pieter is right about the solar panels, most modern solar's will at least maintain a watches battery charge with only 500 lux light of standard office illumination using fluorescent bulbs.
As a reference, thats about the amount of light that will reach the solar panels using a 60 watt incandescent light 2 feet away from the watch.
A typical cloudy day outside is about 10,000 lux. Full bright sun is 100,000 lux, and this all depends on season. I'm in the Eastern U.S. and the best you can hope for on a clear sunny day in the winter is only 40,000 lux. Summer is over 100,000 lux on the same clear day.
A much cooler Compact Fluorescent light that's rated for 30 Watts will give your watch about 5,000 lux when the watch is 5 inches from it. And it get's exponentially higher when you get closer to the cfc bulb, but the watch might still get too hot being to close. Your mileage may vary, depending on the light you use.
I checked my light meter, and about 1 inch from a 100 w equivalent (30W Cfc bulb) I get about 30,000 lux, a little warm, but not burning hot.