Heat wave: what impact on our electricity production?

This Monday, July 18, it was up to 39.3 ° C in Brest. More than 4°C above the previous record heat which dated from July 1949. And many, many other records have been broken all over the western side of the country. But, for several days already, particularly high temperatures have been recorded throughout France. A difficult situation to live with. For our electrical system too.

To understand, let us first note that, contrary to what can happen in winter, when it is very hot in summer, consumption peaks in the middle of the day. When the air conditioners are running full blast. The International Agency forenergy reminds him, the air conditioner is one of the posts that has caused the most demand for electricity in the building in recent years. A cause for concern, even more so when this electricity is produced from fuels fossils.

Let’s see how our electrical system worked this Monday, July 18. Bad news first for our emissions of greenhouse gas. Since no less than 11% of the electricity consumed at the time of the peak was produced from fossil gas. But the good news is that with a peak in the middle of the day, solar photovoltaic can provide good production. No less than 21% this Monday. Hydraulics and nuclear, sources that are also low carbonaccounted for 12% and 51% of production respectively.

The heat wave, what problems for nuclear power plants?

The trouble is that these two energy sources, through their interactions with the environment, are impacted by periods of high heat. Let us first examine the case of nuclear power. In recent days, several power stations have announced that they will reduce their production. A choice for nuclear plant Golfech (Tarn-et-Garonne), located on the banks of the Garonne, for example. And this, since July 13 and possibly until the 24th, according to EDF estimates. Safety reason? No way.

What happens is that nuclear power plants take water from rivers to cool their reactors and turbines. So far, no fear on this side. The cooling of nuclear power plants remains possible, even in periods of heat wave. Safety is fully assured.

So why reduce production? For environmental reasons. Because the water used to cool nuclear power plants is then discharged into rivers or streams. In the operation, it will have been somewhat warmed up. In France, regulatory limits are set for the temperature of discharges. Under normal summer conditions, at 28°C downstream of the Golfech power plant, for example, and at 30° in exceptional climatic conditions. The heating between the upstream and downstream of the plant is also controlled. In any case, it should not exceed 1.25°C on the Tarn-et-Garonne side. Limits imposed to protect the environment: the wildlife and flora that live in the waterways concerned.

A first major use of derogations

But exceptions are possible. ” If necessary for the proper functioning of the electrical network “, according to EDF. The device had so far only been implemented once. In 2018, for the Golfech plant, precisely and for a duration only 36 hours. This time, four nuclear power plants made the request to the Nuclear Safety Authority (ASN). The Golfech plant – again it -, the Blayais plant (Gironde), the Bugey plant (Ain) and the Saint-Alban plant (Isère). A request accepted, but limited “ situations where the electricity transmission system operator requires the operation of the installation to ensure network security or the consumption/production balance “. And this, until July 24 for the moment.

To return to our example of the Golfech power plant, let us underline that EDF has chosen to run it at only one-fifth of its power. In order to comply with the regulatory limit as much as possible. Note also that only the discharge limit temperatures are suspended. The temperature rise limits between the upstream and downstream of the plant – this is perhaps where the real impact of the activity on the environment is measured – are not.

The effects of global warming on nuclear production

Should we conclude that the global warming anthropogenic activity also endangers nuclear production? In part perhaps, if we consider our current nuclear fleet, made up of large reactors with relatively large cooling requirements. But the climate hazard does not seem sufficiently critical today. The derogation request made today is also the result of the current state of our fleet. With part of the reactors on our territory currently shut down for other reasons, maintenance and corrosion, notably. In his report on the “Energy Futures 2050”Electricity transmission network (TEN) underlines that the loss of production over one year due to climatic hazards alone is estimated today at less than 1%, but recognizes that for certain power stations, in particular on the banks of the river, the risk of unavailability of units could increase in the future with production losses which could be multiplied by ten, for example, for the Golfech plant.

To those who are concerned about the impact of these derogations on aquatic life, here is what the ASN answers: “EDF’s proposals are acceptable in view of the feedback from environmental monitoring specifically carried out during previous heat waves as well as long-term monitoring on ecosystems concerned. » But perhaps we also have our say in the debate. By asking ourselves, once again, to what extent our comfort — which, in summer, involves the sometimes excessive use of air conditioner — must take precedence over the preservation of the environment.

Hydroelectric plants under tension

Another production to watch closely in the climatic situation we are experiencing today: hydroelectric production. Did you know that it was the second source of electricity supply in France? Just behind nuclear. And what is worrying in this respect is not so much the heatbut the drought quite exceptional, too, which our country has been experiencing for a few months.

In Portugal and California, hydroelectric plants have already had to be shut down. Lack of water in the dams. We are not there. Even if a deficit of precipitation is recorded for the beginning of this year 2022 on the whole of the metropolitan territory. As a consequence, a filling rate in volume dams in our country by 72%. That is ” only “8 points below average. Thanks to dynamic management of hydraulic stocks by EDF. Dynamic management based on close monitoring of the weather report and debits waterways. Declines in production of between 25 and 30% have nevertheless been recorded in recent weeks. If the situation persists, greater difficulties could arise at thefall.

Because it is interesting to remember that, if EDF manages more than 7 billion cubic meters of surface water in mainland France in its dams and reservoirs, this water is not only used for electricity production. It is also used for the supply of drinking water, irrigation and even the preservation of biodiversity. And it’s, ultimately the prefect who sets the priorities for use, knowing that drinking water and civil security take precedence over everything else.

In the context of climate change, the RTE report on “Energy Futures 2050” specifies that “the management of hydraulic stocks will have to evolve. While the capacity of the park has been stable for several years, significant variations in production could be observed in the future on the scale annual. But the production capacity by 2050 remains equivalent to that which we know today. »This conclusion must, however, be taken with caution given the uncertainty that continues to hover over the evolution of river flows in the decades to come. Depending also on a possible evolution of uses – more irrigation, for example.

Other means of production also impacted

To conclude, let us specify that if nuclear power andhydroelectricity seem to want to be the first means of production to depend on heat and drought, the others can also be impacted. The production wind turbine may suffer from the presence of a anticyclonefor example.

More unexpected perhaps, the impact of the drought on the production of electricity from… coal ! It is the German Federal Institute forhydrologywhich alerts on this subject, pointing out that the rivers of Central Europe are at levels “abnormally low”. And continue to decline. However, goods sometimes circulate on these rivers. On the Rhine, in particular, coal is transported: 17 million tonnes in 2020. A lot of products derived from oil too.

With a historically low level, the Rhine can no longer accommodate fully loaded freight ships. Since July 13, the coal supply of two German power plants has been disrupted. Even though, under the pressureof the war in Ukraine, the government decided to relaunch this type of production in the country.