| The open desert areas are ideal places to build ground-mounted solar photovoltaic(PV)power stations,because these are rich solar and thermal resources and the cost of using the land is very low.Many desert surfaces,especially those with high silt and clay contents,are much more prone to wind erosion when mechanically disturbed.Lands are disturbed when utility-scale solar facilities are built.The field surface air flow characteristics can be altered with the installations of PV facilities,resulting loss of soil under the surface of PV panels and formation of sand ridge landforms between the panels,and then lead to instability of the PV panel infrastructure.In addition,the geomorphological changes of PV power stations caused by the surface erosion processes can aggravate the release rate of surface dust and increase the dust deposition on PV panels.In this study,field experiments were conducted to investigate the characteristics of the wind flow field and sediment transport under the interference of a solar PV array in a 200 WM-p PV power station in the central Hobq Desert,northwestern China.And the geomorphology development process was investigated at different wind regimes within the PV panel array.The aim of this study was to provide a theoretical basis for determining a technical scheme for wind-sand hazard prevention and control near PV power stations and to ensure operational stability and safety.The result shows that:(1)After the construction of the solar PV power station,wind-sand flow interference effect commonly occurs at the near-surface of solar photovoltaic array and the main performance of this effect was the positive effect of sand-fixation and shelter efficacy.The interference effect was maximum with the intersection angle close to ±90° between solar PV array and wind direction.Wind speed within the height range of 200 cm for solar PV array was less than 35% of that above the shifting dunes with the angle range from85° to 90°,and the sediment transport rate was less than 15% of that above the shifting dunes with the angle range from 56° to 83°.When the intersection angle was Close to22.5°,the interference effect was minimum.The wind speed at the height of 20 cm in a solar PV array was reduced by 0-20%,and there is even wind speed amplification effect at the height of 50 and 100 cm.The sediment transport rate was less than 70% of that above the shifting dunes at this time.The results show that the interference effect of PV array on near surface wind sand movement varies with the angle as follows: the angle is0°?22.5° The interference effect decreased by 22.5°?45° The effect increased rapidly,45°?90° The effect increased slowly to peak;0?-90° The law is basically the same,but when the angle is negative,it is more obvious than when the angle is positive.(2)The near-surface wind flow field characteristics around the PV panels are different under different wind directions.When the intersection angle is close to 90°,the wind speed distribution presents a flat inverted “V” shape,and the wind speed in front of the panels was better than that between and behind the panels.When the intersection angle is close to 0°,the wind speed distribution presents a flat“W”shape,the wind speed in front of the panels,between and behind the panels was better than that under the panels,and the wind speed in the middle part is higher than that on both sides at the under panels zone.The wind speed distribution with the positive intersection angle is similar to the intersection angle of 0°,with the intersection angle increasing,the wind speed in front of and under the panels increases,while decreases at the between and behind panels.When the intersection angle is negative,the wind speed in front of and between the PV panels is higher,it shows a linear downward trend at the under panels,and it gradually rises at the behind panels.The aeolian sediment transport above the solar PV array was affected significantly by the free-stream wind direction of the environment.It was found that the existence of solar PV array does not change the sediment transport rate model.The two-parameter exponential function provides adequate description of the aeolian flux density profiles under the interference of solar PV array.However,with the intersection angle increasing,the saltation height of sand particles for the sites between and behind the panels increased significantly.The saltation height decreased in the case of the observation site before the panels.(3)Through the analysis of sand-fixation and shelter efficacy and surface geomorphology development characteristics under the interference of a solar PV array,it was the main dynamic interval of landform development in the solar PV array when the intersection angle was greater than-45° and less than 45 °.When the intersection angle was 0°,there was a zone of dramatic wind velocity change at the down edge of the PV panels,there was a certain difference in the wind velocity to both sides,and the difference in velocity caused a difference in pressure,the airflow moved from the side with high pressure to the side with low pressure.Due to the combined action,the airflow direction became inclined at the lower edge of the PV panels.And then the PV panels produced a downward guiding effect on the inclined airflow,this effect increased the shear force of the wind on the surface soil in front of the panels,thus causing the erosion.When the intersection angle is positive,the PV panels have an accelerating effect resulting in the wind speed increasing at the down edge of the PV panels,and then causing the erosion,deposition is formed in front of the PV panels.When the intersection angle is negative,the “venturi effect” occurred at the lower edge of the PV panels resulting in the formation of air flow acceleration zone and then causing the erosion,deposition is formed on the side near the upper edge of the PV panels.Thus,under the interference of different wind regime,wind erosion led to the formation of trenches in the immediate vicinity of the down edge of the PV panels(4)Our results will facilitate the design and control engineering plans for solar PV array in sandy areas that operate according to the wind regime.For the solar PV array of panels facing south and east-west arrangement,we need to focus on the near-surface sand control engineering measure for the surrounding edge zone.Meanwhile,for the solar PV array east and west sides,we need to reduce wind energy entering the solar PV array,not only sand fixing.Our study solar PV array was located in Northwest China,where the primary-harm wind direction is the W or NW.Therefore,the protection engineering structures in west side of the solar PV array should be better than that in east side.For the hinterland area of the solar PV array,in order to weaken the intensity of near surface erosion and accumulation activities,the transport of wind-blown sand flow near the surface is close to the equilibrium state,the “wind guide trenches” should be set in the immediate vicinity of the down edge of the PV panels. |
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