TECHNICAL FIELD

The present disclosure relates to an energy harvester, in particular but not limited to, an energy harvester wrapped and secured to a human's limb. The present disclosure also relates to an electrical device, in particular but not limited to a wearable device, incorporating the energy harvester for energy supply to the device.

BACKGROUND

Wearable devices such as smartwatches and activity trackers are changing our lifestyle towards a more convenient and healthier way. The huge market potential of wearable devices is widely recognised.

Along with the widespread market adoption of wearable devices, problems of the power source battery become increasingly distinct. Batteries have limited lifespans and require frequent recharging. The end-of-life battery disposal also poses severe environmental problems.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the present invention, there is provided an energy harvester comprising: an inner band; an outer band arranged to surround the inner band, wherein the inner band is coupled to the outer band at a fixed end and the inner band is spaced from the outer band at a free end; and an energy generator arranged to generate electric energy through relative movement between the inner band and the outer band at the free end.

In an embodiment of the first aspect, the energy generator is positioned on the surface of the outer band.

In an embodiment of the first aspect, the energy generator is positioned along the length of the outer band between the fixed end and the free end.

In an embodiment of the first aspect, the outer band is elliptic whereby the inner band and the outer band intersecting with each other at the fixed end and separating from each other at the free end.

In an embodiment of the first aspect, the energy generator is positioned at a vertex of the ellipse of the outer band.

In an embodiment of the first aspect, the outer band is formed by a composite layer.

In an embodiment of the first aspect, the composite layer includes an elastic substrate layer and a piezoelectric layer attached thereto, whereby the piezoelectric layer is arranged to generate electric energy in response to deformation of the substrate layer.

In an embodiment of the first aspect, the elastic substrate layer is sandwiched between two said piezoelectric layers.

In an embodiment of the first aspect, the piezoelectric layer is further covered by a protection layer.

In an embodiment of the first aspect, the outer band is of uniform thickness or width across its length along which one or more energy generators are disposed thereon.

In an embodiment of the first aspect, the outer band is of variable thickness or width across its length to form one or more spots at which the stress is concentrated and on which the energy generator is disposed, thereby facilitating the generation of electric energy by the energy generator.

In an embodiment of the first aspect, the energy harvester further includes one or more linkage extending across the inner band and the outer band and the linkage includes said energy generator.

In an embodiment of the first aspect, the energy harvester further includes an elastic membrane arranged to wrap the inner band and the outer band together to form a composite band.

In an embodiment of the first aspect, the elastic membrane is at least one of waterproof and dustproof.

In an embodiment of the first aspect, the wrapped inner band and outer band are invisible through the elastic membrane.

In an embodiment of the first aspect, the inner band is formed by a first material and the outer band is formed by a second material with a higher stiffness than the first material.

In an embodiment of the first aspect, the energy harvester further includes a mass at a position proximate to the free end to facilitate the movement of the outer band through its vertical movement, thereby increasing the magnitude of generated electric energy by the outer band.

In an embodiment of the first aspect, the energy harvester further includes an electronic device arranged to receive electric energy from the energy generator.

In an embodiment of the first aspect, the electronic device is received by the mass.

In an embodiment of the first aspect, the energy harvester includes at least two said energy generators and the two energy generators are in at least one of serial connection and parallel connection.

In an embodiment of the first aspect, the energy harvester further includes a rectifier arranged to receive generated electric energy from the energy generator and to convert received electric energy in alternating current to direct current.

In an embodiment of the first aspect, the inner band includes a first arm and a second arm connectable together to form a closed loop and releasable from each other to form an open loop.

In an embodiment of the first aspect, the inner band is arranged to secure to a human limb for generating electric energy in response to the movement of the outer band activated by the movement of human limb.

In accordance with a second aspect of the present invention, there is provided a wearable device comprising: a wearable strap formed by the inner band and the outer band of the energy harvester of the present invention, and a mass arranged to receive at least a portion of the wearable device.

