Industry Market Trends

Power by the People: Generating Electricity From Human Activity

May 02, 2011

"Small Is Beautiful," proclaimed economist E. F. Schumacher in his 1973 book of that title, extolling the virtues of a decentralized economy. And when it comes to power generation, what could be more decentralized than the harvesting of energy from everyday human activities? (See this introduction to E. F. Schumacher by Noah Enelow.)

Recent news reports have cast the spotlight on a Portland, Ore., health club that is generating electricity from its exercise machines. Such developments call attention to the advances companies are making in harvesting kinetic energy from everyday activity and movement.

Using new energy technologies, transportation agencies could conceivably collect such power on a large scale fromroadways, railways, and pedestrian walkways. But electricity can also be generated at the level of an individual person. As a well-known example, a small pedal-driven generator can power a bicycle headlight. A rechargeable battery charged up with a crank can power a personal device such as a flashlight or radio. Such applications have long been available commercially.

Technology companies are continuing to develop personal electronics such as mobile phones and music players -- or even implanted medical devices -- that require ever-smaller levels of electricity. For these small-scale applications, electrical energy generated by an individual could serve as a power source when channeled to a rechargeable battery. This promises to be a less expensive and cleaner source of power for such devices.

More Than Just a Workout

The health club I mentioned before, the Green Microgym, based in Portland, Ore., bills itself as the "world's first electricity generating" gym. Company background information says that in 2009 the club generated 36 percent of its own electricity by combining human and solar power. The Green Microgym claims that it saved 37,000 kWh, or 85 percent compared to regular gyms.

PlugOut cross-trainer exercise machineThe company employs many conventional methods for saving energy, such as using LCD televisions rather than plasma TVs, using energy-efficient ceiling fans and lights, and controlling electrical devices such as lights and televisions so they are on only when needed. Solar panels on the building exterior generate power.

But one of the key features of the gym for our purposes is the specialized exercise equipment that generates electricity from human power. The Green Microgym's equipment includes cross-trainers and stationary bikes that use the power of a human workout to turn a dynamo and generate electricity at up to 250 watts. The equipment plugs into a standard wall outlet so it can feed power back to the electric grid. The club's exercise equipment is made by PlugOut, a company founded by Adam Boesel, also founder of the Green Microgym. (Photo used with permission from PlugOut Inc.)

Pavement Power

A company in Rotterdam, Netherlands, is pioneering another source of human kinetic energy: the fancy footwork and gyrations of dancing nightclubbers. Sustainable Dance Club (SDC) has developed a patented technology, Sustainable Dance Floor, that converts dancers' energy into electricity to power the club's lighting and special effects. The technology has been installed at Club Watt, a nightclub in Rotterdam; at Eco House, an event location in Sao Paulo, Brazil; the Miami Science Museum, where the floor powers music and lighting; and the Australian Museum. (Drawing used with permission from Sustainable Dance Club.)

Sustainable Dance Floor drawingPerhaps the most practical application of the Sustainable Dance Floor is in Toulouse, France, where the city is employing the technology for a "pavement power" project. Foot traffic along a stretch of sidewalk in the city center is used to power street lighting in the area.

A group of researchers at San Jose State University writes that the SDC dance floor "utilizes a spring-loaded flooring system of independently moving tiles ... each tile can compress up to 2 cm, activating a flywheel mechanism which powers a small electrical generator ... LEDs embedded in the floor are sustained entirely by the approximately 20 watts generated by each dancer." ("Piezoelectric Harvesting: A sustainable approach to clean energy generation in airport terminals," Christopher Scholer et al, entry for FAA Design Competition for Universities, April 2009)

Jaap van den Braak, SDC's marketing director, told The Guardian in 2010 that Rotterdam's football stadium had signed up to do a pilot project with the technology. He said that other pilot projects were under consideration "which use the modules in public spaces where there is a high traffic movement, such as train stations and sports stadiums." (See "Pavement Power Lights Up Toulouse," by Lizzy Davies, April 13, 2010.)

Power Walker

Bionic Power PowerWalk Bionic Power, a Canadian company, has developed the PowerWalk, a wearable device for harvesting human energy. The PowerWalk, now in prototype form, is a leg brace worn from thigh to shin with a pivot at the knee, where a generator captures a walker's movement to charge up a battery pack. Intended initially for military use, the device "uses principles similar to regenerative braking in hybrid cars to unobtrusively generate electricity from the natural motion of walking and then use it to charge a wide range of portable battery-powered devices," according to company background materials. (Photo used with permission from Bionic Power Inc.) The company describes its technology in this way:

It resembles an athletic knee brace and weighs about 750 grams (1.7 lbs) per leg. With a device on each leg, a user walking at a comfortable speed generates an average of 12 watts of electricity. At this rate, a little over one hour of walking generates enough electricity to charge four mobile phones. The PowerWalk M-Series intelligently adjusts the amount of energy that it harvests as a function of walking speed and terrain, harvesting more energy when available and dialing back energy harvesting when it might be obtrusive.

Rather than forcing a walker to do extra work, it sounds to me as if the PowerWalk could actually provide some relief for those of us whose knees have seen better days. Discussing their technology, Bionic Power says,

The knee is the best location for energy harvesting as it primarily performs negative work during walking, unlike the hip or the ankle joints, making it a good candidate for generative braking. While the knee power profile varies substantially during level ground walking ... there is significant negative power during swing extension, stance flexion, and swing flexion. It is desirable to target these regions for power generation as the generator can assist the muscles in slowing down the body.

Visit the company's YouTube channel to see demonstrations of the PowerWalk.

The Power of Rolling Wheels

A technology developed in Israel is harvesting human energy on a much larger scale. Israel's National Railway Company is testing a technology by Israeli company Innowattech that captures energy from trains rumbling along railroad tracks. In January of 2011, Innowattech replaced 32 conventional railroad pads along a stretch of railway with the company's IPEG pads containing piezoelectric disks. (Piezoelectric technologies collect the electricity that is generated when certain crystalline materials are compressed.) A report from Selected Science News says that

Preliminary results suggest that areas of railway track that get between 10 and 20 ten-car trains an hour can produce 120 kWh of renewable energy per hour, which could be used to help power trains and/or signals, or be routed to the power grid for use elsewhere.

Innowattech also makes power-generating pedestrian tiles, pads for highways, and tiles that can be installed under heavy machinery to harvest kinetic energy normally wasted in manufacturing. The company has also developed an accompanying information technology solution that monitors and analyzes the movement of vehicles along a roadway or railroad track while energy is being generated.

This YouTube video shows how Innowattech's system could be used in a roadway application.

Think "small" is beautiful? Like the idea of decentralized power generation? Your opportunity might come soon to turn your own body into a renewable energy source.