Hi Ken—Good for you all to do this calculation. I was in a meeting here in DC a few years ago where a prominent physicist from the Royal Society argued that one could not get more than 7%, apparently having calculated how much kinetic energy there was in the boundary layer. I challenged him, noting that this would mean that the atmosphere would have to become still, and this could not happen as it would lead to the equator-pole gradient building up, and this would force movement such that a lot more energy was available than the kinetic energy present at a particular time. Despite my admittedly qualitative reasoning, I think it was Burt Richter who was there and agreed with the UK physicist, both arguing that Mark Jacobson was greatly overestimating how much renewable energy was available, particularly from wind. This seemed a question that could be readily addressed in a quantitative manner by an appropriate model simulation, and I am glad that it has now been done.
Now we just need to find the ways to extract the energy. Mike On 9/9/12 3:50 PM, "Ken Caldeira" <[email protected]> wrote: > http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1683.html > (I believe this is a free download. Let me know if it does not work.) > > 9 September 2012 > Nature Climate Change doi:10.1038/nclimate1683 > Geophysical limits to global wind power > * Kate Marvel > <http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1683.html#a > uth-1> , > * Ben Kravitz > <http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1683.html#a > uth-2> > * & Ken Caldeira > <http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1683.html#a > uth-3> > There is enough power in Earth’s winds to be a primary source of > near-zero-emission electric power as the global economy continues to grow > through the twenty-first century. Historically, wind turbines are placed on > Earth’s surface, but high-altitude winds are usually steadier and faster than > near-surface winds, resulting in higher average power densities1 > <http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1683.html#r > ef1> . Here, we use a climate model to estimate the amount of power that can > be extracted from both surface and high-altitude winds, considering only > geophysical limits. We find wind turbines placed on Earth’s surface could > extract kinetic energy at a rate of at least 400 TW, whereas high-altitude > wind power could extract more than 1,800 TW. At these high rates of > extraction, there are pronounced climatic consequences. However, we find that > at the level of present global primary power demand (~ 18 TW; ref. 2 > <http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1683.html#r > ef2> ), uniformly distributed wind turbines are unlikely to substantially > affect the Earth’s climate. It is likely that wind power growth will be > limited by economic or environmental factors, not global geophysical limits. > > > We did not go into this in this paper, but if you look at Figure 2a, high > levels of wind power extracted from the whole atmosphere has a cooling > influence, especially in the Arctic, which suggests that extraction of vast > amounts of kinetic energy from the atmosphere might be considered another > form of 'geoengineering'. > > _______________ > Ken Caldeira > > Carnegie Institution for Science > Dept of Global Ecology > 260 Panama Street, Stanford, CA 94305 USA > +1 650 704 7212 [email protected] > http://dge.stanford.edu/labs/caldeiralab @kencaldeira > > Our YouTube videos > The Great Climate Experiment: How far can we push the planet? > <http://www.youtube.com/watch?v=ce2OWROToAI> > Carbon turnover rates in the One Tree Island reef: A 40-year perspective > <http://www.youtube.com/watch?v=gnCt5NXL_U0> > More videos <http://www.youtube.com/user/CarnegieGlobEcology/videos> > -- 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.
