If wind turbines are to be used productively then there the wind must be reliably forecast.
NETA produce a prediction of the wind power contribution to the grid. They produce a sliding three day window using their initial and latest predictions with the actual outcome shown for the (usually) first day and a half of the window.
NETA (New Electricity Trading Arrangments site) are the people who sort out trading in wholesale electricity. As part of this they have produced a really informative and detailed site that is constantly updated. They do their very best to stay on top of many different changing parameters that affect electricity generation.
In my post yesterday (and using their data), I indicated that the national output from the turbines looked like it was about to rise to 16% of their maximum rating. This was from around 4-5% per cent - where it has been languishing for days.
While 16% is still pathetically poor, the predicted wind has not arrived. The output prediction has now been ramped down to 147MW ( 6%)
Believe me, I am not getting at NETA for the variability in the figures. NETA is doing the very best job it can in exceptionally difficult conditions.
We call know about the unpredictability of the weather. We know how often the Met Office foul up on really short term weather forecasts. This again is not an issue of competence it is an issue of how very difficult predicting the weather is.
These figures underline in thick black pencil that nationally wind power is unreliable and unpredictable.
It should also be noted that the absolute maximum output that was very briefly reached on the 18th December was barely 23% of their advertised rating. Most of the time during these four days the national output of all metered turbines on the grid has been well below 10%.
I have added the last four sliding window graphs below. Remember they all overlap so you can see the initial forecast (orange), the latest forecast (blue) and the actual outcome (red line) for three of the four days. The settlement period indicates the time. NETA settle accounts in 48 half hour blocks, so block one starts at midnight, block 24 at midday and so on.
(Note: the vertical scale changes between graphs 2 and 3)