This is an updated version of the solar thermal (Stirling) vs solar cells video. The conclusions have not changed but a commenter pointed out that I didn't use the correct power density for the MHD generator estimate. The 500 watts per kilogram figure in that paper wasn't for just the MHD, it was for the entire system, mirrors and radiators included. The real power density is 600w/kg or 1,666 kg for 1 megawatt which puts the crossover at about 5% so this video has been updated to reflect that. I know it's a small difference but I can't sleep at night knowing I published bad info or misrepresented someone's work. I also decided to fold the power transmission cable video into this one after publishing it as a stand alone it didn't sit right... it definitely belongs here with the other energy-friends :)
So I've watched both the Stirling video and the Solar video. First of all, I want to say you've done a fantastic job making these tables, and compiling a very in depth overview. It's people like you that truly push scientific discourse. I do want to make a small note that while mass is in fact a decent approximation for energy expenditure, producing thin pieces of glass from Silica to deposit A-Si film onto and producing thin foil of aluminim does have a difference. Glass has a "melting" point around 1700C (it is amorphous), compared to the melting point of aluminum around 660C. While glass has a better specific heat of 750J/kgK vs aluminum's 890J/kgK, the difference in melt temp results in 1.27MJ vs 590kJ, a 2X expenditure in energy just to reach melting point. While aluminum does need an extra 400kj/kg to fully melt, and glass is pretty much ready to work once in it's glass transition phase, the aluminum is still saving 20% ish in terms of energy. Note that raw aluminum is not available on the moon, and we will need to expend energy to convert alumina, with it's high melting temperature of around 2200C to aluminum. However, if we compare this to silicon, it has a heat of fusion of 1093kJ/kg vs silicon's 1787kj/kg. While I agree with you that prices on earth are highly dependent on the whims of the average consumer, and my work boots cost less than a pair of Air Jordans, there's something to be said about aluminum foil costing $11 for 200sqft while solar panels run around $186 for merely 20sqft. Rolling something between a pair of wheels is in fact simpler and more consistent than delicately spraying glass in silane, even if the vacuum pump for the vacuum chamber is free. An interesting thought could be to combine the faster and less energy intensive production of using aluminum foil with photovoltaics. While yes, solar panels do lose performance at elevated temperatures, they also increase efficiency with higher light intensity, so there's probably a decent tradeoff point where it may be advantageous, perhaps around 20x to 30x concentration. I also want to draw note that instead of extracting the power during the lunar day, a Stirling engine may be best used during the lunar night, where the additional 250 Kelvinish difference in temperature will substantially improve Carnot efficiency. Perhaps instead of looking at this as an exercise in power output, we look at this in terms of a total energy expenditure. Is it more energy efficient to build solar panels and banks of batteries? Or perhaps it may be more efficient to use PV panels to power our 360hr lunar work day and then use thermal batteries and a Stirling engine on our night off? Is manufacturing a battery at around $0.20 per kWh of storage LCOS on earth the same as around the predicted $0.07 per kWh LCOS for cooking some sand? Does this translate to a lunar economy. Is the cost of shoveling some lunar regolith into a mountain and heating it up using mirrors cheaper than building a battery factory? Is charging a battery at 16% efficiency as nice as using a less area and maybe pushing 70% carnot efficiency for a two week long lunar night? In terms of loss of surface area of solar panels is it worth it? These are all fascinating questions.
Note that we could use a combination of systems as well. Batteries do offer a longer term storage solution that is not susceptible to radiative losses, but again, we are charging them with 16% ish PV system, compared to taking a perhaps 40% loss on the back end. Note also that humans do need thermal control, so this may be a decent idea for lunar night time ECLSS
@@feraldegenerate1743 Good points, though one of the most power intensive aspects of aluminum refining isn't just melting its ore, its the electrolysis necessary to break the really stable Aluminum oxygen bonds. Aluminum refining takes a pretty obscene amount of electricity, the main reason for aluminums cheap price is its ore's abundance and the cheap price of electricity now. The process takes a theoretical minimum of 22.428 Mj/kg, though in practice its more like 55.332 Mj/kg.
Thanks for reuploading, but I do feel the need to point out that the 600 watt/kg figure is still the total system power density. The authors don't make that very clear, but whenever they are talking about the power density in general and not specifying a component, they are talking about the power density of the whole system, radiators and mirrors included. To get the power density of just the electrical generating parts, you need to look at the masses of the different components they listed in the paragraph right above the one you quoted at 27:34 "From the above estimations at optimal specific power, mass of the compressor stages together with the electric engine is 300 kg, and mass of the pipe heat exchanger is 500 kg. Mass of the MHD generator together with the superconducting magnetic system may be estimated as 400 kg for the electric power level of 10 MW. Mass of the mirrors and the vortical chambers determined by power consumed by them of 30 MW will constitute 1800 and 3000 kg." The mass of all those components minus the mirrors is 4200 kg, and the system is accepting 30 MW of thermal power as input and since it is 31% efficient it is outputting around 10MW of electricity and 20 MW of waste heat. That's an electrical power density of 10MW/4200 kg, aka 2380 watts per kilogram, or 420 kg for 1 Megawatt.
You started this presentation with a statement that you don't need to run your machines all the time, and then went on to design your system based on an assumption that you need to radiate when the sun is up, so you can't get below 121 C. In practice, you have much a much cooler reservoir, either 4 meters below the surface (-20 C) or 14 days away in time (-183 C). In the same vein, you could heat up and store your hot fluid so you could generate power even when the sun goes down.
This is a great point. I've been toying around with similar ideas for home heat pump setups to take advantage of day-night temperature differences here on earth. I don't know if you'd have a buried reservoir or a surface one. Conductive ground losses vs radiative surface losses is something I've not run the numbers on yet. But I imagine that buried would be better because it's more constant, and any conductive losses would be minimized compared to a surface reservoir given the lower difference in Temperature between whatever fluid at 100-200°C and -20°C compared to the night time surface of -180°C which can mostly be alleviated by using a butt ton of insulation if I had to guess.
@@Nomenius1 On earth, it is much more challenging to benefit from day-night differences because of the atmosphere. Also, with good engineering it should be possible to do much better with day time radiation than the base design used by Anthrofuturism, as pointed out by several commenters.
14:07 Yikes. I imagine you're not doing your math in Celsius directly, but having a graphic that shows 200C° being twice the temp of 100C° is a bit of a red flag. Those kinds of equations only work in Kelvin.
This video reminded me that solar photovoltaic cells don't completely ignore the temperature of their environment. They do lose efficiency as they get hotter. In the 120 degree Celsius environment of the moon, PV cells will be only half as efficient as the same cells at room temperature(which is what they are rated for.)
That's why my votes for nuclear, whether it's fission or RTGs. Nuclear RTGs can have a half life of 90 years, they never shut down, you can bury them and they still work.. A 300 watt electric output RTG outputs 4kw of thermal which is useful for a habitat and hey you could even use the thermal output as your hot side for a Stirling engine, either converting that heat directly into rotational energy for powering mechanical devices or having the Stirling engine spin a generator setup. They'll run nonstop for those full 90 years without a hiccup (maybe not the stirling engines but that can be improved)
Thanks for reuploading, really glad your willing to go back and fix stuff. On that point though, I do still see a few mistakes in this one. Biggest one is probably the part where you say MHD's don't need thermal gradients to work. MHD's are still ultimately heat engines subject to the same thermodynamic laws that a Stirling engine or turbine is, which is that they are taking heat and converting it to electricity. Like, the reason *why* heat engines get more efficient from larger thermal gradients is because the more heat energy you extract from your input to convert into electricity, the colder your output is going to be, because it has less thermal energy now. MHD's still work on that principle, you can't have an MHD that takes in plasma at 1 temp and pressure and outputs plasma at the same temp and pressure, not just because of risk of the MHD melting, but because that would mean there is no change in the energy of the plasma, so the MHD didn't extract any energy from it. The reason why MHD's make radiators so much easier is not because they don't care about output temp, its just that its way easier to give them a useful thermal gradient even with high output temps, because the input temp can be so high. You can raise the output temp a lot, and rather than having to accept lower efficiency, you can just increase the input temp to compensate. Though in the case of solar thermal concentrators there is an upper limit to how hot you can make the input temp, which is that a solar concentrator can't ever get something hotter than the surface of the sun, but that's a pretty generous upper limit. The second mistake is the 600 watt per kg figure in that paper is again, the power density of the whole system. I get why that keeps happening because these papers do not do a good job of making that clear, though a hint is that the authors said that the 600 watt/kg power density figure happens when the radiator temp is 350K, and the main reason they would specify that is cause the radiator mass was being included. To get the mass of just the power converting stuff, if you look at the screen shot at 27:34 where you highlighted the 600 watt/kg figure, you can see a breakdown of the mass of each component in the paragraph right above. "From the above estimations at optimal specific power, mass of the compressor stages together with the electric engine is 300 kg, and mass of the pipe heat exchanger is 500 kg. Mass of the MHD generator together with the superconducting magnetic system may be estimated as 400 kg for the electric power level of 10 MW. Mass of the mirrors and the vortical chambers determined by power consumed by them of 30 MW will constitute 1800 and 3000 kg." The mass of all those components minus the mirrors is 4200 kg, and the system is accepting 30 MW of thermal power as input and outputting 20MW of heat and 10MW of electricity. That's an electrical power density of 10MW/4200 kg, aka 2380 watts per kilogram, not 600. If you want a more conservative figure, the MHD from the paper you mentioned last video, "Multi-MW Closed Cycle MHD Nuclear Space Power Via Nonequilibrium He/Xe Working Plasma ", it's overall power density was 333 watts per kilogram, but over half of that mass was radiator and nuclear reactor. Once you removed those, the power density of the MHD and supporting gubbins was 808 watts per kilogram. That paper had a nice pie chart of the different masses of the components on page 6. Though that might not be as useful an example, because it was using a lower temp heat source than a solar concentrator would, cause it was limited by the meltdown temp of the nuclear reactor, so its performance was lower. 900-1000 watts per kilogram might be a good lower bound at the higher temps you're dealing with.
