Energy harvesting device

• US 8,421,313 B2
• Filed: 01/24/2012
• Issued: 04/16/2013
• Est. Priority Date: 01/29/2007
• Status: Active Grant

• Current Assignee: Drexel University
• Original Assignee: Drexel University
• Inventors: Shih, Wei-Heng, Shih, Wan Y., Yegingil, Hakki
• Primary Examiner(s): DOUGHERTY, THOMAS M
• Application Number:
  US13/357,291
• Publication Number:
  US 20120119625A1
• Time in Patent Office: 448 Days
• Field of Search: 310330-333, 310/339
• US Class Current: 310/339
• CPC Class Codes: H02N 2/188 adapted for resonant operation
• CPC Class Codes: H10N 30/306 Cantilevers
• CPC Class Codes: H10N 30/8548 Lead-based oxides

Abstract

A piezoelectric energy harvesting device (PEHD) comprising a driving element, conducting element, piezoelectric layer and non-piezoelectric layer capable of converting ambient mechanical energy into electrical energy. The piezoelectric layer may be constructed from PMN-PT or PZT having a thickness of about 1-150 μm. The PEHD may be used to generate about 1 W. The harvested energy may be stored and used to power microelectronic devices and rechargeable battery technologies.

Claims

1. A piezoelectric energy harvesting system comprising:

a cantilever, wherein the cantilever comprises

a conducting element,

at least a first piezoelectric layer constructed from a freestanding piezoelectric film and

a non-piezoelectric layer bound to said at least a first piezoelectric layer,

wherein said piezoelectric layer has a thickness of about 1 μ

m-about 150 μ

m, and

an electrical connection to a device which stores or uses energy harvested by the piezoelectric energy harvesting system.

2. The system of claim 1, wherein said piezoelectric layer and non-piezoelectric layer have different lengths.

3. The system of claim 1, wherein said piezoelectric layer has a thickness of about 8 μ

m-about 127 μ

m.

4. The system of claim 1, wherein said piezoelectric layer is selected from the group consisting of PZT and PMN-PT.

5. The system of claim 1, wherein said first piezoelectric layer has a different length from the non-piezoelectric layer.

6. The system of claim 1, wherein a ratio of a thickness of the piezoelectric layer to a thickness of the non-piezoelectric layer is from about 0.04 to about 12.5.

7. The system of claim 1, wherein the freestanding piezoelectric film is made by a tape casting method.

8. The system of claim 1, wherein the freestanding film has a piezoelectric coefficient −

d₃₁ of at least about 2000 pm/V at E=about 10 kV/cm.

9. The system of claim 8, wherein the dielectric constant of the freestanding film decreases with increasing electric field.

10. The system of claim 9, wherein the freestanding film has a strain of at least 0.3% measured under an applied electric field of from about 8 kV/cm to about 12 kV/cm.

11. The system of claim 9, wherein the freestanding film is unpoled and has a strain of at least 3% measured at an applied electric field of about 10 kV/cm.

12. The system of claim 1, comprising a plurality of cantilevers to form an array, and wherein each said cantilever is electrically connected to a device for storing or using electrical energy.

15. The system of claim 1, wherein the freestanding film has a piezoelectric coefficient −

g₃₁ of at least about 0.137 V/m/N at an applied electric field of about 10 kV/cm.

16. The system of claim 1, wherein a ratio of a thickness of the piezoelectric layer to a thickness of the non-piezoelectric layer is from about 0.05 to about 6.25.

13. A method harvesting energy harvesting comprising the steps of:

a. exposing a piezoelectric cantilever system comprising

at least one piezoelectric cantilever including a driving element,

at least a first piezoelectric layer having a thickness of about 1 μ

m-about 150 μ

m, wherein the first piezoelectric layer is constructed from a freestanding piezoelectric film,

a conductive element, and

a non-piezoelectric layer,

to a mechanical or vibrational force,

b. harvesting electrical energy generated by conversion of said mechanical or vibrational energy into electrical energy, and

c. transporting the harvested electrical energy to a device which is capable of consuming or storing the harvested electrical energy.

14. The method of claim 13, wherein the harvested electrical energy is stored in the device.

17. The method of claim 13, wherein in said exposing step the piezoelectric cantilever is exposed to one of:

a force of nature, human motion and machinery.

18. The method of claim 13, wherein the piezoelectric cantilever is operated at a resonance frequency of the first piezoelectric layer.