Cool form of passive indoor lighting during the day


I was browsing on Facebook when I came across this YouTube video of how people used old soda bottles and turned them into a bright light source for their homes.

You cut a hole in a galvanized steel roof and slide in a water bottle completely filled with water and bleach. (I imagine the bleach will prevent algae growth) They then seal up the area around the bottle to keep the roof water tight.

This method provides the equivalent of a 50W incandescent light bulb and doesn’t use any electricity. The team, Liter of Light, have installed 350,000 of these light bulb water bottles in 15 countries.

I thought this was incredibly cool. If I had a little shed with a steel roof I would like to try this and see how long the bottle and water lasts before needing to be replaced. I find passive forms of energy use so interesting.

Another form of passive energy use that I thought was genius is the soup can solar heater. You take a bunch of old soup cans and spray paint them black to attract as much heat from the sun as you can. Place these in a box and the sun will heat up all the air inside. The air is then pumped out using a small computer fan and reaches temperatures of 140 degrees. Another super smart idea to add to a shed or something like a greenhouse. I imagine it would keep a shed from dropping below freezing and you could run the computer fan off a $10 solar panel. 


I think it is smart to know about things like this and even build and try them so if something like an EMP hits and we lose power for years, we still have ways to recycle trash into light and heat. But like I said above, these could be great ways to provide light and heat to an off-grid shed or greenhouse even during good times.


  • Comments (1)

    • 6

      That’s pretty creative!

      One man’s trash is another man’s treasure, or in this case another man’s light and heat.