Flat roof lights can be very useful in buildings because of the direct daylight but also have the problem of overheating and nightly radiation. So the application of a shading system can solve these problems.
Flat roof sky-light.
The first possibility is to make a horizontal solar shading. This can be placed above the roof light and completely cover the roof light. This will give maximum shading. The disadvantage is that the energy production of the PV module will be reduced with 10 to 30 % depending on the location. Second disadvantage is the cleaning of the PV module. A horizontal module will need more maintenance then a tilted module.
So the second option is to give the modules a certain angle. This solves the above mentioned PV related problems but it has the disadvantage that the PV module can not shade the roof light all of the time. This is the same type of problem as with the solar overhang above the window. A solution can be found by doubling the PV modules.
Another problem is that a row of tilted PV modules need a certain distance to avoid self-shading. This almost completely eliminate the shading function for the roof light. So the modules have to be placed much closer and to avoid self shading only 50% of the surface is suitable for solar cells.
SL02 PV module.
To install the modules a sub-structure is needed to support the PV modules. The substructure is optimised for the existing roof lights and the structure use the same tilt (angle) as the modules.
Roof with single shading PV modules.
Double row of shading PV modules to get the maximum shading effect.
First prototype of shadow module SL02.