When India went into lockdown for two months due to COVID-19, small and big industries were shut, cars were locked in garages and people in their homes. The chimneys and exhausts stopped spewing poison, bringing a whiff of cleaner air to breath and more blue skies to stare at. While many people also went through tremendous economic hardship, a group of researchers from Germany, the USA and Singapore seemed to have found sunshine, quite literally, during these gloomy days. In a recent study, they have shown how cleaner air during the lockdown in Delhi, one of the most polluted cities in the world, has led to a hike in solar power generation.
The study, published in the journal Joule, provides supporting evidence of how clean air leads to better capture of solar energy.
“The study was conducted to quantify the impact of reduced air pollution on the energy generation of photovoltaic installations”, says Dr Ian Marius Peters. He is a research scientist at the Helmholtz-Institute Erlangen-Nuremberg in Germany and the lead author of the study.
In the 18th century, the amount of sunlight received in a region depended just on the cloud cover. However, with the industrial revolution gaining pace and the atmosphere becoming polluted, many complex factors played a role in determining the sunlight received. Today, methods of measuring sunlight take into account the cloud cover, amount of suspended particles in the air, and water droplets in the form of mist—all of which affect the light received by solar panels and the electricity generated.
The researchers collected irradiance data—a measure of radiant energy from the Sun—from a solar power plant in Paschim Vihar, Delhi. They gathered the data in four phases—well before the lockdown in February, the first 20 days of March just before the lockdown, the last ten days of March into the first phase of the lockdown, and the month of April during the lockdown. They also monitored the amount of fine solid and liquid pollutants and aerosols for the last four years from the US Embassy in Delhi, as a proxy to estimate air pollution in the city.
The study found that cleaner skies and lesser aerosol particles in the atmosphere led to higher capture of solar energy by photovoltaic installations. These installations consist of solar panels, inverters, racks, cables and other associated components. They capture solar energy and convert it to electricity, making it available for supply at power grids.
In the later-half of March, when the lockdown had just set in with strict movement restrictions, the sunlight captured by the photovoltaic installation was 8% higher than the last three years. This rise led to a corresponding increase in the amount of power generated. A smaller increase of 6% was also observed for April. In February and early March 2020 no significant differences from previous years were found.
A recent article, published in Green Tech Media in late April this year, claims that Spain, UK and Germany have had the highest-ever solar power generation this spring, and mentioned that this may, in parts, also be because of cleaner skies, since the coronavirus lockdown. The researchers of the study tried to test this claim by conducting similar research from data collected in a rural area in Northern Italy. Interestingly, they found no statistically significant reductions in anthropogenic (man-made) air pollution there. .
The observed impact, as claimed by the article, could be due to two reasons, say the researchers. It is either because European countries are less polluted than developing nations or that April 2020 was the brightest April in history.
“Their claim is not wrong, but the lack of air pollution is not the leading contributor.”, says Dr Peters.
With the lockdown being slowly eased and industries gradually opening up, people have started to move out of their homes much more than they did in the last two months. As a result, the traffic on the roads will also increase, leading to a drop in the air quality to pre-lockdown levels. What should we now do to maintain quality air, which was a gift for Delhiites during the lockdown?
“Better air quality would be achieved by electrifying transportation through electric cars and bikes, and by electrifying processes like cooking or heating. Additional research and development efforts are needed to make these technologies more available, affordable and appealing”, suggests Dr Peters.
This article has been run past the researchers, whose work is covered, to ensure accuracy.