Power Walking – Smart Shoes Generate Power from Walking

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Wearable devices, such as health monitors and sensors, are of great interest. One of the major limitations in making these devices a practical reality has been the power supply – the need for large, heavy batteries. Movement generates power and a human can produce 10s of Watts just from walking and up to a kilowatt when sprinting. Harvesting this energy has the potential to overcome the power supply problem and German researchers have recently built power harvesting devices which are small enough to fit inside a shoe. The researchers have produced two devices, a swing harvester and a shock harvester. Both creations exploit the interaction between magnets and conductive coils to generate power.The aim was to create a self-lacing and unlacing shoe for the elderly, but this technology has many potential applications and could be used to power wireless devices.

3 Running shoe integration - Swing harvester

4 Running shoe - x-ray 1


As the name suggests, the swing harvester generates power when the foot is in motion. Multiple magnets are stacked within conductive coils. When the foot swings, this stack of magnets moves through the coils, inducing a voltage and causing current to flow though the windings. The amount of power produced depends on the speed of movement – the faster you run, the more power you generate.

The second invention, the shock harvester, produces power when the heel strikes the ground. This device is composed of a spring loaded magnetic circuit, containing three pairs of magnets, two coils and a magnetic suspension system. When the heel hits the floor, the two magnets in the magnetic suspension system begin to approach. This creates a repulsive force, pushing the magnetic circuit back up. The spring loading causes the magnetic circuit to oscillate, leading to power generation by resonant magnetic induction.

The energy output is small, up to 4 mW for the shock harvester. A smartphone requires around 5 W (5000 mW), but these devices are still capable of powering small sensors and wireless transmitters. As the output is directly related to the size of the system, making the devices larger would yield more power. Previous designs have produced up to 250 mW, but were impractically large. The same researchers are currently working on new models, which promise a significant increase in power without a large increase in size.

Details about the project entitled "Energy harvesting from human motion: exploiting swing and shock excitations" (Authors: K. Ylli, D. Hoffmann, A. Willmann, P. Becker, B. and Y. Manoli Folkmer) are published in IOP Publishing's journal "Smart Materials and Structures" at:


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