Of Earth's seven billion people, the nearly two billion who live in rural Asia and Africa are without electricity. In order to cook, sew, read, or study when the sun sets, they must rely on kerosene lamps.
While Americans may view the kerosene lamp as a symbol of tradition and the good old days, people who must use them are well aware of their drawbacks.
Kerosene is not only expensive and may represent up to a fifth of the income of people living on an average of $3 per day, it is also very dangerous, causing fires and explosions that annually injure and kill thousands of men, women, and children. It is also a health hazard. Data from the World Health Organization (WHO) warns that being in a room lit by a kerosene lamp is like smoking multiple cigarettes. The very tiny particles of carbon that burning kerosene releases into the air are drawn deeply into the lungs where they settle and increase the risks of respiratory illnesses, coronary problems and cancer. (Lam, Smith, Gauthier, & Bates, 2012)
Given these facts, it is clear that using kerosene as a way to light homes is at best a poor solution.
Among the many individuals and organizations working to develop ways to replace kerosene lamps are two British engineers, Jim Reeves and Martin Riddiford. When they began to work on the kerosene problem in 2009 they believed that the problem could be solved if people had access to solar powered charging stations that would make it possible to substitute rechargeable electric lamps for kerosene.
However, as they worked on the details, "we found out that the cost of the solar panel was too expensive for people with very, very limited finances."
Electrification in the United States in the 1930s was made possible by building a system of wires that would connect rural homes to electrical generating stations.
Reeves and Riddiford wondered if the solution was to simply connect individual homes to an electrical generator.
Much has changed since the 1930s. Then, light was produced by incandescent bulb that worked by pushing large amounts of electrical power (wattage) through high resistance wire like tungsten, causing the wire to incandesce, to glow.
The development of the light emitting diode means that a bright light can be generated using a small amount of current (~0.031 A and 0.085 W) that can easily be generated locally on an as needed basis by a small generator.
The problem was now defined as finding a way to turn the rotor of a small generator fast enough to generate enough electricity to cause the LEDs to light up enough to replace a kerosene lamp on demand.
The technology to generate rotary motion is and has been central to human activities: oxen or horses pull a wagon mounted on wheels connected by an axle, using wind or water to turn an axle to turn a gear that turns a millstone to grind grain. Human ingenuity has also made use of another force that is cost-free and reliable: gravity.
Do some work: raise a rock. Let the rock go and you convert the potential energy of position into kinetic energy that ends with the rock striking the ground.
Harnessing this force is the challenge if you mean to use the energy over an extended period of time, say to generate current for usable electric illumination.
How to harness the force of gravity by controlling the fall of a weight had been solved by at least 1387 by the monks at Salisbury Cathedral who had a mechanical clock to track the prescribed religious activities over an entire day. The power to operate the clock came from a rope with a weight on one end with the other attached to an axle (the winding barrel).
As the weight pulled the rope downward, a ratchet device alternatively stopped and released its movement, dividing the hour into a series of ticks and tocks. At the end of an hour, a mechanism was triggered ringing the bells in the tower to tell the hour.
It was this technology that controlled a falling weight with gears and ratchets that was used by Reeves and Riddiford to generate electricity.
The product, called the GravityLight, consists of a case containing a LED that the user is to hang on a wall about 6 ft above the floor. There is a rope with a bag to be filled with rocks or sand weighing about 12 kg (~27 lbs). To work the lamp, the user pulls the weighted bag up to the light case. When the rope is released, the weight pulls one end of the rope downward, setting in motion a gear train that slows the downward motion of the weight to about 1 mm per second and at the same time an arrangement of gears spins the generator's rotor at 1600 r.p.m. immediately causing the LED to emit light that is about 5 times brighter than a kerosene lamp, with no obnoxious by-products. The light will provide 20 minutes of light for each pull.
Once the initial cost of the GravityLight is paid, there are no further costs associated with operating the device.
The original GravityLight has given way to a new version called the NowLight. The new version will give an hour of light per one minute pull based on "efficient biomechanics and the latest battery technology...to generate the maximum power with minimum effort."
STEM is driven by curiosity about the what, why, and how of interesting puzzles, especially if the answers will have the potential to improve the human ecosystem. Reese and Riddiford's efforts to work out how to generate useful amounts of electrical energy on a small scale are driven by the challenge of an interesting problem whose solution will likely save lots of men, women, and children from the risks of kerosene lamps.
As the what, why, and how questions are answered they lead to questions and more innovation. Twenty minutes of free light in GravityLight leads to the development of more efficient electrical generation that quickly (one minute) charges batteries with enough power to provide an hour of light in the NowLight.
Gravity Light Foundation https://gravitylight.org
INDIEGOGO: nowlight: the next generation GravityLight
Lam, N. L., Smith, K. R., Gauthier, A., & Bates, M. N. (2012). KEROSENE: A REVIEW OF HOUSEHOLD USES AND THEIR HAZARDS IN LOW- AND MIDDLE-INCOME COUNTRIES. J Toxicol Environ Health B Crit Rev Journal of toxicology and environmental health. Part B, Critical reviews, 15(6), 396-432. doi:10.1080/10937404.2012.710134
Page 1 kerosene lamp. Page 3 GravityLight and Boy Studying GravityLight Foundation https://gravitylight.org/
Page 3 Salisbury Cathedral, https://historyimagined.wordpress.com/2015/12/11/from-sarum-to-cathedral/
Page 2 Salisbury Clock: Public Domain https://commons.wikimedia.org/wiki/File:Salisbury_Cathedral,_medieval_clock.JPG
Dr. John Holton
Dr. John Holton joined the S²TEM Centers SC in July of 2013, as a research associate with an emphasis on the STEM literature including state and local STEM plans from around the nation.