Solar and wind replace nuclear?

A small interruption from my 6-years-of-blogging series. This blog documented several meaningless (or even wrong) remarks from our (now former) Flemish Minister of Energy. I was a bit sad when I heard that he chose to be mayor of Ostend in stead of Minister of Energy, but apparently he doesn’t have to be Minister to utter such remarks. On a congress organized by his party (OpenVLD) he made following claim (translated from Dutch):

Today, offshore wind turbines provide 1.2 GW of energy production.

That is not even remotely true. Belgian offshore wind provides much less than that. The 1.2 GW is the capacity. The real production will vary, but will be on average a fraction of that number.

He obviously is confusing capacity with production. Why am I not surprised? Strange however is that the error is still not corrected yet at the time I published this post (now more than a week later). Didn’t they notice it? Or do all the energy experts of that political party stand behind this number?

Then comes the interesting part that leads to the subject of this post (translated from Dutch, my emphasis):

“By 2026 we will increase this to 4GW without subsidies. From then on, the offshore wind farms will provide 20% of the total electricity requirement. This is just as much as the total electricity consumption of all Belgian families, “says Bart Tommelein.

This claim reminded me of the new energy pact made by the Flemish Green party, published a few days before the congress. It has a similar claim (translated from Dutch, my emphasis):

An accelerated development of offshore wind energy ensures almost 20% of our electricity consumption by 2023 (a capacity of 4.3 GW offshore wind turbines). We do this by means of a cost-efficient tender like the Netherlands did.

That is hard to believe. It took us roughly 20 years to get to a offshore wind capacity of 1.2 GW with the help of generous amounts of subsidies and now we are supposed to more than triple that capacity in less than 5 years, this time without subsidies…

The party of our former Minister of Energy is a bit less ambitious. They would triple offshore wind power by 2026 and this is even more ambitious than a previous proposal by the federal government to do the same by 2030.

Why the hurry of the Flemish Greens? Well, they are eager to prove that solar and wind could replace ALL our nuclear power plants that are scheduled to be closed by 2025 (translated from Dutch):

Onshore and offshore wind turbines, solar panels and small-scale sustainable biomass and bio-gas plants and hydro-electric plants will provide enough renewable energy in 2025 to meet half of our electricity demand. This is therefor enough to replace all nuclear energy.

But then what do they expect to form the other 30% (translated from Dutch, my emphasis):

With an ambitious growth path for sun and onshore wind, we will achieve a tripling of electricity produced from sun and onshore wind by 2025.

They aim for a 3.5 times increase of offshore wind and a 3 times increase of solar and onshore wind to replace nuclear power (about 6,000 MW). Is that enough? Since I can find the data on solar and wind capacity on the Elia site, I am able to calculate the total capacity they envision:

4,300 [projected offshore wind capacity] + ((3,369.05 [current solar capacity] + 1,978.985 [current onshore wind capacity]) * 3) = 20,344.11 MW

That is surely ambitious! 2023 is only 5 years away… This is how the goal of 20,344.11 MW by 2024 looks like:

I think this is their reasoning:

  1. 20,044 MW generates 175.585 TWh at maximum load
  2. To calculate theoretical production I will need a capacity factor. Downloading the solar and wind data of 2018 from and calculating the average capacity factor that year gives me a capacity factor of 24.62% for solar + onshore wind + offshore wind.
    Multiplying 175.585 with 0.25 gives 43 TWh of potential production.
  3. That is only one part of the equation. The other part is consumption. Is this theoretical production enough to meet the theoretical consumption? They seem to work with 2016 data and they claim that electricity consumption in that year was 83 TWh. Half of that means 41.5 TWh.

So yes, mathematically speaking, at least tripling the capacity of solar and wind can produce (on average) half our electricity consumption.

If that is how they calculated, then it also shows that they didn’t account for much backup from these “small-scale biomass” and “hydro-electric plants”. Which should not be very surprising. They don’t like these energy sources at all. We also don’t have much hydro-electric plants anyway and unless they envision loads of small-scale biomass plants (which are not sustainable in Belgium), most of the heavy lifting will have to be done by solar and wind.

Also, backup and storage are very expensive to build and money spend on it can not be spend on other things. That is even more important if countries are behind the schedule of their EU goals. Or when a political party are keen to prove that the energy transition will not hurt the people in their wallets.

But we are now comparing two completely different power sources. One is produced reliably, the other one is intermittent. Production of solar and wind will fluctuate depending on how much the sun shines and the wind blows. In 2018 the production of solar and wind fluctuated between 3.56 MW (January 20, 2018 at 19:15) and 5,295.04 MW (December 21, 2018 at 15:00). Let’s have a look what happened on January 20:

Production of electricity by solar and wind kissed the x-axis (3.56 MW) when 11,391.11 MW was needed, see the black vertical line. Even when production of solar and wind would have been three times the value on January 20, we would get a minimum of 11 MW, which is still a deficit of 11,380 MW that has to be filled in. When about 6,000 MW capacity is replaced by an intermittent power source that only produces 0.1% of its capacity at that moment, then the rest has to come from somewhere else. We have some import capacity, but not enough to accommodate such a difference.

Caveat 1: this is not the worst case scenario. The maximum expected capacity (to meet demand on a working day in winter during the evening peak) is around 14.250 MW.

Caveat 2: all our neighbor countries are also evolving to solar and wind because they want to meet their EU goals, so they probably will be confronted with the same problem. If we are not too keen on building backup/storage, other countries need to do this if we want to be able to profit from additional backup capacity when all players are focusing on solar and wind.

The pact mentions in passing two types of storage: hydrogen and electric vehicles. They stay deliciously vague about both. What is for example the size, efficiency of that (new to build) hydrogen network? There is only 400 million euros per year that is allocated to making the energy system flexible. According to the pact, this includes:

  • demand control
  • storage
  • smart grid
  • interconnection
  • power to gas
  • integration of heat networks/transport/electricity.

That storage will probably be not that big (as also was suggested by the calculation above).

That they mention electric vehicles as potential storage is a bit puzzling. This puts them in a catch 22 situation. If they want to use electric vehicles to store electricity and release it at times of deficit, then there need to be a lot of them to have some effect. Even if that would be possible in five years time (current share of plugin and all electric cars is less than 1% of all vehicles), this means the need for a higher capacity of the grid in order to accommodate for the loading of those vehicles and that “half of the consumption” might not be sufficient anymore (unless drivers of electric cars can refrain themselves from loading their vehicles or can live with smaller cruising range when there is not much sun/wind).

Another aspect of their plan is energy saving. They aim at 25% energy saving by 2024. That is pretty steep. How they want to do that is not really clear. In their pact they explained savings by better isolating houses and reduction in the use of materials, but how exactly they want to save electricity (preferably at peak demand) is not explained. It is a nice wildcard though.

So, is it possible to replace our current nuclear capacity completely by solar and wind by 2025? On average, that is no problem at all if they can reach their projected capacity of solar and wind. However, in practice it is a completely different ball game due to the unreliable output of solar and wind combined with the higher peak demand in winter. It is not really clear how exactly they are going to solve those issues in the real world.


2 thoughts on “Solar and wind replace nuclear?

  1. vuurklip

    “… It is not really clear how exactly they are going to solve those issues in the real world …”

    Many scientists and all politicians don’t live in the real world.



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