13 ms·
A tall chimney to facilitate heat exchange in the atmosphere
- pmoriarty 9y agoHow much will one of these cost?
- jack_pp 9y agoVideo says at the end that one 20m diamater chimney would cost 5MM and that 25k chimneys would solve global warming. Video is from 2013.
- kawera 9y agoI guess nobody really knows although the author touches the subject here: http://www.superchimney.org/build.html http://www.superchimney.org/build.html
- iokevins 9y agoFrom another page: PRICE It is difficult to estimate the price at this point. Materials should be more expensive than those used for hot air balloons, since they have to be multilayered. Even if they are ten times as expensive the price should be under 10/ m2 (see http://www.alibaba.com/showroom/hot-air-balloon-fabric.html http://www.alibaba.com/showroom/hot-air-balloon-fabric.html). To build 20 m diameter chimney would require as much fabric as 300,000 m2 of fabric or $3,000,000. Outside roping, mushroom cap, ground base, labor and machinery to inflate will increase the price. However, I do not see it bringing above $5 million. Thus, if 25,000 chimneys of such size are enough to stop global warming, the investment will be less than 1,250 billions (annual US budget deficit). Furthermore, as we get more experienced with building super chimneys, we can make them more powerful by making them taller and wider. The benefits will be millions of acres of arable land in deserts around the world, fresh water, electricity etc. It is quite possible that we can end up making profit on solving Global Warming problem. Link: http://www.superchimney.org/build.html http://www.superchimney.org/build.html
- zyb09 9y agoIts 125 billions, not 1250 billions. Also US deficit is around ~500 bil now (way less then 1250b, but more then 125b)
- iokevins 9y agoWikipedia[1] reports deficit was ~1,250 bilions in the 2011-12 timeframe, dropping significantly in 2013. Wayback machine[2] seems to indicate the author wrote the page in the 2013 timeframe, so the figures probably need updating. [1] https://en.wikipedia.org/wiki/United_States_federal_budget#/media/File:U.S._Total_Deficits_vs._National_Debt_Increases_2001-2010.png https://en.wikipedia.org/wiki/United_States_federal_budget#/... [2] https://web.archive.org/web/20131210100653/http://superchimney.org/build.html https://web.archive.org/web/20131210100653/http://superchimn...
- bousaid 9y agoApparently people didn't watch the video. The author estimates $5M
- stephengillie 9y agoWould this be an efficient source of air pressure for the Hyperloop?
- LeifCarrotson 9y agoHyperloop needs vacuum, not pressure.
- erikpukinskis 9y agoPressure can be efficiently converted to vacuum I believe.
- wolfgang42 9y agoI'm not sure why this is being downvoted. The method that immediately comes to mind is using the Venturi effect, though admittedly I don't know the efficiencies involved.
- deleted 9y ago[deleted]
- snerbles 9y agoCouple the tower to an enormous array of venturi tubes. Whether the vacuum generated from the flow is adequate for hyperloop use, and how to actually connect the vacuum lines from the absurd contraption to the hyperloop tube in a structurally sound manner are left as exercises for the reader.
- deleted 9y ago[deleted]
- Jaepa 9y agoAre you suggesting that the hyperloop built 5km up? Also no, as LeifCarrotson mentioned, the hyperloop is removed air to reduce drag.
