Satellites

2020
Li, Xiaoyuan, Denise L. Mauzerall+, and Mike H. Bergin. “Global reduction of solar power generation efficiency due to aerosols and panel soiling.” Nature-Sustainability (2020).Abstract
Air pollution and dust prevail over many regions that have rapid growth of solar photovoltaic (PV) electricity generation, potentially reducing PV generation. Here we combine solar PV performance modelling with long-term satellite-observation-constrained surface irradiance, aerosol deposition and precipitation rates to provide a global picture of the impact of particulate matter (PM) on PV generation. We consider attenuation caused by both atmospheric PM and PM deposition on panels (soiling) in calculating the overall effect of PM on PV generation, and include precipitation removal of soiling and the benefits of panel cleaning. Our results reveal that, with no cleaning and precipitation-only removal, PV generation in heavily polluted and desert regions is reduced by more than 50% by PM, with soiling accounting for more than two-thirds of the total reduction. Our findings highlight the benefit of cleaning panels in heavily polluted regions with low precipitation and the potential to increase PV generation through air-quality improvements.
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Gerlein-Safdi, Cynthia, Gretchen Keppel-Aleks, Feng Wang, Steve Frolking, and Denise L. Mauzerall. “Satellite Monitoring of Natural Reforestation Efforts in China’s Drylands.” One Earth 2 (2020): 98-108.Abstract
China has been a leader in reforestation efforts with multiple large-scale projects. In this study, we found that satellite data sensitive to water and photosynthesis activity in plants in drylands is tightly linked to reforestation efforts in the Three-North Shelterbelt Program area. In particular, both traditional active reforestation and new natural reforestation increased vegetation activity. This is important because natural reforestation has advantages, such as increasing biodiversity. China’s successful implementation of natural reforestation could become a model for other regions.
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2017
Li, Zhongshu, Junfeng Liu, Denise L. Mauzerall, Xiaoyuan Li, Songmiao Fan, Larry W. Horowitz, Cenlin He, Kan Yi, and Shu Tao. “A potential large and persistent black carbon forcing over Northern Pacific inferred from satellite observations.” Scientific Reports 7, no. 43429 (2017).Abstract
Black carbon (BC) aerosol strongly absorbs solar radiation, which warms climate. However, accurate estimation of BC’s climate effect is limited by the uncertainties of its spatiotemporal distribution, especially over remote oceanic areas. The HIAPER Pole-to-Pole Observation (HIPPO) program from 2009 to 2011 intercepted multiple snapshots of BC profiles over Pacific in various seasons, and revealed a 2 to 5 times overestimate of BC by current global models. In this study, we compared the measurements from aircraft campaigns and satellites, and found a robust association between BC concentrations and satellite-retrieved CO, tropospheric NO2, and aerosol optical depth (AOD) (R2>0.8). This establishes a basis to construct a satellite-based column BC approximation (sBC*) over remote oceans. The inferred sBC* shows that Asian outflows in spring bring much more BC aerosols to the midPacific than those occurring in other seasons. In addition, inter-annual variability of sBC* is seen over the Northern Pacific, with abundances varying consistently with the springtime Pacific/North American (PNA) index. Our sBC* dataset infers a widespread overestimation of BC loadings and BC Direct Radiative Forcing by current models over North Pacific, which further suggests that large uncertainties exist on aerosol-climate interactions over other remote oceanic areas beyond Pacific.
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Li, Xiaoyuan, Fabian Wagner, Wei Peng, Junnan Yang, and Denise L. Mauzerall+. “Reduction of solar photovoltaic resources due to air pollution in China.” Proceedings of the National Academy of Sciences (2017).Abstract
Solar photovoltaic (PV) electricity generation is expanding rapidly in China, with total capacity projected to be 400 GW by 2030. However, severe aerosol pollution over China reduces solar radiation reaching the surface. We estimate the aerosol impact on solar PV electricity generation at the provincial and regional grid levels in China. Our approach is to examine the 12-year (2003–2014) average reduction in point-of-array irradiance (POAI) caused by aerosols in the atmosphere. We apply satellite-derived surface irradiance data from the NASA Clouds and the Earth’s Radiant Energy System (CERES) with a PV performance model (PVLIB-Python) to calculate the impact of aerosols and clouds on POAI. Our findings reveal that aerosols over northern and eastern China, the most polluted regions, reduce annual average POAI by up to 1.5 kWh/m2 per day relative to pollution-free conditions, a decrease of up to 35%. Annual average reductions of POAI over both northern and eastern China are about 20–25%. We also evaluate the seasonal variability of the impact and find that aerosols in this region are as important as clouds in winter. Furthermore, we find that aerosols decrease electricity output of tracking PV systems more than those with fixed arrays: over eastern China, POAI is reduced by 21% for fixed systems at optimal angle and 34% for two-axis tracking systems. We conclude that PV system performance in northern and eastern China will benefit from improvements in air quality and will facilitate that improvement by providing emission-free electricity.
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