The ornamental design for a double-side solar panel, as shown and described.
FIG. 1 is a front elevational view of a double-side solar panel showing our new design;
FIG. 2 is a rear view thereof; and
FIG. 3 is an enlarged view of portion 3 in FIG. 1;
FIG. 4 is an enlarged view of portion 4 in FIG. 2; and,
FIG. 5 is an enlarged view of portion 5 in FIG. 2.
The dash-dash broken lines shown represent the portions of the double-side solar panel that form no part of the claimed design. The dash-dot broken lines define the bounds of the claimed design and form no part thereof. There is no substantial thickness of the claimed design and all the elements of the claimed design are flat and coplanar.