They can be built 20' off the ground, but they will always be built 2' shorter than the most important truck that needs to park there 10 years after the ribbon-cutting.
If that's really a concern, just build them with the clearance required of bridges over interstate highways, which is ~16 feet.
Or provide a separate area for huge vehicles - even if people transporting 200-ton mining haul trucks want to stop off at Wal-Mart en route, it's not like they'll expect to pull into standard bays.
Unlike for a bridge, having an articulation which pulls the panels out of the way adds little expense. Solar panels are light enough that keeping them still in high winds is the main constraint.
Sending 2 larger trucks to do the job if 3 smaller trucks is innately more efficient.
The 18-wheeler format (even with 2x trailers or even 3x trailers) has built in efficiencies. We probably should think about how to support those kinds of efficiencies in grocery stores / Walmart centers.
In fact, I'm pretty sure Walmart uses larger trucks like that on a consistent basis as a cornerstone of its logistic strategy.
In the case of my local (urban) grocery store, it seems to be the reverse. Coke and beer arrive on their own 18 wheelers that barely fit down the street. Produce is another 18 wheeler owned by the grocery company. Bread, fish, meat, dairy, and chips all have their own medium to large box trucks.
And this is at a grocery store with only 2 loading dock bays directly off a fairly busy street, and a total of about 8 customer parking spaces. This is the absolute best case for unloading everything at a warehouse and shipping point to point with a few box trucks instead of making it a stop on everyone's literal or figurative milk run, yet they don't do it.
I'm pretty sure reducing truck-miles barely registers when it comes to "efficiencies" in logistics.
I'm pretty sure that the areas those trucks drive through and park in can be easly determined and separated from the main customer parking lot. In the absolute worst case, you might have to dismantle some of the solar canopies when a problem appears.
