Battery storage is the key to the minute-long puzzle

November 2, 2026

Source: E & M powernews

For years, the grid frequency has been dropping briefly every minute. Researchers from Jülich have now identified the cause: Large battery storage systems synchronously query their state of charge.

The transmission system operator Tennet has been observing a striking phenomenon for several years: The frequency in the European power grid drops briefly every 60 seconds. The deviations are not safety-critical, but they are clearly measurable and occur with unusual regularity. Their cause remained unclear for a long time. Now, a team led by Dirk Witthaut from the Jülich Research Center has identified the cause, in collaboration with researchers from the University of Cologne and the Karlsruhe Institute of Technology (KIT). The scientists report their findings on the Nature Energy web portal.

Detective Work with a Stopwatch

“It really was years of detective work,” said Witthaut. This is because many factors overlap in the grid frequency, such as electricity trading—which causes power plants to be abruptly turned on or off—fluctuating feed-in from renewable energy sources, or a variety of other disturbances. However, the exact 60-second periodicity could only be explained by something controlled by a clock. Furthermore, the effect had to affect many devices consuming electricity at the same time. A single consumer or generator was therefore ruled out.

The decisive clues came from the Living Lab Energy Campus, a research infrastructure on the Jülich campus where highly integrated energy supply systems are developed and tested. The team installed measurement points on end devices at a total of 80 locations. Where large battery storage systems were connected, the same periodic pattern in consumption was observed. At one of these storage systems, a power spike was ultimately detected at the start of every minute due to the power query.

There are no binding standards for such power requests. Witthaut suspects that most manufacturers considered a 60-second interval to be reasonable and simply set the start of each minute as the test time. Battery storage systems may be only part of the problem: “It cannot be ruled out that other digitally controlled appliances—such as air conditioners, heat pumps, washing machines, and dishwashers—exhibit similar patterns.”

Random Queries as a Solution

These periodic fluctuations are already affecting hydroelectric power plants. The brief spike in demand temporarily slows down the turbines, after which they are accelerated back to their original rotational speed, increasing wear and tear.

Since the number of battery storage systems has increased sharply worldwide in recent years, this is not a German or European phenomenon, but a global one. With the accelerated expansion of storage capacity currently underway, the problem is likely to grow further. In Ireland, for example, where data centers with large battery storage systems account for about one-fifth of the national electricity demand, the amplitude of the one-minute signal quadrupled between 2016 and 2021.

The solution would be simple: “You would simply have to distribute the queries randomly instead of always starting them at the same time,” says Witthaut. Less simultaneity would relieve the strain on the grid and could make the power supply more robust. (gd)

The article“One-minute frequency disturbances from unintended synchronization in cyber–physical power systems”can be found on the Nature Energy website.

Author: Günter Drewnitzky