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Solar Water Bottle Bulbs

Alfredo Moser with his solar water bottle bulbs


Thomas Alva Edison lit up the world with his electric bulb in the nineteenth century. In this century it is the solar bottle bulbs of Alfredo Moser which are illuminating thousands of houses of under-privileged people in many countries. This simple invention of the Brazilian mechanic is going viral and is been implemented in remote villages throughout the world. This article is the story of this invention — the solar bottle bulb or “Moser lamp” and how it is transforming people’s lives.

It all started in the year 2002 in the Brazilian city of Uberaba. Alfredo Moser got the idea of a solar bottle bulb as he was figuring out a way to illuminate his workshop during one of the frequent power cuts. He realized that he can light up his workshop by hanging plastic bottles on the roof filled with water. Well, is it so simple? Surprisingly, yes.

How it Works

Construction of this device is quite simple. A clean two litre plastic bottle is filled with water. Two cap-fulls of bleach is added to prevent the growth of bacteria and algae. An empty film container is fitted to protect the cap from sun. Next a hole is cut in the roof and the bottle is pressed half way into the hole. Then, the gap between the hole and the bottle is sealed off with polyester resin and made waterproof, preventing rain from seeping in. The device works on the principal of refraction. Sunlight which falls on the exposed surface of the water bottle gets refracted and illuminates the room below. When measured, its luminosity is equivalent to that of a 40-60 watt incandescent electric bulb, depending upon the amount of solar insolation available on a given day.

Clean plastic bottle filled with water

Two cap-fulls of bleach

A protective cover for the cap

Bottles ready for installation

Hole drilled into a roof tile

Hole diameter slightly bigger than the bottle external diameter

Plastic water bottle fitted into the tile hole

Gap sealed up to prevent leakage

Roof tile with plastic water bottle installed in the roof

Refracted sunlight as received in the interior of the house

In Alberto Moser own words, as said to BBC, "It’s a divine light. God gave the sun to everyone, and light is for everyone. Whoever wants it saves money. You can’t get an electric shock from it, and it doesn’t cost a penny." (4). This simple invention lights up dark rooms during the day and a proper installation can last for about five years. Once Moser figured out the magic recipe, he placed the lamps in his neighbour’s home and his town’s supermarket. This way, the idea of solar bottle bulbs attracted attention and started to spread by word of mouth.


This innovation provides free energy without carbon emissions and is environmentally friendly. The carbon footprint of manufacturing one incandescent bulb is 0.45kg CO2. A 50 watt light bulb running for 14 hours during the daytime has a yearly carbon footprint of 200kg CO2. Moreover, approximately 90 percent of the power consumed by an incandescent bulb is emitted as heat rather than visible light. As per calculations, 15000 water bulbs at 200kgs will reduce pollution at 3 million kgs for a year of use (3).
Although it has the limitation of only working during the daytime, it has potential for further improvisation — like fitting with solar panels and battery to collect and store energy which can then be utilized during the night.

Even in its basic form it has the potential to transform the lives of millions of poor people. There are 1.5 billion people throughout the world without electricity. They live in shanty houses without proper windows and depend on candles and kerosene lamps to illuminate their homes. Kerosene lamps give poor light and produce noxious gases. Every year two million people die because of indoor air pollution. In such circumstances, these inexpensive and easy to make solar water bottle bulbs come as a breath of fresh air for these people. There is no air pollution and no possibility for accidental burns or fires. This simple idea which anybody can build and implement, with no expense, solves a lot of problems at once.

Large scale implementation

Even though Moser invented it in 2002, it has had limited reach and the world at large was unaware of it. It was the ‘local entrepreneur’ business model implemented by the MyShelter Foundation in the Philippines which has helped to spread this innovation throughout the world at a more rapid rate. The MyShelter Foundation was established by Illac Diaz in 2006 with the aim of providing sustainable building solutions to the grassroots level — the people who are in most need of low-cost infrastructure (1, 2, 3).

In April 2011 the Foundation launched the project ‘Liter of Light’, or ‘Isang Litrong Liwanag’, with a ‘local entrepreneur’ business model, whereby bottle bulbs are put together and installed by locals who can in turn earn a small income for their work. The Liter of Light began in the Philippines with one bottle light. Eventually, the movement grew to brighten up 28,000 homes and the lives of 70,000 people in Metro Manila alone. In less than a year since inception, over 200,000 bottle bulbs were installed in communities around the world. Liter of Light has a goal to light up 1 million homes by the end of 2015 (1, 2).

Liter of Light project in Philippines (Duration: 6:14 mins).

Spreading across the world

This simple invention is now spreading around the world fast. Over the last two years it has spread to more than 20 countries, like India, Bangladesh, Indonesia, Fiji, Tanzania, Kenya, Argentina and Switzerland. Thanks to the internet for spreading this knowhow to the poorest people who live in pitch dark houses without any windows. The video below is an example of how Matayo Magalasi, a youngster from Kenya, got to know about solar water bottle bulbs through the internet and how he has been able to make change in Nairobi’s slums.

Plastic bottles light up Kenya’s slums (Duration: 4:22 mins).

DIY video

In order to transfer this knowhow to as many people as possible, the MyShelter Foundation have come up with a video for how to build a bottle bulb. Here is the do-it-yourself video, explained by Illac Angelo Diaz, executive director of MyShelter Foundation.

A DIY video: How to build a solar bottle bulb (Duration: 16:55 mins).

Concluding remarks

It’s a wonder that such a simple idea has the potential to bring enormous impacts in local living conditions, the economy and the environment. Whether or not the governments and scientific community appreciates Alfredo Moser’s innovation, millions of poor people throughout the world will definitely be thankful to him over the years to come.



Ravindra Krishnamurthy

Ravindra Krishnamurthy is a freelance science writer covering science, tech, the environment, health, food, and culture.


  1. Great idea, although an optional way to avoid the bleach could be to place a small piece of copper or brass inside the bottle. It’ll kill the algae and it’s almost permanently recyclable even if the bottle needs to be replaced.

    1. With a little expenditure of money a user can AVOID the whole waterbleach problem by using an edible grade of “mineral oil” as the refractory medium (~$5.00/Liter); especially in temperate climates when the ‘Liters of Light’ are used to illuminate tool sheds, garages, chicken coops, and the likes & where the solar lamp could be subject to freezing. “Mineral Oil” has a freezing point of -30 degrees C or -20 degrees F!

  2. To be truthful and honest, to unschool dogmas imposed by economical interests, it was not Edison (he made it a business, it was not him who discovered the technology). It was Nikola Tesla.

    1. wow. Edison didn’t discover the electric bulb?
      I’d like to share this.
      Also, tell me more about Tesla. Do you have a compact story in video form?


  3. Nikola Tesla was born in 1856. Edison filed patents for an incandescent bulb in 1879. The first incandescent light was created around 1800. Neither man invented it, not Edison, who perfected it to be long lasting and mass produceable, nor Tesla, who worked for Edison for a brief period starting in 1884. You might be confused but all this is easily verified with a simple internet search. Tesla was gifted in his strange way, but so was Edison in his dogged determination.

  4. Am very much interested in this project but it can only used in slum when it is dark,how can it be use in the night I want to help some widows and orphans who can not afford eletice bill

    1. Margaret
      As shown in the first video ‘Liter of Light project in Philippines’, the same device can be used during night by adding a solar panel and a battery. Maybe you can contact ‘liter of light’ for more details.

    2. What they now do is to hang an inexpensive solar powered lantern (Luci Lantern) to receive the solar rays to charge the lantern during the day and use that very same solar lantern to illuminate the dwelling in the late evening & at night!

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