Enhancement of Cloudless Skies Frequency over a Large Tropical Reservoir in Brazil

Abstract

Several studies show the effects of lake breezes on cloudiness over natural lakes and large rivers, but only few contain information regarding large flooded areas of hydroelectric dams. Most Brazilian hydropower plants have large water reservoirs that may induce significant changes in the local environment. In this work, we describe the prevailing breeze mechanism in a Brazilian tropical hydropower reservoir to assess its impacts on local cloudiness and incoming surface solar irradiation. GOES-16 visible imagery, ISCCP database products, and ground measurement sites operated by INMET and LABREN/INPE provided data for the statistical analysis. We evaluate the cloudiness frequency assuming two distinct perspectives: spatial distribution by comparing cloudiness over the water surface and areas nearby its shores, and time analysis by comparing cloudiness prior and after reservoir completion. We also evaluated the solar irradiance enhancement over the water surface compared to the border and land areas surrounding the hydropower reservoir. The results pointed out daily average cloudiness increases moving away from the reservoir in any of the four cardinal directions. When looking at the afternoon-only cloudiness (14 h to 16 h local time), 4% fewer clouds were observed over the flooded area during summer (DJF). This difference reaches 8% during autumn (MAM) and spring (SON). Consequently, the irradiance enhancement at the water surface compared to external areas was around 1.75% for daily average and 4.59% for the afternoon-only average. Our results suggest that floating solar PV power plants in hydropower reservoirs can be an excellent option to integrate both renewable energy resources into a hybrid power generation due to the high solar irradiance in Brazilian territory combined with the prevailing breeze mechanism in large tropical water reservoirs.

Effects of atmospheric low-level jets on the mixing process of a large tropical reservoir

“…The ABL over the Furnas reservoir remains unstable (Tw > Ta) about 5/6 of the time on an hourly scale (Figure 3a). This behavior is similar to those observed in other tropical Brazilian reservoirs (Gonçalves et al 2020, Curtarelli et al 2014a, and tropical lakes and reservoirs worldwide (MacIntyre et al 2002, Verburg et al 2011. Unstable ABL conditions were prevalent throughout most of the year, but for August and September, we observed a tendency towards neutral conditions on a monthly scale (Figure 3b).…”

Editorial for the Special Issue: Assessment of Renewable Energy Resources with Remote Sensing

“…The long time series of surface solar radiation and cloud cover indexes are crucial indicators of the solar power resource. Two articles [8,11] in this Special Issue focus on analyzing remote sensing data in the land-water interface in a large hydropower reservoir or coastal areas, respectively. Gonçalves et al [8] used GOES-16 visible imagery, ISCCPdatabase products, and ground measurement sites operating close to a large hydropower reservoir, providing data for the statistical analysis.…”

“…Two articles [8,11] in this Special Issue focus on analyzing remote sensing data in the land-water interface in a large hydropower reservoir or coastal areas, respectively. Gonçalves et al [8] used GOES-16 visible imagery, ISCCPdatabase products, and ground measurement sites operating close to a large hydropower reservoir, providing data for the statistical analysis. Their results suggest that floating solar PV power plants in hydropower reservoirs can be an excellent option to integrate renewable energy resources into a hybrid power generation due to the high solar irradiance in the Brazilian territory combined with the prevailing breeze mechanism in large tropical water reservoirs.…”

“…This Special Issue is comprised of ten research papers [1][2][3][4][5][6][7][8][9][10] and one letter [11]. Figure 1 shows a pictorial word cloud of the Abstract contents of the eleven manuscripts, where the strong multi-disciplinary character of the remote sensing approaches applied to renewable energy is apparent.…”