Before counting one has to define the term dark doldrums quantitatively. I've looked at four ways to do it and will start with what @leonhardprobst.bsky.social & @energy-charts.bsky.social from Fraunhofer ISE put forward in this podcast: https://buff.ly/41SPgtN 4/
Probst & Burger define a doldrum day to be one where renewable production in average covers less that 20% of demand. Over 35 years we find the following: 5/
Next two definitions by Ohlendorf & @wpschill.bsky.social, doi:10.1088/1748-9326/ab91e9. A doldrum hour is defined as an hour with mean wind and PV power of less than 10% of installed capacity. A dd event of type cbt10 (const. below threshold)
is a period of consecutive doldrum hours. 6/
Last but not least a definition proposed by Solardoktor on https://buff.ly/3Pggcwj: A dd event is a period where residual load stays positive after smoothing with batteries and DSM. 8/
Comments
is a period of consecutive doldrum hours. 6/
7/