Ambient energy scavenging, also called energy harvesting or power harvesting, is the process of obtaining usable energy from natural and human-made sources that surround us in the everyday environment.
In most locations on earth, there is abundant ambient electromagnetic (EM) energy from cellular, television and radio transmitters, as well as satellite and other wireless communication systems. Other sources include physical motion, visible light, heat from the sun and the earth's interior, wind, ocean waves, ocean tidal currents, river currents and sound waves.
Human activities inevitably produce waste energy that can go to productive use if harnessed and stored. For example, when you walk down the street, you move your arms and legs, generating kinetic energy to propel yourself, and also thermal energy as friction with your clothes, the surrounding air, and the pavement beneath your feet. An ambient energy scavenging device can convert most or all of this wasted energy into electrical energy that you can use (for example) to charge your cell phone battery.
The concept of ambient energy scavenging has existed for decades. In recent years, mounting interest in alternative energy has accelerated the pace of research. Here are a few examples of current research:
- The U.S. Defense Advanced Research Projects Agency (DARPA) is developing an integrated energy scavenging and storage system for use with portable electronics, weaponry and vehicles, among other things. The integration of renewable energy with storage could enable batteries that would constantly remain charged.
- Technology from a company called Voltree harvests the metabolic energy of trees and converts it to electricity that power wireless sensor networks used to detect and control forest fires.
- Piezoelectric (PE) generators, created with crystals that give off a charge under pressure, are being used or tested under roadways, walkways and in sports stadiums to obtain usable energy from traffic and activity above them. For example, an Israeli company called Innowattech placed PE generators beneath 33 feet of highway. The company estimates that such devices under a half-mile of a busy highway could generate enough electricity to power 250 homes.
Continue reading about ambient energy scavenging:
Faruk Yildiz outlines several ambient energy scavenging methods.
Engineers at Georgia Tech have developed a method of harvesting ambient electromagnetic energy.
See more about DARPA's energy scavenging and storage system project.
Piezoelectric materials may provide an alternative for scavenging energy from physical vibrations such as sound waves.