The access to electricity for indoor lighting in developing countries is very important for growth, both socially and economically. A growing problem with access and affordability of indoor lighting in developing countries has led to the renewed interest in studies of solar lights. 

The rising cost of power in Kenya, where 40% of the population lives on less than $2 a day, leaves many unable to afford electricity.

Some use candles as a light source but, when generations of family members share a small, dark space in slums areas in most towns, accidental and destructive fires are often the result.

The Litre of Light project will be launched by Al­-Khair foundation Kenya office which aims to provide indoor lighting to a number of homes which are based in slum areas where houses are constructed in a very congested manner allowing little or no light to penetrate even during the day.

The scheme uses plastic bottles filled with a solution of bleached water installed into corrugated iron roofing sheets – which then refract the equivalent of 55W of sunlight into the room ­during the day. It takes five minutes to make, and costs $1.5 to produce using a hammer, rivet, metal sheets, sandpaper and epoxy.

A one-way lock system using a metal sheet is used, with a 2 litre plastic bottle, so that the container will not slip down.

Even if the roof expanded or contracted with the heat, it would not affect the waterproofing and would keep the bottle intact for many years to come.