A light bulb and fridge that need no electricity

This post is part of our volunteering experience at the Wonder Years Centre of Excellence in The Gambia. A great project that brings free education and healthcare to the people of Madina Salam. To find out more about volunteering at this project, click here…

Madina Salam is an off-grid village. Diesel generators are expensive, as is the fuel to power them and solar is out of the reach of most ordinary people. In between working with the cycle mechanics and building a cargo bike, we experimented with other devices which might prove useful in the village on a day to day basis.

Electricity-free Light bulb

Houses in Gambia are typically dark in the daytime because of the mosquito meshes that cover the windows and curtains across the doorways. However, the skies are clear and bright with plenty of sunlight. Alfredo Moser is the Brazilian mechanic that invented the bottle light, a simple device that mixes water and a tiny bit of bleach in a plastic bottle to create a solar powered light bulb with an estimated ‘output’ of 50 watts. These bulbs are fitted into the roof of a house and as the sun hits the top of the bottle, the bleach and water combination illuminates the space within the house.

Plastic bottles weren’t readily available in Madina Salam. Most drinks are sold in returnable glass bottles, just like they were back in the day in the UK. However, we managed to find one to experiment with.

The process is simple. We filtered the water, added a bit of bleach, popped on the cap and sealed it with some black gaffer tape. Then we cut out a hole in some corrugate to install it into. We tested it in a blacked out room in one of the WYCE houses…


Not the best picture, but the illumination is still apparent.

This video illustrates the practical application of these light bulbs far better.

Electricity-free fridge

fridge 4

The ‘pot in pot’ fridge, or to give it’s full title – the pot in pot preservation cooling system – was developed by Mohamed Bah Abba in the 1990s in Nigeria.

The basic design is as follows:

  • One small terracotta pot is placed inside a larger pot.
  • A layer of sand is poured between the two pots. 


  • A cover with added insulation and bottle top weights is sewn by Livvy to hold the cover in place.

fridge 5 sewing the topweights to hold down edges

  • Cold water is poured onto the sand.

 SAM_1681 fridge 3

  • A damp cloth is placed over the top of both pots and an old bicycle innertube can be used as a floor rest for the pot.

fridge 1

  • Finally, spilt water is mopped up by the local wildlife.

SAM_1715 SAM_1717 SAM_1718SAM_1714

As the water evaporates, it cools the pots, thereby also cooling the food and keeping it fresh for longer.

From Wikipedia, here are the positive impacts of these fridges.

  • “Increased profits from food sales: As there is no rush to sell food to avoid spoilage, farmers are able to sell their produce on demand and can command higher prices.
  • Increased opportunities for women: Women can sell food directly from their homes, decreasing their dependence on their husbands as sole providers. Also, because girls traditionally take food to market to sell, and because food in thezeer stays fresh long enough that they can go to market once a week rather than once a day, there is more time for them to attend school.
  • Rural employment opportunities: Farmers are able to support themselves with their increased profits at market, slowing the move into cities. Also, the creation of the pots themselves generates job opportunities.
  • Increased diet variety because food is available for longer into the year.
  • The ability to store vaccines and medicines that would otherwise be unavailable in areas without refrigeration facilities.”

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