An opposite approach to a different problem:
A village in the foothills of the Italian Alps that sees no sun for nearly three months a year is to brighten its winters by using a giant mirror to reflect sunshine onto its main square.
When I was an undergrad, I lived in a very small cottage with little southern exposure. I had a set up of a couple of 1 square foot mirrors that would project sunlight into the east facing windows. Of course I had to move them often, but they sure brightened the place up!