Fun fact, the Amazon facility i deliver from has a fleet of approximately 325 rivian electric delivery vans by my count, when all charging at night consuming just over 9,000 watts each, we alone are drawing 3 megawatts
I'm at 7:30 min into the video so this comment might be answered later but isn't nighttime the only "cold side" you need for a heat engine. Like just store heat in the day and release at night.
yeah i feel like he gave the heat engine its worst shot by assuming it needs to radiate all energy away continuously, above ground, during the day you could optimise this radiator much more efficiently by a) conducting the heat out through lunar regolith and b) having a large enough thermal mass that it doesn't saturate in a day and radiates through the night
You cannot really store heat until the cold gets there, but you *can* do the reverse, freezing material during the night and then using the latent heat of fusion to keep your radiator cold
Question: At around 34:20 you mention burying transmission lines in the regolith not only for insulation but also for cooling. Wouldn’t this also work for cooling in a solar thermal energy system? Use the Moon itself as the heat sink, similar to geothermal systems here on Earth? How would this affect the calculations for energy density and total mass requirements?
the problem there is, rock can hold onto a lot of heat, and itll move slowly away from the source, you can on really do this once and then you have to wait however long it takes the heat to move
I saw an article posted Dec 9, 2021 called "Analysis of radial-outflow turbine design for supercritical CO2 and comparison to radial-inflow turbines" which claimed that these turbines could achieve isentropic (idealized) efficiencies ranging from 85% to over 90%. The turbines are smaller and easier to design then the axial-flow turbines. You mentioned that in practice, typical efficiencies range from 50% to 70% of the idealized efficiencies. Then consider another 5% loss due to the generator so the range would be 42.5% to 63% less another 5% for generator losses leaving 40.38% to over 59.85%. The article did not mention these real-world adjustments, so good to know. Thank you.
Why are we assuming heat needs to be radiated? Could you not just stick the radiator underground and conduct your heat out into the regolith? This would also improve your cold end temps as the subsurface temperature of the moon is -20 degrees. Assuming a surface radiator seems like a major oversight.
Your radiator discussion is missing the idea that by shielding the radiator from the surface and sun, the radiation sees only the sky, at a temp of a few K. Shielding from the sun means putting the radiator in a shadow. Shielding from the surface means placing a reflector below and around the radiator. In fact, if you point a parabolic solar thermal system at empty space, it generates cold. But the difference is that the sun is point source and needs a focus, while space needs no focus, just shielding.
That can work near the poles, but at the equator you don't have much options. Assuming you want to put down square kilometers of power generation. Your just radiating into the radiator next to you. The radiator is basically sandwiched between the moons surface and the radiation of the sun. But, like someone else already commented, you can dump heat into the ground and radiate that away at night.
Assuming the radiators are a plane, then only the edges 'see' each other, which is very little thermal effect. Imagine placing reflective foil between the radiator and any warm surface, basically a layer of foil acres in extent under the acres of radiators. Then arrange a shadow for the sun. Maybe put panels up facing all directions and point some at the sun and some at the cold sky, switching plumbing
12:46 Maybe we can shield not only from the sun, but also from the surface of the moon. Depending on the latitude of the location, we will have a sector of space where the sun never shines. Probably about 5-10 degrees above the horizon in the direction of the pole. The open end of the shield-tube can be directed into that sector so that the heat is radiated into outer space. The other end of the tube is a heat radiator. The shape of the tube allows it to be shielded from radiation from the side of the tube. If you install a tracking system, you can radiate heat to any point in space and avoid the sun. About the problem that the insulator itself will heat up from the ground, hmm ... On a lunar night, you can cover the entire surface around the emitters with sun protection refractive foil in several meters around and wait until the regolith cools completely. The lower temperature limit will be the temperature of the lunar rock massif close to 250K (-23 °C). Maybe it will even be possible to cool the soil massif even lower by installing more of these cooling emitters. Result: -heating from above from the sun is cut off by a tubular reflector, as well as heating from the sides; -heating from below is limited by a temperature of -23°C. The tubes can be made of aluminum foil, connected in a hexagonal shape using the same technology as cardboard. Costs: a lot of foil for the tubes, a lot of foil to cover the soil around, a more complex installation of the emitter, since it will stand more vertically to allow it to be directed at an angle of ~5° to the horizon. Cons: since the sector to which the heat is radiated is now limited, the total capacity of the cooler will decrease. To compensate for this, the number of emitters needs to be increased even more. I think 2-3 times, since we have limited the sector of space to which the heat is radiated by this many times. And then the question is, do we need a system that reaches -20°C, but is ten times larger and more complex than a system with 120°C?
11:37 Yes you are limited by the ambient heat but you have easy access to deep space. A radiator is limited by the ambient heat on earth because of air and water vapor carrying heat around, but the moon's surface is at a pretty good vacuum, and with insulation from ambient heat you will loose heat more like in deep space. You can use a thermal battery cooled at night, or an insulated structure simulating a polar crater. You can easily calculate how much heat you can possibly absorb with your collection area and design an appropriate battery. Specialized sterling engines can run off of that when it needs to dump the heat into space, or you could have a hotter running battery for that, and a colder battery to keep things consistent for the "normal" generators. You might be limited by space, and you might need more reflective materials for the cooling bowl/tower, it can add complexity, and its not going to keep all the ambient heat out, but its closer to being cooled in deep space than anything else could be and it raises your maximum efficiency. The radiator can also increase the efficiency of solar cells if you use it to cool them. A thermal battery might also be the best way to store energy over time because you gain efficiency by not converting the heat into electrons which need batteries that need to be kept happy, but here you just need thermostats, reflectors, pipes, pumps, insulation, and Nak or gallium, and with thermophotovoltaic cells.
So a question about heating. Do we know the ambient temperature underground on the Moon? Moreover how would the calculus change if we built it on the south (eternally day) pole.
Aluminium doesnt resct with NaK: NaK has average free electron density of 1.5 per atom, same as elemental Na. Bothsodium and aluminium are reducing agents as the energy required for both to get rid of a valence electron is very low (converselyvery high to accept an electron), to gain an electron and thus react, one would need to be a relative oxidizing agent aka one must be a much stronger reducing agent than the other to the point that it overcomes the weak atomic force neccessary to rip off an electron, this is not the case with Al-NaK as the energy given to accept an electron is higher than the energy required to rip off that electron. Under extremely high temperatures this may differ.
Hello, I enjoyed your theorizing. Though, I havent heard anyone talk about solar mirrors ORBITING THE MOON, directing concentrated light beams onto the surface. Those structures could be larger than anything on the surface and be held together with less material, such as thin reflective films held tight by rotational forces and cables, rather than on a ground based mounting platform. It would also keep the reflectors free from dust. And it could supply sunlight to the surface during night. You would then need fewer heat engines on the actual surface because its no longer as spread out.
Not sure how well that would work, as orbit decay might cause serious problems. (I think I heard somewhere that you can't even orbit the moon for that long because it eventually just decays into an Earth orbit? Not sure how reliable this info is though) Then there's also the fact that you'd need a bunch of these before they're able to supply power all the time (They can't beam power down from the other side of the moon, unless there's something simple that I'm missing here) and you need the launch capacity on the lunar surface to do that which means you probably already have a mass driver or some other launch infrastructure
@MrWeli I think the reflector satellites could be built and sent from Earth, but you're onto something about the orbits potentially decaying. If they can't be stationary orbits then you'd need a rotating fleet of them, making it costly and junking up space. There is a Lagrange point between the Earth and Moon, but that's probably not okay. Perhaps there's a spot on the Moon's opposite side, where the reflector satellite could orbit the Earth from behind the Moon. That spot would experience gravity of both bodies but feel like only one. So it could just take the same orbit as the Moon but a little farther. But I don't know what kinds of orbit are possible or not.