- hossbeast 9y agoUnreadable on mobile
- stephengillie 9y agoThis embedded 10-minute Youtube video contains the core ideas: https://www.youtube.com/watch?v=BfITeN76Thc https://www.youtube.com/watch?v=BfITeN76Thc Notes: - Warm air naturally moves up, and cool air naturally moves down. A chimney is like a hot air balloon - The taller the chimney, the faster the smoke rises. Exponentially. - The temperature drops 10 C every 1000 meters we go up. This is because there is more heat at the ground than in the sky (Transcriber's note: Dense air at the surface can store more heat than thin air near space can.) - Consider a 5km chimney - the air at the base will be 50c warmer than at the top. This will cause dramatic airflow, up to 300 mph. While the air inside will be like the air outside, it will be hotter inside, due to the lack of Adiabatic cooling. When air rises, it pushes on the air it's passing, causing it to exchange heat with the air it's passing. - By contrast, the chimney compresses air and causes it to gain heat and rush up, cooling the chimney. - When warm air exits the top, the hot air causes precipitation in the cool air it's entering. AKA sudden clouds for deserts, or Oasis_aaS. - Deserts are ideal, as they allow year-round operation. (Transcriber's note: Does that mean the ground and the upper atmosphere are less than 50C difference in northern areas?) - The rains will cause carbon fixing, as more plants consume it and biodegrade into dirt. - Global warming isn't caused by the planet receiving more heat, but by the planet storing more heat. (Transcriber's note: As an amateur astronomer, I disagree slightly. Part of the problem is how even our orbit is, which will change over the next 100,000 years.) - This is basically a heat pump for the planet, like a reverse hurricane. - There's less atmosphere between the upper atmosphere and space, than there is between the surface and space, so more heat will be radiated away by the air in this way. And the thinner atmosphere will reabsorb less of that heat than the denser atmosphere near the surface would. - The chimney will be suspended entirely by the buoyancy of the air leaving it - it will have a "mushroom cap" which will direct exiting air downward, to push the chimney upward. - They're expecting to use Hot Air Balloon fabric, and that it will be sturdy enough to be 3 miles (5 kilometers, 1640 story building) tall, and withstand winds and other shearing forces. - Close the mushroom caps, and use hot air balloons, during initial inflation; then open the mushroom caps once it's fully inflated. - 20 meter diameter chimney is estimated to cost ~ $5000. - 25k super chimneys needed to completely address global warming, estimated cost $125,000,000. - Total global economy estimated at $71,277,000,000,000, so this is a 0.17% global GDP investment opportunity. (Transcriber's note: IANAL nor fiduciary.) There's a table included too, it's not easy to reproduce: Height m - 2000 - 3000 - 4000 - 5000 - 5000 - 5000 - Diameter m - 500 - 500 - 700 - 1000 - 10 - 20 - Air Temperature at the base ?C - 30 - 30 - 30 - 30 - 30 - 30 - Air Temperature at the upper end ?C - 10 - 0 - -10 - -20 - -20 - -20 - Air Speed m/s - 52.7 - 80.4 - 109.2 - 139 - 139 or 500km/h or 300mph - 139 or 500km/h or 300mph - Air Flow kg/s - 12,034,838 - 18,379,911 - 48,938,418 - 127,292,000 - 12,729 - 50,916 - Producing electric power Mega Watt - 4447 - 15790 - 77542 - 327,786 - 32.8 - 131.1 - amount of water condensate/precipitation kg per second - 0 - 73,520 - 327,887 - 929,231 - 93 - 371 - CO2 uptake by irrigated desert tons - 0 - 147835 - 946,146 - 1,478,354 - 148 - 592 - number of super-chimneys needed to cool the atmosphere - 224 - 99 - 27 - 10 - 100,000 - 25,000 Edits complete.
- jcrawfordor 9y agoThe short story "Shortstack" by Walt Richmond and Leigh Richmond depicts this idea and was published in Analog in '64. Likely coincidental, but amusing to see '60s science fiction apparently made flesh.
- desertrider12 9y agoThe scifi novel "Omega" by Jack McDevitt also had this.
- chroem- 9y agoWhoever made this assumes that the chimney wall would be a perfect insulator, which absolutely cannot be the case if it's supposed to be a thin cloth or film barrier. The air would cool to the same temperature as the surrounding atmosphere. This will not work.
- sp332 9y agoIt only has to be a reasonably good insulator. And anything that can stand up to winds at kilometer altitudes will do fine.
- roceasta 9y agoI doubt it has to be a good insulator. The air is travelling up the tube at high speed and there isn't time for it to cool significantly before it emerges.
- chroem- 9y agoNo, it would have to be a very, very good insulator. You're talking about three miles of tubing exposed to high speed winds and large convective heat losses. Anyone who's taken a course on thermal power systems would know that this is absolutely preposterous.
- sp332 9y agoI'm not saying it's feasible or anything, but he's talking about moving air at over 100 miles per hour. It would only take a couple of minutes to get to the top.
- roceasta 9y agoRight, plus it's a 30 metre diameter tube. The bulk of the air moving up the centre would be insulated by the outer layers of air near the inner skin of the tube.
- stefantalpalaru 9y agoIf a constant air flow is needed to keep the chimney upright, what will happen during the night, when the desert cools down?
- ajmurmann 9y agoThat is a very good question. I was wondering about this myself but guessed that the upper atmosphere will still be significantly colder.
