Liter of Light is an open source design for a low-cost light tube that refracts solar light to provide daytime interior lighting for informal dwellings with thin roofs. Daylighting is cheaper than using indoor electric lights during the day. The device is simple: a transparent two-liter bottle is filled with water plus a little bleach to inhibit algal growth and fitted into a hole in a roof. 

Given that it is an open source design made from reusable materials, it is there is a high motivation to use it by Fogg’s indicators of low time, low money, low effort and low cognitive cycles whilst simultaneously serving a large number of communities around the world that are considered as often.