A few comments. First, I think it is important to be cautious about concluding that anything is unworkable when it is in the early conceptual stage; important not to discourage idea building that sometimes leads to novel places.
That said: I think of the thermal diode as a means of enhancing heat transfer to the atmosphere, and eventually to space. One application of this is to simply increase the rate of cooling of ocean water, independent of ice formation. Some years back a student and I pondered what humans might do if ice melting reduced the strength of the Gulf Stream. (The Gulf Stream is the replacement current for sinking North Atlantic Deep Water, NADW, a 15 Sverdrup downwelling of cold salty water in the Greenland/ Iceland/ Norway (GIN) area. The irony is that the consequence of excessive fresh melt water in the North Atlantic during warm periods is that northern Europe plunges into a deep freeze because NADW, a density driven current, slows or stops. This occurred about 12,000 years ago, for 1300 years, in a period known as the Younger Dryas when glacial Lake Agassiz flowed into the North Atlantic.) Our conceptual scheme for enhancing NADW was supplementing ice formation in the winter by pumping water to surface (we noted that this would only work if salt was trapped in the ice formed on the surface). It would be interesting to see if long thermal diodes might be an alternate scheme for generating cold downwelling water. But this need not focus on NADW: if the goal is to cool the earth or stop the thermal expansion of the ocean, get more heat out of it. The key engineering question would be, I think, the magnitude of heat transfer from diodes compared to that from the ocean surface itself: how much enhancement takes place. I think it is harder to conceptualize thickening sea ice with a thermal diode. If the diode is in the ice itself it will subcool the ice substantially, getting around the self-insulating property of ice. However, the diode gets farther away from sea water as ice forms at the bottom of the sheet. If the diode is below the ice sheet one wonders if the chilled water would sink away from the bottom of the ice sheet. This is not a problem for a thick glacier, which is riding on a lubricating layer of water: could one pin the glacier in place by freezing the bottom layer in winter, subcooling it enough to last through the summer season, since the insulating property of ice would now work in the opposite direction? Andrew's observation that open ice behind ice breakers quickly freezes over in cold weather is intriguing. Might one herd ice south from the Arctic Ice sheet, time and again, to increase the area of annual ice formation? The question of salt disposition if one thickens ice by pumping water on top of it is a persistent unknown. How I would love to see a test of this; as Ron points out, a submarine could easily be equipped to do a small scale test. Does the salt stay in the ice on the surface, or does brine find a way down to the sea, through microchannels. If the salt does stay, what is the impact in the spring. Peter Flynn Peter Flynn, P. Eng., Ph. D. Emeritus Professor and Poole Chair in Management for Engineers Department of Mechanical Engineering University of Alberta peter.fl...@ualberta.ca cell: 928 451 4455 -----Original Message----- From: Doug MacMartin [mailto:macma...@cds.caltech.edu] Sent: January-15-14 5:36 PM To: andrew.lock...@gmail.com; 'Ronal Larson' Cc: 'Keith Henson'; 'Geoengineering'; 'John Nissen'; 'Peter Flynn'; 'RAU greg' Subject: RE: [geo] Making ice (change of thread title) The only advantage is the disposition of the salt - making ice thicker at the bottom ensures that the salt stays in the water, not the ice. As has been pointed out before, we don't know what happens with the salt if you flood the ice from the top, nor whether higher-salinity ice creates a problem by melting earlier. However, given that the oil industry seems to use this approach regularly, it seems like it ought to be relatively straightforward for the right person to actually collect some data rather than simply trading hypotheses. (The right person almost certainly isn't me, much though I'd love the excuse to head up to the Beaufort sea.) -----Original Message----- From: geoengineering@googlegroups.com [mailto:geoengineering@googlegroups.com] On Behalf Of Andrew Lockley Sent: Wednesday, January 15, 2014 4:24 PM To: Ronal Larson Cc: Keith Henson; Geoengineering; John Nissen; Peter Flynn; RAU greg Subject: Re: [geo] Making ice (change of thread title) Personally, I can't see these thermal diodes being at all practical. Far cheaper and simpler to just break up the ice, or pump water on top of it. The maths is pretty simple. The thermal diode can only be at a temperature of the water, at a maximum. It's heat transfer is a function of the surface area exposed to the air. This heat exchanger is a manufactured item, and thus expensive, with a small surface area. Flooding the ice with seawater gives a far higher surface area and thus far higher heat transfer. A On 15 January 2014 21:58, Ronal W. Larson <rongretlar...@comcast.net> wrote: > Keith: > I go through line by line - but deleting as much as I can. Mine > all in bold caps. > > > On Jan 15, 2014, at 10:28 AM, Keith Henson <hkeithhen...@gmail.com> wrote: > > On Tue, Jan 14, 2014 at 9:50 PM, Ronal W. Larson > <rongretlar...