Yet another meaningless metric: contribution of solar and wind to total load

“A new record for solar and wind”. This is stated in a tweet by our Flemish Minister of Energy:

The hashtag “stroomversnelling” (the Dutch word for “rapids” and used in expressions it roughly means “speeding up” or “moving faster”) and he often uses it in relation to his policies. So, do I understand it correctly that he connects the current policies are the reason that this record was broken?

That “new record” was solar and wind producing 45% of the Belgian electricity load on Saturday July 28 at 15:00. My first reaction was: “So what?”. It probably would boil down to a few minutes in the weekend. The Minister has a history of unnuanced and misleading tweets, so I thought it would be a good idea to check what that record is all about. I turns out that this record was even less significant than I expected.

The data for July 28 can be found on the Elia website (solar, wind and total load) and this is how it looks like combined in one graph:

The yellow, blue and gray stacked columns are for solar, wind and total load on the left Y-axis. The contribution of solar and wind to total load (red line) is on the right Y-axis (contribution = (solar + wind) / total load x 100).

The data confirms a maximum value occurring at 15:00. The contribution of solar and wind was 44.1% between 15:00 and 15:15. This is an average value over 15 minutes, so it is more likely that the contribution of solar and wind indeed got to 45%, but only for a few minutes before dropping down again.

It is also clear that this is not the usual situation: solar and wind both had their peak at around the same time of the day. This is not the normal situation. There was quite some luck involved to get this “record”.

What also helped was that July 28 is a Saturday. Consumption in the weekend is traditionally low, especially in summer when days are long and many are on holiday. This is a specific situation (low electricity consumption due to holiday and a weekend) combined with the lucky strike of wind and solar reaching their peak at about the same time for a brief moment. It has very little to do with progress in wind and solar, as the Minister seems to suggest with his hashtag.

The next question is how meaningful this metric is. The Minister is rather notorious for using some pretty meaningless metrics, like spring and summer production of wind and solar “compensates” for poor performance in winter and the utterly meaningless metric of MWh/km2 (in which we Belgians excel).

The tweet referenced a tweet by Elia (the Belgian grid manager), containing this graph:

It shows the highest contribution of wind and solar to total load per month for the last 11 months. It is a rather misleading graph. It seems that, except for the first value, the graph is going up. Not looking deeper, one could (mis)understand that there is steady progress and then the hashtag of the Minister seems to make sense.

Looking a bit deeper, a different story emerges. Just look at the days in which those “records” are established. I will put them in a list for clarity:

Day Date Hour
Sunday September 10, 2017 14:15
Sunday October 22, 2017 13:00
Thursday November 23, 2017 03:45
Sunday December 31, 2017 04:30
Monday January 1, 2018 03:30
Saturday February 24, 2018 13:30
Tuesday March 20, 2018 13:00
Sunday April 22, 2018 15:45
Wednesday May 2, 2018 15:00
Friday June 21, 2018 13:45
Saturday July 28, 2018 15:00

What immediately caught my eye is that seven of the eleven maximums are recorded on a day in the weekend or on a holiday (when electricity demand is low).

Also, look at the time when the maximum values were recorded in the winter months. These maximums were on the account of wind energy (which is not surprising) and occurred deep in the night (also when electricity demand is low). That is, production of electricity by solar and wind was high on a time when there was not much need for electricity.

I am ot impressed by this “record”? I, for one, am not. That record was accidental and it even shows the problem of electricity production by solar and wind in our current electricity grid. These follow the availability of sun and wind, which does not necessarily coincide with the consumption of electricity.

How meaningful is the fact that we had a record contribution of wind at 03:30 AM during a winter night? Or a record contribution in a weekend in summer when most people are in holiday anyway? The contribution of solar and wind to total load is a meaningless metric when dealing with intermittent energy sources that don’t follow consumption.

Yet this “record” was presented as some kind of special performance of solar and wind. For those who didn’t look deeper into this “record” probably would perceive it as the result of the current policies, while it is in fact an anticlimax. Solar and wind didn’t break the record because they are strong, but because electricity was produced at times of low demand. Therefor dividing a smaller number (demand that was low) by a higher number (production that was high), et voilà, there you have your record! The intermittent, non-dispatchable nature of solar and wind made that a lot of electricity was produced when there was no need for it (which is in fact a bad thing) and this weakness is then framed as an accomplishment.

If you ask me, that is brilliant PR. It is not honest communication though.

via Trust, yet verify

August 4, 2018 at 02:29PM

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