Solpy is a python library to model solar system power performance similar to
PVWatts or NREL's System Advisor Model (SAM).  I initially started writing this
while working in Bangladesh as fairly crude calculator to go from a fisheye
panorama to a csv of vectors for shading calculations, however there were
several pieces that were added to make it a bit more useful for both analyis
and design. Daniel Thomas did work adding the Tang evacuated glass tube
model. Pyephem was added for solar positioning.
There is also a simple module for reading TMY3 data. This tool is rudimentary,
but functional. This is primarily a research and analysis tool and there is no
guarantee on the calculations