- undersuit 9y agoThe video shows the chimneys mostly being built in deserts and their table has an example of 2km tall chimneys working on only a 20 °C difference. If you're building in a place where the winters or nights are particularly cold you should just built higher to exploit the colder temperatures further in the troposphere.
- deleted 9y ago[deleted]
- mikeash 9y ago"The inside and outside air will be rising up. However, the air outside will be cooling adiabatically, so its temperature will be dropping. The air inside will be not affected by adiabatic cooling and will maintain its energy, so it will be warmer and less dense than outside air." Is this a joke, or a crazy person? Air in the tube will expand and cool just like air outside the tube does.
- humanfromearth 9y agoFrom the FAQ. His answer is: > Air inside the chimney is not affected by adiabatic cooling. Unlike freely rising parcel of air, the air in the chimney is restricted in its horizontal expansion and thus, it is not free rising. When air rises in the chimney, it also expands but only into upper direction. It compresses the layer of the air above it, heats it up and loses its own heat. At the same time the air below does the same thing. And that how it goes all the way until the chimney exit: layers of air are being pushed and push themselves. That results in maintaining the same amount of heat in every layer of air, and that is why the chimney works.
- mikeash 9y agoSounds like complete bullshit to me. Expanding upwards will accelerate the air above, not compress it.
- deleted 9y ago[deleted]
- erikpukinskis 9y agoWhy not both? And why can't you state your analysis without calling other analyses offered in good faith bullshit?
- mikeash 9y agoThis site is pretty much on the same level as sites advertising perpetual motion machines. I don't need every little detail to observe that it's bullshit. Unless you confine a parcel of air in all directions, it will match the pressure of the surrounding air. Consider an arbitrary cubic meter of air at 15°C at sea level at the base of the tube. Now raise it 1,000m inside the tube. That air now occupies roughly 1.12 cubic meters and is at a temperature of roughly 5°C, the same as if it had risen 1,000m outside the tube. The tube will work sometimes, but only when the atmosphere is unstable. Since the chimney is 5km tall, that means thunderstorm conditions. You can only extract energy from a tube like this if there's some energy potential between the two ends. The atmosphere is constantly erasing differences in energy potential, so large-scale differences are ephemeral.
- humanfromearth 9y agoFor the 5km chimney it needs to hold on 500km/h winds. For scale a category 5 hurricane is 250 km/h. Is it even possible to have that kind of structure with existing materials?
- foota 9y agoI'm not a real engineer, but most structures don't have the ability to flex like this tube could.
- totalZero 9y agoRich Homie Quan couldn't even flex like this tube could. Making really tall stuff is hard.
- ErikVandeWater 9y agoWhile I am generally skeptical of this idea, 500km/hr winds occur at much higher altitudes - the force is much less than it seems because there is much less air doing the pushing. If a human can get to the edge of space and freefall safely, I imagine that will not be the sticking point.
- robotresearcher 9y agoThe falling human is free to move with the wind. No shear forces. Unlike a tower attached to the ground.
- kbenson 9y agoThey are proposing a fabric chimney. For sure that has its own challenges, but shear force isn't as much a problem, from I would intuit the setup to be.
- robotresearcher 9y agohttp://www.wavyads.com/images/skyfly-dancer-yellow2.jpg http://www.wavyads.com/images/skyfly-dancer-yellow2.jpg
- SubiculumCode 9y agoWatched the video. Sounds miraculous :) Anyone here knowledgeable of atmospheric thermodynamics?
- Tarrosion 9y agoSo many signals suggesting this is a wild physics-defying idea that could never work, e.g. how many websites claiming 'this one neat trick solves global warming' really hold the key to solving global warming? I hope that's not the case and by this time next decade we're all laughing about that century and a half where we put so much carbon in the atmosphere wow wasn't that a hoot... Realistically, I am sympathetic to the idea that geoengineering, massive structures and engineering projects enabled by modern materials, etc. deserve more thought.
- erikpukinskis 9y agoYour critique of the proposal is ascientific.
- vermilingua 9y agoAnd your lack of justification is ascientific.
- ajmurmann 9y agoUnfortunately no concrete concern was voiced that could be addressed other than vague comparison to hoax websites.
