How many wind turbines are needed to replace a nuclear power plant?

It takes almost 700 wind turbines to replace the electricity production of a nuclear power plant the size of Mühleberg, which represents only 10% of the power of our nuclear park.

If we consider wind turbines with an output of 2 MW, which is the standard in Switzerland, then 190 wind turbines are needed to match the output of Mühleberg power plant (373 MW). But capacity isn’t everything; you still have to produce! A power plant such as Mühleberg produces 24 hours a day, 7 days a week (apart from maintenance shutdowns, for about four weeks a year). A wind turbine runs on average 75% of the time, but at different speeds and therefore at different capacities depending on the wind conditions. Thus, in full power equivalent, it actually produces only about 25% of its capacity. The installed capacity of a wind turbine must therefore be multiplied by 4 to equal the electricity produced by a traditional power plant. So it will take not 190, but 190 x 4 = 760 wind turbines to replace a plant like Mühleberg. Adjusting the calculation to take into account the maintenance downtime of any nuclear power plant, it would take only 700 wind turbines to replace Mühleberg’s electricity production.

If these wind turbines were installed in the same park, the area required would be around 150 km2, which is roughly the same as the total area of the lakes of Lugano (49 km2), Thun (48 km2) and Biel/Bienne (40 km2). It should nevertheless be pointed out that the ground surface under a wind turbine remains available for certain uses, particularly agricultural.

That said, it would be too simplistic to compare nuclear and wind power on the basis of their production capacities alone. Other specificities have to be taken into account, in particular their production profile. Nuclear power produces electricity continuously and at almost constant power, known as “ribbon” electricity, whereas wind power is produced intermittently (when the wind blows). This intermittency complicates the task of the grid operator who must constantly balance production and demand for electricity. It will have to integrate new expertise in fine weather forecasting to enable it to predict the future production of its wind farm as accurately as possible.

It should be noted that wind power is not the only unpredictable energy. Nuclear power can also be subject to unpredictable shutdowns with much greater consequences given its production capacity and relatively long restart time. In addition to possible emergency shutdowns, power plants may be forced to massively reduce their production in periods of heat waves because they are unable to draw sufficient water from rivers to cool them while complying with environmental constraints to protect aquatic fauna. Such a situation occurred particularly in France in 2003, forcing our neighbour to reduce its exports in order to balance its own network.


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