Monday, 23 November 2015

Storm Barney - Too Strong for Wind Turbines

Storm Barney hit Ireland's shores last week bringing strong winds, the fuel for our wind farm fleet. But a noticeable thing happened. Between 1pm and 6pm, wind energy output dropped by as much as 44% :

Let's have a look at wind speeds during the day. As you can see below, the highest wind speeds occurred during 12 and 6pm, the period when wind energy output began declining. Wind speeds reached between 30 and 50 knots, or 15 and 25 metres per second. Air pressure went as low as 980 hpa. Not as low as The Night of the Big Wind in 1839 where it went down to 920hpa or the hurricane in 1988 where it went down to 950hpa.

Dublin Airport

Cork Airport


Mace Head

The diagram below shows the cut in and cut out speed of a wind turbine in metres per second :

Typical power curve

All stations in Ireland record wind speeds at 10m above ground level. Wind turbines are 8-15 
times higher than this. So at station level, we are still within the cut out speed, but higher up
at hub height, the wind speeds are stronger and most likely outside cut out speed. 

So this might explain why during the highest winds of the storm, wind turbines were being shutdown. 

Which means we need back up dispatchable power stations during storms aswell as calm 


  1. I deal with this in my video valmartinireland you tube "calculating the output of a wind turbine" There is no output below about 12.5 miles per hour and they have to be shut down as they approach danger speed. Check it out, it does not have a number

  2. My video No 7 might be useful. valmartinireland you tube myth about wind energy from 30.45 minutes in. Check it out.