2-Dimensional modelling to simulate stormwater flows at photovoltaic solar energy sites

Thomas E. Barnard, Mohamed Agnaou and James Barbis


Solar farms (sometimes known as solar parks or solar fields) are the large-scale application of solar photovoltaic  panels to generate green, clean electricity at scale, usually to feed into the grid. Solar farms can cover anything between 1 acre and several hundred acres, and are usually developed in rural areas. Solar farms consist of arrays of ground mounted rectangular panels with that are sloped toward the sun at either fixed or adjustable angles.  Stormwater runoff is allowed to fall freely to the ground.  

Amec Foster Wheeler assessed several candidate solar farm sites in Texas for stormwater issues and designed the stormwater management system for a site in Georgia using 2-dimensional hydrologic and hydraulic (H&H) models to simulate the infiltration and overland flow.  The FLO-2D software package was used to develop a rectangular grid for calculation.  Runoff the cells was calculated with the SCS method and  with the shallow water equations were used route flow across the grid. Results were exported to ArcGIS for preparation of maps that displayed maximum velocities and flow depths. 

Most of the data required for the models were obtained from public data sources including 1/3 arc-second elevations, land use/land cover, soils maps, and hydrography.  These data were supplemented with site survey.  GIS software and other tools were used to process the data for assignment of curve numbers and friction factions to the model grid cells.  HEC-HMS models were used to develop runoff hydrographs from these off-site sources which were then added to the FLO-2D model as a boundary condition.  At two of the sites the operation of upstream dams was also considered in developing inflow from upstream sources.

Models have been created  to identify the flooding risks on a conceptual level,  to evaluate the final grading design, and for stormwater permitting.  Model results were also used estimate the scour potential at the piles that supported the panels. This work demonstrates how the use of spatially varied 2-dimensional H&H models help to assess potential sites and design stormwater control measures for solar farms.

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