What when the sun doesn’t shine and the the wind doesn’t blow: batteries!?

The big question was asked again. Remember, a few posts ago, our Minister of Energy tried to answer the question “What happens when the wind doesn’t blow?”, a question she apparently got asked a lot. Back then she managed to evade answering that question.

The question came back in an interview (Dutch ahead) about the energy transitions she gave to a news magazine from Brussels. Initially, it seemed we would not get an answer (the interview was interrupted at the exact moment when the question was asked), but fortunately the reporter was persistent enough to ask the question again later in the interview (translated from Dutch, my emphasis):

Reporter: … what when the sun doesn’t shine and the wind doesn’t blow?
Minister of Energy: Batteries! Our electric cars actually act as one large battery, especially if they can charge bidirectionally, and the car battery can be used as a home battery when the demand is high. In addition, a very large battery of 100 megawatts will be built in Zeebrugge, where the power from the wind turbines comes ashore. It can supply energy for four hours.

Reporter: Four hours…
Minister of Energy: At peak times, eh.

Reporter: Okay, but sometimes there is no wind for a few days.
Minister of Energy: These situations are rare, but that’s why we still need those gas-fired power stations: only for a short time, at the very beginning. We will gradually replace them with green hydrogen power stations. We already have agreements with Oman and Namibia, two democratic countries, regarding the import of these products. Although it is not the intention to replace one dependency with another.

What I understand is that batteries will do a lot of the balancing. She proposes a vehicle-to-grid solution combined with a “very large” battery acting as a peak shaver (loads when there is surplus production and discharges during peak demand) and gas-fired power plants to fill in where needed. Only in the “very beginning”, she wants to replace natural gas with imported hydrogen from “democratic” countries. I think her definition of a “democratic country” is a bit different from mine (Oman is a absolute monarchy in which all legislative, executive, and judiciary power ultimately rests in the hands of the hereditary sultan) and neither of the two countries score particularly good on the corruption perception index). Also not sure how “green” that hydrogen would still be after being hauled from the other side of the globe to Belgium. That aside.

She did answer the question, but unfortunately, she took the question super literally, making it seems like the issue with intermittency is some rare days without any wind whatsoever (that would indeed be extremely rare).

This reminds me of a post I wrote a couple years ago in which I was looking into the statement that “wind power needs to have enough backup to bridge five consecutive days of no wind”. At that time I tried to model the ideal scenario of just enough solar and wind plus batteries to meet demand at all times. The output of that model run showed something unexpected. After the accumulation of power into the batteries during spring and summer, these built-up reserves were almost completely drained between the second half of October and the end of November (the drop in the orange square):

The Amazing November Dip

Something was creating a serious deficit during that time and it was not just a few rare days without any wind. It was an array of factors like subpar electricity generation by solar and wind during those 1.5 months, shorter days in autumn and winter, sub-zero temperatures and therefor higher demand, finally leading to a situation where the reserves could not be replenished before the next deficit came along. It also shows the limitations of those batteries: all the electricity that they provide needs to be in the battery before the deficit starts and for as long that the deficit lasts.

The problem at our latitude is that there is a discrepancy between intermittent production and demand. In summer, supply by intermittent sources is rather regular. There is a lot of electricity produced by solar (long days with lots of sun) and less by wind. Electricity is produced at the time when most electricity is used (during the day) and demand is the lowest of the year. Filling in with for example batteries would be relatively easy because of this regularity and low demand.

It is a completely different story in winter. Then there is much less sun (short days, often cloudy), so it mostly will be on wind to produce electricity. Although wind is stronger during winter time, it is still intermittent and not reliable. At the same time, demand is highest of the year, that is what is causing that big drop of battery load from half October until the end of November. Meaning that there is a need for seasonal storage at our latitude. Solving that with batteries will require a massive amount of them and that comes at a price.

Looking at it more fine-grained, the highest demand will be at peak demand in the morning peak and even more pronounced in the evening peak of working days in winter. During that time, the sun isn’t shining yet (at the morning peak) or is already set (at the evening peak). When there is no(t much) wind at that time, where does the electricity needed to meet peak demand will come from?

Let’s look at what will change in our grid and its impact on peak demand in winter:

  • Belgium will keep 2 GW nuclear capacity for the next ten years, so luckily there will be some base load at peak demand in the coming years
  • The other 4 GW nuclear capacity will be replaced with only 2.3 GW natural gas capacity → that is 1.7 GW less capacity than Belgium currently has
  • There will be more solar and wind capacity to compensate for this. However, solar will be irrelevant during peak demand in winter and wind can’t be relied upon (it is not necessarily windy during peak demand)
  • That “very large battery” of 100 MW can discharge for about 4 hours. That is just peanuts in the Belgian grid and it is also possible that it will not be able to reload before the next day in winter, meaning that there might be no peaks to shave
  • The vehicle-to-grid solution doesn’t exist yet, it still seems to be a distant dream (no information on her website or that of her party and when it is mentioned somewhere, it is in passing and rather vague). It is likely that it could be implemented after the last 2 GW of nuclear is decommissioned.
    If implemented, the system will also be more restricted in winter:

    • Batteries don’t work that well under cold conditions
    • Cars will need more battery power themselves in winter
    • Not all cars will be connected to the grid when they are needed most, some will for example in the process of commuting
    • Some cars will need to load their battery when it is not convenient for the grid
    • Some owners probably don’t want to participate in this scheme in the first place (for example because of battery degradation)
  • Import from abroad is possible, but remember, neighboring countries like Germany and the Netherlands will experience the exact same problem because they are focusing on the same intermittent power sources in their transition. Electricity will be in high demand during winter peaks.

Basically, Belgium will end up with less dispatchable power than it currently has, so hopefully the neighbor countries keep enough dispatchable power to share with Belgium.

In the end, she managed to evade the tricky subject of seasonal storage, so it is still not entirely clear how she envisions to keep the lights on in winter with the changes in the grid she proposes and that is not exactly reassuring.


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