Someone forgot to tell the National Grid about the solar eclipse

The UK will experience a sharp reduction in sunlight on Friday morning, 20th March as a result of the 80% solar eclipse. This will reduce the power coming into the electricity grid from solar PV by at least an equivalent percentage. However the forecasters at the UK National Grid don’t seem to have been reading the newspapers. The chart below shows the published forecast for solar PV output for the 19th, 20th and 21st March. (1)

Source: National Grid

Source: National Grid

At the time of the peak eclipse, about 9.30am, solar output is expected to be higher than the two adjoining days. There’s no sign of even the smallest dent as the nation goes into twilight for a couple of hours.

I hope someone has remembered to tell the people in the National Grid control room in Wokingham.

Contrast this with the forecast for solar in Germany in the chart below.

Germany has about 6 times as much PV as the UK. The challenges posed by the fall in PV output as the eclipse starts are regarded as tricky but manageable. At  peak – if it is sunny – the German electricity network would be losing 400 MW of PV-generated power every 60 seconds. To compensate for this means turning on a new 1GW power station every two and a half minutes over a period of a half hour or so. If Germany succeeds in dealing with the eclipse it will help show that variations in PV output - even extremely rapid changes - can be handled by a modern electricity network.


(1) Look for DemandData_Update.