The snapshot I used is available HERE
The first graph below is a frequency plot of power output against half hour billing slots. It shows how often, within the 3 month period wind power contributed a particular power level (power level - X axis number of half hour periods - Y axis. (Sorry forgot to label the graph properly)
The most shocking outcome from this graph is that the most common output from the whole of the national metered wind power system is 300MW. That equates to 12% of their maximum rating of 2430MW. They were running at this level, or less for more than 30% of the 3 month period.
The graph indicates that while in the 3 month period the output fell to close to zero (less than 100MW ) for no less than (in-total) 147 hours, at no no time it ever reach anywhere near the often hyped maximum rating. In fact the total output never even reached 85% of this rating. The absolute maximum achieved was 2065MW (84.8%). This was achieved for (in-total) one hour in the three month period.
This graph below shows the half hourly power ratings linearly from low to high. Wind energy is governed by a cube law. Double the wind speed and get 8 times as much power (unfortunately the reverse is also true - halve the speed get 1/8th the power). Here you can see the cube law in action and how it skews the output so most of the time wind power generation is BELOW the Capacity Factor
The raw average (or capacity factor), which is arrived at by simply adding all readings up and then dividing by the number of readings gives an capacity factor of 25%. (608MW) On their website the BWEA suggest it is 30%. Often the figure gets inflated further. The press blindly accept what they are told.
This otherwise laudable Daily Mail Article falls into exactly this trap.
Remember these NETA figures include offshore as well as onshore sites so the Capacity Factor is certain to be even poorer for on shore turbines alone.
The BWEA suggest that the capacity factor taken in isolation is meaningless. I (sort-of) agree with this. As electricity generation cannot be stored, the duration of the power generation operation is as important (or arguably more so) than the averaged value.
In this three month period the wind output only managed to reach or exceed this capacity factor (25% - 608MW) for less than 40% of the time. If you use the much hyped BWEA figure of a 30% capacity factor, then this value was only reached or exceeded for 23% of the 3 month period.
Due to the cube law relating wind speed and power output, we find that half the 3 months energy arrived in less than 25% of the time leaving the other half to cover the remaining 75% of the period. This is actually an improvement on the single facility figures of about 15% found in the USA (Lee Ranch Sample Data (1/2 way down this page) .
This improvement from 15% to less than 25% is the contribution from the grossly overstated "if its not blowing here its blowing somewhere else" argument. Clearly, in the UK, the power averaging due to the geographic separation of the turbines falls very far short of the usual bland statement that "things even out".
This is a graph of nuclear power output over this 3 month period. Notice how steady it is as it provides us with essential, solid, predictable Base Load generation. The variation is where the Power generator is matching demand not the result of a lack of "fuel" or wind (interestingly, there does appear to be a drop-out. and that, my friends is exactly what spinning reserve is for!)
The mess below is the wind power output for the same period.
It is a chaotic unpredictable set of short duration spikes smeared over a grindingly low background. How anyone could suggest that this can be used to reliably provide 30% of our power is beyond me. There are those though who even suggest that this could be used for base load power generation.
God help us all if the likes of Chris Huhne is stupid enough to continue pushing us down this road.
Love & Kisses