Then, they systematically analysed the data and were surprised on two accounts. Two surprises in one analysis Firstly, they collated measurements from Europe, Japan, and the USA. But what impact would this division into small cells and additional renewable generators have on the power grid? To answer this question, scientists from Forschungszentrum Jülich and MPIDS analysed the grid frequency fluctuations in power grids in different regions of the world – and using mathematical models, they predicted potential vulnerabilities and their causes. This would allow a community with a combined heat and power unit and its own wind and photovoltaic generators, for example, to operate its energy systems in an autonomous manner. A frequent suggestion for integrating renewable energy generators into the power grid involves breaking the grid down into small autonomous cells known as microgrids. 'Deviations from the nominal value of 50 hertz must be kept to a minimum, as otherwise sensitive electrical devices could be damaged.' Renewable energy generation also causes grid frequency fluctuations because the wind does not always blow at the same speed and clouds constantly alter the feed-in from photovoltaic systems. 'When a consumer uses more electrical energy from the power grid, the grid frequency drops slightly before an increased energy feed-in re-establishes the original frequency,' explains Benjamin Schäfer from the Max Planck Institute for Dynamics and Self-Organization (MPIDS) in Göttingen and lead author of the study. Our power grid works at a frequency of 50 hertz – usually generated by turbines, for example in hydro- or coal power plants, which rotate at a speed of 50 revolutions per second. Their study was published today in the peer-reviewed journal Nature Energy. But what impact do these fluctuations have on security of supply? To answer this question, scientists from Jülich and Göttingen worked together with colleagues in London and Tokyo to analyse different types of fluctuations in several power grids in Europe, Japan, and the USA – and came to surprising conclusions. Diverse causes behind frequency fluctuations in power grids The use of renewables like the sun and wind can cause fluctuations in power grids.

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