1.4 billion people don't have access to a reliable power grid. This affects every aspect of their lives, from personal safety to economic stability. And it means they also don't have a safe, reliable source of light when the sun goes down.

And most of them live in equatorial latitudes, where the sun sets quickly and there's only a brief twilight.

For the last four years, two London, England-based designers, Martin Riddiford and Jim Reeves, have been working on a lighting solution for people without access to electricity.

It's called GravityLight, and it does what the name implies: creates electricity and light using only gravity.

The device has a weight hanging from it. When the weight is lifted, it generates electricity.

Lifting it for only a few seconds creates 30 minutes of light, with no battery or fuel supply needed.

And it's not just a light: it also has inputs that make it capable of providing electricity to charge other devices.

The GravityLight project is crowdfunded on IndieGoGo. At the moment they're about a quarter of the way to their $55,000 goal, with 38 days to go. If they reach their target, they will distribute at least 1,000 free lights to villagers in both Africa and India to use regularly.

Once the lights are being used in the field, they will refine the design for a second version. From there, they hope to link up with NGOs and partners to mass produce and distribute the light.

Their target price for the product once it's in mass production is $5 per light.

GravityLight is far from the only sustainable lighting initiative that's trying to provide clean light to developing countries. There are already many projects underway that use solar technology.

But GravityLight's creators say that the high cost of solar technology and the need to use batteries to store the energy when the sun isn't shining are stumbling blocks.

Still, one of the main goals of both GravityLight and solar lighting technology is the same: getting rid of kerosene.

In many developing countries, the only readily available lighting option is the kerosene lamp.

But there are several problems with those lamps: one is the cost of kerosene. According to studies conducted at Berkeley Laboratory at the University of California, kerosene costs end users a total of $38 billion every year.

And the Economist cites a study that found Tanzanian households spend more than 10 per cent of their income on kerosene, while other studies have put the figure as high as 25 per cent.

Another is the environmental impact. Another study from Berkeley and the University of Illinois found that kerosene lanterns are a significant source of black carbon pollution, which is a significant factor in global warming, and very damaging to people's health.

Stefano Pagiola, in his book 'Generating Public Sector Resources to Finance Sustainable Development', estimates that exposure to indoor air pollution causes over two million deaths each year, and kerosene lamps are a big part of that.

Patrick Avato, director of the Lighting Africa program, describes some effects of using kerosene inside:

"Indoor air pollution from kerosene wick lamps can cause fatal respiratory problems over time," he says. "Deaths from accidental fire are also all-too common, particularly among cramped, built-up settlements."

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