Thank you for proving the case for building Thorium reactors on the moon. The Thorium Nuclear cycle can be fueled by the thorium already on the moon, there is a need for Iconel, Hat alloy martials, but at measured energy densities of 70Mw/meter cube you need very few of them and 70megawatts probably could power any installation for a LONG time before capacity limits were reached. All the materials in those square kilometers could go to other purposes.
so, on the radiator, use thermocouples to direct convert heat to electricity and use that to run LEDs and focus their light back on the hot side collector. so the heat is dissipated by the thermocouples And peltier effect from the LEDs, remaining heat is disappeared in the normal radiator. would this help or even work?
and relatedly... can we make mirrors that work well in infrared wavelengths? if so then you could just directly radiatively return bb radiation to the collector side, or direct it into empty space
It only doesn't if there is competition that can stay open 24/7. "Not making economical sense" are other words for "There are better options to achieve the same goal".
If I'm correct, the upper limit of steam engines of 650 C is set by the water medium. At higher temperatures water starts do disassociate into hydrogen and oxygen and you'll get all kinds of undesirable side effects. Unless you're in the business of creating hydrogen, the you want those side effects. But, in a turbine blades get more mechanical stress and need to stay further away from critical temperatures. I'm curious how alloying with nickel improves the working temperature range.
Use multiple pv farms. With mechanical batteries! Spin up a heavy flywheel. About a 20' diameter, filled with moon dust. With magnets places on its edge possibly electro magnets. Powered by a solar array on it . And powered by a larger solar array. With a high mass flywheel, the rpm can be kept relatively low. Use magnets and air bearings maybe nitrogen or CO2 . A very heavy flywheel, in the multiple ton range. Spinning in the 1,000's rpm range say 3k to 5000 rpm. Place pv arrays miles apart, from the pole so at least one stays in the sun. Operating at 10,000k vdc using a large lithium super capacitor bank to build a DC to DC converter. To drop the 1-5 amps (roughly) @ 8-12kv DC to much higher current lower voltage say 2k amps at 340-400 vdc that that in inverted to 120/240vac or whatever is required or possibly use DC, 180vdc with small inverters to convert as required. With the solar array operating at high voltage, low current even 2kv at 1 amp can be sent over 20-22 gauge wire, still capable of pulling another 1+ amp, at a length of miles , it would have losses. Say the base was on the pole with arrays 5 miles south 120° from each other. With 10 miles of 18 gauge wire at least. To carry 5 amps (+/-) at 2kv+ 2kv @ 5amps eq. 10 kw, with 5 amps the most allowed on a 16-18 gauge wire , maybe 10-12 gauge with 5-10 amps at 5 miles there will be losses. Placing the wires inside a reflector to keep the sun off them will help. Use a copper core wire possibly, with a polished aluminum outer, with aluminum rings or beads to reflect and dissipate heat and cost with a varnish possibly holding glass dust. Being semitransparent it still reflects light and heat.. with the flywheel being so large , id dig a hole to place it in with only 4'-6' space around it. Use a 2kw array to power the electro magnets on the flywheel. Using mirrors to reflect the sun on to the panels. Or use a dozen permanent magnets to get it going. Use a positive feedback using the power it generated to generate more power.. say start with a dozen 2"x 4" x 1/8" n52 magnets plus a few 1/8" x 2"x 1/2" to make a Halbach Array, placed in certain areas around the wheel. Using high voltage pulses to push the magnets getting the wheel spinning. Maybe use a 10 kw bldc motor to assist on start up. The wheel possibly weighing 10k lbs even spinning at 100 rpm will be a huge amount of torque. With nearly zero friction and near zero resistance. Using the spinning mass to generate 10 kwh, and using only 100 wh to get it spinning over weeks, and 10wh to help maintain the speed over days until it is needed . Post generating power for a week until the next solar array is fully under the sun. It could work. More likely and easier, would be to put multiple arrays 10 miles south or north of the pole. Use around 10 gauge wire. With 10kv+ use a DC to DC sub station to boost the voltage up. As required , if required. With the array only putting around 1-2 amps on the cable, place another array 2-5 miles south or north east or west 45° from the last so it is about 10°-20° on the rotation with a sub station matching the voltage to the array. So it's 1 amp at 10kv can be added to the "DC GRID" going to the base. Maybe lithium titanium batteries can improve their efficiency so they still have the life of a capacitor and round trip efficiency being high as lithium ion LMC, or lifepo4 at least, so lithium titanium cell batteries could be used. With a 20+ year life. A 800 kwh battery bank used to smooth out the brown outs until the solar gets back under the sun. To produce 100% of it's power. With the arrays at 20° and 120° from each other with only 100° with no array its only a short time without full power if another array is placed 20° east/west of the last with the grid carrying 3 amps at 10,kv for a short time possibly 5-9 days then fade to one then no power for a week until the next array starts production. Maybe smaller arrays closer to the pole would work placed at 30° with 5kw arrays. 5kw 24/7 is a ton of watt hours. Sorry to ramble , happy holidays!
Sometimes I just imagine we dig kilometer deep spaces under the moon cover up the surfaces and pressurize the space inside. Then make angled tunnels that leads all the way from kilometers down to the moon surface that will accelerate stuff to orbit using some of the methods you mentioned in your previous vids.
Regolith weighs about 2.5 ton/m3 and with a lunar gravity of 1,625 you'll need about 25 meter of regolith to have a roof pressure of 1 bar. About 10 meter is the minimum for radiation shielding, so a roof of 25 meters is perfect. I'll do a bit more, so the roof construction is always under compressive loads, even when some mishaps happen.
You missed the opportunity to put heat engines on the light/dark boundary. That would offer HUGE efficiency gain due to the magnitude of the temperature difference on that boundary.
It might not have been thought of - but water boils at 100 degrees Celsius and you said daytime temperatures reach 127 degrees Celsius, so water could be boiled using the sun and put through steam engines to turn generators and make electricity. The torque from the steam engines would generate a lot more electricity than solar panels. Steam after going through the steam engines could be condensed in underground metal radiators. As long as the sun 🌞 was shining on the boilers, the steam engines would turn generators to make electricity . The trick would probably be to take metal tubes for pistons to run in and pistons and camshaft there and build the engine blocks out of concrete manufactured on the moon. Fortunately things lighter than metal could be used to manufacture the necessary components of the steam engine like carbon fibre and possibly powdered metal used with 3d printers to make more durable components for the parts of the steam engines like the metal sleeves the pistons move in, the pistons and the camshafts. If aluminium could be mined and used in manufacturing on the moon the harder metals brought from earth would likely just need to be used on metal edges of the pistons that touches the metal sleeves the pistons run up and down in. Potentially if a steam engine could be manufactured on earth using no metal parts but say kevlar for the pistons and sleeves they move in it would mean less metal would need to be sent to the moon to save on weight sent in the rockets. Camshafts used in the engines might be made of kevlar or have metal wire in them and have 3d printers build the camshaft around the metal wires once on site on the moon or the camshaft could be a finished product sent to the moon.. Essentially no clouds or shade on the moon would mean the steam engines could run whenever the sun was shining on the boilers. If all necessary components were made of kevlar it could be that titanium or another metal could simply be sprayed or electronically bonded to the necessary moving parts of the steam engines once manufactured on the moon. With the idea of sending the least amount of metal necessary on the rockets to save weight. Would probably be done eventually assuming a large manned base eventually gets built. Such steam powered generators might run for hundreds of years if they were built good enough. Possibly a metallised form of Teflon could be used on moving parts to reduce friction.😊
P.s. If a refrigerant was used instead of water that easily self condensed once trough the steam engine and into the underground condenser radiator the steam engines would likely last longer and be more efficient as the expanding refrigerant would possibly expand a few hundred times more than the steam.
The only thing I could say about radiators is that instead of deploying them on the surface, you can just drill a few holes into the moon's crust a few hundred feet deep and tap the cold rocks below. Sort of a reverse of what current geothermal heat systems do on earth. You dont even really need to drill honestly. just create a bunch of piping then cover it with regolith.
Can you make a video on lunar tunnels? I know Elon mentioned that he wanted to transport one of the boring company’s machine to the moon and use it to dig tunnels. I want to know how having tunnels may end benefiting the lunar colony. Also, loved the video. Keep at it.
you COULD radiate it into space or... use it to bake your delicious alloys and metals through the same technology as refrigeration. Yes you can claim "laws of thermal dynamics" but, joules being put into an item would absorb those joules, joules being compressed into a tank with decent insulation would store those joules, repeat it enough times and you end up with temperatures hot enough to smelt just about any metals you like using solar power and compression technology. Sometimes, you WANT that heat, sometimes you REALLY want that heat
Pure, un alloyed, aluminium is quite ductile and quite useless for things other than conducting heat and electricity. I don't know if it is more ductile than pure copper.
Water become steam in a vaccum at 30c meaning you don't need to get crazy with materials and operating temperatures it has near enough the same expansion rate no mater the temp you get it to boil making it a great medium to use.
