This custom component lets you quickly export series of shadow study frames. Down and dirty, yet fast and effective. To install, place the .gha file in Grasshopper's library folder. It is now part of the Earthworm plugin.
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.
If you would like to learn how to script something like this, I have a blog post on it. Go to the web link under the download button on the right --->