Jed Rothwell wrote:
A 60 m wind turbine in Aomori Japan fell over mysteriously. There was no
strong wind at the time.
The cause of failure is probably unrelated, but I'm reminded of problems
which happened when sailboats first started using heat-treated rod
rigging. The rigging would occasionally break -- but it often happened
when the boats were riding at anchor or peacefully in the harbor, in a
light breeze with no sails set.
Apparently the cracking of the rods would proceed just to a certain
depth under constant load, and then the rods would finally snap when the
load became extremely variable (i.e., they "wiggled around" a lot), as
would happen when sitting in the harbor or at anchor.
The heat treatment, which made the rods stronger, also made them harder
and more crack-prone. IIRC, some early heat-treating was done with the
rod still on rolls, after which it was straightened -- which sure sounds
like a recipe for disaster (and, of course, it was).
See (in Japanese with photo):
http://www.yomiuri.co.jp/national/news/20070110i501.htm?from=main5
wind turbine accidents are more common than you might think. I doubt
that any large-scale energy generation technology can be made perfectly
safe. See:
http://www.responsiblewind.org/docs/wind_turbine_accidents_in_pictures.pdf
- Jed