1. Solar Cells still need cooling. And I find no reason for that not to be a heat engine... 2. Sterling Engines can be no different than steam engines in that you can make them multistaged. One stage feeding the next, that will have a wider Start and end.
I was surprised to learn the subsurface of the moon is hotter than the surface and just gets more so. I presumed it was like the earth where a meter or two down it's quite cool, even in a hot environment, or like a cave is. Is it the lack of organic material, water, or the makeup of the moon itself? Edit: That's what Google's AI summary said, but then I watched a video by Astrum that says the Indian rover/lander took temps and it got cooler the deeper it went. So, I don't know...
It just occured to me that stirling may not be as useless as one would think? We have this "nifty microwave plasma drill" it is experimental technology and two prototypes will be (hopefully) field tested here on earth in 2025, the thin is you have to start with a conventional drill since the top soils are too soft and watery on earth, a problem we don't have on earth. We also need to pump gas down to flush the hot vaporized minerals on earth, on teh moon though? there's a near vacuum, the hot gas would push itself out for the most part, only at the end do we need to flush the rest gasses out with something else. This means this experimental tech would actually be much cheaper and easier on the moon and drilling down would not only allow for more science, but also open up mantle and possibly deep mantle geothermal. This could make this trick much more viable than pushing around nuclear reactors for long term outposts and localized power grids. I already pointed out on the other video that a radiator with a white reflective box could be used to direct the waste heat directly into the sky while keeping the suns infrared out due to geometry. Combine these two tricks and you get 24/7 localised small size factor power with a rather big punch for its size. We can reuse the drill, so only transportation costs apply, we can reuse the radiator, the stirling engine and that is rather managable in terms of transport and production, it could be easily mass produced. The hole of the drill is glassed already to stabilise it something that is pointed to as an advantage on earth as well, you basically only need to lower a pipe with a heat collector down into the hole, fill the pipe with a high temperature fluid NaK would be the prime candidate and the hole is rather insulated already. Put another heat exchanger to the NaK pipe and your stirling engine to teh other side of the heat exchanger and you get a somewhat "simple and around teh clock" solution that doesn't need a nuclear reactor and can be domestically produced on teh moon. In all of this teh most expensive thing is setting it up and drilling the hole, but it's only expensive due to teh energy requirrement for teh microwave laser adn transport costs. Btw. a positive aspect of this drilling is that you basically have very little down time for repairs and very few components with damage, regolith plays havoc with machinery and moving parts, but the microwave laser doesn't have any moving parts. The catch: The biggest downside to all of this seems to be that to get 800°C, you need to ONLY drill about 300km down, not unfeasable with that microwave drill, but using that heat is a case of "no luck", I also couldn't find a good chart for how hot it gets at which depth, the limiting factor seems to be getting a "good temperature" though? Also here's something from NASA about that idea, coudn't find where to read it yet, will try again tomorrow. ntrs.nasa.gov/citations/19660026223 Edit START: Yes, the "big brain move" is not shade itself, that is a requirrement, but not the solution, the suns heat would be unwanted on a radiator meant to disperse waste heat. No the "cheap parlor trick" is the reflective box with specific geometry, it allows us to radiate directly into space, this also works to a degree on earth, only the pesky atmosphere is an annoyance, it isn't on the moon though. The upside of this parlor trick, cheap as it is, is that you only need the "whitest white", or better yet, the best IR reflecive material and the "balckest black", also in regards to IR, the geometry means we can direct the waste IR by reflection and due to geometry even directly into the vastness of space itself, with a variable/movable outlet we can even make sure the sun doesn't reach into the box to begin with. This tech wouldn't exactly be usefull on the ISS, too heavy and with 90mins for one orbit this just isn't usefully to begin with, the moon is however way slower, during the night we can easily "beam teh waste heat into space" during the lunar day planing where to aim and generally building the box in a direction "where the sun don't shine" is paramount. Notheworthy, although something our dear host doesn't quite believe in, even if this was proven on earth already, curtesy of TechIngridients, if they can do that in their backyard, so can we on the moon! Edit END
Still think solar thermal would be better suited for crude von neuman machines but concede the point that moon solar labs should be persued at the earliest opportunitiy. Guess solar thermal should be primarially reserved for industrial process heating/preheating of regolith+derivatives.
There truly is no reason to use anything but nuclear for a moon base. RTGs could easily handle a moon bases needs, and while they do not produce much power on an individual basis (I think the most powerful is 300 watts currently) that same unit produces over 4kw of thermal. Chain up enough of these and you have some serious output! You could even put sterling engines to use to capture whatever excess heat you do not need for habitat purposes making the efficiency go up! Maybe even a small nuclear fission reactor could be useful.. Cooling would be an issue.. One benefit to an RTG is their lifespan, a plutonium-238 device would have a half life of 90 years.. Solar panels on earth only last 20ish years or so and I guarantee without big advancements the space environment will shorten their lifespan dramatically. RTGs can be buried for radiation protection etc
The weight of the solar cells is about 10%-20% of what they are on Earth. I don't think you've included any support structures / frames in your calculation.
mmm mirrors in space are too risky because of micro particles and debris. glass and mirrors are very fragile and could crack or shatter if dust or high moving particles strike the surface. Good idea though but too expensive and too risky.
If there are permanent dark zones on the moon's poles, wouldn't this make for better solar thermal sites? More so with vertical arrays rather then horizontal, using the back fore radiators as most the sky is away from the sun. You'd also have constant power making it perfect for human habitation. From there we could spread to the equator with mostly automated systems that use the cheaper solar electric.
Like they wouldn't have a fucking solar array that can direct the solar light to array of solar and mirrors to heat sterling engines and charge panels for ultimate power and then have cheap power
its all so tiresome. a million smart speculations about energy needs in space, but zero awareness that engineering has to start back from zero. literally every single machine and structure on planet earth is engineered with the idea that there is earth like pressure, speed of sound, and gravity. you literally cannot use the same machines or build the same structures using structural engineering principles on the moon, mars, or anywhere without at the very least ~0.9 earth gravity if we are being ludicrously generous with tolerances. just on the industrial stuff alone we would have to rework centuries of ore smelters requiring earth like convection and gas flow. blast furnaces engineered for earth pressure and gravity. refinery distillation columns relying on 1g fluid separation. pulp and glue mills counting on earth atmosphere drying. concrete and other aggregated bonded material batching dependent on earth gravity mixing. calibrated large scale hydraulic presses. drilling rigs designed for earth downforce and friction. our entire science of fracking and soil mechanics is based on earth subsurface pressures. steel mill rolling lines depending on 1g material transport. open pit mining excavators built around earth soil bucket loads. cargo and crane systems balanced on earth gravitational torques. conventional conveyor belts sized for earth friction and weight. on and on. going to mars or the moon means we have to re-invent the industrial age. energy is not the problem and engineering is not free you cant just expect us to 'make it work'
This is an updated version of the solar thermal (Stirling) vs solar cells video. The conclusions have not changed but a commenter pointed out that I didn't use the correct power density for the MHD generator estimate. The 500 watts per kilogram figure in that paper wasn't for just the MHD, it was for the entire system, mirrors and radiators included. The real power density is 600w/kg or 1,666 kg for 1 megawatt which puts the crossover at about 5% so this video has been updated to reflect that. I know it's a small difference but I can't sleep at night knowing I published bad info or misrepresented someone's work.
I also decided to fold the power transmission cable video into this one after publishing it as a stand alone it didn't sit right... it definitely belongs here with the other energy-friends :)
No wonder this felt so familiar lol.
Thanks for going to the effort to make corrections though. That's a really great thing.
So I've watched both the Stirling video and the Solar video.
First of all, I want to say you've done a fantastic job making these tables, and compiling a very in depth overview. It's people like you that truly push scientific discourse.
I do want to make a small note that while mass is in fact a decent approximation for energy expenditure, producing thin pieces of glass from Silica to deposit A-Si film onto and producing thin foil of aluminim does have a difference. Glass has a "melting" point around 1700C (it is amorphous), compared to the melting point of aluminum around 660C. While glass has a better specific heat of 750J/kgK vs aluminum's 890J/kgK, the difference in melt temp results in 1.27MJ vs 590kJ, a 2X expenditure in energy just to reach melting point. While aluminum does need an extra 400kj/kg to fully melt, and glass is pretty much ready to work once in it's glass transition phase, the aluminum is still saving 20% ish in terms of energy.
Note that raw aluminum is not available on the moon, and we will need to expend energy to convert alumina, with it's high melting temperature of around 2200C to aluminum. However, if we compare this to silicon, it has a heat of fusion of 1093kJ/kg vs silicon's 1787kj/kg.
While I agree with you that prices on earth are highly dependent on the whims of the average consumer, and my work boots cost less than a pair of Air Jordans, there's something to be said about aluminum foil costing $11 for 200sqft while solar panels run around $186 for merely 20sqft.