@comcast.net> wrote: > > Keith: > > Again thanks > > Re- being able to make thicker ice in the Arctic - from the bottom, > not the > top. > > > I don't see it being the bottom. The ocean is thousands of feet deep > and I can't see making these thing more than a 100 feet, say 30 meters > long. > > [RWL1: I am projecting only adding like a meter to ice that is already > (hypothetically) a meter thick - so it can get through a September > area/extent minimum. Most Arctic ice forms from the bottom - only a little > from falling snow. Asking Peter for more input here on best thickness > change projections. > I project something that can be thrown from a helicopter wherever > an opening crack appears. Only operates when there is already a little ice. > This might work also to extend the area of Antarctic ice, keeping > the area/extent up for more months. By not deploying in some areas, > you can keep some transport lanes open. > > > > <Snip two> > > > The Antarctic case seems a bit harder - with a need for stiffer, > stronger pipe. Any reason the floating Arctic unit couldn't be made of > a thinner plastic and get closer to a $1 or so per foot (with a total > of (?) less than > 10 feet?) > > > I doubt it. The floating versions have to stand a fair amount of > pressure just from the water pressure on them. But no matter the > cost, who is going to pay for them? Polar bears? > > [RWL2: I don't get the "pressure" issue. These can be relatively > thick walled plastic, and the shape is appropriate for compression forces. > I don't see much shear for floating ice a few meters thick. Again - Peter? > > > I hope you can find your earlier cost calculations. I think we have a > chicken and egg situation. The person finding the money (John > Nissen?) will > have to have some cost calculations. > > > It would take a few days with a spreadsheet. I think I figured them > out years ago on the basis of a 5 year ball of ice several hundred > feet in diameter. But that's just the start of the complexity. The > wind blows the ice around and in spite if being in the middle of some > very hard ice, the heat pipes are going to get broken on a regular > basis. > > Make a case that someone would pay for it and I can run off the calculation. > > Then again, you can probably ignore the hardware cost since the legal > expenses are likely to dominate. > > [RWL3: We have very different geometries in mind - as above, I > am hoping for diameters like yours , but only a thickness like a > meter. I ask > Peter Flynn for support on whether this might seem possible. Re breakage, > that would be the purpose of some early testing. > I'm afraid in this game there are no design funds - all open source. > > <again snip a bit> > > > It would be great if anyone could make a synthetic char, starting with > CO2. > > > That's been done decades ago. NASA had a project that would reduce > CO2 to carbon flakes and oxygen. It's also an energy hog, not as bad > as synthetic wax or oil, but you can't pump char. > > [RWL4: I don't want carbon, I want something that has big interior > surface area and very low density; charcoal. I have not looked into the > NASA literature on recycling CO2 and will. But hope someone can comment. I > doubt it will lead to a structure that looks like charcoal (needed to > get high CEC - cation exchange capacity and other desirable features > that cost nothing with char.). > > > I once read that no-one knows how to make a > synthetic volcanic lava (maybe no longer true, anyone? It would make a > great material for simple char-making carbon-negative stoves.) > > > Melted rock is easy. But I don't get a "carbon-negative stove." > Plants *and* a char process together are carbon negative, sort of. > The carbon returns to the air in less than geological time. > > [RWL5. Sorry, I didn't explain enough on the lava question. I am > looking for a very light weight porous but very strong, heat resistive > material. I have seen an ideal product that is "sawn"commercially > out of a > solid lava mountain in Nicaragua. Melted rock is not what is needed - > too dense. > Any char-making stove (look up the word "TLUD") can be carbon negative > if the char is placed in soil (then changing name to "biochar"). Yes > lifetime is an issue, but char is used for anthropological dating > going back > millions of years. We will be happy with a commonly used value of > 1000 - and can live with less. > > > Your proposed diode will operate with the "hot" side always around 0 > oC, and > the cold side dependent on the nighttime air temperature that (not > looking anything up) might average -30 or -40 oC. > > > No, the hot end goes down to the lowest temperature of the air, less > relatively minor heat leakage. > > [RWL6: Not understanding. Ask for Peter Flynn's help again. If > you are boiling a fluid at the bottom the thermal energy movement is upward. > Maybe we are not disagreeing - but the bottom "hot end" in a heat pipe sense > has to be a good bit warmer than the atmospheric above ground > (condensing) temperature to have heat transfer. > > <snip remainder to help keep lengths down> > > -- > You received this message because you are subscribed to the Google > Groups "geoengineering" group. > To unsubscribe from this group and stop receiving emails from it, send > an email to geoengineering+unsubscr...@googlegroups.com. > To post to this group, send email to geoengineering@googlegroups.com. > Visit this group at http://groups.google.com/group/geoengineering. > For more options, visit https://groups.google.com/groups/opt_out. -- You received this message because you are subscribed to the Google Groups "geoengineering" group. 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