Too much green power

We had a holiday yesterday in Belgium. The weather was nice: sunny, although somewhat cold, and windy. Good weather for a long walk.
In those first Spring days, windmills and solar panels were producing a lot of energy while consumption of electricity was very low because of the holiday, leading to an enormous overproduction of electricity. The grid operator had to export electricity to France and had to power down some plants to prevent overloading the grid.

This reminds me of a similar situation before. Almost one year ago (the end of May last year) we encountered exactly the same problem. We also had a sunny and windy extended weekend which brought our power grid almost to its knees. Last year it was probably worse than it was now and back then a collapse of the grid was only just averted by exporting some excess electricity to France.

But, in the end, is more energy not a good thing? Doesn’t this mean that wind and solar can produce a lot of energy in our country? I think there are more things to consider. Let me explain.

Wind and solar are intermittent energy sources. Windmills only generate electricity when there is enough wind, but not too much. Between these two boundaries, the more wind, the more energy.
The same with solar. At night, nothing will be produced. In the morning, the evening and on very cloudy days only little. When there is a lot of sun, a lot of energy is produced.
This seems very simple and straight forward, but it is important to realize this.

On the other hand we have the consumption of electricity. There is a specific consumption pattern throughout the day. In the morning, consumption will increase and a small peak will form. There is a second (larger) peak in the early evening. After this evening peak, consumption will decrease rapidly and during the night there isn’t much consumption. During the weekend, these peaks are much lower.
Electricity has the downside that it is difficult to store. The power grid operator will have to balance the production according to the consumption. Too little production or too much consumption and we will risk a brownout (not sufficient power) of a blackout (no power at all). Too much production or too little consumption and there will be a waste of electricity (it is difficult to store) or it can overload the grid (with a possible blackout).

The different (dispatchable) energy sources will have different ability to increase or decrease output on demand. For example nuclear and coal don’t have much flexibility, they are very slow in powering up or down. They are mostly used as base load (the minimum level of demand on an electrical grid over a span of time). Gas is more responsive and it can be used to increase or decrease according to demand (depending on the type, more or less rapidly).

Wind and solar are a different breed. They are intermittent energy sources. They produce energy that is not necessarily in accordance with the consumption pattern of that moment. The more intermittent energy sources in the power grid, the more challenging it will be to balance the output against consumption.

So what happened yesterday in Belgium? At first glance it seems a bit counter intuitive. Wind and solar in Belgium are only a few percent of the output. How can that small amount overload our power grid?
There are several reasons for this and they all came together yesterday:

• It was very sunny and windy. Therefor wind and solar, which normally produce suboptimal, suddenly produces (more) optimal in a very short time frame.
• Less power will be consumed during a holiday than during a working day. In both cases we had an extended weekend (the weekend plus the Monday that followed was a holiday).
• We do have a peak shaver at Coo that can pump up water and release it later to produce electricity when more power is needed. But this system only has a very limited capacity of a few hours.
• Belgium has older conventional power plants that are not that flexible in powering up or down. They kept producing energy while wind and solar also performed very well.

The power grid operator had to balance this overproduction. France was willing to absorb our surplus power… saved …
Last year it was the same story. Too much production in a too short time frame. The Netherlands and Germany were contacted, but they apparently had the same problem. At the last minute, France agreed to import some surplus power, again saving our grid in the meanwhile.

And yes, Belgium paid to be able to export that energy (there was no demand for it). But now comes the sad part. Belgium imports a lot of energy from abroad. Shouldn’t we have more than enough wind and solar to keep up for the demand this time? Well, no. Although there was an overproduction during some parts of the day, in the morning and evening there wasn’t much wind or sun. Apparently, that day we paid both ways. We paid to import electricity because we didn’t have enough of it at the beginning and the end and at peak output we paid to export some of it because there was too much production and needed to protect our grid.

How do you call this … free wind … free solar … or something? At this moment, wind and solar are minor energy sources in our country. We escaped fairly unharmed this time. But what if we increase our renewables to let’s say 20% (the goal imposed by Europe)? If we don’t drastically change our grid by then, I don’t dare to think about what could happen.

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