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Does Nuclear Really Help The Integration Of Renewables?

Originally published on Renewables International.
By Craig Morris

“French nuclear exports help Germany, the UK, Italy and Spain accelerate their renewable uptake,” writes shale gas proponent Nick Grealy. What do the data show?

April was a relatively cold month in Europe, which led to slightly higher demand and power prices. Today, I investigate April 25, a Monday with a cold spell, to see when exactly France imports and exports electricity on a day when demand is high.

The narrative that Grealy falls prey to is that nuclear can be ramped up as need be. This alleged flexibility is held to be crucial in backing up solar and wind power. Here is what April 25 looked like in France.


Nuclear fluctuates from a low of 41.3 GW at 3 AM to 42.6 GW at 8 AM, a variance of 1.3 GW, equivalent to a fluctuation of just over three percent. Yet, power demand fluctuated from 41.4 GW at around 5 AM to 56.8 GW at around 1 PM – an increase of nearly 50 percent. Note as well that nuclear power practically covered 100 percent of French power consumption during the night. The import curve for that day is therefore quite revealing.


Here, we see a clear pattern: heavy exports in the middle of the night and in the late afternoon/evening. But from around 6 AM to 3 PM, France is a net importer of electricity. The pattern matches French consumption roughly; the chart below shows a high level of consumption from around 9 AM to just before 3 PM. The significant ramp from 6 AM to 9 AM is the reason why the country switches from exporting electricity to importing it.


We do not have a daily view at for Germany, so we will have to make do with the weekly depiction below. It shows the opposite pattern for Apr 25. Everything below the baseline is exports. At times of low demand, Germany exports less, with the lowest point occurring at 6 AM. But by 2 PM, Germany has a net export balance of nearly 9 GW. The balance of trade then tapers off towards midnight, but over the entire day Germany is a net exporter of electricity for 23 out of 24 hours.


What does this comparison tell us?

First, France clearly prefers to sell electricity at low prices at times of low demand rather than ramp down its nuclear plants. Second, the German power fleet has enough flexibility in comparison to ramp down rather than sell at low prices – and then ramp up again as prices increase at times of high demand.

French nuclear therefore does not facilitate the integration of wind and solar in neighboring countries. Rather, it clogs up the grid and reduces flexibility. In contrast, production of solar power in particular from 9 AM to 3 PM leaves conventional power plants in Germany at a relatively modest level; note that conventional generation actually falls from around 50 GW at 7 AM to 40 GW at 2 PM in the chart for Germany above. Without the 9 GW of exports, the German conventional power fleet would be pushed down to 30 GW – hence the tremendous exports.

Reprinted with permission.

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