http://www.digitaljournal.com/business/air-pollution-in-urban-settings-can-put-a-dent-in-solar-power/article/530921

Air pollution in urban settings can put a dent in solar power

Posted Sep 1, 2018 by Karen Graham
Urban haze is a multifaceted threat. Foremost a major health hazard, it also affects the passage of light through the lower atmosphere. This can significantly reduce the power output from solar panels, and impact on the industry.
Medium rooftop solar power installation on South Beach roof in 2012.
Medium rooftop solar power installation on South Beach roof in 2012.
B137 (CC BY-SA 4.0)
Ian Marius Peters, now an MIT research scientist, was working on a solar energy project in Singapore in 2013 when much to his surprise, the city was engulfed in a major cloud of pollution one day. He says the foul-smelling cloud was so thick, you could not see buildings on the opposite side of the street.
The event was triggered by forest fires in Indonesia and because of air circulation patterns, became concentrated over the Singapore region, lasting for about two weeks. Stores ran out of face masks and hospital admissions rose due to respiratory problems brought on by the thick pollution.
And while others were addressing the public health issues, Peters and his co-worker Andre Nobre from Cleantech Energy Corp., whose field is also solar energy, wondered what kind of impact such hazes would be having on the output of solar panels in the area.
People eat breakfast at a roadside stall shrouded in thick haze in downtown Palangkaraya  a city at ...
People eat breakfast at a roadside stall shrouded in thick haze in downtown Palangkaraya, a city at the epicentre of Indonesia's haze crisis
Bay Ismoyo, AFP
Their curiosity turned into a years-long project to try to quantify just how urban-based solar installations are affected by hazes, which tend to be concentrated in dense cities. The results of their work were published in the journal Energy & Environmental Science on August 3, 2018.
Perhaps not surprisingly, the results of the study found the effects of urban haze or air pollution are indeed substantial. In some cases, it can mean the difference between a successful solar power installation and one that ends up failing to meet expected production levels, or even worse - operates at a loss.
The impacts of air pollution on photovoltaics
The study looked at pollution impacts 18 cities around the globe, starting with Singapore and then Delhi, India. The team first had to collect data on both the amount of solar radiation reaching the ground and the amount of particulate matter in the air as measured by other instruments.
Work on solar cells using perovskite material has advanced rapidly as a result of the materials exce...
Work on solar cells using perovskite material has advanced rapidly as a result of the materials excellent light absorption, charge-carrier mobilities, and lifetimes, resulting in high device efficiencies with significant opportunities to realize a low-cost, industry-scalable technology.
National Renewable Energy Laboratory
With the help of MIT associate professor of mechanical engineering Tonio Buonassisi and three others, the researcher team worked to find a way to calculate the amount of sunlight that was being absorbed or scattered by haze before reaching the solar panels, and this proved to be somewhat difficult.
However, using long-term, high-resolution field data from Delhi and Singapore they were able to derive an empirical relation between reduction in insolation and fine particulate matter (PM2.5) concentration. This provided a fairly strait-forward way to estimate air pollution-related losses to photovoltaic power generation anywhere on the planet.
So after getting Singapore and Delhi figured out, the researchers looked at 16 additional cities around the globe. But, back to Delhi for just a moment. The study found that unlike Singapore, Delhi never had a day without pollution, said Peters. In Dehli, they found the annual average level of attenuation of the solar panel output was about 12 percent.
The Indian capital New Delhi is one of many world cities struggling to deal with air pollution
The Indian capital New Delhi is one of many world cities struggling to deal with air pollution
DOMINIQUE FAGET, AFP/File
In other words, the research team found that the amount of solar radiation received by the solar panels was reduced by about 12 percent a year. When extending the analysis to the other cities on their list, they found attenuation in Singapore to be at 2.0 percent, and in Beijing, 9.1 percent, along with Dakha, Ulan Bator, and Kolkata.
What do the figures have to do with solar panels?
Looking at the difference in Singapore, at only 2.0 percent loss of solar radiation a year, and then Delhi, with 12 percent solar loss, it does make a huge difference monetarily.
Peters points out that the 12 percent is larger than the profit margins for some solar installations, and thus could literally be enough to make the difference between a successful project and one that fails. And this could not only affect the solar project itself but could have a ripple-effect, turning potential customers away from solar.
In other words, Peters is saying that if a solar installation is based on expected levels of sunlight reaching the ground in that area, without considering the effects of haze, then the project will fall short of meeting its intended output and its expected revenues.
Flames are seen behind a mansion in the luxurious Bel Air neighborhood threatened by the "Skirb...
Flames are seen behind a mansion in the luxurious Bel Air neighborhood threatened by the "Skirball" Fire in west Los Angeles, California on December 6, 2017
Robyn Beck, AFP
"When you're doing project planning, if you haven't considered air pollution, you're going to undersize, and get a wrong estimate of your return on investment," Peters says
And here is something else the study discovered - Different types of solar cells were impacted differently by haze. The study found that gallium arsenide, cadmium telluride, and perovskite were all impacted in varying degrees by haze because of their different spectral responses.
According to the study, "all of them were affected even more strongly than the standard silicon panels they initially studied, with perovskite, a highly promising newer solar cell material, being affected the most (with over 17 percent attenuation in Delhi)."
According to Inverse, in Delhi alone, the lost revenue from power generation could amount to as much as $20 million annually; for Kolkata, it’s about $16 million; and for Beijing and Shanghai, it’s about $10 million annually each, the team estimates. Planned installations in Los Angeles could lose between $6 million and $9 million.