Kevin Warnock

Entrepreneurship, ideas and more

Litre of Light – nearly free solar lights made with plastic water bottles and bleach

with 12 comments

Sometimes I learn of an idea that shocks me with its brilliance.

Today I will describe such an idea. It’s called the Litre of Light.

Here’s the summary from the project’s website, Isang Litrong Liwanag, which translates to ‘A litre of light’:

“Isang Litrong Liwanag (A Liter of Light), is a sustainable lighting project which aims to bring the eco-friendly Solar Bottle Bulb to disprivileged communities nationwide. Designed and developed by students from the Massachusetts Institute of Technology (MIT), the Solar Bottle Bulb is based on the principles of Appropriate Technologies – a concept that provides simple and easily replicable technologies that address basic needs in developing communities.”

A Solar Bottle Bulb is a clear water or soda bottle filled with tap water and a little bleach. This bottle in embedded into the roofs of houses, with part of the bottle outside, and part of it inside. There is sealant around the hole to keep the roof weather proof. When the sun hits the outside part of the bottle, a lot of light reaches the inside part of the bottle. The water inside the bottle makes the light omnidirectional, mimiking an electric light bulb. The bleach keeps the water clear for years. Without the bleach, the water would quickly turn green with algae. Without the water, there would be a bright spot on the floor, surrounded by relative darkness.

Each Solar Bottle Bulb produces about as much light as a 60 watt incandescent light bulb, according to the video transcript linked to in this sentence.

Solar Bulb installed and 'on' (picture from

Solar Bulb installed and 'on' (picture from

I wish I could take my Canon 5D Mark II into some houses with these bulbs installed and get some really high quality still photographs and video, to help spread the word about this really bright idea. Light bulb entrepreneur and proponent Thomas Edison would be pleased.

On the right, Alfredo Lim, the mayor of Manilla, Philippines, holding a litre of light 'bulb'

On the right, Alfredo Lim, the mayor of Manilla, Philippines, holding a litre of light 'bulb'

The beauty of the Solar Bottle Bulb is that it works and it’s really affordable, at about P150 to P200 (USD $4.66 at today’s exchange rate) per home, installed, according to Alfredo Lim, the mayor of Manilla in the Philippines, pictured above on the right. That 150 to 200 peso cost is per home, not per bulb.

I am going to install these in any eco home I build down the road. I have a big collection of glass bottles to choose from. I’m not sure if glass is as suitable as plastic, but I would prefer to use glass if it can be made to work reliably.

Written by Kevin Warnock

July 17th, 2011 at 5:00 am

12 Responses to 'Litre of Light – nearly free solar lights made with plastic water bottles and bleach'

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  1. wow,i’d love to have one ,too

    wisly princime

    19 Jul 11 at 5:18 pm

  2. indeed a brilliant idea. does the bottle also give light at night ? as this is when it is most needed. sorry for asking such a stupid question

  3. Indeed Dr Bash-Taqi’s question is the only one to to ask. It’s only when its dark that a lightbulb is required – and the answer obviously is that no light comes through at night. This a wasteful deceptive scheme

    Peter Vander Sar

    19 Sep 11 at 8:54 am

  4. Wasteful Mr Peter Vander Sar???
    Depending on where on lives, the nights are rather “bright”, more in the north then in the south, as well there are people living in big cities with costant lights on making nights to almost days, and what about poor people living in a hut without windows and no electricity around, or e.g. workers in some areas of the world where they are exploited, having to work in long dark halls without windows, no fresh air, poor to no lightning,etc etc.
    Only spoiled, rich people are able to call such A GREAT INVENTION useless.


    19 Sep 11 at 12:09 pm

  5. Wasteful? really?
    I suppose you never turn your lights on during the day. Granted it won’t replace every light bulb but it will certainly reduce the amount needed and the frequency they are used. Its refreshing to see such a simple and elegent solution and its a pity you don’t see it as such.

    Two Sheds

    19 Sep 11 at 12:54 pm

  6. This is a light you can’t switch off. Sometimes you want darkness.


    20 Sep 11 at 2:19 am

  7. This is really a good idea…I like it as long as it support people who are suffering…Kudos


    20 Sep 11 at 2:55 am

  8. Actually you can “turn the Bulb off” If you watch the video, the presenter hold a bucked over the “Bulb” it would be an easy solution to add clips on the ceiling to hold a bucket or other cover in place. This is a simple and Brilliant Idea! And yes there is a need for lights on during the day, just try turning your lights off in a room with no windows during the day, it will be pitch black as described in the video. I have seen a Cost Co here in Halifax, Nova Scotia Canada with hundreds of skylights cut in the roof, and the manager told me it cuts his power bill in half, and there is such a think as a SkyTube as well, so this kind of passive solar system can work for everyone, rich (to save money on energy use) and poor, to replace electric light bulbs they can’t afford to run.

    Mike Redmond

    20 Sep 11 at 11:35 am

  9. Such a great idea!


    25 Sep 11 at 1:02 am

  10. I guess they will be getting much more light if they fill those bottles with petrol instead of water, and through them to the houses and palaces of all the corrupted governors they have


    4 Oct 11 at 1:03 am

  11. It’s a tiny skylight with a diffuser.
    Only useful where roof is exposed to the sky.
    Good idea for developing countries.


    15 Oct 11 at 4:37 am

  12. I am flatly amazed anyone would criticize this.


    6 Nov 11 at 11:05 pm

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