The ships are called Flettner vessels, after their designer Anton Flettner. The ships in question consist of a single hull with three rotor stacks on top, like funnels. The stacks have fins on them and are rotated by the motion of the wind. The stacks are hollow and so draw water up themselves when rotated. The water forms a spray / mist and the aerosol formed rises into the atmosphere, increasing the concentration of water in the atmosphere and increasing the likelihood of clouds forming. It's an ingenious idea but the cost $5.3 Bn is too rich for anyone's blood at the moment as this project hasn't seen any progress since 2009.
The main inhibitor to the production of these vessels is cost. The huge cost is too much for even the richest countries. It's a good concept though, built on sound engineering principles. I'd like to see some progress and the project taken forward but it's the stuff of dreams, cloud seeding ships sailing the seas on autopilot.
Read more at : http://www.zdnet.com/blog/emergingtech/1500-ships-to-fight-climate-change/1030
