Have you ever wondered how powerful you are? Not the power of fame, fortune or knowledge but rather how much power is in your body. On average, a human consumes about 3,300 watt-hours of energy every day but has the potential to produce more than 3 times that amount -- up to 11,000 watt-hours of power -- from normal bodily functions such as motion and the production of body heat. Walking, for example, produces 163 watts of power, while sprinting generates more than 1,600 watts [source: SPACE.com]. What if this wattage could be turned into usable energy?
Renewing the Grid Image Gallery
The wattage a body generates is potential energy, and only a small percentage of it can be captured. NASA's Defense Advanced Research Projects Agency (DARPA) estimates that a single footstep could provide 1 to 2 watts [source: SPACE.com]. Turn a single footstep into 84,162,203 steps and a group of people could generate enough power to launch a space shuttle [source: Christian Science Monitor].
The idea of harnessing the power of people isn't just a concept being explored by engineers, scientists and "The Matrix," it's also an experiment making its way into green design. A small number of dance clubs around the world are starting a dance revolution outside of Xbox and Nintendo. Sustainable Dance Club in Rotterdam, Holland, and Surya in London, among others, have embraced eco-friendly philosophies that manifest in everything from the renewable and recycled materials of their décor to their commitment to building environmental awareness in young patrons.
An ordinary dance club -- house music thumping three nights a week -- uses 150 times more energy than a household of four people each year [source: Popular Mechanics]. To minimize their consumption, eco-friendly dance clubs green themselves by providing amenities such as organic wines and beer, waterless urinals and toilets that flush with recycled water (including, yes, clubgoers' sweat). Some even get their power from solar, wind and dance energy. Dance energy? Special dance floors, known as piezoelectric floors, turn the power from clubbers' feet into electricity used to power the club.
Could we solve the energy crisis by harnessing the energy of clubgoers with piezoelectric flooring?
Harvesting Energy from Human Movement
Piezoelectricity is electrical energy produced from mechanical pressure (including motions such as walking). When pressure is applied to an object, a negative charge is produced on the expanded side and a positive charge on the compressed side. Once the pressure is relieved, electrical current flows across the material.
Let's look at how the principle works in a motion such as walking. A single footstep causes pressure when the foot hits the floor. When the flooring is engineered with piezoelectric technology, the electrical charge produced by that pressure is captured by floor sensors, converted to an electrical charge by piezo materials (usually in the form of crystals or ceramics), then stored and used as a power source.
In 2007, two MIT graduate students proposed the idea of installing piezoelectric flooring in urban areas. Dubbed "Crowd Farming," the idea was to install a flooring system that would take advantage of piezoelectric principles by harvesting power from footsteps in crowded places such as train stations, malls, concerts and anywhere where large groups of people move. The key is the crowd: One footstep can only provide enough electrical current to light two 60-watt bulbs for one second, but the greater the number of people walking across the piezoelectric floor, the greater amounts of power produced. It's not beyond the realm of possibility -- approximately 28,500 footsteps generate energy to power a train for one second [source: Christian Science Monitor]. Imagine what the combined power of commuters' footsteps during rush hour could do.
Recently piezoelectric floors have debuted in a handful of innovative dance clubs around the world. These floors represent prototypes of the "Crowd Farm" concept: The movement of a large group of clubbers dancing on energy-capturing floors is collected and used to power LED lights and, in the long-term plan, feed energy into the club's power grid.
The principles of piezoelectricity have been understood since the 19th century but the application in energy-generating floors hasn't yet proven to be a substantial power source. In trials outside of the clubs, a "smart home" student housing experiment at Duke University ditched the idea of installing a piezoelectric floor when the high installation costs and nominal amount of power produced got in the way. In the clubs, initial estimates suggest an individual clubgoer could generate roughly 5 to 10 watts, and on a night where the dance floor is packed with moving bodies, the energy from the floor could supply about 60 percent of the club's total energy needs [source: Daily Mail]. Enough to save us from the world's energy crisis? Not yet.
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More Great Links
- Baard, Erik. "People Power: Capturing The Body's Energy For Work On and Off Earth." Space.com. 2001. http://www.space.com/businesstechnology/technology/body_power_011128-1.html
- "Britain's first eco-nightclub powered by pounding feet opens its doors." Daily Mail. 2008. http://www.dailymail.co.uk/sciencetech/article-1027362/Britains-eco- nightclub-powered-pounding-feet-opens-doors.html
- "Frequently Asked Questions." Sustainable Dance Club (SDC). http://www.sustainabledanceclub.com/index.php?t=txt&tx=11
- Gaylord, Chris. "Power Harnessed One Step At A Time." The Christian Science Monitor. 2007. http://www.csmonitor.com/2007/0926/p14s02-stgn.html?page=1
- Kanellos, Michael. "Harvesting energy from falling raindrops." CNET News. 2008. http://news.cnet.com/greentech/?keyword=%22piezoelectric%22
- Ma, Wayne. "Eco-Disco: Self-Sufficient Dance Floor to Power First Green Nightclub." Popular Mechanics. 2007. http://www.popularmechanics.com/blogs/science_news/4224574.html
- "MIT duo sees people-powered 'Crowd Farm'." MIT News Office. Massachusetts Institute of Technology. 2007. http://web.mit.edu/newsoffice/2007/crowdfarm-0725.html
- Piezo Systems, Inc. http://www.piezo.com/
- "Power From the People." Wired. 2006. http://www.wired.com/culture/lifestyle/commentary/imomus/2006/08/71582
- "Power Generating Floor Tested at JR Tokyo Train Station." Japan for Sustainability. 2008. http://www.japanfs.org/db/2073-e
- "Residential Piezoelectric Energy Sources." Duke Smart Home Program. Duke University. http://www.smarthome.duke.edu/projects/piezo_energy.php
- Sodano, Henry A. and Daniel J. Inman. "Estimation of Electric Charge output for Piezoelectric Energy Harvesting." Center for Intelligent Material Systems and Structures. Virginia Polytechnic Institute and State University. 2004. http://www.cimss.vt.edu/pdf/Journal%20Articles/Park/J09.pdf
- Thompson, Andrea. "'Crowd Farm' Converts Footsteps into Electricity." LiveScience. 2007. http://www.livescience.com/technology/070731_crowd_farm.html