Harvesting Energy from Soccer Balls

Fidel Hernandez
November 28, 2010

Submitted as coursework for Physics 240, Stanford University, Fall 2010

Fig. 1: The sOccket with a connected LED light. (Source: Harvard Gazette.)


As developed nations continue their search for energy sources that will meet their high demand, Third-world countries merely struggle to find alternatives to sources that pose significant health hazards. Currently, developing nations across the world rely heavily on the burning of kerosene for lighting, cooking, and other day-to-day tasks. [1] In "The Specter of Fuel-Based Lighting," Evan Mills estimates the burning of kerosene for lighting generates approximately 190 million metric tons of carbon dioxide emissions per year, equivalent to the atmospheric impact of about 38 million cars. The dependence on kerosene has largely prevented the Third World from developing access to electricity, as it is more expensive and straining to do so.

The Solution: The sOccket

Four students from Harvard University are capitalizing on the world's interest in sports and the rising global popularity of soccer to addressing the need to eliminate the developing world's dependence on kerosene. [2] In partnership with the Laboratory at Harvard think-tank, the students developed a soccer ball they call the sOccet that generates electricity from normal kicking during game play. The energy captured during game play is used to charge LED lights, batteries, and even cellular phones. The creators of the sOccket claim any child can take the ball home to use as an outlet for an LED lamp to read, study, and even light up the home.

The ball uses an inductive coil mechanism, functioning similar to that of common shake-to-charge flashlights, where the rapidly-changing movement and kinetic energy of the soccer ball forces a strong magnet to move back and forth through a long metal coil, producing a current and inducing voltage in the coil to generate electricity. The electrical circuit includes a bridge rectifier that ensures the electricity flows in the current direction, essentially accounting for the constant back and forth movement of the magnet, especially as the soccer ball rolls around and is kicked in every-which direction. A capacitor onboard stores the pulses of energy, like a battery, only that it can do so instantly. Although the team states the product is still in the prototyping phase, their beta tests throughout Africa during the summer of 2010 suggests the sOccket can currently capture energy for 3 hours of LED light from only 15 minutes of standard play.

The sOccket inventors are working on making their soccer ball easy to produce, manufacture, and use in their target population of Africa. [3] In fact, the ball weighs in at 21 ounces, including the on-board DC jack, which makes it only 5 ounces more than a standard soccer ball. The design team reports future iterations will be even lighter and will utilize materials native to Africa where they hope their product will be mass-manufactured.

The Inspiration: London Eco-Club

The soccer ball developed by the four Harvard students is not the first time inventors have attempted to use recreational human movement to generate electricity. In fact, the four developers of the ball claim they were initially inspired by dance floors that collect energy in a similar fashion. [4] In London, the Eco-Club uses a revolutionary dance floor that harvests the energy of jumping, gyrating dancers into useful forms of electricity. The Eco-Club's dance floor is essentially created to "bounce" through a series of springs and power-generating blocks that provide the underlying support. These power-generating blocks product small electrical currents when compressed through processes known as piezoelectricity. When dancers at the club move around and continuously shift their weight, these power-generating blocks contract and expand because of the bounce effect created by the springs. The current generated by the blocks is fed into nearby batteries, which are constantly recharged and use to power various parts of the nightclub.


Capitalizing on the kinetic energy spent on sports and recreation is a creative and smart means of collecting energy. While current prototypes of the sOccket do not nearly suggest this idea can serve as a primary source of power for any country, it is a non-intrusive means of collecting power to accomplish important, simple, day-to-day tasks in countries where current energy sources pose serious health hazards. The ball weighs about the same as a standard soccer ball and would yield no significant change in the field of soccer. This unique feature suggests this source of energy would not require any fundamental human behavioral change. In fact, in utilizes the growing popularity of soccer, especially after this year’s World Cup in South Africa, to harvest energy for practical uses.

Getting rid of the dependence on kerosene is important for the Third World, and the key figure to consider is the fact that several tests of the sOccket suggest 15 minutes of play could be converted into three hours of LED lighting. [5] According to official soccer rules, soccer balls must have a mass between .41 and .45 g - we will use 0.43 kg as an approximate average. A soccer ball is kicked about once every 12 seconds at a speed of about 25 m/s. The power, in watts, generated by the ball is given by

P = 1/2 × 0.43 kg × (25 m/s)2 × 1/12 sec = 11.2 W

We then conservatively assume the sOccket technology has an efficiency of 10% in terms of converting and storing the energy in the onboard batteries. We then multiply the result by 60 and 15, to give us about 1000, the amount of joules delivered by the soccer ball after 15 minutes of play. This amount of joules is enough to power LEDs that consume less than 100 mW of power for 3 hours, as these will consume around 1000 J or less.

Those three hours, used for reading, cooking, and other important tasks, would alone save citizens of developing nations 13% of their daily kerosene dependence and intake through inhalation. Based on research from the World Bank, that means residents of kerosene-dependents countries would reduce their health-impact to the equivalent by about .25 cigarette packs (or about 5-6 cigarettes) per day. Similarly, Third World countries would produce almost one less ton of carbon dioxide every year. This huge impact would come from only 15 minutes of soccer play per day, a startling figure that shows great promise in the potential impact of the sOccket in developing countries around the world.

© Fidel Hernandez. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.


[1] E. Mills, "The Specter of Fuel-Based Lighting," Science 308, 1263 (2005).

[2] J. Witkin, "Using Soccer to Supplement Kerosene Use?," New York Times, 26 Jan 10.

[3] J. Salton, "Energy Generating sOccket Soccer Ball Scores a Goal in Off-Grid Villages," Gizmag, 8 Feb 10.

[4] D. Melanson, "Power-generating Dance Floor Hits UK Club," Engadget, 17 Jul 08.

[5] S. Lover, Official Soccer Rules Illustrated (Triumph Books, 2009).