Meta-material vibration energy harvester

Abstract

A meta-material vibration energy harvester includes a housing element encapsulating a multiplicity of oscillators capable of harvesting a significant percentage of the total mechanical energy diffusely distributed throughout the vibrating structure, the harvester design resulting in a rapid transfer of mechanical energy entering it via the housing element from the element to the oscillators wherein the energy remains trapped while accumulating over an extended time, the percentage of energy transfer primarily depending on the ratios of the sum of the oscillator masses to the sum of the housing mass and of the measure of the mass of the vibrating structure and of the width of the band spanned by the oscillators to its center frequency, both the relevant measure of the vibrating structure mass and the values of the mass and frequency ratios that maximize the percentage of internal energy transfer depending on the harvesting scenario.

1 . A meta-material mechanical/electrical energy converter (MMMEEC) for converting mechanical energy to an electrical current, comprising a rigid housing element of mass M encapsulating N oscillators each joined with a mechanical/electrical converter element, and each having a mass m j  and a resonance frequency ω j , together with electrical circuitry for collecting individual electric currents from each of the combination oscillator-mechanical/electrical-converters and outputting the sum of currents via the housing element,
 wherein the source of mechanical energy inputted to the MMMEEC is a time-varying external force acting on the rigid housing element, and 
 further wherein N is substantially large and the distribution of ω j  is substantially uniform across a frequency band of width Ω so that the frequency band is densely filled, and wherein the masses m j  are substantially equal to one another, and 
 further wherein the ratios of the sum of the m j  masses to M and the width of the frequency band Ω to the center frequency of the band, ω c , have predetermined values, and 
 further wherein the value of ω c  equals the frequency for which the spectral content of the time-varying external force is near its maximum, 
 whereby the MMMEEC has the capacity of converting a substantially larger quantity of mechanical energy than would a device for which the housing element of similar mass, comprising any material but no internal oscillators, is combined with a mechanical/electrical converter element. 
 
     
     
         2 . A meta-material vibration energy harvester (MMVEH) for harvesting mechanical energy from a vibrating structure (VS) that is the source of a time-varying external force acting on the rigid housing element, comprising the MMMEEC according to  claim 1  adapted to be connected to at least one local region of the vibrating structure,
 wherein the predetermined value of the ratio of the sum of the m j  masses to M further depends on a measure of the inertia of the VS and a measure of the resistance to deformation of the VS, said measures depending on the geometry and composition of the VS; the coherence of the vibrations contained in the VS; and, the type connection of the MMVEH and the VS, 
 whereby the MMVEH has the capacity of harvesting an other than infinitesimal percentage of the total mechanical energy diffusely distributed throughout the vibrating structure. 
 
     
     
         3 . A deformable meta-material mechanical/electrical energy converter (DMMMEEC) for converting mechanical energy to an electrical current, comprising a deformable housing element containing a naturally occurring material with spatially varying mechanical properties, which includes a spatially varying mass density ρ, and encapsulating N oscillators each joined with a mechanical/electrical converter element, and each having a mass m j  and a resonance frequency ω j , together with electrical circuitry for collecting individual electric currents from each of the combination oscillator-mechanical/electrical-converters and outputting the sum of currents via the housing element,
 wherein the source of mechanical energy inputted to the MMMEEC is a distribution, whether discrete or continuous, of time-varying external forces of limited spectral content acting over a region of the boundary of the deforming housing element, and 
 further wherein N is substantially large and the distribution of internal elements is substantially uniform so that the volume of the housing element is densely filled, and further wherein the distribution of ω j  is substantially uniform across a frequency band of width Ω so that the frequency band is densely filled, and further wherein the masses m j  are substantially equal to one another, and 
 further wherein the distribution of the internal elements are such that the ratios of the sum of those m j  in a representative unit volume element to ρ, and the width of the frequency band Ω to the center frequency of the band ω c , have predetermined values, and 
 further wherein the value of ω c  equals the frequency for which the spectral content of the time-varying external force is near its maximum, and 
 further wherein the spatially varying mechanical properties are predetermined so as to maximize the mechanical energy inputted by the external forces acting, 
 whereby the MMMEEC has the capacity of converting a substantially larger quantity of mechanical energy than would a device for which the housing element of similar mass, comprising any material found in nature but no internal oscillators, is combined with an external distribution of mechanical/electrical converter elements. 
 
