NewScientist dissects the scheme below. I'm with Tim in thinking it's bonkers, partly because of the lack of any clear proposal for stabilizing the CO2. I haven't done the energy calculations, but I don't fully agree with Tim. You can use a heat exchanger to cool incoming air as you warm stripped outgoing air. (MEGTEC use this tech in their ventilation air methane oxidizers.)
Perhaps it would be worth one of the more numerically-minded engineers on the list doing some calcs? A http://www.newscientist.com/article/dn22244-could-we-geoengineer-the-climate-with-co2.html Could we geoengineer the climate with CO2? 13:57 05 September 2012 by Michael Marshall Schemes for artificially cooling the planet can often seem wild and woolly. The latest such geoengineering scheme is no different: it involves frozen carbon dioxide, Antarctica and a whole lot of freezers. While the proposal is not as daft as it sounds, the numbers may not stack up. Ernest Agee and colleagues of Purdue University in West Lafayette, Indiana, propose installing gigantic freezers in the heart of Antarctica, where temperatures are already tens of degrees below zero. Once the air inside the freezers is cooled to -140 °C, the carbon dioxide within it will freeze out as "CO2 snow". The solid CO2 could then be stored underground. Agee's calculations suggest that it would be possible to remove 1 billion tonnes of CO2 per year this way, using the energy provided by 16 wind farms, each generating 1200 megawatts of electricity. "There's a lot of wind energy in the Antarctic," Agee says. Our annual greenhouse gas emissions reached 33 billion tonnes of CO2 in 2010, and are likely to keep rising for years to come, so Agee's proposal would only go so far. The sheer scale of our emissions is a problem for similar concepts for sucking CO2 out of the air, such as fertilising the ocean with iron. Feasible? Their calculations are also rather optimistic, says Tim Kruger of the Oxford Geoengineering Programme at the University of Oxford. For instance, they assume that the power plants are 100 per cent efficient, which is impossible. Furthermore, CO2 makes up only slightly less than 400 parts per million of the atmosphere. This means for every volume of carbon dioxide that gets frozen, Agee would have to cool 2500 volumes of air – so a lot of the energy used would be wasted. It will also be difficult to store the CO2 once it is frozen. Either it will have to be permanently cooled below its freezing point, which means running the freezers forever, or the CO2 will have to be stored in sealed chambers that can withstand intense pressure once it warms up and expands. "This is not really a credible solution," Kruger says. On 25 August 2012 07:40, Andrew Lockley <[email protected]> wrote: > http://journals.ametsoc.org/doi/abs/10.1175/JAMC-D-12-0110.1?af=R&; > > Poster's note: Seems a dangerously unstable way to store CO2. > > > Abstract > A scientific plan is presented that proposes the construction of CO2 > deposition plants in the Antarctic for removing CO2 gas from the > Earth's atmosphere. The Antarctic continent offers the best > environment on Earth for CO2 deposition at 1 bar of pressure, and > temperatures closest to that required for terrestrial air CO2 snow > deposition, 133°K. This plan consists of several components, > including: (a) air chemistry and CO2 snow deposition, (b) the > deposition plant and a closed-loop liquid nitrogen refrigeration > cycle, (c) the mass storage landfill, (d) power plant requirements, > (e) prevention of dry ice sublimation and (f) disposal (or use) of > thermal waste. Calculations demonstrate that this project is worthy of > consideration, whereby 446 deposition plants supported by 16 1200-MW > wind farms can remove 1 B tons (1012 kg) of CO2 annually (a reduction > of 0.5 ppmv), which can be stored in an equivalent “landfill” volume > of 2 km x 2 km x 160 m (insulated to prevent dry ice sublimation). > > The individual deposition plant, with a 100m x 100m x 100m > refrigeration chamber, would produce approximately 0.4m of CO2 snow > per day. The solid CO2 would be excavated into a 380m x 380m x 10m > insulated landfill, that would allow one year of storage amounting to > 0.00224B tons of carbon. Demonstrated success of a prototype system in > the Antarctic would be followed by a complete installation of all 446 > plants for CO2 snow deposition and storage (amounting to 1B tons > annually), with wind farms positioned in favorable coastal regions > with katabatic wind currents. > > 1 Correspondence information: Ernest M. Agee, Department of Earth and > Atmospheric Sciences, Purdue University, 550 Stadium Mall Drive, West > Lafayette, IN 47907-2051; Email: [email protected] > > Journal of Applied Meteorology and Climatology 2012 ; e-View > doi: http://dx.doi.org/10.1175/JAMC-D-12-0110.1 > CO2 Snow Deposition in Antarctica to Curtail Anthropogenic Global Warming > > Ernest Agee,1 Andrea Orton and John Rogers > Department of Earth & Atmospheric Sciences, Purdue University, West > Lafayette, Indiana -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en.
