GravityLight is a gravity-powered lamp designed by Deciwatt for use in developing or third-world nations as a replacement for kerosene lamps. It uses a bag filled with rocks or earth, attached to a cord, which slowly descends similar to the weight drive in a cuckoo clock. This action powers the light for up to thirty minutes. With neither batteries nor need for the sun, the lamp provides light instantly, can be stored indefinitely and used in many different environments.
Watch GravityLight in action.
Kerosene lamps, candles. Large market of solar lanterns, with products such as the d.light series.
GravityLight was designed for individual consumers with limited access to electricity, as well as NGOs and government agencies.
Mass produced in Kenya
The lamp will be distributed through local distribution partners and sales agents (door-to-door networks, farmer groups, and more traditional market stalls).
Design of GravityLight: 1. A 12kg weight – a bag of rocks or sand – is attached; 2. The weight is lifted by pulling down on a bead cord. On release, the weight falls very slowly, transforming potential energy into kinetic energy as it powers a drive sprocket, which rotates very slowly with high torque; 3. A polymer gear train running through the product turns this input into a high speed, low torque output that drives a DC generator at thousands of rotations per minute; 4. It generates just under a tenth of a watt, to power an onboard LED and ancillary devices. GravityLight has a DC jack where auxiliary lights (SatLights) and other devices, such as a radio, can be attached; 5. Once the weighted bag reaches the floor, which depends on how high it was installed, it is simply lifted to repeat the process. 6. A pulley system, so users of any height or strength can lift the bag right up to the top – giving the maximum drop time. 7. 2 SatLights included.
Installation guide is given (pictorial, English and ki-Swahili instructions).
-A 6ft (1.8m) drop gives over 20 minutes of light
-Weight falls very slowly: about 1mm / second
-It produces a light over 5 times brighter (lux) than a typical open-wick kerosene lamp
-LED efficiency: 208 to 212 lumens/W
-Power output for 12.5 kg load: one setting ~ 0.075W
-Environmental conditions: Operating: minus 5˚C – plus 40˚C; Storage: minus 15˚C – plus 80˚C
-Load Weight; Min: 8kg (17.6 lb); Max 12.5kg (27.5 lb)
-The product is designed to pay for itself within 3 months, saving families an average of 70 USD per annum
Extremely heavy load applied, especially caution must be taken for children. Therefore a way of protecting the system has been designed for GravityLight. It will allow an overloaded bag to descend to the ground in a safe and controlled manner, repeatedly.
GravityLight suspends the bag from a pulley, which reduces the strain on the cord and the gearing.
Possibility to add SatLights which can be daisy- chained around the room and used as task lights.
Gravity Light. Appropriate Technology. Published: Dec 2013. 60-61.
Compliance: CE, General Product Safety Directive 2001/95/EC, EMC Directive 2014/30/EU, IEC/EN/BS 55015, IEC/EN/BS 61547, IEC/EN/BS 61000-3-2, IEC/EN/BS 61000-3-3, IEC/EN/BS 62493, IEC/EN/BS 62471, RoHS Directive 2011/65/EU, WEEE Directive 2012/19/EU, IEC/EN/BS 60598-1, IEC/EN/BS 60598-2-4, FCC Part 15
GravityLight is tested in Deciwatt workshop and out in the field. In 2014, it was tested in 1000 households across 26 countries to assess functionality and ease of use
GravityLight was called one of The 25 Best Inventions of the Year 2013 by Time Magazine.
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