Could a nuclear power plant be closed when households save 1 percent of energy?

The subject of this post is a statement made in a current affairs program on the Flemish television back in February. In that program there was a debate on smart meters and one of the arguments against was that a savings of only 1% was expected which would not be in proportion to the costs. The reaction was this remarkable statement:

1% savings of energy, if all households do that (we are not even talking about the industry), then you can close one nuclear power plant. That is how much that 1% is.

Apparently, his reasoning was that a 1% savings as a result of that smart meter is already a huge achievement since it would be enough to close a nuclear power plant. Even with some basic knowledge of our energy infrastructure, it should be clear that this is an absurd claim. It didn’t take long before it was debunked, even on national television (which shows that it is an absurd claim indeed).

However, it kept bugging me. How could someone come to this absurd conclusion? I wanted to understand the reasoning that one has to follow to come to such a conclusion. It would be interesting to know where that statement came from, especially because the guy who made the claim is apparently viewed as an “energy expert” of his political party…

Let’s first look at the fact check on national television (in the same program the next week).

It was a rather lame fact check. The fact checker just took the yearly total electricity consumption of Belgium in 2016 (77.1 TWh), took 10% of that (0.771 TWh) and then concluded that even the smallest Belgian reactor produces way more electricity (the smallest Belgian nuclear power plant produced 2.9 TWh in 2016, which is more than the 0.77 TWh savings).

Okay, that surely is mathematical correct (0.77 is less than 2.9, so those savings will not come even close of being able to shutting down a plant), but it is not exactly what the claim is all about.

The claim is about the electricity consumption of HOUSEHOLDS, excluding industry, while the fact check was about ALL electricity consumption (households + industry). Sure, this would obviously make the difference even worse and it was more than enough for the fact checker to put that claim to rest, but I wanted to understand the thought process that resulted in that 1% figure.

The fact check put me on the wrong leg initially. I tried to make some sense of it by taking production numbers of Belgium and consumption of Belgian households, loosely inspired by the fact check. But whatever I tried, I failed to replicate the calculation. After a while I had to let it go and pursue other things, though it still bugged me.

Until I got the idea to do the reverse of what the fact checker did: start from the capacity of the smallest power plant, take 1% of the household consumption and then see where that would get me. Io and behold, that solved it!

This is how I think that the calculation is done:

  1. The smallest Belgian nuclear reactor has a capacity of 433 MW (or 433,000 kW)
  2. The average electricity consumption of a Belgian household is 3,500 kWh per year or 9.6 kWh per day
  3. 1% of that is 0.096 kWh
  4. A power plant with a capacity of 433,000 kW can accommodate 4.5 million households with a consumption of 0.096 kWh.

Bingo!!!

I recognize that number: 4,5 million is the number of households in Flanders and is a subset of the 8,5 million Belgian households that I used in my calculations. That is why I initially couldn’t make sense of the numbers, I assumed all Belgian households and then I couldn’t confirm the 1% statement. Most probably, the base of the statement is that the smallest Flemish reactor could be closed is the Flemish households saved 1% on their electricity consumption.

If this is how the calculation was really done, then I see at least two major errors:

  1. The smallest (Flemish) nuclear power plant has a capacity of 433 MW and, without technical error or maintenance downtime, it produces 433 MW continuously at full power. Per day it produces 433 x 24 = 10,392 MWh (= 10,392,000 kWh). That is 24 times more than the 1% of the average consumption of those Flemish households. There seem to be a switch from the consumption per day to the consumption per hour.
  2. The capacity of the system is not dimensioned using the average consumption, but by peak demand. At our latitude this is in the early evening at work days during the winter months. The highest needed capacity is 14 GW at the highest winter peak, compared to around 6 GW in summer. Calculating with the average demand is not a very smart thing to do, especially when there are intermittent power sources in play.

There is another way in which the statement could be debunked and it was showed in the fact check: we already save energy year by year. According to the fact check, demand in 2006 was 89.5 TWh, in 2016 this dropped to 77,1 TWh). This means a drop of 14 percentage points in 10 years.

Yet this drop of (much) more than 1% in consumption did not result in the closure of any power plant. If the 1% statement would be true, then we should have seen the closure of several nuclear reactors by now. That clearly didn’t happen.

Looking at it from whatever side, the statement that “a 1% savings would result in the closure of one nuclear power plant” is absurd and I find it worrying that it is used in a discussion by an “energy expert”.

via Trust, yet verify

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December 28, 2017 at 04:21PM

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