- ChuckMcM 9y agoPresumably you just lay a pipe that goes up the side of Everest and free power! I wonder if the author asked the question "Why don't we have tornadoes all the time?" If they had, that would have lead them to the physics of tornadoes. In my case it was the physics of so called 'dust devils' in the desert which are much smaller phenomena but based on the same ideas. Warm air rising through cooler air. You might ask, but why don't we have them all the time? And the answer is that as air goes up, it spreads out, and as it spreads out it becomes less dense, and the lack of density is perceived as a colder 'temperature' even though the air molecules still have more kinetic energy and are thus 'hotter'. In the video the tube is supposed to constrain the air (which it will) and the warmer air will rise inside of it, but without an energy source the warm air rises until its 'weight' is equivalent to the un-risen air underneath it, at which point it stops rising and the system is stable. If you were to cool off the bottom the air would start sinking again. This has been experienced time and again by inexperienced makers of fires in their fireplaces. If you don't put enough energy into the air to make it rise, it comes back down the chimney and fills your living space with smoke. A fireplace is a remarkable little machine, where the fire heats the air, which pulls in more air as the air above rises, which puts more oxygen into the fire and increases its energy output etc. But without the fire burning in the fireplace the air stops moving. Tornadoes benefit from a mass of really cold air sitting on top of warm air. This does two things, one the cold air above pushes down on the warm air to pressurize it, and two when a "hole" begins forming in the cold air mass it operates like an inverted tub drain and the warm air starts draining out of the tub. The energy source for a tornado is the temperature differential that is set up by the result of moisture condensing out of the air and super cooling the air around it. Similarly a hurricane is powered by the temperature differential between the ocean and the air above it. All three systems (fireplace, tornado, hurricane) share a common theme, there has to be a source of energy for them to operate. Without it, the air reaches equilibrium and just sits there. No magic allowed. That said, if instead you built a tunnel, then you could connect two different air masses and extract energy from two different pressure differentials. The most interesting ideas have a tunnel under the Rockies or under the Sierras between the Mojave desert on one side and the milder (and moister) climate on the other. To the delta you can get from that is linear with respect to distance and/or a geographic feature that can inhibit the natural balancing of the air masses (like a range of tall mountains). Sadly neither super chimneys nor lighter than air vacuum balloons are workable ideas. Edit: It occurs to me that if you could make the chimney high enough you could put the top in the underside of the jetstream, then you could suck air up using the venturi effect.
- pdonis 9y agoWe already have something that does the same thing as this claims to (facilitate heat transfer from the surface to the upper atmosphere): it's called the hydrologic cycle.
- deleted 9y ago[deleted]
- vmarsy 9y agoThis reminds me of Solar updraft tower prototypes [1], which concentrates heat at the bottom of the chimney instead of expecting cold air at the top of the chimney. There's still a delta of temperature between the top and the bottom, but instead of T_bottom_chimney = T_hot_ambient_air_bottom T_top_chimney = T_cold_ambient_air_top it is : T_bottom_chimney = T_much_hotter_than_ambient_air_top T_top_chimney = T_ambient_air_top Everytime I start reading things like this, I wish I had a home with similar 'magic', like Solar chimneys[2] and other techniques[3], [1] https://en.wikipedia.org/wiki/Solar_updraft_tower https://en.wikipedia.org/wiki/Solar_updraft_tower [2] https://en.wikipedia.org/wiki/Solar_chimney https://en.wikipedia.org/wiki/Solar_chimney [3] https://en.wikipedia.org/wiki/Ground-coupled_heat_exchanger https://en.wikipedia.org/wiki/Ground-coupled_heat_exchanger
- SubiculumCode 9y agoThis may be relevant: Free-standing inflatable solar chimney: experiment and theoryhttps://works.bepress.com/nima-fathi/9/ https://works.bepress.com/nima-fathi/9/
- SubiculumCode 9y agoI was getting convinced by the comments below that this is a nutty idea, but then ran across this review by real researchers in a real journal (impact factor: 8) in which they discuss super chimneys and other methods. Abstract and links below: Fighting global warming by climate engineering: Is the Earth radiation management and the solar radiation management any option for fighting climate change? Abstract The best way to reduce global warming is, without any doubt, cutting down our anthropogenic emissions of greenhouse gases. But the world economy is addict to energy, which is mainly produced by fossil carbon fuels. As economic growth and increasing world population require more and more energy, we cannot stop using fossil fuels quickly, nor in a short term. On the one hand, replacing this addiction with carbon dioxide-free renewable energies, and energy efficiency will be long, expensive and difficult. On the other hand, meanwhile effective solutions are developed (i.e. fusion energy), global warming can be alleviated by other methods. Some geoengineering schemes propose solar radiation management technologies that modify terrestrial albedo or reflect incoming shortwave solar radiation back to space. In this paper we analyze the physical and technical potential of several disrupting technologies that could combat climate change by enhancing outgoing longwave radiation and cooling down the Earth. The technologies proposed are power-generating systems that are able to transfer heat from the Earth surface to the upper layers of the troposphere and then to the space. The economical potential of some of these technologies is analyzed as they can at the same time produce renewable energy, thus reduce and prevent future greenhouse gases emissions, and also present a better societal acceptance comparatively to geoengineering. Here are links to the paper: http://www.sciencedirect.com/science/article/pii/S1364032113008460 http://www.sciencedirect.com/science/article/pii/S1364032113... or the research gate link: https://www.researchgate.net/publication/278826192_Fighting_globalwarmingbyclimateengineeringIstheEarthradiation_managementandthesolarradiationmanagementanyoption_for_fighting_climatechange https://www.researchgate.net/publication/278826192_Fighting_...
