Do we need only 45 offshore wind turbines to replace a nuclear reactor, as Mélenchon claims? – Release

Mélenchon presidential candidate 2022dossier
No wind turbine today can provide such power. The team of the rebellious candidate explains that he was talking about “the future large wind turbines at sea”.


You asked us about a particularly commented statement by Jean-Luc Mélenchon. Repeating on France Inter his plan to phase out nuclear power by 2050, the presidential candidate insisted on the potential for substituting renewable energies, in particular wind power: “I’ll give a simpler example, a nuclear reactor is 45 offshore wind turbines.”

On social networks, many Internet users considered the comment eccentric, some opposing an article that CheckNews wrote in December 2019: when asked about the number of wind turbines to “replace” the Fessenheim plant, we then mentioned the figure of 500 offshore wind turbines. A figure which applied to the two reactors of the Haut-Rhin power station, but which varies according to the type of reactors and wind turbines mentioned.

In France, the fifty or so nuclear reactors have powers of 900 megawatts (MW) – for the majority – to 1,450 MW. It is therefore necessary to choose the reactor we are talking about.

The same goes for offshore wind turbines with which we decide to replace it. In our previous article, we based our calculations on the following data: the Fessenheim plant had two 900 MW reactors, for a total power of 1,800 MW. To estimate the number of wind turbines needed to “replace” this power, we relied on offshore wind turbines of “standard” unit power (6 MW).

It is not enough to make a simple division from the unit power. It must be taken into account that the two energy sources do not produce at their maximum capacity all the time (this is called the capacity factor). Based on a capacity factor of 40% for offshore wind (higher than that for onshore wind), and considering that Fessenheim had produced 11.9 TWh in 2018, we arrived at 500 offshore wind turbines to “replace »Two reactors.

The same calculation for 1 reactor of 900 MW (based on the production of Fessenheim in 2018) would therefore lead to 250 offshore wind turbines with a power of 6 MW (starting from a capacity factor of 40%).

Sea monsters

We are far from the calculation of Jean-Luc Mélenchon who – contrary to what his formulation in the present suggests – does not place himself in a current framework and evokes “The future large wind turbines at sea”, explains his entourage. On a visit to the Ecole Centrale de Nantes at the end of November, the candidate had visited the marine energy laboratories of the engineering school, with a particular interest in “new generation” wind turbines. In the article by West France relating this visit, we read as follows: “Offshore, each of these machines, with huge blades, 250 m in diameter, is capable, according to engineers, of providing 20 megawatts each. “It would be advisable to install 45 of them to replace a nuclear reactor”, calculates a technician. “

We can bet that this is the source of Jean-Luc Mélenchon’s statement on France Inter, which is therefore based on a scenario, still theoretical, of wind turbines each having a unit power of 20 MW / h. Ditto for the capacity factor, where the candidate assumes that offshore wind turbines, due to their better exposure to the wind, will reach a capacity factor not yet reached today. “These offshore wind turbines could approach a load factor of 60%”, says the candidate’s team. By retaining these theoretical hypotheses, we would thus arrive at 45 wind turbines “of the future” providing the equivalent of what a nuclear reactor with a capacity of 900 MW produces. The account is good. But on paper only, for now.

Currently, offshore wind farms are clearly below this performance. In France, the first marine wind farm should see the light of day at the end of 2022 with 80 6 MW wind turbines installed 15 kilometers off the coast of Le Croisic (Loire Atlantique). The Hornsea 2 project Danish company Orsted, presented as the largest offshore wind farm in the world, has just started producing energy and is due to deploy 165 8 MW wind turbines 90 kilometers off the Scottish coast this year. Other fields, still in the draft stage, such as that of Dogger Bank, 130 kilometers from the north-east coast of England, plan to use theHaliade-X de General Electric, a wind turbine with a capacity of 12 MW which could be boosted to 14 MW, and promises a capacity factor between 60 and 64%.

Source: Libération by

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