How strong does the wind have to blow for the wind turbines to work?
Wind turbines start operating at wind speeds of 4 to 5 metres per second (around 16 kilometres an hour - ie. a "gentle breeze", where leaves and small twigs on trees are in constant motion) and reach maximum power output at around 15 meters/second (around 54 kilometres per hour - ie. "stong breeze" to "near gale" - when whole trees are in motion, and it becomes hard to walk against the wind). At very high wind speeds, i.e. gale force winds, (25 metres/second, 90+ kilometres/hour) wind turbines shut down.
 
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