Saturday, 26 April 2014


There is an old campers trick when you create a lantern by shining a torch into a water filled bottle. Imagine how much brighter that bottle would have been if it were lit directly by the Sun. Bright enough, it turns out, that it could brilliantly light up the interior of a one-room house. That's the idea for indoor lighting to the homes of the poor in the Philippines, by installing water-filled plastic water bottles through holes in the roof.

The Solar Bottle Bulb, as it is called, was originally designed by students from the MIT (Massachusetts Institute of Technology). Its construction and installation is simple. A clear one-liter pop bottle is filled with water, chlorine is added, then the bottle is squeezed part way through a hole in a piece of corrugated tin. A corresponding hole is cut in the tin roof of a house, the tin-and-bottle is secured over the hole so that the bottom of the bottle hangs down through the ceiling/roof, then caulking is applied to prevent rain from getting in.

When sunlight hits the roof and the top of the bottle, its rays are carried down through the water and dispersed into the interior of the home, giving off about as much light as a 55-watt bulb. Given that many of these homes lack windows, they might otherwise be nearly pitch black inside. Not only does the system produce light during daylight hours, but it is also providing a living for locals who build and install the Solar Bottle Bulbs, and it diverts bottles that might otherwise end up in a landfill. While the bottles don't provide light once the Sun sets, home owners do at least have the option of performing indoor activities that require illumination during the day, when the light is available. Additionally, some homes do have limited electrical lighting, but the Solar Bottle Bulbs allow their owners to save electricity by not using that lighting before dark. They could also turn to solar-powered lamps such as the Solar Pebble.

A major problem in parts of the world are paraffin lamps. Which can lead to fires and toxic
fumes. However, paraffin lanterns are often used for lighting and localised heating. That’s why Plus Minus has developed a solar-powered light called the Solar Pebble, that is targeted for humanitarian use in sub-Saharan Africa, or for patio use in suburban Britain.  The water proof LED Solar Pebble is powered by batteries that are charged by a small-but-efficient 6-volt solar panel. One 12-hour charge can light a room for an entire day. Not only is the Solar Pebble cleaner than paraffin but it’s also cheaper. Plus Minus hopes to launch the Solar Pebble, funded by sales of the product in the UK so it could also be just the thing for boaters and campers. 

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