A device includes an enclosure mounted to an end portion of a photovoltaic panel and has an interior, an opening, an inclined ramp within the interior, a door pivotally disposed at the opening, and a latch mechanism. The door is on a panel surface in an open position, and blocks the opening in a closed position. The latch mechanism latches the door closed and releases the door to the open position. A flexible material blocks light from reaching panel photovoltaic cells and includes a first end coupled to the inclined ramp within the enclosure and an opposite second end coupled to a rod. The flexible material is rolled up about the rod and rests on the inclined ramp. The door's closed position blocks deployment of the material. In the open position, the material rolls down the inclined ramp and covers the panel surface. The door is automatically or manually deployed.