A plastic bottle filled with water might not look like much, but when placed through a roof, it can act as a simple daytime light source, according to Lifestyle website.
The idea, known as the “Moser lamp,” uses sunlight to brighten dark indoor spaces without relying on electricity.
The low-cost technique was developed in Brazil and later became popular in communities across several countries. Its appeal is pretty straightforward: it uses readily available materials and can bring natural light into rooms with few windows or little direct sunlight.
According to several reports, the idea is credited to Alfredo Moser, a Brazilian mechanic from Uberaba. He developed the concept in the early 2000s, when parts of Brazil were facing problems with electricity supplies.
The basic design involves filling a transparent plastic bottle with water and fitting it through a hole in the roof. The top portion remains outside, where it can receive sunlight, while the lower section extends into the room.
Instead of generating electricity, the bottle simply redirects daylight indoors. That makes it particularly useful in buildings where adding conventional windows or electrical lighting may not be practical.
The concept gained wider international attention in 2011 when the MyShelter Foundation promoted the Liter of Light program in the Philippines. The initiative used the bottle-and-water system as an inexpensive lighting solution that communities could build themselves.
According to figures cited by the program, during its first 20 months, it reached more than 150,000 households in the Philippines and around 350,000 homes across 15 countries.
The idea subsequently spread further, with UNESCO references noting that the initiative had reached more than 30 countries.
The technique became attractive because it does not require complicated equipment. A transparent PET bottle and water are relatively inexpensive and can often be sourced locally.
The lamp works during daylight hours, so it is not a replacement for electric lighting at night.
