Gary Rockswold was a little too general for my taste with his talk on reality and mathematics. He has given me lots of practical examples for class through his RPI and his xMAP eras though. It was an interesting talk, just not directly applicable to my teaching in the short term.
James Cliber gave an overview of the mathematics of solar cells. You can make finding the current depend on up to 5 angles depending on what you want to hold constant and how complicated you want a project to be. Hour of the day, latitude, date (declension angle), angle between the array and horizontal, and angle of the array off due south are all factors. I might play with this the next time I teach pre-calculus instead of the sunlight hours per day project.