Impact of a solar eclipse on surface radiation and photovoltaic energy

We investigate the impact of annular solar eclipse (26 December 2019) on the surface radiation and photovoltaic (PV) energy generation observed at Gadanki (13.48 degrees N, 79.18 degrees E), located in southern peninsular India. Spectral and broadband irradiances are found to be sensitive to the solar obscuration, and follow the curvature resembling the fraction of non-obscured area of the Sun during the eclipse. Rapid changes are noticed in the spectral and broadband irradiances during the decreasing and increasing phases of solar obscuration. The diffuse fraction exhibits weak spectral dependence during the peak solar obscuration and under the influence of clouds. Although the deviation in the diffuse horizontal irradiance (DHI) at different wavelengths is highly sensitive, the deviations in the global horizontal irradiance (GHI) and direct normal irradiance (DNI) are found to be comparable among different wavelengths during the eclipse period. At peak obscuration, the reduction in both GHI and DNI shows an increasing trend from 414 nm to 671.2 nm. On the contrary, DHI decreases from 495.9 nm to 869 nm. Also, the deviation in broadband irradiances range between 72% and 98% with differing magnitudes of reduction at the peak obscuration. Apart from this, it is observed that the time of occurrence, strength of solar obscuration and prevailing sky conditions exhibit varying impact on the surface radiation components. The PV energy generated on the eclipse day is found to be reduced by 37% in comparison to that on a clear-sky day.

Automated summary

The study found that during the annular solar eclipse, there were significant changes in spectral and broadband irradiances, with diffuse fraction showing spectral dependence while deviations in global horizontal irradiance and direct normal irradiance were comparable at different wavelengths. Furthermore, there were varying reductions in broadband irradiances at different wavelengths during the eclipse, with PV energy generation being reduced by 37% compared to a clear-sky day.