An updated version of this tool can be found in the PCPA_GH plugin
This custom component lets you quickly export series of shadow study frames. Down and dirty, yet fast and effective. To install, place the .ghpy file in Grasshopper's library folder. Also make sure to import display mode PCPA_AO and PCPA_SS in Rhino options. The script will identify these display mode by name so keep their names. However you can customize the look of them freely to suit your needs. The export is set to be of the dimensions of your active viewport. Contact me if you are looking for deeper tailoring of the tool.
The component is written for Rhino6 GH1. Use at your own risk. By default, a skylight is on and that might compete with sun and produce over exposed images. Type "lights" to bring up the dialog where you can turn off skylight and on sun. In Rhino's Sun menu double check you are at the correct location and correct time zone. This tool is under MIT license so credit creator when distributing. You can learn its open source on the linked webpage/blog.