Hello, Such devices are what I have been thinking about for the last years.
First, remember that the atmosphere is naturally ventilating itself, through convection. Could it be useful to tame or to enhance this natural phenomenon? Two "yes" answers are possible. 1st "Yes": in order to harvest the corresponding power, more efficiently than if building wind turbines all over the planet. This means obliging the heated air to pass through the ducts which the message describes, i.e. not letting it convect freely. This means creating a very large transparent barrier, i.e. the horizontal "solar collector" of a "solar chimney", a concept which has been experimented in the 80's in Manzanares (Spain) and is currently studied for full scale implementation in Australia, Namibia, China, Spain again, ... The idea of building the chimney not stand-alone vertically (rather difficult for a 10000 m height), but along a mountain, is a good one, but solar chimneys are better fitted to hot deserts, which haven't experienced ice ages recently, so that cliffs or long and sharp slopes are scarce (only a few volcanoes and the sides of the Red Sea - Ethiopia rift). 2nd "Yes": when convection is driven by latent heat (upwards movement of a moist air, which later turns to clouds and rain), an absence of convection is metastable: during the first hm of its rise, the moist air would only be cooled down by adiabatic cooling, and no buoyancy would be generated. This is typically what happens in the hurricane regions at the beginning of the summer: nothing. If it was possible to build a 2000 m high duct, the buoyancy (i.e. energy) budget would compensate this low-altitude negative buoyancy, thanks to stronger high-altitude positive buoyancy (where the latent heat would, at last, be converted to real temperature advantage). Then a little cloud-system could develop inside this duct, and funnel the ocean heat upwards. It would be both a renewable energy source, and a hurricane prevention tool (i.e. a quieter way, for the ocean surface, to dispose of its excess heat). An important problem for both "Yeses": a supple duct isn't enough, because, unless you choose the 1st "yes" and you put the turbine at the duct's top, the inner air of this duct is at a lower pressure than the outer air, and it gets squeezed by the outer air's higher pressure. If you really want to build an inflatable and buoyant chimney, you must design it as a collection of gigantic tori (plural of torus), like car tyres. This is more complicated to implement than the simplest idea which has been first developed by Ch. Papageorgiou (www.floatingsolarchimney.gr<http://www.floatingsolarchimney.gr/>). One of my conclusions is that they should be filled, not by too expensive Helium, but by hot air coming from the heat collector itself. Other ideas could be discussed, such as Atmospheric Vortex Engines, or "Energy towers" which have been studied in Israel. All are interesting, but all are facing very serious challenges. Some others have a connection with some branches of Geoengineering, such as CO2 capture from the ambient air, or CH4 catalytic oxidation. The thermodynamics and economics of growing vegetables under a solar chimney collector are also tricky. Renaud de Richter and I recently completed the redaction of a French book, "20 unusual renewable energies", to be published soon, and whose content is mostly about such ideas. As neither of us is a professional scientist, an English translation is not due very soon, unless somebody would boost us this way. Best, Denis Bonnelle [email protected]<mailto:[email protected]> De : [email protected] [mailto:[email protected]] De la part de Raymond Law Envoyé : lundi 26 octobre 2009 11:29 À : [email protected] Cc : geoengineering Objet : [geo] Re: ventilation concept Hi everybody, This atmospheric ventilation concepts is the best one I have read so far and I have just a couple of points on this method of enhancing the cooling of warm air in the bottom rung of the atmosphere by pushing them higher up for easier and more efficient radiation of its heat energy into space and beyond. 1. What about using huge-diameter ducting lying on the ground of a warm/hot land/plain and have it run all the way up the nearest hill or mountain. I think that this ducting's structural strength would be much less demanding and thus, drastic reduction in material, construction and servicing/maintenance costs. 2. If a more rapid ' pumping ' of surface air is needed, or, to building up the initial air column's upward moving momentum, huge booster fans could be easily put in place to do the job. Again, costing would be minimal when comparing with other expensive and complicated solutions. If more rapid pumping is required for a much longer period or more land area, just install more sets of ducting with or without booster fans. In any event, the reduction and/or removal of this cooling capacity would be completely under easy and low costs control, so we do not have to worry the activation of un-intended global cooling. Just doing my bit, Raymond Law On Mon, Oct 26, 2009 at 12:53 PM, global_frozing <[email protected]<mailto:[email protected]>> wrote: You know, the crocodiles have a four-chambered heart. They are also the top predators in their environment. The humans who could use the fire to support their body temperature got strong advantage over the mammoths. Hordes of pastoral nomads conquered the hunter-gatherers, then agriculturists forced the nomads out. The armies equipped with guns beat the archers and were then defeated by automatic guns. Aviation using 100000 hp engines made senseless the tanks, which use 1000 hp engines. Evolution goes its way. The countries and economical systems, which are able to use the energy in more intensive way usually have additional resources to control others and then enforce their own type of economic activity. So the human quest for the energy hardly will be stopped as the relationships between the countries and systems are still based on competition principles. Even after the open declaration of the state of global warming one of the main political tasks of main countries is still the search for new sources of oil and fighting for the access to these sources. All the geoengineering options suggested by last Royal Society report mostly require additional energy or limit the using of energy, so they will go against main evolutional trend and so their political future is uncertain. Meanwhile, what we have is 1) problem: excess energy ( high surface temperatures ) 2) reason: humans' insatiability for energy Obviously the most natural way will be to feed the first to the second. In case of the planet the role of cooling system is played by the weather processes such as typhoons, tornados and cyclones, which move the hot air up. They use the temperature gradient between the surface and the tropopause. Their working body is simple wet air. If you want to create the slight typhoon your main problem is the size of the device. The higher it will be the bigger gradient you will use. 10000 meters height looks appropriate. At this point most of potential investors stop to respond. The device, which is bigger then Mount Everest looks impossible. This is a prejudice. Large Hadron Collider is almost the same size if has been put vertically. It was made for $4.5 billion only. Your device should cost about several times less, because it is in fact mostly the big toroidal balloon filled with wet air. The usual balloon about 50 meters high costs about $25000, $3 per square meter, so the torus with radiuses 250 and 5000 meters will cost about 150 million. It is similar to the price of oil tanker. You understand that you will be able to produce the rain and the cold snap within a radius of ten kilometers and more as the device will move to the next point with the wind. If the speed of the internal air flow will be 30 m/s then the device will contain about 3 Terajoules of energy. If it will be possible to consume 1% every 5 minutes then it will gives about 111 Megawatt with very humble $1350 per kW initial capital cost. It will be interesting to know 1) the minimum size of it 2) the minimum cost of it 3) the maximum output power for the minimal configuration 4) can it provoke the weather changes much bigger than its own size? 5) how many of such devices necessary to stop global warming? 6) how much to get the answers to the questions 1) - 5)? 7) which organization can calculate the answers to the questions 1) - 6)? Some initial sketches are still here: http://www.globalfrozing.com/Atmospheric_powerplant_synopsis.html <br --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "geoengineering" group. 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