When I first started with Solar Lighting it was to create a simple robust street light.
Created a Light that was good and robust. It was a typical Solar Street Light.
The LEDs were superflux capable of being driven to 50mA - The cooling was provided by the four leads and the PCB was made with lots of copper area to dissipate the little heat.
The design as based around a PIC micro-controller and the output was switching via the controller.
This was in 2005.
Since then I have tried various designs in lighting streets, gardens, porches and pathways.