Aerosols Key Factor In Declining Solar Irradiance In India- IIT Delhi Researchers

Researchers from the Centre for Atmospheric Sciences Solar at IIT Delhi have come out with a report that looks at multi decade data to evaluate trends in solar irradiance in India. The researchers, Sushovan Ghosh, Alok Kumar, Dilip Ganguly and Sagnik Dey, make the case for seeking reductions in aerosol release into the atmosphere over the country, to increase solar output and other benefits.

Radiation is not constant, instead, it undergoes multi-decadal variations, commonly referred to as ‘dimming’ (indicating a decreasing trend) and ‘brightening’ (indicating an increasing trend). These fluctuations have profound implications for the efficiency of photovoltaic generation systems. To secure a sustainable and reliable solar energy future, it is imperative to reassess India’s solar resources. This entails a comprehensive examination of the roles of atmospheric aerosols and cloud cover in the context of dimming and brightening. Further, the scarcity of land is another major challenge for the rapidly growing solar industry in India.

In their recently published article in the journal CELL, they explored the following key research inquiries:

1. How has solar radiation varied across different regions of India over the past decade?
2. What roles do aerosols and clouds play in shaping the fluctuations in solar radiation?
3. To what extent can the Indian subcontinent be deemed suitable for photovoltaic resources, considering radiation levels and land availability criteria?
4. What implications do dimming and brightening have on the state of solar resources in India?

 Key findings include:

• Surface solar radiation, primary for photovoltaic generation, is decreasing at a rate of -0.29±0.19 Wm^-2 per year during the last two decades.
• Solar radiation over nearly 98%, 40%, and 39% of the Indian landmass are significantly impacted by aerosols, clouds, and both aerosols and clouds respectively.
• Clearly, role of aerosols dominates over clouds in modulating the observed trends in solar radiation over India.
• Based on the received radiation, land availability constraints we found that 29.3% of the Indian landmass is suitable for effective photovoltaic generations. They are mostly spreading across the western and southern India.
• But this is further declining by -0.21% annually, causing a presumptive loss of 50 GW solar potential, translating 75 TWh power generation.
• Lowering two decades of aerosol burden can make 8% additional landmass apt for photovoltaic use.
• Alleviating aerosol-induced dimming can fast-track India’s solar energy expansion.
• Interestingly, aerosol-induced dimming is increasing over forest-fire hotspots (over central Himalaya, central and north-east India) and decreasing over Thar Desert.
• Over the Thar Desert, the role of clouds (and specifically high-level clouds) outweighs the aerosol loading. If the current trend continues, then the existing solar parks over that region of Rajasthan will be more sensitive to changes in cloud characteristics (in response to global warming), even though they experience desert dust inherently.
• The full article can be accessed here.