Status: 07.03.2021 8:39 a.m.
Germany is gradually phasing out nuclear and coal-fired electricity. But if the country is only supplied with renewable energies: What happens if the sun is neither shining nor wind blowing?
By André Kartschall,
When it gets cold and dark in winter, Germans use more electricity than usual: heaters, lights and televisions run more when people are inside. So far, so normal. But that could become a problem, warns Professor Harald Schwarz from the Brandenburg Technical University in Cottbus.
Because when it is dark, no solar power is produced: “Then photovoltaic generation is de facto zero, although we have installed solar systems with 50 gigawatts in Germany.” If there is no breeze at the same time, the wind power will also largely fail. “We’re talking about two to five gigawatts of actual output, although systems with 60 gigawatts of output are installed,” explains Schwarz. What then arises is the so-called “cold dark doldrums”.
Will “Day X” be a serious problem?
The horror scenario is an extreme situation that theoretically only occurs on a few days a year. But these “days X” could decide in the future whether the energy transition with nuclear and coal phasing out will succeed. Because until now, Germany has always been able to rely on its conventional power plants in the event of an emergency – especially those made of coal and nuclear power.
But it is precisely these power plants that will be shut down in rows over the next few years. According to Schwarz, Germany is threatened with a classic “electricity shortage” as a result – even if only on a few days. “As early as 2023 we will be missing 15 to 20 gigawatts of secured output,” said Schwarz – and that is exactly what will be a problem on “Day X”.
In the following years the problem would get worse – because the nuclear phase-out is immediately followed by a step-by-step phase-out from coal-fired power generation. And electricity storage systems have not yet been able to solve the problem. “Today we have capacities with which we can supply Germany for a full 30 to 60 minutes, but not for long periods of dark doldrums,” warns Schwarz. In other words: power generation and power consumption must be identical every minute.
The Federal Network Agency calculates differently
Up until three years ago, the following was true in Germany: the “secured generation output” must be able to cover the maximum electricity demand at all times. In other words: it must always be mathematically clear that enough electricity is available even for extreme cases. This is no longer the case. The Federal Network Agency responsible for security of supply calls this calculation method outdated.
Instead, one now calculates how likely it is that such a case will occur. The result of the “stress test”: On average, the entire power supply is not secured for around 40 minutes a year. But even then the lights in Germany did not simply go out: “During this time, most of the load can be covered, only a very small part could not be served on the market,” emphasizes the Federal Network Agency.
Agency relies on several emergency mechanisms
The “very small part” is a few large industrial plants that would be taken off the grid for a short time – aluminum smelters, for example. Such regulations are contractually agreed with these bulk buyers. There are also replacement power plants that would then be started up: “For such cases, the capacity reserve in Germany is ready.” This will be two gigawatts from October next year. According to the Federal Network Agency, this is enough to ensure the power supply for the masses at all times.
In addition, according to the Federal Network Agency, it is no longer appropriate to only look at the German power plants. After all, the European electricity market has long been a reality. And if Germany needs more electricity, it can usually get it on the market.
Here, energy expert Schwarz disagrees. In the case of a Germany-wide dark doldrums, “nobody is prepared to supply Germany in every case.” In addition, little wind could blow in the neighboring countries and the sun could not shine. Another problem are the lines: “The European network was never built to supply entire countries with electricity across borders.”
“Series of scenarios with extreme cases calculated”
The Federal Network Agency explains that all of this has been taken into account in the simulations. Precisely for this purpose, a number of scenarios with extreme cases have been calculated. These did not show any uncontrollable problems for the next few years – and the forecasts are constantly being updated. If there is a bottleneck, there is enough time to react. “We see something like that in the bills ten years in advance,” assures the agency.
Expert Schwarz does not want to be seen as a refuser of the energy transition. “There is absolutely no doubt that we have to move towards lower-carbon electricity generation, and I would be happy if it works,” he says. “But I can’t see how that is guaranteed.” But if it works as the Federal Network Agency has calculated, people in Germany will probably notice a “dark doldrums”: nothing at all.