- foota 9y agoAny idea how tall one of these would need to be in theory to support itself? I think that would be a cool sight to see and a great way to prove feasibility.
- Cheapshotx 9y agoits bunk science i have no clue why this got top of hacker news
- yohann305 9y agoAnyone here could run a super tall chimney software simulation ? I'm super interested in seeing someone confirm or debunk this. Anyone else interested, upvote please
- microcolonel 9y agoProbably nearly impossible. Fluid dynamics simulations are horrendously time consuming even at low resolution and small scale. This is bound to be more of an engineering stunt than a scientific endeavor.
- foota 9y agoHere's my analysis from maybe wrong principles. If you have slightly more dense air beneath slightly less dense air, the air will experience a net force upwards. If this net force is stronger than gravity, then the air will experience upwards acceleration. This will continue as long as there is a difference strong enough. At the top of the tube, there is no more force since the density will be the same since the air will spread out after exiting. (If it's not already at the same density after going through the tube). Looking at it this way this seems sound to me, am I wrong?
- ChuckMcM 9y agoIt is a bit different than that. Air is compressible. And because of that the mass of air that is being pulled toward Earth by the gravitational attraction of the rest of the planet means it compresses as much as it can as close to the surface as it can get, and then becomes less and less dense as you increase the distance from the center of the Earth. This is nominally a stable state. Air doesn't move. When you inject energy into air, that increases the kinetic energy of the air molecules. They bounce off each other and push themselves apart. As a result they have "more space" between them that air molecules than ones that aren't currently heated. What will happen then is the 'less energetic' molecules will 'fill in the spaces' left by the more energetic ones bouncing apart. You might visualize this like sand filling in a hole you are digging by throwing other sand up into the air. If you do nothing, more energetic molecules end up higher up, and less energetic ones end up lower. Colloquially, "hot air rises". And if you constrain it in an envelope of some form (a balloon for example) then you can create a mass of air that has a lower average density than the air around it and that results in a lifting force. Here is the rub, as long as you put heat into the air it will stay less dense and your balloon will stay in the air. However, stop adding heat (energy) and the balloon cools and begins to sink. Finally, there is a point where you cannot add any more energy to the air to get it less dense than the air around it. In balloonist terms that is your balloon's ceiling height. 2004 record was 4.1 miles[1]. This is a balloon where you have a super hot flame shooting up into it, and it won't go up any more because you have reached the point where you cannot put enough energy into the air to make it less dense than the surrounding air. As a result, if you surround a column of air, it might initially rise because energy inside the column is unable to diffuse into the air around the column, but it will only do that until it reaches a new equilibrium point. Early on in the process not being able to spread out allows the air to keep its heat, but at it moves up in the tower/chimney the chimney prevents it from becoming less dense, so relative to the air above it, it gets heavier and heavier per cubic foot. These two effects balance out and the air stops moving. [1] https://en.wikipedia.org/wiki/Flight_altitude_record#Hot-air_balloons https://en.wikipedia.org/wiki/Flight_altitude_record#Hot-air...
- randyrand 9y agoThis will also function as a hell of a bird vacuum.
- animex 9y agoThis model must be able to be simulated somehow! To Minecraft!