Rolling something between a pair of wheels is in fact simpler and more consistent than delicately spraying glass in silane, even if the vacuum pump for the vacuum chamber is free.
An interesting thought could be to combine the faster and less energy intensive production of using aluminum foil with photovoltaics. While yes, solar panels do lose performance at elevated temperatures, they also increase efficiency with higher light intensity, so there's probably a decent tradeoff point where it may be advantageous, perhaps around 20x to 30x concentration.
I also want to draw note that instead of extracting the power during the lunar day, a Stirling engine may be best used during the lunar night, where the additional 250 Kelvinish difference in temperature will substantially improve Carnot efficiency. Perhaps instead of looking at this as an exercise in power output, we look at this in terms of a total energy expenditure. Is it more energy efficient to build solar panels and banks of batteries? Or perhaps it may be more efficient to use PV panels to power our 360hr lunar work day and then use thermal batteries and a Stirling engine on our night off? Is manufacturing a battery at around $0.20 per kWh of storage LCOS on earth the same as around the predicted $0.07 per kWh LCOS for cooking some sand? Does this translate to a lunar economy. Is the cost of shoveling some lunar regolith into a mountain and heating it up using mirrors cheaper than building a battery factory? Is charging a battery at 16% efficiency as nice as using a less area and maybe pushing 70% carnot efficiency for a two week long lunar night? In terms of loss of surface area of solar panels is it worth it?
These are all fascinating questions.
Note that we could use a combination of systems as well. Batteries do offer a longer term storage solution that is not susceptible to radiative losses, but again, we are charging them with 16% ish PV system, compared to taking a perhaps 40% loss on the back end. Note also that humans do need thermal control, so this may be a decent idea for lunar night time ECLSS
@@feraldegenerate1743 Good points, though one of the most power intensive aspects of aluminum refining isn't just melting its ore, its the electrolysis necessary to break the really stable Aluminum oxygen bonds. Aluminum refining takes a pretty obscene amount of electricity, the main reason for aluminums cheap price is its ore's abundance and the cheap price of electricity now. The process takes a theoretical minimum of 22.428 Mj/kg, though in practice its more like 55.332 Mj/kg.
Thanks for reuploading, but I do feel the need to point out that the 600 watt/kg figure is still the total system power density. The authors don't make that very clear, but whenever they are talking about the power density in general and not specifying a component, they are talking about the power density of the whole system, radiators and mirrors included. To get the power density of just the electrical generating parts, you need to look at the masses of the different components they listed in the paragraph right above the one you quoted at 27:34
"From the above estimations at optimal specific power, mass of the compressor stages together with the electric engine is 300 kg, and mass of the pipe heat exchanger is 500 kg. Mass of the MHD generator together with the superconducting magnetic system may be estimated as 400 kg for the electric power level of 10 MW. Mass of the mirrors and the vortical chambers determined by power consumed by them of 30 MW will constitute 1800 and 3000 kg."
The mass of all those components minus the mirrors is 4200 kg, and the system is accepting 30 MW of thermal power as input and since it is 31% efficient it is outputting around 10MW of electricity and 20 MW of waste heat. That's an electrical power density of 10MW/4200 kg, aka 2380 watts per kilogram, or 420 kg for 1 Megawatt.
You started this presentation with a statement that you don't need to run your machines all the time, and then went on to design your system based on an assumption that you need to radiate when the sun is up, so you can't get below 121 C. In practice, you have much a much cooler reservoir, either 4 meters below the surface (-20 C) or 14 days away in time (-183 C). In the same vein, you could heat up and store your hot fluid so you could generate power even when the sun goes down.
This is a great point. I've been toying around with similar ideas for home heat pump setups to take advantage of day-night temperature differences here on earth. I don't know if you'd have a buried reservoir or a surface one. Conductive ground losses vs radiative surface losses is something I've not run the numbers on yet. But I imagine that buried would be better because it's more constant, and any conductive losses would be minimized compared to a surface reservoir given the lower difference in Temperature between whatever fluid at 100-200°C and -20°C compared to the night time surface of -180°C which can mostly be alleviated by using a butt ton of insulation if I had to guess.
@@Nomenius1 On earth, it is much more challenging to benefit from day-night differences because of the atmosphere. Also, with good engineering it should be possible to do much better with day time radiation than the base design used by Anthrofuturism, as pointed out by several commenters.
⚡👏🏻🥃
14:07 Yikes. I imagine you're not doing your math in Celsius directly, but having a graphic that shows 200C° being twice the temp of 100C° is a bit of a red flag. Those kinds of equations only work in Kelvin.
The stuff that you’ve put together is super impressive. You must be spending a ton of time on this. I’m always excited to watch whatever you upload
Yes! I am addicted
This video reminded me that solar photovoltaic cells don't completely ignore the temperature of their environment. They do lose efficiency as they get hotter. In the 120 degree Celsius environment of the moon, PV cells will be only half as efficient as the same cells at room temperature(which is what they are rated for.)
However they'll be more radiation-tolerant, as they'd essentially be constantly annealing in the moon-day (month) thermal cycle
That's why my votes for nuclear, whether it's fission or RTGs. Nuclear RTGs can have a half life of 90 years, they never shut down, you can bury them and they still work.. A 300 watt electric output RTG outputs 4kw of thermal which is useful for a habitat and hey you could even use the thermal output as your hot side for a Stirling engine, either converting that heat directly into rotational energy for powering mechanical devices or having the Stirling engine spin a generator setup. They'll run nonstop for those full 90 years without a hiccup (maybe not the stirling engines but that can be improved)
I spent three nanoseconds deciding to watch your latest entry! You fill me with hope! I love your content and your insights!
Thanks for reuploading, really glad your willing to go back and fix stuff. On that point though, I do still see a few mistakes in this one. Biggest one is probably the part where you say MHD's don't need thermal gradients to work. MHD's are still ultimately heat engines subject to the same thermodynamic laws that a Stirling engine or turbine is, which is that they are taking heat and converting it to electricity. Like, the reason *why* heat engines get more efficient from larger thermal gradients is because the more heat energy you extract from your input to convert into electricity, the colder your output is going to be, because it has less thermal energy now. MHD's still work on that principle, you can't have an MHD that takes in plasma at 1 temp and pressure and outputs plasma at the same temp and pressure, not just because of risk of the MHD melting, but because that would mean there is no change in the energy of the plasma, so the MHD didn't extract any energy from it.
The reason why MHD's make radiators so much easier is not because they don't care about output temp, its just that its way easier to give them a useful thermal gradient even with high output temps, because the input temp can be so high. You can raise the output temp a lot, and rather than having to accept lower efficiency, you can just increase the input temp to compensate. Though in the case of solar thermal concentrators there is an upper limit to how hot you can make the input temp, which is that a solar concentrator can't ever get something hotter than the surface of the sun, but that's a pretty generous upper limit.
The second mistake is the 600 watt per kg figure in that paper is again, the power density of the whole system. I get why that keeps happening because these papers do not do a good job of making that clear, though a hint is that the authors said that the 600 watt/kg power density figure happens when the radiator temp is 350K, and the main reason they would specify that is cause the radiator mass was being included. To get the mass of just the power converting stuff, if you look at the screen shot at 27:34 where you highlighted the 600 watt/kg figure, you can see a breakdown of the mass of each component in the paragraph right above.
"From the above estimations at optimal specific power, mass of the compressor stages together with the electric engine is 300 kg, and mass of the pipe heat exchanger is 500 kg. Mass of the MHD generator together with the superconducting magnetic system may be estimated as 400 kg for the electric power level of 10 MW. Mass of the mirrors and the vortical chambers determined by power consumed by them of 30 MW will constitute 1800 and 3000 kg."
The mass of all those components minus the mirrors is 4200 kg, and the system is accepting 30 MW of thermal power as input and outputting 20MW of heat and 10MW of electricity. That's an electrical power density of 10MW/4200 kg, aka 2380 watts per kilogram, not 600.
If you want a more conservative figure, the MHD from the paper you mentioned last video, "Multi-MW Closed Cycle MHD Nuclear Space Power Via Nonequilibrium He/Xe Working Plasma
", it's overall power density was 333 watts per kilogram, but over half of that mass was radiator and nuclear reactor. Once you removed those, the power density of the MHD and supporting gubbins was 808 watts per kilogram. That paper had a nice pie chart of the different masses of the components on page 6. Though that might not be as useful an example, because it was using a lower temp heat source than a solar concentrator would, cause it was limited by the meltdown temp of the nuclear reactor, so its performance was lower. 900-1000 watts per kilogram might be a good lower bound at the higher temps you're dealing with.
Fun fact, the Amazon facility i deliver from has a fleet of approximately 325 rivian electric delivery vans by my count, when all charging at night consuming just over 9,000 watts each, we alone are drawing 3 megawatts
I remember how well your other video was researched and presented. This one is its equal. Thank you.
All pains disintegrate the moment anthrofuturism uploads.
Your channel is amazing. Truly an inspiration. Keep up the quality work.
