Most operators and developers avoid side slopes, but a few are trying to take them on, at least to some degree.
Landfill operators who are considering installing solar on their sites (usually post closure) want to maximize their space for the largest, most potentially profitable project, and side slopes tend to have the most space to accomplish this. But if those slopes are steep, installing solar on them is difficult to impossible, presenting barriers around engineering and economics.
Most operators and developers avoid side slopes, though a few are trying to take them on, at least to a degree. They have found ways around some problems in some scenarios, for instance challenges tied to supportive anchoring systems and heavy racking systems, among others.
Cincinnati-based RBI Solar rarely works on landfills with more than a 30 percent slope, where for every 10 feet of horizontal structure, there are 3 feet of vertical.
“There’s not much you can do with more than a 30 percent slope on a landfill, with one big reason being that the equipment required to install solar modules can’t exceed a certain pounds per square inch (psi) pressure requirement,” says Mike Freshwater, ground mount design manager for RBI.
The typical landfill has a maximum bearing capacity requirement of 7 to 10 psi that can’t be exceeded, while the psi exerted by tracked equipment can vary between 5 and 20 psi. Some equipment may not get enough traction, could get stuck and, in general, has limited ability to maneuver on steep slopes.
So, there needs to be a good anchor system to hold panels in place.