     
     
         4 . A deformable meta-material vibration energy harvester (DMMVEH) for harvesting mechanical energy from a vibrating structure (VS) that is the source of a time-varying external force distribution acting on the deformable housing element, comprising the DMMMEEC according to  claim 3  adapted to be connected to at least one local region of the vibrating structure,
 wherein the predetermined value of the ratio of the sum of the m j  masses in representative unit volume to ρ further depends on the geometry and composition of the VS; the coherence of the vibrations contained in the VS; and, the type connection of the DMMVEH and the VS, 
 whereby the DMMVEH has the capacity of harvesting an other than infinitesimal percentage of the total mechanical energy diffusely distributed throughout the vibrating structure. 
 
     
     
         5 . The meta-material vibration energy harvester (MMVEH) according to  claim 2 ,
 wherein the MMVEH is directly connected to a local region of a resonant vibrating structure (RVS), in which the measure of inertia is the total mass of the VS and the measure of resistance to deformation has a substantial linearly elastic component,   wherefore the spectral content of the time-varying force acting on the rigid housing element is centered at a frequency close to a resonant frequency of the structure, and   wherein the ratio of the sum of the m j  masses to the sum of housing element mass and the mass of the VS is about 0.01 and the ratio of Ω to ω c , is about 0.1,   whereby the MMVEH has the capacity of harvesting a substantial percentage of the total mechanical energy diffusely distributed throughout the vibrating structure   
     
     
         6 . A MMVEH system comprising a multiplicity of MMMVEH's according to  claim 2 ,
 wherein each harvester is joined at a predetermined location of the VS, such that the multiplicity is distributed across the entirety of the VS, and further wherein the combined sum of the internal oscillator masses of each of said MMVEH has a given value as large as practical subject to the restriction that the value is less than 1% of the total mass of the vibrating structure,   whereby the capacity for harvesting the mechanical energy diffusely distributed throughout the vibrating structure is at a maximum.   
     
     
         7 . The meta-material vibration energy harvester MMVEH according to  claim 2 ,
 wherein the MMVEH is directly connected to a local region of a non-resonant vibrating structure (NRVS), in which the measure of inertia is the mass of the region of the VS near the connected MMVEH and the measure of resistance to deformation has a substantial dissipative component, wherefore the spectral content of the time-varying force acting on the rigid housing element depends on the spectral content of the external forcing of the VS,   wherein the ratio of the sum of the m j  masses to the sum of the mass of the housing element and the mass of the local region of the VS has a predetermined value that depends on the resistance of deformation of the VS and on ω c ,   whereby the MMVEH has the capacity of harvesting an other than infinitesimal percentage of the total mechanical energy diffusely distributed throughout the vibrating structure   
     
     
         8 . The DMMMEEC according to  claim 3 , wherein the housing element is a rod, and further wherein the source of mechanical energy inputted to the MRMEEC is a pair of equal and oppositely directed time-varying forces of limited spectral content, acting at the two end sections of the rod. 
     
     
         9 . The DMMVEH according to  claim 4 , wherein the housing element is a rod joined at two locations to a VS. 
     
     
         10 . The DMMMEEC according to  claim 3 , wherein the housing element is a beam. 
     
     
         11 . The DMMVEH according to  claim 4 , wherein the housing element is a beam joined, whether discretely or continuously, along a line on a boundary surface of a VS. 
     
     
         12 . The DMMMEEC according to  claim 3 , wherein the housing element is a plate. 
     
     
         13 . The DMMVEH according to  claim 4 , wherein the housing element is a beam joined, where discretely or continuously, over a region in the boundary surface of a VS