3 ms·
Modern turbines can extract at most about 50% of the energy passing though the disc. The physical limit is the Betz limit, just a shade under 60%. Even if you c
by adhesive_wombat 3y ago
Modern turbines can extract at most about 50% of the energy passing though the disc. The physical limit is the Betz limit, just a shade under 60%. Even if you could arrange them just so (which you can't, because circles don't tessellate and wind directions vary), you'd only be able to get that from the wind at the height of the discs, from a single rank. Mixing from air that went over (or under) the turbine entirely would restore quite a bit of the wind after some distance. The biggest turbine in the world, installed about a month ago off the Fujian coast, has a disc 250m across, centred about 150m from the sea, so it's still only a small fraction of the depth of moving air.
By one estimate there's about 250TW of "extractable" power (after which you can add turbine capacity but the whole ensemble doesn't produce more power, and the global wind speeds after saturation would be 50% lower). Humanity uses roughly 10TW, so even if we used wind for everything, it would only be a small fraction of the energy in the moving air.
That paper also has calculations of the effects of a single wind turbine averaged across a 5km area (tl;dr: sub-0.5% downstream wind speed change)
https://web.stanford.edu/group/efmh/jacobson/Articles/I/SatWindPotential.pdf https://web.stanford.edu/group/efmh/jacobson/Articles/I/SatW...
- seanmcdirmid 3y agoRather than plant the gobi with trees (which need lots of water), could China just put in a bunch of wind turbines to prevent erosion? Like, is a wind turbine better than a tree at blocking the wind (well, it also doesn’t have a root system to keep dirt in place). In eastern WA, we have special trees planted to block wind (mostly to reduce erosion), I wonder if those could be turbines instead? (Although, as long as water isn’t a problem, we should probably still use trees)
- adhesive_wombat 3y agoI don't think the primary aim of the project is erosion control, but the Gobi desert is already the site of the largest on-or-off-shore wind farm in the world[1], by many multiples, with a planned 20GW nameplate capacity, 10GW online now (next on the list being 2GW at Markbygden in Sweden). I suppose if there is anywhere in the world where wind power installations can cause a significant reduction in wind speeds, it would be there. [1]: https://en.wikipedia.org/wiki/Gansu_Wind_Farm https://en.wikipedia.org/wiki/Gansu_Wind_Farm
- seanmcdirmid 3y agoI wonder if they've looked into yet. Anyways, nice to see Lanzhou going from one of the most polluted cities in the world to much less than that.