The use of renewables like the sun and wind can cause fluctuations in power grids. But what impact do these fluctuations have on security of supply? To answer this question, scientists from Juelich and Goettingen worked together with colleagues in London and Tokyo to analyse different types of fluctuations in several power grids in Europe, Japan, and the U.S., and came to surprising conclusions. Their study was published today in the peer-reviewed journal Nature Energy.