Monolithic energy harvesting system, apparatus, and method
An energy harvesting device utilizing a monolithic, mesoscale, single-degree-of-freedom inertial based resonator in which the support structure, beam-spring, and proof mass are a single component without joints, bonds, or fasteners. Frequency tuning features include holes in the proof mass in which mass can be added to change the devices resonance frequency as well as levers which add curvature to the beam-spring system and adjust system stiffness. Robustness is increase by designing the resonator to exhibit nonlinear behavior such that its power density is maximized for low vibration amplitudes and minimized for high amplitudes. The device structural resonance modes are designed to be much higher than the resonators proof mass-spring resonance frequency. Electromechanical transducers are used to convert the resonators mechanical energy to electrical energy. Electrical circuitry is included to extract and condition the electrical charge.
1. An apparatus for harvesting energy from vibratory motion of a host structure, the apparatus comprising:
a vibration resonator, the resonator having a monolithic construction including
a rigid structure;
at least one spring member connected with the rigid structure, the spring member including a beam member having a first portion connected with the rigid structure; and
a proof mass, the proof mass being connected with the beam member such that the proof mass is coupled with the rigid structure,
wherein a portion of the proof mass, the at least one spring member, and the rigid structure are fabricated from a single piece of material.
2. The apparatus of claim 1 , wherein the beam member extend from the rigid structure in a cantilevered manner.
3. The apparatus of claim 2 , wherein the beam member includes a first end and a second end.
4. The apparatus of claim 3 , wherein said first portion of the beam member connected with the rigid structure is the first end.
5. The apparatus of claim 3 , wherein the proof mass is connected with the second end of the beam member.
6. The apparatus of claim 1 , further comprising an electromechanical transducer coupled with the resonator and configured to convert vibratory energy of the resonator to electrical energy.
7. The apparatus of claim 6 , wherein the electromechanical transducer comprises a piezoelectric element.
8. The apparatus of claim 1 , wherein the beam member includes a first end and a second end, the first end comprising said first portion of the beam spring.
9. The apparatus of claim 8 , wherein the first end has a thicker cross-section and higher stiffness than the second end.
10. The apparatus of claim 6 , further comprising an electrical circuit, the circuit being collocated with the energy harvester transducer in a single housing.
11. The apparatus of claim 1 , further comprising a mounting surface configured to interface with a host structure.
12. The apparatus of claim 11 , wherein the resonator is configured such that the fundamental resonant direction of motion of the proof mass is perpendicular to the mounting surface.
13. The apparatus of claim 1 , wherein the proof mass accounts for a majority of the total mass and/or total volume of the energy harvester.
14. The apparatus of claim 1 , wherein the proof mass is configured with receptacles to accept additional mass for frequency tuning of the resonator.
15. The apparatus of claim 1 , further comprising at least one mounting member configured to fasten the apparatus to a host structure.
16. The apparatus of claim 15 , wherein the proof mass has a center gravity centered over the at least one mounting member.