Is wind energy really unpredictable?

I know that I’m probably biased on this subject but I want to spend a few words on a recurrent subject that pop up often in my discussion about wind energy with people from different sectors and way of life.

Basically, a standard argument about wind energy is that it’s unreliable and unpredictable.

In my opinion the reality is different (or at least, much more complex that that).

Obviously wind power fluctuate over time, basically under the influence of meteorological conditions.

Variations occurs at several scales: seconds (e.g. gusts), hours (e.g. day and night), months (e.g. summer and winder) and so on.

The electricity demand as well is highly variable, changing not only with well-known seasonal and night/day patterns but also incorporating several other variables such as the economic cycles.

Basically, the grid operator tries to match constantly demand and offer.

They will also need to have a reserve capacity in case of errors in the prediction of the demand or unexpected problem like power plants disconnecting from the grid for whatever problem.

The key point here is that wind energy is variable, not intermittent.

Even during severe storms, the turbines will need several hours to shout down – they will not disconnect all together.

Also, the failure of a turbine has usually no effect on the system as they are modular and diffused. This is usually not the case in other type if power plants.

It is also predictable within a reasonable margin of error – is not a random event like the number you get when you throw dices.

From the point of view of the grid, variations within the seconds or minutes are not felt.

Variation within the hours are felt by the system only when wind has a great penetration level (at least 5%-10%). This currently happen in very few countries, for instance in Denmark.

 

Note: the main source for this post was an interesting (at least for me) chapter of the book “Powering Europe: wind energy and the electrical grid”.

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