- pbhjpbhj 9y agoWell we have pipes that go up the side of mountains, open both ends, add a skirt to the bottom, measure if there's a temperature rise at the top? Then you can start working on viability of materials and such, no?
- desireco42 9y agoI think this, however flawed some of the explanation of the effect might be, is something we can try and experiment with fairly easily. Either it can be done, or not. And I believe it can. Now, we can't let Musk do all the cool things, maybe someone else could step in and fund a project to explore application of updraft towers.
- lend000 9y agoFor those skeptical of the science, note that there are large caves that exhibit this property, such as: https://en.wikipedia.org/wiki/P%C4%B1narg%C3%B6z%C3%BC_Cave#Wind https://en.wikipedia.org/wiki/P%C4%B1narg%C3%B6z%C3%BC_Cave#... It seems like if the inside of the chimney column had a spiral shape, similar to a screw socket, the upward air pressure might alleviate some of the stress and make the column more structurally feasible. Granted, it would also dissipate some of the energy as heat.
- fenomas 9y agoCaves like that presumably connect two areas of air that are not otherwise connected, and not in equilibrium with each other, no? Unless I'm missing something, TFA suggests that you can take a big system that's generally in equilibrium, and run a tube from one part to another, and get a similar effect. This seems like a very different proposition from what's happening in caves like you mention.
- koverstreet 9y agoThe atmosphere is emphatically _not_ in equilibrium. Why would you think it was? There's a giant fusion engine pumping energy into it, resulting in a fuck of a lot of activity (wind). In particular, the upper atmosphere would not be colder than the lower if it was at equilibrium. Think about it.
- fenomas 9y agoI didn't say the system was closed. Why would you think I did? All I meant was that energy is free to flow around the atmosphere if it wants to; any macroscopic flow that wanted to occur would have occurred already. In other words, caves like the GP mentioned (presumably) connect two systems between which energy is not otherwise free to move. That is not the case for a tube connecting two different sections of the atmosphere. Make sense? > In particular, the upper atmosphere would not be colder than the lower if it was at equilibrium. Think about it. Temperature varies inversely with pressure for a volume of gas. If low- and high-atmosphere gas had the same temperature, despite being at different pressures, that would be an imbalance.
- ryanobjc 9y agoA spelling error makes it hard for me to take the proposal seriously. For something as important as this, the details count. A loose approach to spelling is disturbing.
- millstone 9y agoIt's clear from reading that English is not the author's first language. This isn't a case of sloppiness.
- dghughes 9y agoWouldn't such a chimney take off like a Chinese lantern?
- shoefly 9y agoWhatever we do, it's important that we learn how to control the "ingredients" of our atmosphere. There are so many things that could go wrong with our atmosphere and result in mass extinction. Global warming, ice ages, massive volcanic eruptions, etc. If we can find a way to quickly filter out the crap and rebuild our atmosphere... well, this technology could be used for protecting our Earth and future pursuits in space.
- scythe 9y agoThese geoengineering proposals should be understood as mitigation strategies to be implemented after we have reduced carbon emissions, since even then we still have a problem. But this one seems very dubious. >Speaking in terms of thermodynamic, we can say that chimney prevents adiabatic cooling of a rising parcel of air. Normally, when hot air freely rises in atmosphere, it expands as it gets higher and pushes the surrounding air. That causes surrounding air to heat and rising air to cool. That process continues until equilibrium is reached. At that point air stops its ascending. Unlike freely rising parcel of air, the air in the chimney is restricted in its horizontal expansion and thus, it is not free rising. When air rises in the chimney it also expands but only into upper direction. It compresses the layer of air above it, heats it up and loses its own heat. At the same time air below does the same thing. And that’s how it goes all the way until the chimney exit: layers of air are being pushed and push themselves. That results in maintaining the same amount of heat in every layer of air, and that is how the chimney works. This explanation ignores gravity. Air above you exerts more pressure on you than air below you, albeit by a tiny amount. But when the only thing moving is air in a 5-kilometer chimney, you can't get something for nothing. For intuition, just imagine the chimney is full of water. The water at the bottom is obviously under more pressure than the water at the top. The chimney faces the same consideration, but the ideal gas law applies. Furthermore, the equation used in the "Calculations" section: >q = Π dh2 /4 [ (2 g (po - pr) h ) / ( λ (l pr / dh) + ∑ξ pr ) ]½ is sourced from this website: http://www.engineeringtoolbox.com/natural-draught-ventilation-d_122.html http://www.engineeringtoolbox.com/natural-draught-ventilatio... which rather obviously works from the assumption that the chimney is placed inside of a heated house. This all seems to be a sort of Sokal effect in climate science, I'm afraid. The paper 'SubiculumCode cited does not really analyze the thermodynamics used for the chimney and points more to the unrealistic dimensions (1 kilometer diameter and 10 kilometers high).
