As it happened: Germany's grid grapples with solar eclipse

pv magazine Head of Publishing Dr Michael Fuhs headed out in the (rapidly dimming) sunshine in the German capital to observe the eclipse and its affect on German grid frequency, demand response mechanisms and overall power supply.

10:20: Live blog begins. Effects of eclipse should soon be felt. Sky is clear in many parts of Germany and solar production tops 13 GW before the event compared to 15.8 GW that had been expected if there hadn’t been any clouds at all. This means, the German grid was going to experience almost the most stressful situation which could have been anticipated during the eclipse

10:23: Network frequency drops from 50.02 to 50.00 Hertz. Unclear if this is a trend that will be compensated for by the dropping solar output. According to the SMA monitor, PV output has dropped from more than 13 GW to 10.7 GW.

10:24: Blue skies in Berlin. Still nothing visible to the naked eye. The highpoint [of the eclipse] will be at 10:47am.

10:25: Frequency drops 49.98 Hertz. Bloggers covering the grid [Stromhaltig] affect see this as fluctuation, not as a clear trend.

10:30: Transmission service operator 50 Hertz reports in the period from 9:30am, to 10:00am negative secondary operating reserve from minus 50 MW to minus 141 MW. Zero minute reserve.

10:33: It is now noticeably darker and more drab. Just 9.1 GW of PV generation. Network frequency back to 50 Hertz. There is enough power in the grid.

10:36: On the website http://wetter.htw-berlin.de/ you can clearly see the plunge PV power generation.

10:37: Stromhaltig blog: The solar eclipse is clearly discernible in intraday trading on the electricity exchange. This was correctly predicted by Energy Brainpool and offers shrewd spot traders a money-making opportunity.

10:41: With a pinhole camera, a very pretty solar crescent is visible. Much more than half of the sun is covered.

10:42: 7 GW solar output, 40.97 Hertz network frequency – significantly below 50 Hertz.

10:44: PV generation continues to slide. Just 6.6 GW. Network frequency still below 50 Hertz.

10:47: Actually, fluctuations in network frequency could occur every 15 minutes.

10:50: Highpoint, according to an HTW study, passes at 10:42am. Generation begins to rise again.

10:54: Here comes the big stress test. The greatest change in PV power generation takes place between 11:00am and 11:15am.

10:56: The SMA monitor now reads just 4.8 GW. How much of a delay in this data? May be due to server problems.

10:59: Network frequency ready exactly 50 Hertz on the monitor of the transmission service operator. Is that delayed too?

11:00: Between 10:00am and 10:15am at 50 Hertz transmission network operator reports positive 220 MW of operating reserve.

11:04: It appears to be more of a stress test for the web servers for sites that monitor solar power generation and network frequency than for the power grid.

11:07: PV power generation growing significantly higher again.

11:09: It is already much brighter.

11:12: Frequency constantly stable, although this is the period of the fastest rise in PV generation.

11:16: Frequency still stable. Actually, the greatest load on the power grid should have passed by now.

11:20 According to SMA monitor, back up to 7.1 GW photovoltaic power in the grid. Still unclear if there is a delay in its reaction. A comparison with insolation figures the HTW http://wetter.htw-berlin.de/ shows that the value could be too low.

11:24: Discovery says that PV output has already exceeded the period prior to the solar eclipse.

11:25: Live blog end. Watch this space for more background and assessments later.

After midday, SMA reported 20.2 GW of solar power generation.

Translation by Tim Haynes.