Army

Heel-strike shoe energy generator

Shoe insole works with the body’s natural movements to generate power on the go

Energy Electronics

A scientist from the U.S. Army has recently invented a shoe insole with an embedded energy-harvesting mechanism that produces energy with every step.

Nathan Sharpes, CERDEC CP&ID engineer, demonstrates the energy-harvesting mechanism he has inserted into the heel of a combat boot insole. Each time a soldier’s heel strikes, it activates a generator, which spins to produce energy. (U.S. Army Photo CERDEC/Kathryn Bailey)

The patent-pending technology is available via license agreement to companies that would make, use, or sell it commercially.

Electronic devices have a wide variety of uses and applications in modern society. These devices require electrical energy to function. For some, this energy is derived from a battery. As the devices are used, the battery level lowers and ultimately reaches a level so low that the electronic device no longer functions without a new battery, which can be expensive and cumbersome, or the battery being recharged.

A need exists for a way to efficiently recharge batteries. In response, an Army scientist has developed a technique to convert movement from a heel strike into a rotational movement. This rotational movement causes the interior of an electrical generator to rotate, which causes electricity to be produced. The electricity generated can be used to charge a battery.

Designed to fit within a shoe insole, the system receives pressure from a downward step or heel strike. A rack and pinion system converts the heel strike into a rotational movement, which ultimately produces energy. The rack and pinion gear can be in line. As the rack moves, the pinion gear rotates. When the pinion gear experiences a rotation, the coupling mechanism rotates. The rotation of the coupling mechanism causes rotation of the electrical generator such that electricity is produced. The pinion gear can have a variable gear ratio so that the gear ratio is lower at a start to overcome initial resting inertia and increases so the gear ratio is higher toward an end of the rotation to maximize speed.

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