- kpil 9y agoIs it really a good idea to move more water vapor, a potent greenhouse gas, significantly higher up in the atmosphere?
- tempestn 9y agoDoesn't water vapor high in the atmosphere reflect more energy upward than downward? I recall another geo-engineering proposal that involved autonomous ships that would spray water up into the atmosphere to reflect the sun's energy.
- kpil 9y agoAs far as I know, it gets colder on the ground when there is a clear night. Presumably the radiation is absorbed by the clouds and the heat stays in the atmosphere. I have absolutely no idea how it compares to reflective clouds during the day.
- robocat 9y agoNice debunking write up here: http://climateboy.blogspot.com/2009/04/super-chimney-that-will-save-us-all.html http://climateboy.blogspot.com/2009/04/super-chimney-that-wi...
- abainbridge 9y agoI don't find the debunking article persuasive. It says, "Imagine you take a blob of warm air from the surface up to some height... this transformation has to change the temperature of the air in the blob." No it doesn't. The nearest it gets to supporting that claim is, "It turns out to be very easy to derive an equation that says that the temperature decreases by 10 degrees C per about 1000 m of height with no vertical motion. That explains why the air above the surface is colder than the air at the surface." I'd like to see the assumptions of deriving that equation. Without seeing how the equation is derived we can't jump straight to the "That explains why" part. I guess the equation he's talking about assumes the atmosphere is static and is simply deals with how the upper atmosphere is colder because it can radiate into space, whereas the lower atmosphere can only exchange radiation with warm ground or the cold-but-still-warmer-than-space upper atmosphere. If so, it says nothing about what happens when you "move a blob of warm air". Maybe building these things is not feasible or maybe the effect is not significant, but it doesn't look physically impossible to me.
- frede 9y agoThe air cools down when raising in the chimney because the air pressure decreases, leading to adiabatic expansion.
- kashkhan 9y agowhen any gas expands, it does work in expanding against the outside "surface" of the control volume, which comes from the internal energy - temperature - of the molecules. The equations are commonly derived in thermodynamics undergrad courses. look up adiabatic expansion. here's a video: https://www.youtube.com/watch?v=ObnWb7yspxA https://www.youtube.com/watch?v=ObnWb7yspxA
- 9y ago
- gtt 9y agoI've tried to simulate 1km chimney in Comsol, but I cannot make it converge to a solution. If anyone is interested, the model is here https://mega.nz/#!jFgBxI6J!jdxloYFwcuk_YyGcIMlOmJTKcPbxyD2B4Hvuo1OIoFM https://mega.nz/#!jFgBxI6J!jdxloYFwcuk_YyGcIMlOmJTKcPbxyD2B4... (may be I'm doing something wrong with simulation parameters, help would be very much appreciated!)
- gus_massa 9y agoI don't have Comsol. Does it make nice graphics? Can you post a screenshot (in imgur)? [Disclaimer: I think this idea doesn't work. If you wish to make it work try adding a huge glass bell like the one explained in other comment.]
- gtt 9y agoYes, it does, the problem is, the basic setup isn't converging to solution so nothing to plot, which is unusual and probably means I choose wrong boundary conditions or something.
- the_rosentotter 9y agoSo five kilometers of flailing inflatable tube man. I get that the upwards wind force can sustain the fabric structure, but it is hard to imagine that it could also carry a bunch of huge turbines, as well as the cabling required to carry the generated electricity. Not to mention safety concerns. Does this seem unrealistic to anyone else? Also, would it be possible to do a proof-of-concept using an existing man made structure like Burj Khalifa class skyscrapers? Presumably it would be easier to deploy a tube off the top of one of these than to build one from scratch.
- fastball 9y agoWould the radiant heat from the ground be enough to continue this effect at the same rate during the nighttime?
- Thetawaves 9y agoThis line of inquiry is the key to proving or debunking this. Apparently a few here think that the chimney will fall over when the sun goes down. This analysis fails to capture the fact that the upper troposphere also cools when the sun goes down - resulting in a maintained differential between the input and the output.
