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.
There are currently two models of GravityLight produced and supported by Deciwatt, the GL01 and GL02.
Kerosene lamps, candles, and solar lanterns such as Consol Solar Jar, MPOWERED Luci Original and Crush Light
Goal 7: Affordable and clean energy
GravityLight was designed for individual consumers with limited access to electricity, as well as NGOs and government agencies.
Mass produced in Kenya
The lamp is distributed through local distribution networks, partners and sales agents (door-to-door networks, farmer groups, and more traditional market stalls). International distribution is handled by various international partners listed on the GravityLight webpage.
Distribution started in December 2016, with about 140 products being made each day in Kenya.
Within 3 years of launch they plan to have sold 450,000 GravityLights.
Type of light bulb
Number of light points
A measurement of the brightness level of the lantern
Can the brightness level be adjusted?
Duration of lighting after a full charge
Can the user easily replace the light bulb if needed?
Type of energy used to power the lantern
Type of battery used
Peak power rating of the solar panel in standardized sunlight conditions, provided by the manufacturer
Manufacturer-specified battery capacity
Manufacturer-specified battery voltage
Can the user easily replace the battery if needed?
Can the user easily replace the light bulb if needed?
The tech inside the GravityLight:
Diagram of the basic principle of the gravity light.
A toll-free support line via SMS or over the phone
Deciwatt also provide an support webpage, with links to installation guides, instruction manuals and other relevant documentation.
GL01 model: 3 months – 1 year of continuous use
GL02 model: >3 years of continuous use
The GL02 also comes with a 1 year warranty.
Pull the cord for instant light
One lift creates 20 minutes of light
Totally weather independent
No battery or external power required
GL02 has 50% greater efficiency than and 12 times the lifespan of the GL01.
The product is designed to pay for itself within 3 months, saving families an average of 70 USD per annum.
Testing performed by the manufacturer found that the GL02 has a lifecycle of >3 years of continuous use on their testing rig, however no third-party testing has been performed.
No third-party organizations, only testing performed by the designer.
The GL02 instruction manual includes the following safety advice, due to the heavy weight of the bag:
GravityLight suspends the bag from a pulley, which reduces the strain on the cord and the gearing.
This device complies with part 15 of the FCC Rules in not producing harmful interference.
Possibility to add additional SatLights (connected light points) which can be daisy- chained around the room and used as task lights.
Anonymous, 2013, Gravity Light. Appropriate Technology, 40(4), pp. 60-61.
Blackley, S., & Sheffield, R., 2016, Environment: Re-negotiating the E in STEM Education. ECO-THINKING, 1.
Sahota, J., 2017, GravityLight. Alternatives Journal, 43(2), pp.12-12.
Yakubu, Y.F., 2017, GravityLight in Nigeria. Energy Planning and Analysis Department, Energy Commission of Nigeria.
Deciwatt’s Declaration of Conformity for the GravityLight highlights all of the regulations it complies with in various jurisdictions. These include:
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 the Deciwatt workshop and out in the field.
The GL02 Inventors’ Pack describes some aspects of the testing process, including their custom built Accelerated Life Testing rig.
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.
1. The user fills the bag with 12kg of heavy objects such as rocks or sand
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
A pulley system is included, so users of any height or strength can lift the bag right up to the top – giving the maximum drop time.
The 2 SatLights as additional light points connected to the main unit are included with the GravityLight.
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