable skills from the oil industry too. Problem, oil extraction happens far from cities. If I remember right, electricity can only travel 50km(miles?) before the resistance depletes the energy. Charging and transporting batteries?

  4. I just remembered a David Jones / Daedalus piece from New Scientist relevant to this discussion. I was shocked to realize it’s from 1978:

    In the article, Daedalus realizes that the only reason the earth surface is cool is because it radiates away its heat. He proposes to cover a patch of earth surface with some insulation, allowing the heat from the core to warm the crust, eventually to the melting point, at which point you’ll have a convective river of molten core material coming to the surface: An artificial volcano, ready to tap for as much heat as you want.


      1. many, many square kilometers. go read the piece. it’s short and funny.

        Wikipedia says the heat flux through the crust is just ~100 mW/m^2, a tiny, tiny fraction of the solar power falling on the same square meter.

        I have not bothered to do the calculations, but I’m guessing the energy consumption of a typical country exceeds the total geothermal energy flux from below it.

  5. There are numerous geothermal springs where the water a few meters below surface is already boiling. That’s a small power station just waiting to happen. Getting around preservation laws – that will take some time. And then you have to weigh the relative benefits, high maintenance and operational costs of geothermal sourced energy against other methods.

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