Research On Eco-environmental Effects Of Large-scale Photovoltaic Development In Qinghai Desert Area

China has put forward the goal of carbon peaking by 2030 and carbon neutrality by 2060(’dual carbon’ goal).which requires China’s energy structure to undergo profound changes and complete energy transformation as soon as possible.Solar energy is the most promising and sustainable energy.Several million-kilowatt photovoltaic power generation bases have been built in the northwest desert region of China.Large-scale PV development in desert areas not only makes rational and efficient use of land and solar energy resources.promotes the low-carbon transrormation of energy system.but also has important scientific value for the coordinated development of PV carbon reduction and ecological exchange enhancement.Large-scale PV development has changed land use patterns and surface albedo,causing local climate changes.which may have potential impacts on ecosystem processes and functions.At present,there is a lack of in-depth research on the local climate effects of large-scale PV development and the impact on the ecosystem.Based on this,this paper takes Qinghai Gonghe Talatan PV Industrial Park as the research area,and builds monitoring stations in the PV field.transition zone,and the control area outside the PV field,as well as different PV subarray areass(flat singe axis(FSA).oblique single axis(OSA).fixed axis(FIX)PV subartay).The monitoring time is from January 2019 to December 2020 for two consecutive yars.The changes of local microclimate.soil characteristics and vegetation community structure in desert large-scale PV development zones arc analyzed,and the ecological environmental effects caused by PV development are evaluated,which provides a theoretical basis for the sustainable development and operation management of large-scale PV in desert areas.The main research results areas follows:(I)Revealed the impact of PV development on local climate① Air temperature:The influence of PV field on temperature has diurnal and seasonal different.The PV field has the effets of daytime warming and nighttime cooling,and the nighttime cooling can reach 1.44℃.In the PV filed,different sub-array regions also have the same performance.Solar field has warming effect in spring and summer;winter days have cooling effect;autumn days have little effect on temperature.The PV field has cooling effect in four seasons at night,and the cooling in winter at night can reach 2.18℃.②Air relative humidity:The influence of PV field on air relative humidity has diurnal and seasonal differences.The PV field has a dehumidification effect during the day and humidification at night,and the nighttime humidification can reach 5.12%.In the PV field,different PV sub arrays show day and night humidifying effect.The PV field has a dehumidification effect in spring and summer;there is humidifying effect in winter days;autumn daytime has little effect on air relative humidity.The PV field has a humidifying effect at night in four seasons,and the humidifying rate can reach 6.93%at night in winter.③ Wind field:the PV field significantly reduces the wind speed and has wind-proof effect.The maximum threshold wind speed in the PV field decreases by 41.19%.The influence of PV field on wind direction has seasonal difference.There is no significant difference in wind speed between spring and autumn inside and outside the PV field.The wind direction in the PV field is single in autumn,and the change of wind direction in winter is opposite to that in autumn.(2)Revealed the impact of PV development on soil① Soil physical and chemical properties:The soil clay content in the PV field(OSA and FIX PV sub-array areas)was significantly higher than that in the off-site control area,and the soil under the PV panels had a tendency to refine.On the whole,there was no significant difference in soil nutrient content between inside and outside the PV field.Only the FIX PV sub-array area has a decrease in alkali hydrolyzed nitrogen and an increase in available phosphorus.There was no significant difference in soil total nutrients at different positions of PV panels,but the available nutrients of the alkali hydrolyzable nitrogen,available phosphorus and available potassium have significant differences.②Soil temperature and soil water content:The influence of PV panels on soil temperature has seasonal differences.PV panels have warming effect in winter,but cooling effect in spring and summer,and no significant effect in autumn.In the annual cycle of day and night,PV panels have cooling effects on soil during day and night.The PV panels had a humidifying effect on soil,and the average annual soil water content of 10 cm layer under the FIX PV panels increased by 14.34%.③ Soil quality evaluation:The key indicators were selected by principal component analysis and an evaluation system was established.The results showed that the soil quality of the PV field was at a medium level and the fertility quality was not high.(3)Revealed the impact of PV development on vegetation① The plant communities in the PV field were dominated by perennial herbs and dense perennial herbs,while the plant communities outside the PV field were dominated by shrubs such as Caragana korshinskii and small shrubs.② The richness index inside field is significantly higher than that outside PV field;while the Shannon-Wiener index,Simpson index and Pielou index outside the PV field are greater than those inside the field.Aboveground and underground biomass under FIX and FSA PV panels were higher than those between panels,while OSA PV panels were the opposite.③ The relationship between plant community distribution characteristics,species diversity and environmental factors showed that soil available phosphorus was an important environmental factor affecting plant community distribution in the study area.Soil water content,pH and available phosphorus had great impacts on species diversity.(4)Assessment of ecological environmental effects of PV developmentThe economic value of ecological service in PV development zone was evaluated by value equivalent factor method.Based on the four ecosystem service functions of carbon fixation and oxygen release,soil fertility maintenance,climate regulation and biodiversity protection,the ecological environment quality evaluation system of PV development zone was constructed.The results showed that the ecological environment quality of desert PV development zone was in the general and poor level,and there was great potential to improve from the excellent level.