Scientific Method / Science & Exploration

Kerosene lamps face gravity-powered usurper

A bag of rocks and some height provide the power for GravityLight.

GravityLight ships in its own ballast bag.

A London design consultancy has developed a cheap, clean, and safer alternative to the kerosene lamp. Kerosene burning lamps are thought to be used by over a billion people in developing nations, often in remote rural parts where electricity is either prohibitively expensive or simply unavailable. Kerosene's potential replacement, GravityLight, is powered by gravity without the need of a battery—it's also seen by its creators as a superior alternative to solar-powered lamps.

Kerosene lamps are problematic in three ways: they release pollutants which can contribute to respiratory disease; they pose a fire risk; and, thanks to the ongoing need to buy kerosene fuel, they are expensive to run. Research out of Brown University from July of last year called kerosene lamps a "significant contributor to respiratory diseases, which kill over 1.5 million people every year" in developing countries. The same paper found that kerosene lamps were responsible for 70 percent of fires (which cause 300,000 deaths every year) and 80 percent of burns. The World Bank has compared the indoor use of a kerosene lamp with smoking two packs of cigarettes per day.

The economics of the kerosene lamps are nearly as problematic, with the fuel costing many rural families a significant proportion of their money. The designers of the GravityLight say 10 to 20 percent of household income is typical, and they describe kerosene as a poverty trap, locking people into a "permanent state of subsistence living." Considering that the median rural price of kerosene in Tanzania, Mali, Ghana, Kenya, and Senegal is $1.30 per liter, and the average rural income in Tanzania is under $9 per month, the designers' figures seem depressingly plausible.

Approached by the charity Solar Aid to design a solar-powered LED alternative, London design consultancy Therefore shifted the emphasis away from solar, which requires expensive batteries that degrade over time. The company's answer is both more simple and more radical: an LED lamp driven by a bag of sand, earth, or stones, pulled toward the Earth by gravity.

It takes only seconds to hoist the bag into place, after which the lamp provides up to half an hour of ambient light, or about 18 minutes of brighter task lighting. Though it isn't clear quite how much light the GravityLight emits, its makers insist it is more than a kerosene lamp. Also unclear are the precise inner workings of the device, though clearly the weighted bag pulls a cord, driving an inner mechanism with a low-powered dynamo, with the aid of some robust plastic gearing. Talking to Ars by telephone, Therefore's Jim Fullalove was loath to divulge details, but did reveal the gearing took the kinetic energy from a weighted bag descending at a rate of a millimeter per second to power a dynamo spinning at 2000rpm.

The company has turned to indiegogo to crowdfund an initial run of 1,000 GravityLights. These will be given to rural villagers in India, and in several African countries for testing, with their feedback informing the design of an improved Mark II version for wider manufacture. Though GravityLights are expected to cost $10, it's hoped that the refined, more efficient Mark II GravityLight will cost $5 or less. Its makers assert that for villages in the developing world, a $10 GravityLight would pay for itself within three months by negating the need to buy kerosene.

Ultimately, GravityLight's creators envision a time when the device could become a low-powered off-grid energy hub for remote homes, powering not only a light (or a string of lights) but perhaps also phones or e-reader Wikipedia clients that connect, with or without cables, to the GravityLight. These are all long-term projects that form the company's deciwatt research initiative, though such projects may be dependent upon cell tower or satellite availability. Their goal for now, though, is to establish the GravityLight itself.

At the time of writing, the funding campaign has received over $380,000—well in excess of the $55,000 goal and enabling the development of accessories. Among the available pledges, $25 will sponsor a GravityLight for shipping to the developing world, while $60 will do the same—and secure a GravityLight of your own.

GravityLight in action.

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