Maybe this would work.......
Get two lengths of thin wall pvc pipe the length or width (whichever you choose) of your solar panel plus 2 or 3 inches.
Cut a 1/4th inch wide slit lengthwise along one pipe.
Take the other pipe and drill small aligned holes lengthwise down the side but do not drill holes into the outside 3 or 4 inches at both ends. Cover these holes with garden cloth glued to the pvc but not obstructing the drilled holes.
The slit pvc pipe can now be inserted into the pvc pipe with the holes drilled into it. By rotating the slit pvc pipe, you can cover or uncover the holes of the outer pvc pipe. Insert this contraption into the side wall of your solar panel. Block the end of the pvc pipe on the end not exposed thru the side wall of the solar panel. Now, you have a chamber which can be filled with silica granules which have been rolled inside a long narrow piece of garden cloth and inserted into the pvc pipe. By turning the inside (slit) pvc pipe, you can block air entering into your solar panel during the few minutes it takes to change the silica granules. When done replacing the silica granules, turn the slit so that it opens the inside of the solar panel to the silica granules. All you need now is to seal the end of the pipe that is sticking out of the panel side with a cork or something that will allow you to re-enter the chamber to change the granules.