EnergyPlus has an DaylightingDevice:Shelf object type that should be used to simulate a light shelf. This will require drawing the following surfaces in the model's geometry:

• a fenestration surface for the upper or clerestory window
• if using an outside shelf, draw a shading surface to reflect light through the clerestory window towards the ceiling
• if using an inside shelf, draw a building surface to reflect light that has already passed through the clerestory window towards the ceiling

When you install EnergyPlus, there is an example files folder that has IDFs (EnergyPlus input data files) for models that showcase nearly every object type available in EnergyPlus. If you open C:/EnergyPlusV9-5-0/ExampleFiles/ExampleFiles-ObjectsLink.html and search for the object type you're interested in, you should find one or more IDFs to review. For the DaylightingDevice:Shelf object, it looks like there is only one example file -- DaylightingDeviceShelf.idf.

You can also read a few other posts on Unmet Hours for modeling a daylight shelf in EnergyPlus here and here.