According to a new study, airborne particles and their accumulation on solar panels are cutting energy output by more than 25% in certain parts of the world. The regions hardest hit are also those investing the most in solar: China, India and the Arabian Peninsula.
Cleaning boosts efficiency 50%
With colleagues at the Indian Institute of Technology-Gandhinagar (IITGN) and the University of Wisconsin at Madison, lead author Michael Bergin measured the decrease in solar energy gathered by the IITGN’s solar panels as they became dirtier over time.
The data showed a 50% jump in efficiency each time the panels were cleaned after being left alone for several weeks.
‘My colleagues in India were showing off some of their rooftop solar installations, and I was blown away by how dirty the panels were. I thought the dirt had to affect their efficiencies, but there weren’t any studies out there estimating the losses. So we put together a comprehensive model to do just that.’
Professor of civil and environmental engineering at Duke University and lead author of the study
The researchers also sampled the grime to analyse its composition, and found that 92% was dust. The remaining fraction was composed of carbon and ion pollutants from human activity.
While this may sound like a small amount, light is blocked more efficiently by smaller man-made particles than by natural dust. As a result, the human contributions to energy loss are much greater than those from dust, making the two sources roughly equal antagonists in this case.
Help from NASA and the Taj Mahal
Having previously analysed pollutants discolouring India’s Taj Mahal, Bergin already had a good idea of how these different particles react to sunlight. Using his earlier work as a base, he created an equation that accurately estimates the amount of sunlight blocked by different compositions of solar panel dust and pollution buildup.
But grimy buildup on solar panels isn’t the only thing blocking sunlight – the ambient particles in the air also have a screening effect.
For that half of the sun-blocking equation, Bergin turned to Drew Shindell, professor of climate sciences at Duke and an expert in using the NASA GISS Global Climate Model.
Because the climate model already accounts for the amount of the sun’s energy blocked by different types of airborne particles, it was not a stretch to estimate the particles’ effects on solar energy. The NASA model also estimates the amount of particulate matter deposited on surfaces worldwide, providing a basis for Bergin’s equation to calculate how much sunlight would be blocked by accumulated dust and pollution.