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Dealing With Uneven Topography for PV Layouts

by Greg Lewis, Business Development Manager

There are numerous challenges to deal with on every photovoltaic ground mount project, but one of the most pressing hurdles to overcome is how to design the most efficient system when facing significant topographical variances.

Typically, system designers will try to produce the densest layout, in order to maximize the system output on the predetermined amount of land. Differences in topography create many issues to take into consideration:

  • South-facing slopes, probably the ideal scenario, produce the narrowest row spacing, and hence, the densest layout. The only issue is if the slope is too steep to the south — then the difficulty may be the actual construction of the site, especially for the foundation installation.
  • North-facing slopes present just the opposite of the above scenario, and produce the widest row spacing and the least-dense site layout.
  • Varied terrain in the east-west direction is perhaps the most challenging type of topographical scenario to work out, and will be the primary focus of this discussion. This is a situation where proper planning and proper equipment is critical to achieve the optimal and most efficient array to construct.

When facing topographical variances in the east-west direction, most developers will try to have each of the rows follow the contour of the land, thus providing the highest possible output from the PV array through increased density. Otherwise, the less- undesirable method is to “step the racks” and keep them parallel with the horizon, while leaving sufficient space in-between the racks in the east-west direction to eliminate the “uphill” rack from shading the lower, adjacent rack.

A project engineer may also design the system using a combination of both of these approaches — having the racks follow the contour using the highest angle that their racking solution will allow, then “stepping” the racks for the balance of the slope.

For example, if the ground is sloped down to the east with a 15% grade and the rack can only accommodate up to a 10% grade, the site may be laid out with the racks angled with the terrain (using the rack-determined maximum of 10%), then stepping the rack to account for the 5% remaining difference.

But the optimal solution would be a racking system that can work with the entire slope variance and completely follow the 15% grade.

One company that has listened to the industry and understands how to tackle vast topographical challenges by using innovative features is Solar FlexRack. The design of the Solar FlexRack Ground Mount incorporates a liberal range of tolerances to account for all directions. It can even be designed to handle east-west slopes all the way up to a 20% grade with plumb foundations. Few, if any, other racking solutions are as efficient with such steep slopes.

The result is smooth-flowing rows, regardless of the terrain variances, and the tightest possible layout to give optimal power output for the array’s given space.