All he did was use plastic bottles filled with water and a bit of bleach. Basically you fill a 2 Litre empty bottle with water and 2 capfuls of bleach to prevent algae. Drill a small hole in your roof, pop the bottle through, caulk the opening, stick something black over the cap (which is outside) and you're good to go. He uses black film canisters - which might be hard to get so I''m going to start collecting them now.
Read the details and see photos at Alfredo Moser: Bottle light inventor proud to be poor
Credits: Image from BBC News Magazine