Thank you my friend for doing all you do for us . I've always loved space science and your insight and devotion is awesome. Truly thanks !
I'm at 7:30 min into the video so this comment might be answered later but isn't nighttime the only "cold side" you need for a heat engine. Like just store heat in the day and release at night.
yeah i feel like he gave the heat engine its worst shot by assuming it needs to radiate all energy away continuously, above ground, during the day
you could optimise this radiator much more efficiently by a) conducting the heat out through lunar regolith and b) having a large enough thermal mass that it doesn't saturate in a day and radiates through the night
You cannot really store heat until the cold gets there, but you *can* do the reverse, freezing material during the night and then using the latent heat of fusion to keep your radiator cold
Question: At around 34:20 you mention burying transmission lines in the regolith not only for insulation but also for cooling. Wouldn’t this also work for cooling in a solar thermal energy system? Use the Moon itself as the heat sink, similar to geothermal systems here on Earth? How would this affect the calculations for energy density and total mass requirements?
the problem there is, rock can hold onto a lot of heat, and itll move slowly away from the source, you can on really do this once and then you have to wait however long it takes the heat to move
I saw an article posted Dec 9, 2021 called "Analysis of radial-outflow turbine design for supercritical CO2 and
comparison to radial-inflow turbines" which claimed that these turbines could achieve isentropic (idealized) efficiencies ranging from 85% to over 90%. The turbines are smaller and easier to design then the axial-flow turbines.
You mentioned that in practice, typical efficiencies range from 50% to 70% of the idealized efficiencies. Then consider another 5% loss due to the generator so the range would be 42.5% to 63% less another 5% for generator losses leaving 40.38% to over 59.85%. The article did not mention these real-world adjustments, so good to know. Thank you.
Why are we assuming heat needs to be radiated? Could you not just stick the radiator underground and conduct your heat out into the regolith? This would also improve your cold end temps as the subsurface temperature of the moon is -20 degrees.
Assuming a surface radiator seems like a major oversight.
Your radiator discussion is missing the idea that by shielding the radiator from the surface and sun, the radiation sees only the sky, at a temp of a few K. Shielding from the sun means putting the radiator in a shadow. Shielding from the surface means placing a reflector below and around the radiator. In fact, if you point a parabolic solar thermal system at empty space, it generates cold. But the difference is that the sun is point source and needs a focus, while space needs no focus, just shielding.
Also the fact that you can probably drill down to a thermally stable depth of rock and dump heat there
That can work near the poles, but at the equator you don't have much options. Assuming you want to put down square kilometers of power generation. Your just radiating into the radiator next to you. The radiator is basically sandwiched between the moons surface and the radiation of the sun. But, like someone else already commented, you can dump heat into the ground and radiate that away at night.
Assuming the radiators are a plane, then only the edges 'see' each other, which is very little thermal effect. Imagine placing reflective foil between the radiator and any warm surface, basically a layer of foil acres in extent under the acres of radiators. Then arrange a shadow for the sun.
Maybe put panels up facing all directions and point some at the sun and some at the cold sky, switching plumbing
Is this a reupload?
This content is crazy good
Is there any depth of the moon cold enough to get your cold source from geothermal sources?
Amazingly well explained stuff. thanks
Heck of a spreadsheet!
12:46
Maybe we can shield not only from the sun, but also from the surface of the moon. Depending on the latitude of the location, we will have a sector of space where the sun never shines. Probably about 5-10 degrees above the horizon in the direction of the pole.
The open end of the shield-tube can be directed into that sector so that the heat is radiated into outer space. The other end of the tube is a heat radiator. The shape of the tube allows it to be shielded from radiation from the side of the tube.
If you install a tracking system, you can radiate heat to any point in space and avoid the sun.
About the problem that the insulator itself will heat up from the ground, hmm ...
On a lunar night, you can cover the entire surface around the emitters with sun protection refractive foil in several meters around and wait until the regolith cools completely. The lower temperature limit will be the temperature of the lunar rock massif close to 250K (-23 °C). Maybe it will even be possible to cool the soil massif even lower by installing more of these cooling emitters.
Result:
-heating from above from the sun is cut off by a tubular reflector, as well as heating from the sides;
-heating from below is limited by a temperature of -23°C.
The tubes can be made of aluminum foil, connected in a hexagonal shape using the same technology as cardboard.
Costs: a lot of foil for the tubes, a lot of foil to cover the soil around, a more complex installation of the emitter, since it will stand more vertically to allow it to be directed at an angle of ~5° to the horizon.
Cons: since the sector to which the heat is radiated is now limited, the total capacity of the cooler will decrease. To compensate for this, the number of emitters needs to be increased even more. I think 2-3 times, since we have limited the sector of space to which the heat is radiated by this many times.
And then the question is, do we need a system that reaches -20°C, but is ten times larger and more complex than a system with 120°C?
Thermal storage would be better here, similar effect, less complexity.
"On the moon we have no mother nature" 😢
11:37 Yes you are limited by the ambient heat but you have easy access to deep space. A radiator is limited by the ambient heat on earth because of air and water vapor carrying heat around, but the moon's surface is at a pretty good vacuum, and with insulation from ambient heat you will loose heat more like in deep space. You can use a thermal battery cooled at night, or an insulated structure simulating a polar crater. You can easily calculate how much heat you can possibly absorb with your collection area and design an appropriate battery. Specialized sterling engines can run off of that when it needs to dump the heat into space, or you could have a hotter running battery for that, and a colder battery to keep things consistent for the "normal" generators. You might be limited by space, and you might need more reflective materials for the cooling bowl/tower, it can add complexity, and its not going to keep all the ambient heat out, but its closer to being cooled in deep space than anything else could be and it raises your maximum efficiency. The radiator can also increase the efficiency of solar cells if you use it to cool them.
A thermal battery might also be the best way to store energy over time because you gain efficiency by not converting the heat into electrons which need batteries that need to be kept happy, but here you just need thermostats, reflectors, pipes, pumps, insulation, and Nak or gallium, and with thermophotovoltaic cells.
Can I have a heart for no reason, pls?
❤
❤
watched this entire video with my eyes glazed over, not understanding a goddamn thing. 10/10
So a question about heating. Do we know the ambient temperature underground on the Moon? Moreover how would the calculus change if we built it on the south (eternally day) pole.
I was thinking about when you upload and just i was thinking about it you upload not one but 2 video wow thats crazy
Aluminium doesnt resct with NaK:
NaK has average free electron density of 1.5 per atom, same as elemental Na.
Bothsodium and aluminium are reducing agents as the energy required for both to get rid of a valence electron is very low (converselyvery high to accept an electron), to gain an electron and thus react, one would need to be a relative oxidizing agent aka one must be a much stronger reducing agent than the other to the point that it overcomes the weak atomic force neccessary to rip off an electron, this is not the case with Al-NaK as the energy given to accept an electron is higher than the energy required to rip off that electron.
Under extremely high temperatures this may differ.
Hello, I enjoyed your theorizing. Though, I havent heard anyone talk about solar mirrors ORBITING THE MOON, directing concentrated light beams onto the surface. Those structures could be larger than anything on the surface and be held together with less material, such as thin reflective films held tight by rotational forces and cables, rather than on a ground based mounting platform. It would also keep the reflectors free from dust. And it could supply sunlight to the surface during night. You would then need fewer heat engines on the actual surface because its no longer as spread out.
Not sure how well that would work, as orbit decay might cause serious problems. (I think I heard somewhere that you can't even orbit the moon for that long because it eventually just decays into an Earth orbit? Not sure how reliable this info is though) Then there's also the fact that you'd need a bunch of these before they're able to supply power all the time (They can't beam power down from the other side of the moon, unless there's something simple that I'm missing here) and you need the launch capacity on the lunar surface to do that which means you probably already have a mass driver or some other launch infrastructure
@MrWeli I think the reflector satellites could be built and sent from Earth, but you're onto something about the orbits potentially decaying. If they can't be stationary orbits then you'd need a rotating fleet of them, making it costly and junking up space. There is a Lagrange point between the Earth and Moon, but that's probably not okay. Perhaps there's a spot on the Moon's opposite side, where the reflector satellite could orbit the Earth from behind the Moon. That spot would experience gravity of both bodies but feel like only one. So it could just take the same orbit as the Moon but a little farther. But I don't know what kinds of orbit are possible or not.
Thank you for proving the case for building Thorium reactors on the moon. The Thorium Nuclear cycle can be fueled by the thorium already on the moon, there is a need for Iconel, Hat alloy martials, but at measured energy densities of 70Mw/meter cube you need very few of them and 70megawatts probably could power any installation for a LONG time before capacity limits were reached. All the materials in those square kilometers could go to other purposes.