- unabridged 9y agoThings like this are the reason I don't think global warming will ever be a problem. Even if this example turns out to be a pipe dream, we will eventually figure out a way to lower the temperature or remove co2 from the atmosphere.
- Tharkun 9y agoGlobal warming is already a problem.
- mbfg 9y agoGiven this, if successful, is creating storms at the top, won't it continually and repeatedly be hit by lightning? And given that it is some kind of fabric, cause havoc?
- smoyer 9y agoIf the column of air is really moving at 300 MPH, they'd better diffuse that at the bottom so people (and things) aren't sucked into the chimney (it would suck to be ejected at the top without a parachute but you could probably sell a ride to the top to the wing-suiters).
- saalweachter 9y agoSo my question is "why wouldn't this just rip in half from the forces it's under?" The upward force for the 20m chimney is calculated at ~600 tons. 600 tons is not a lot for a building to support in the downward direction, but quite a bit for a fabric tube to support, in tension. It's the rope/(space) elevator problem - you need a super material to handle that much force, don't you? But aside from worrying that our wacky inflatable tube of death will rip free from its tethers and tumble freely in the wind, killing thousands, I actually really like this idea, as geo-engineering. It is a process that can be stopped and started relatively cheaply, unlike a lot of other proposals. If the tube has unforseen effects, it could be deflated and reeled in, unlike eg throwing particulate into the upper atmosphere.
- rlpb 9y agoPerhaps such a chimney could be built inside the shaft of a space elevator, canceling out the forces. I'm only being half serious, but it is nevertheless interesting that the required structural challenges act in opposite directions.
- codecamper 9y agoHate to be a downer, but out of 157 comments so far, nobody has mentioned ocean acidification. If there was a way to build these chimneys... we could then go on burning fossil fuels & so then the oceans would become more acidic, possibly leading to the inability of krill to form exoskeletons, removing a one of the main oceanic bottom of the food chain food sources.
- datadata 9y agoEngineering issues aside, to evaluate if a super chimney would be energetically viable you need to understand the concept of "Convective available potential energy" or CAPE--https://en.wikipedia.org/wiki/Convective_available_potential_energy https://en.wikipedia.org/wiki/Convective_available_potential.... CAPE has dimensions of energy/mass and a describes how much energy is released by raising a mass of air to some higher elevation. CAPE is used to forecast storm development, as updrafts can more likely spontaneously form when there is more energy released by the updraft. CAPE values can also be zero or negative, in which case there would be no available energy to sustain an updraft. From my understanding, CAPE is the only factor that would determine if a super chimney could work at a given time. I have not found a good resource on global CAPE patterns including daily patterns, but it seems very likely that there is any fixed location and fixed elevation that always has a positive CAPE value. It would be an absolute requirement to find such a location for this project to work. You should also be able to calculate a crude bound on the maximum updraft velocity simply as a conversion of potential energy to kinetic energy. Wikipedia says that exceptionally high CAPE values proceeding extreme thunderstorms are around 5kj/kg, which would accelerate a mass from rest to 100m/s (220mph). Of course this is an extreme value, typical values are more like 1kj/kg, which correspond to a velocity of 44m/s (100mph). Here is a really good paper on CAPE and atmospheric convection heat engines: http://journals.ametsoc.org/doi/pdf/10.1175/1520-0469%281996%29053%3C0572%3ANCAAHE%3E2.0.CO%3B2 http://journals.ametsoc.org/doi/pdf/10.1175/1520-0469%281996...
- SubiculumCode 9y agothank you
- LASR 9y agoThis is so dumb. Hot air rises only because there is cold air falling to replace the hot air that is rising. If the principles for this super chimney to work, then why do we even have any air at the surface? The surface air is hot. The air above is cold. Then all the surface air must have all gone up and we would be left with a vacuum at the surface. So why do we have any air at all at the surface then?
- mbfg 9y agoIf you search 'solar tower' on youtube, you will see all kinds of videos of existing installations of things that are similar, albeit most are not as tall, nor are they flexible. But the basic concept appears to be the same. Quite a few of them are from many years ago. So it would seem the idea works to some extent, and perhaps the the idea of a much taller, and flexible variant is the crucial difference that will make a big difference.
- toddh 9y agoWould it be possible to make these into skyscrapers to house people and businesses? That would handle the financing part of it.