Around 1.2 billion people – that’s 16% of the global population – still live without access to electricity. Meanwhile, over 2 billion people rely on wood, field residue, and animal waste, etc. to cook and heat their homes, according to a 2013 World Bank report.

In a bid to tackle this pressing problem, a project called #A Liter of Light was launched in 2012 in the Philippines, a country where nearly half of the total population lives off less than £1.5 a day.

The project uses discarded Plastic Bottles as bulbs by filling them with purified water and two caps of bleach (to prevent the growth of algae). The bottles are then fixed on the roof using small metal braces.

Once the sunlight hits these bottles, the refraction of light helps these DIY bulbs give off about 55 watts of light at a fraction of the cost, without using electricity.

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Launched by an NGO named MyShelter Foundation, A Liter of Light has now spread across around 20 countries worldwide and has lit over 850,000 homes, so far. The project aims to light up 1 million homes by 2018.

According to Nelly Duka, a community leader who is involved with the project, these makeshift bulbs can last up to five years, stated an NPR report.

"Access to energy is absolutely fundamental in the struggle against poverty," said Rachel, Kyte, former World Bank Group Vice President, in a National Geographic report.

"It is energy that lights the lamp that lets you do your homework, that keeps the heat on in a hospital, that lights the small businesses where most people work. Without energy, there is no economic growth, there is no dynamism, and there is no opportunity," she added.

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The Plastic Bottle light bulbs are the brainchild of Alfredo Moser, a Brazilian mechanic who had his eureka moment in 2002 during one of the frequent blackouts in his hometown, Uberaba, Brazil.

“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," Moser told BBC.

A Liter of Light, however, has modified these bulbs to meet local needs. For £3.83, residents can upgrade these plastic bottle lamps to solar-powered LED bulbs.

According to a 2010 study published by the International Energy Agency (IEA), if nothing is done to address energy poverty then by 2030 nearly 4,000 people will die per day, globally, due to the toxic smoke and indoor fires caused by unsafe primitive cookstoves—this is more than the premature death estimates for malaria, tuberculosis, or HIV/AIDS.