With air pollution still on the rise in some regions despite government efforts to improve air quality, changes in surface solar radiation appear to be taking their toll on China’s vast solar fleet.
Amid major concerns about the harmful effects of pollution on human health and China’s ecosystems, a study has found new measures to reduce air pollution would help China tap the full potential of its PV push.
Having long surpassed next year’s PV generation capacity development target of 110 GW, China reached a cumulative 174.63 GW of solar at the end of last year. At its current pace, the world’s largest solar market is on track to realize its goal of 400 GW of installed PV by 2030, to provide 10% of its primary energy and support its Paris Agreement commitment of generating 20% of energy from non-fossil fueled sources.
However, the share of solar in the national energy mix is not only dependent on the pace of installation but also air pollution levels, a study by scientists at ETH Zurich and the University of Amsterdam has found.
The researchers analyzed observational sunlight data from 119 measurement stations across China from 1960 to 2015 to estimate how much the skies have dimmed during that period. The mounting angle of panels – how they are tilted to harvest solar radiation – was factored in to the data collected. After correlating the level of dimming to industrial emissions data, to quantify the role of air pollution in reducing sunlight, the researchers found solar irradiance decreased 11–15% over the 55 years studied.
If China could revert back to 1960s radiation levels, its 2016 solar generation capacity could yield 12–13% more electricity, the equivalent of an additional 14 TWh, the study claimed. The country could enjoy an additional 51–74 TWh of solar power from its anticipated solar generation capacity for 2030, wrote the authors of the study, adding the corresponding economic benefits could amount to $1.9 billion in 2016 and $4.6–6.7 billion in 2030.
Human-driven aerosol emissions and changes in cloud cover were identified as two main factors responsible for solar radiation dimming in China. Air pollution can affect solar power generation in three ways: through particle matter which accumulates on PV panels; through aerosol particles, which interact in ways which scatter or absorb solar radiation; and through cloud formation caused, for example, by the reaction of sulfur dioxide (SO2) with other pollutants, which can increase cloud reflectivity and duration and decrease the solar radiation reaching the Earth’s surface.
Between 1996 and 2010, an estimated 91% of SO2 emissions in China came from coal burning – mostly in industry and power generation, the study stated. For the same period black carbon – a major component of fine particulate matter PM2.5 – was emitted as a result of residential and industrial coal (41%) and biomass consumption (33%). However, since the early 1990s aerosol emission factors of SO2 and black carbon have fallen as a result of China’s air pollution control policies and demographic changes.
With dozens of cities choking under a cloud of smog in early 2013, the Chinese government declared war on air pollution and intensified measures to regulate the emission of PM2.5. From 2013 to 2018, the volume of hazardous airborne particles of PM2.5 fell by 33% in 74 major cities, according to analysis by Greenpeace East Asia. However, pollution readings in the smog-prone northern Chinese region covering the province of Hebei and the cities of Beijing and Tianjin rose 8% from January to April, according to Ministry of Ecology and Environment data.
While such mixed results have raised fears China’s war on pollution is losing momentum, central government has struggled to persuade observers efforts to reduce pollution will not be relaxed this year as the Chinese economy falls to its slowest rate of growth since 1990.
While cleaning the air requires significant investment, the authors of the ETH Zurich-University of Amsterdam study suggested that if such pollution control measures were adopted more widely, solar energy production capacity could increase and significantly offset the cost of pollution control. “The relationship between observed surface radiation and emissions of sulfur dioxide and black carbon suggest that strict air pollution control measures, combined with reduced fossil fuel consumption, would allow surface radiation to increase,” read the study, published in Nature Energy.
The topic of air pollution and its effect on solar PV output has garnered attention among researchers of late. A study published by scientists at Duke University – with colleagues at the Indian Institute of Technology-Gandhinagar and the University of Wisconsin at Madison – found the accumulation of airborne particles on solar panels could cut energy output by more than a quarter in some parts of the world, including China and India, where air pollution is extremely high.
Previous research from the Climate Policy group at ETH Zurich found completely eliminating emissions from the power, transport, industry and household sectors would enable all solar systems in China in 2040 to generate an extra 85-158 TWh of electricity per year. That additional solar power output would generate up to $10.1 billion more for the Chinese electricity industry, that study found.