solar arrays consume PV cells

By making PV arrays consume cells instead of normal maintenance, they hit a soft cap when you can no longer produce replacement cells faster than they are being used. In that way, the PV production chain becomes the limiting factor you can balance around, in the same way that nuclear is balanced around the fuel production chain.
Instead of having a one-and-done process or constantly expanding production, your solar power demands a specialized maintenance industry which can be far more fun to build and simulate.