Using the Nickelback Photograph meme goes so hard 👍
so, on the radiator, use thermocouples to direct convert heat to electricity and use that to run LEDs and focus their light back on the hot side collector. so the heat is dissipated by the thermocouples And peltier effect from the LEDs, remaining heat is disappeared in the normal radiator. would this help or even work?
and relatedly... can we make mirrors that work well in infrared wavelengths? if so then you could just directly radiatively return bb radiation to the collector side, or direct it into empty space
i dont think that its make economical sense to create a factory if half of the time its need to be close
Batteries exist
It only doesn't if there is competition that can stay open 24/7. "Not making economical sense" are other words for "There are better options to achieve the same goal".
0:36 A lunar night is 14 days. Parts could cold-weld in this time if you don't keep them moving.
About halfway through and wondering if you've taken into account that the efficiency of PV drops as temp rises. Pretty extreme drops at that temp too.
what if you have a lot of cooling liquid spear and cool it during the cold lunar night?
Instead of a radiator, why not use the ground as a sink? Just curious.
Solar cells also don't like heat.
The ground will heat up, but it will dissipate over time. That heat may be useful at night as well.
I followed after you said "Celsius" 😂🔥
If I'm correct, the upper limit of steam engines of 650 C is set by the water medium. At higher temperatures water starts do disassociate into hydrogen and oxygen and you'll get all kinds of undesirable side effects. Unless you're in the business of creating hydrogen, the you want those side effects.
But, in a turbine blades get more mechanical stress and need to stay further away from critical temperatures. I'm curious how alloying with nickel improves the working temperature range.
Out of curiosity why would you not want to use orbital solar collection and microwave beaming power to the surface?
Quick note circa 14:08
Physics deals almost universally with *absolute* temperature, measured in Kelvin. Double the 100°C is not 200°C, it's ~470°C
Do orbital reflectors make sense on long dark nights
Have you seen the komatsu video about lunar things?
you can put orbital mirrors to direct light on the solar cells to have production at night time, very reduced but better than 0
Use multiple pv farms. With mechanical batteries! Spin up a heavy flywheel. About a 20' diameter, filled with moon dust. With magnets places on its edge possibly electro magnets. Powered by a solar array on it . And powered by a larger solar array. With a high mass flywheel, the rpm can be kept relatively low. Use magnets and air bearings maybe nitrogen or CO2 . A very heavy flywheel, in the multiple ton range. Spinning in the 1,000's rpm range say 3k to 5000 rpm. Place pv arrays miles apart, from the pole so at least one stays in the sun. Operating at 10,000k vdc using a large lithium super capacitor bank to build a DC to DC converter. To drop the 1-5 amps (roughly) @ 8-12kv DC to much higher current lower voltage say 2k amps at 340-400 vdc that that in inverted to 120/240vac or whatever is required or possibly use DC, 180vdc with small inverters to convert as required. With the solar array operating at high voltage, low current even 2kv at 1 amp can be sent over 20-22 gauge wire, still capable of pulling another 1+ amp, at a length of miles , it would have losses. Say the base was on the pole with arrays 5 miles south 120° from each other. With 10 miles of 18 gauge wire at least. To carry 5 amps (+/-) at 2kv+ 2kv @ 5amps eq. 10 kw, with 5 amps the most allowed on a 16-18 gauge wire , maybe 10-12 gauge with 5-10 amps at 5 miles there will be losses. Placing the wires inside a reflector to keep the sun off them will help. Use a copper core wire possibly, with a polished aluminum outer, with aluminum rings or beads to reflect and dissipate heat and cost with a varnish possibly holding glass dust. Being semitransparent it still reflects light and heat.. with the flywheel being so large , id dig a hole to place it in with only 4'-6' space around it. Use a 2kw array to power the electro magnets on the flywheel. Using mirrors to reflect the sun on to the panels. Or use a dozen permanent magnets to get it going. Use a positive feedback using the power it generated to generate more power.. say start with a dozen 2"x 4" x 1/8" n52 magnets plus a few 1/8" x 2"x 1/2" to make a Halbach Array, placed in certain areas around the wheel. Using high voltage pulses to push the magnets getting the wheel spinning. Maybe use a 10 kw bldc motor to assist on start up. The wheel possibly weighing 10k lbs even spinning at 100 rpm will be a huge amount of torque. With nearly zero friction and near zero resistance. Using the spinning mass to generate 10 kwh, and using only 100 wh to get it spinning over weeks, and 10wh to help maintain the speed over days until it is needed . Post generating power for a week until the next solar array is fully under the sun. It could work. More likely and easier, would be to put multiple arrays 10 miles south or north of the pole. Use around 10 gauge wire. With 10kv+ use a DC to DC sub station to boost the voltage up. As required , if required. With the array only putting around 1-2 amps on the cable, place another array 2-5 miles south or north east or west 45° from the last so it is about 10°-20° on the rotation with a sub station matching the voltage to the array. So it's 1 amp at 10kv can be added to the "DC GRID" going to the base. Maybe lithium titanium batteries can improve their efficiency so they still have the life of a capacitor and round trip efficiency being high as lithium ion LMC, or lifepo4 at least, so lithium titanium cell batteries could be used. With a 20+ year life. A 800 kwh battery bank used to smooth out the brown outs until the solar gets back under the sun. To produce 100% of it's power. With the arrays at 20° and 120° from each other with only 100° with no array its only a short time without full power if another array is placed 20° east/west of the last with the grid carrying 3 amps at 10,kv for a short time possibly 5-9 days then fade to one then no power for a week until the next array starts production. Maybe smaller arrays closer to the pole would work placed at 30° with 5kw arrays. 5kw 24/7 is a ton of watt hours. Sorry to ramble , happy holidays!
nothing is better at locating utilities like a contractor on an excavator.
liked before i watched the video, i love this s***
Haven't seen anyone mention a Fent Reactor
Sometimes I just imagine we dig kilometer deep spaces under the moon cover up the surfaces and pressurize the space inside. Then make angled tunnels that leads all the way from kilometers down to the moon surface that will accelerate stuff to orbit using some of the methods you mentioned in your previous vids.
Regolith weighs about 2.5 ton/m3 and with a lunar gravity of 1,625 you'll need about 25 meter of regolith to have a roof pressure of 1 bar. About 10 meter is the minimum for radiation shielding, so a roof of 25 meters is perfect. I'll do a bit more, so the roof construction is always under compressive loads, even when some mishaps happen.
You missed the opportunity to put heat engines on the light/dark boundary. That would offer HUGE efficiency gain due to the magnitude of the temperature difference on that boundary.
That might be possible in some craters that are shaped just right, but you would have to select your location based entirely on that.
@ …and then run cables everywhere else.
It might not have been thought of - but water boils at 100 degrees Celsius and you said daytime temperatures reach 127 degrees Celsius, so water could be boiled using the sun and put through steam engines to turn generators and make electricity. The torque from the steam engines would generate a lot more electricity than solar panels. Steam after going through the steam engines could be condensed in underground metal radiators. As long as the sun 🌞 was shining on the boilers, the steam engines would turn generators to make electricity . The trick would probably be to take metal tubes for pistons to run in and pistons and camshaft there and build the engine blocks out of concrete manufactured on the moon. Fortunately things lighter than metal could be used to manufacture the necessary components of the steam engine like carbon fibre and possibly powdered metal used with 3d printers to make more durable components for the parts of the steam engines like the metal sleeves the pistons move in, the pistons and the camshafts. If aluminium could be mined and used in manufacturing on the moon the harder metals brought from earth would likely just need to be used on metal edges of the pistons that touches the metal sleeves the pistons run up and down in. Potentially if a steam engine could be manufactured on earth using no metal parts but say kevlar for the pistons and sleeves they move in it would mean less metal would need to be sent to the moon to save on weight sent in the rockets. Camshafts used in the engines might be made of kevlar or have metal wire in them and have 3d printers build the camshaft around the metal wires once on site on the moon or the camshaft could be a finished product sent to the moon.. Essentially no clouds or shade on the moon would mean the steam engines could run whenever the sun was shining on the boilers. If all necessary components were made of kevlar it could be that titanium or another metal could simply be sprayed or electronically bonded to the necessary moving parts of the steam engines once manufactured on the moon. With the idea of sending the least amount of metal necessary on the rockets to save weight. Would probably be done eventually assuming a large manned base eventually gets built. Such steam powered generators might run for hundreds of years if they were built good enough. Possibly a metallised form of Teflon could be used on moving parts to reduce friction.😊
Note that solar cell output is affected by temperature. Cooling may be necessary.
How to get into this business 😏 cheers from Poland
Okay I paid attention this time. Insulation on buried lines seems like a proven method.
P.s. If a refrigerant was used instead of water that easily self condensed once trough the steam engine and into the underground condenser radiator the steam engines would likely last longer and be more efficient as the expanding refrigerant would possibly expand a few hundred times more than the steam.
The only thing I could say about radiators is that instead of deploying them on the surface, you can just drill a few holes into the moon's crust a few hundred feet deep and tap the cold rocks below. Sort of a reverse of what current geothermal heat systems do on earth. You dont even really need to drill honestly. just create a bunch of piping then cover it with regolith.
