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Photovoltaic power generation can directly convert solar energy into electricity, but most of the solar energy absorbed by the photovoltaic panel is converted into heat, which significantly increases the operating temperature leading to a reduction in the power generation efficiency of the panels. To reduce the working temperature of photovoltaic panels and improve the photoelectric conversion efficiency, this paper installs aluminum fins and air channels at the traditional photovoltaic cell back sheets and cools them with forced-circulation cooling through fans. The relationships between fin spacing, fin height, air channel inlet wind speed and panel temperature, power generation, and electrical efficiency were investigated. The results show that the temperature of the photovoltaic panel decreases and then increases with the decrease of the fin spacing during natural convection and gradually decreases with the increase of the fin height. The use of forced-circulation cooling technology can effectively reduce the PV panel temperature and increase the net power generation. When the solar radiation intensity is 1000 W/m2, the ambient temperature is 35°C, the fin spacing is 6 mm, the height is 80 mm, the inlet wind speed is 1 m/s, the net generating power reaches the maximum value, and the net generating power and the electrical efficiency are increased by 14.6% and 2.25%, respectively. [ABSTRACT FROM AUTHOR]

• Cumulative and time-lag effects combined impact vegetation activities. • Solar radiation and temperature are the dominant climate factors in taiga and tundra. • The duration of temporal effects corresponds with ecosystem complexity. • The tundra converted to forests caused by warming enhanced the climate temporal effects. The Northern Hemisphere is experiencing amplified warming and greening; however, the responses of greening to warming remain unclear in terms of the cumulative and time-lag effects of climate factors. We chose Siberia, a hotspot in the Northern Hemisphere, as a study area and identified the relationships between the enhanced vegetation index (EVI) and climate factors (e.g., surface temperature, precipitation, and solar radiation) during 2000–2016. In the growing season, the average cumulative duration of the vegetation response to climate factors was 3.6 ± 2.0 months, and the time-lag period was 1.5 ± 1.2 months, with the longest duration in forests and the shortest duration in tundra. Solar radiation was the dominant driver of vegetation greening in 56% of the study area, followed by temperature (41%) and precipitation (3%). In addition, the temporal effects of the climate factors were separated through partial correlation analysis; vegetation responded most rapidly to solar radiation variations with a cumulative duration of 2.2 ± 1.2 months and a time-lag period of 1.8 ± 0.8 months, followed by temperature (2.3 ± 1.3 and 1.9 ± 1.0 months, respectively). Precipitation showed the longest cumulative effect (3.7 ± 1.5 months) and the shortest time-lag effect (1.2 ± 1.1 months). Our results suggest that vegetation activity is influenced by both cumulative and time-lag effects. The temporal effects vary among the land cover categories, and complex ecosystems generally correspond to long-term temporal effects, and vice versa. Thus, the conversion of tundra to boreal forest due to warming in Siberia enhances the temporal effects of climate. These temporal effects could be incorporated into Earth system models to improve our understanding and monitoring of terrestrial ecosystems. [ABSTRACT FROM AUTHOR]

Photovoltaic (PV) power generation can directly convert solar radiation photons into electrical energy, but PV panels produce a large amount of waste heat during absorption of solar radiation, significantly increasing the working temperature and reducing the photoelectric conversion efficiency of the panels. In this study, a phase-change material (PCM) is used to cool the PV panels, and fins are added to enhance PCM heat transfer. Using numerical simulation, the effects of fin spacing, fin height, solar radiation intensity, and ambient temperature on the heat-dissipation performance of the PV/PCM system were then studied. The fin–PV/PCM structure showed a good cooling effect. With decreasing fin spacing, the increase in the panel temperature gradually decreased. Fin spacing of 6 mm exhibited the best cooling effect, with the battery plate temperature reduced by 31.9 °C compared with that of the natural convection condition without fins. The increase in the panel temperature gradually decreased with increasing fin height, and the cooling effect of the panel improved significantly when the fin height was increased from 30 to 70 mm. The heat-dissipation effect of the fin–PV/PCM system was better with higher solar radiation intensity and higher ambient temperature. The results of this study will have important reference value for performance improvement of PV panels. [ABSTRACT FROM AUTHOR]