Energy harvesting is the conversion of different forms of energy from the environment to electricity that can be used to power a device. As light, motion, friction and thermal gradients are always present in our surroundings, energy harvesting represents an endless yet sustainable energy resource.
Practical applications for energy harvesting are vast. The wearable electronics industry is already using it to create new and exciting products that never have to be connected to a charger. Wearables or body-borne computers are worn under or on top of clothing or they are integrated within the clothing. They may be used as fitness trackers or monitor the health state of the user. Sensors, radios and cellphones may also be recharged by energy harvesting. Smartphones likes Apple’s iPhone can already be charged wirelessly using magnetic induction. As these chargers are still connected to a power source via USB, this does not provide the energy independence of other harvesting approaches. New developments in true energy harvesting aim to to deliver sufficient energy even for power demanding devices.
Energy harvesting does work in three steps. First the energy from an external source has to be captured and converted to electrical energy. Second, the harvested electrical energy needs to be conditioned in order to supply connected electronics. Third, the energy has to be stored in an energy buffer from where it can be directed to the device that has to be powered. Energy harvesting is very flexible because it can use energy from many sources. This could be solar power, wind energy or thermal energy as well as kinetic energy (energy from the movement of the device respectively the body). All these sources have one thing in common that they are available as ambient energy.
Energy harvesting is powerful, because it perfectly suits a mobile lifestyle. Consumers are using their mobile devices everywhere, but a charging device for the battery is not always available. Energy harvesting enables energy autonomy and makes wireless and autonomous devices therefore much more interesting.
It definitely has to be noted that energy harvesting is overcoming its limits now. Energy-harvesting is currently only suitable for low-energy devices. But new developments in material sciences, fabrication technology and ultra-low power electronics might enable to supply even complex devices.
In the right applications, energy harvesting could make a battery completely dispensable and provide unlimited lifetime for wearable devices. It is very useful for wearables and other devices that have a not too high energy consumption.