Can you make a video on lunar tunnels? I know Elon mentioned that he wanted to transport one of the boring company’s machine to the moon and use it to dig tunnels. I want to know how having tunnels may end benefiting the lunar colony.
Also, loved the video. Keep at it.
Lunar space elevator vid when?
you COULD radiate it into space or...
use it to bake your delicious alloys and metals through the same technology as refrigeration.
Yes you can claim "laws of thermal dynamics" but, joules being put into an item would absorb those joules, joules being compressed into a tank with decent insulation would store those joules, repeat it enough times and you end up with temperatures hot enough to smelt just about any metals you like using solar power and compression technology.
Sometimes, you WANT that heat, sometimes you REALLY want that heat
Why not radiate the heat out into the night?
I would be surprised if they don't put a Rolls Royce SMO into space before 2040.
29:54 The better technique is casting a continuous ingot on a spinning wheel and then draw it through dies.
fantastic vid
Aluminum being more ductile than copper is a dubious claim though
Pure, un alloyed, aluminium is quite ductile and quite useless for things other than conducting heat and electricity. I don't know if it is more ductile than pure copper.
Water become steam in a vaccum at 30c meaning you don't need to get crazy with materials and operating temperatures it has near enough the same expansion rate no mater the temp you get it to boil making it a great medium to use.
YIPPEEEEE
ur my goat🙏
1. Solar Cells still need cooling.
And I find no reason for that not to be a heat engine...
2. Sterling Engines can be no different than steam engines in that you can make them multistaged.
One stage feeding the next, that will have a wider Start and end.
I was surprised to learn the subsurface of the moon is hotter than the surface and just gets more so. I presumed it was like the earth where a meter or two down it's quite cool, even in a hot environment, or like a cave is. Is it the lack of organic material, water, or the makeup of the moon itself?
Edit: That's what Google's AI summary said, but then I watched a video by Astrum that says the Indian rover/lander took temps and it got cooler the deeper it went. So, I don't know...
RAHHHH NEW ANTHROFUTURISM VIDEO LETS GOOOOOOOOOOOOOOOOOOO
It just occured to me that stirling may not be as useless as one would think?
We have this "nifty microwave plasma drill" it is experimental technology and two prototypes will be (hopefully) field tested here on earth in 2025, the thin is you have to start with a conventional drill since the top soils are too soft and watery on earth, a problem we don't have on earth. We also need to pump gas down to flush the hot vaporized minerals on earth, on teh moon though? there's a near vacuum, the hot gas would push itself out for the most part, only at the end do we need to flush the rest gasses out with something else. This means this experimental tech would actually be much cheaper and easier on the moon and drilling down would not only allow for more science, but also open up mantle and possibly deep mantle geothermal. This could make this trick much more viable than pushing around nuclear reactors for long term outposts and localized power grids.
I already pointed out on the other video that a radiator with a white reflective box could be used to direct the waste heat directly into the sky while keeping the suns infrared out due to geometry. Combine these two tricks and you get 24/7 localised small size factor power with a rather big punch for its size. We can reuse the drill, so only transportation costs apply, we can reuse the radiator, the stirling engine and that is rather managable in terms of transport and production, it could be easily mass produced.
The hole of the drill is glassed already to stabilise it something that is pointed to as an advantage on earth as well, you basically only need to lower a pipe with a heat collector down into the hole, fill the pipe with a high temperature fluid NaK would be the prime candidate and the hole is rather insulated already. Put another heat exchanger to the NaK pipe and your stirling engine to teh other side of the heat exchanger and you get a somewhat "simple and around teh clock" solution that doesn't need a nuclear reactor and can be domestically produced on teh moon. In all of this teh most expensive thing is setting it up and drilling the hole, but it's only expensive due to teh energy requirrement for teh microwave laser adn transport costs. Btw. a positive aspect of this drilling is that you basically have very little down time for repairs and very few components with damage, regolith plays havoc with machinery and moving parts, but the microwave laser doesn't have any moving parts.
The catch:
The biggest downside to all of this seems to be that to get 800°C, you need to ONLY drill about 300km down, not unfeasable with that microwave drill, but using that heat is a case of "no luck", I also couldn't find a good chart for how hot it gets at which depth, the limiting factor seems to be getting a "good temperature" though?
Also here's something from NASA about that idea, coudn't find where to read it yet, will try again tomorrow.
ntrs.nasa.gov/citations/19660026223
Edit START:
Yes, the "big brain move" is not shade itself, that is a requirrement, but not the solution, the suns heat would be unwanted on a radiator meant to disperse waste heat. No the "cheap parlor trick" is the reflective box with specific geometry, it allows us to radiate directly into space, this also works to a degree on earth, only the pesky atmosphere is an annoyance, it isn't on the moon though. The upside of this parlor trick, cheap as it is, is that you only need the "whitest white", or better yet, the best IR reflecive material and the "balckest black", also in regards to IR, the geometry means we can direct the waste IR by reflection and due to geometry even directly into the vastness of space itself, with a variable/movable outlet we can even make sure the sun doesn't reach into the box to begin with. This tech wouldn't exactly be usefull on the ISS, too heavy and with 90mins for one orbit this just isn't usefully to begin with, the moon is however way slower, during the night we can easily "beam teh waste heat into space" during the lunar day planing where to aim and generally building the box in a direction "where the sun don't shine" is paramount.
Notheworthy, although something our dear host doesn't quite believe in, even if this was proven on earth already, curtesy of TechIngridients, if they can do that in their backyard, so can we on the moon!
Edit END
Still think solar thermal would be better suited for crude von neuman machines but concede the point that moon solar labs should be persued at the earliest opportunitiy. Guess solar thermal should be primarially reserved for industrial process heating/preheating of regolith+derivatives.
how do you ground circuits on the Moon? regolith is not conductive, right? is Earth's earth more conductive?
There truly is no reason to use anything but nuclear for a moon base. RTGs could easily handle a moon bases needs, and while they do not produce much power on an individual basis (I think the most powerful is 300 watts currently) that same unit produces over 4kw of thermal. Chain up enough of these and you have some serious output! You could even put sterling engines to use to capture whatever excess heat you do not need for habitat purposes making the efficiency go up! Maybe even a small nuclear fission reactor could be useful.. Cooling would be an issue.. One benefit to an RTG is their lifespan, a plutonium-238 device would have a half life of 90 years.. Solar panels on earth only last 20ish years or so and I guarantee without big advancements the space environment will shorten their lifespan dramatically. RTGs can be buried for radiation protection etc
The weight of the solar cells is about 10%-20% of what they are on Earth. I don't think you've included any support structures / frames in your calculation.
mmm mirrors in space are too risky because of micro particles and debris. glass and mirrors are very fragile and could crack or shatter if dust or high moving particles strike the surface. Good idea though but too expensive and too risky.
If there are permanent dark zones on the moon's poles, wouldn't this make for better solar thermal sites? More so with vertical arrays rather then horizontal, using the back fore radiators as most the sky is away from the sun. You'd also have constant power making it perfect for human habitation.
From there we could spread to the equator with mostly automated systems that use the cheaper solar electric.
There is two "i" in Aluminium.
Of 270 countries in the world, only one or two say it your way, with one i
Have you considered Thermophotovoltaic? 40% efficient using mirrors...
Like they wouldn't have a fucking solar array that can direct the solar light to array of solar and mirrors to heat sterling engines and charge panels for ultimate power and then have cheap power
Why not build a small nuclear reactor...... space is pretty cool therefore you can save all the water used as you can quickly cool it down...
Moon dust would ruin your 90 percent reflectivity...
its all so tiresome. a million smart speculations about energy needs in space, but zero awareness that engineering has to start back from zero. literally every single machine and structure on planet earth is engineered with the idea that there is earth like pressure, speed of sound, and gravity. you literally cannot use the same machines or build the same structures using structural engineering principles on the moon, mars, or anywhere without at the very least ~0.9 earth gravity if we are being ludicrously generous with tolerances. just on the industrial stuff alone we would have to rework centuries of
ore smelters requiring earth like convection and gas flow.
blast furnaces engineered for earth pressure and gravity.
refinery distillation columns relying on 1g fluid separation.
pulp and glue mills counting on earth atmosphere drying.
concrete and other aggregated bonded material batching dependent on earth gravity mixing.
calibrated large scale hydraulic presses.
drilling rigs designed for earth downforce and friction.
our entire science of fracking and soil mechanics is based on earth subsurface pressures.
steel mill rolling lines depending on 1g material transport.
open pit mining excavators built around earth soil bucket loads.
cargo and crane systems balanced on earth gravitational torques.
conventional conveyor belts sized for earth friction and weight.
on and on. going to mars or the moon means we have to re-invent the industrial age. energy is not the problem and engineering is not free you cant just expect us to 'make it work'
Facts
Why do you go on and on about solar when we can easily import nuclear plants.
Thank you for sharing this in a relatively comprehensive manner for most folks. I've been saying the same thing for quite some time. ☠️⭐oo🕕🕘