A partial solar eclipse on Thursday will likely cause a temporary change in electricity supply on the transmission system of about 600MW, or 3% of the total, according to system operator NGESO.
Working on the experience of previous eclipses, it said they had two opposing effects: a reduction in supply as solar PV generation dipped, and a reduction in demand followed by a rebound as people interrupted other activities to observe the event. This time, with up to a third of the sun eclipsed between around 10am and 12.20pm, it expects a reduction in solar generation of 1.2GW, from 4.5GW that would otherwise be forecast. But it also expects demand to fall.
Cloudy skies will dampen the effect, both for solar PV generation and for those who want to observe the phenomenon – which, of course, should not involve risking eye damage by looking directly at the sun.
With over two hours of partial eclipse, the system operator did not expect any issues to arise from fast changes on the system – as happened in 1999 during a full eclipse in southwest England, when demand fell by 2.2GW and rose again by 3GW within 20 minutes. Thursday’s event would see PV levels change more slowly than regular cloud movements, it said.