Lockdown & Solar Energy: Air Quality Change Over China During COVID-19 for Solar Energy Generation

Now Published: Choi et. al. (2020). COVID-19 lockdown air quality change implications for solar energy generation over China. Environmental Research Letters, doi:10.1088/1748-9326/abd42f. http://iopscience.iop.org/article/10.1088/1748-9326/abd42f

Presented at the NCEO Virtual Conference 2020. Using satellite observations of nitrogen dioxide (NO2) and aerosol optical depth during the COVID-19 lockdown, this study illustrates one of the potential hidden benefits of a cleaner atmosphere is more efficient large scale solar energy generation.

We estimate the change in broadband and spectrally resolved solar direct normal irradiance (DNI) at the surface over China from 15 February to 15 March 2019, and the same period in 2020. The latter period was chosen to coincide with the lockdown enforced due to the COVID-19 pandemic. Between the two periods, satellite observations show a widespread reduction in atmospheric NO2 concentrations and some notable changes to aerosol optical depth. Focusing on Wuhan, the first city to be placed under lockdown due to the pandemic, the combined changes in atmospheric species lead to a 19.8% increase in broadband surface DNI, along with a shift in the DNI spectral distribution towards bluer wavelengths. Feeding these changes into a solar cell simulator results in a 29.7% increase in the power output for a typical triple-junction concentrator photovoltaic cell (3J CPV). Around one-third of the increase in power output arises from the improved spectral matching between the input DNI spectrum and the solar cell, which in turn improved the 3J CPV operating efficiency by 2.6%. Similar spectral effects were also observed over Beijing and Shenzhen. Based on satellite observations, we estimate there was up to a 14% increase in 3J CPV efficiency over parts of China during the lockdown.