sentences:  The reliability of direct drive turbines offshore is still not known, since the sample size is so small.Experts from Technical University of Denmark estimate that a geared generator with permanent magnets may use 25 kg/MW of the rare-earth element Neodymium, while a gearless may use 250 kg/MW.In December 2011, the US Department of Energy published a report stating critical shortage of rare-earth elements such as neodymium used in large quantities for permanent magnets in gearless wind turbines.