Energy Scavenging from Vibrations – Summary Lecture

Problem Review

Energy Harvesting Wind Water Solar Temperature Vibration

Energy Scavenging through Vibration

Piezoelectric Piezoelectricity is the ability of certain materials to produce a voltage when subjected to mechanical stress. Piezoelectric materials also show the opposite effect, where application of an electrical field creates mechanical stress (size modification) in the crystal.

Piezoelectric Frequency Response

Components Provided

Methods for Solving the Problem

Rotary-to-Reciprocating Motion Continuous rotary motion can be generated using motors. Conversion between rotary motion to reciprocating motion can be achieved using an asymmetric cam .

Rectifying Circuit A rectifier circuit can be used to convert an AC electric signal to a DC signal. A four diode bridge can be used as a rectifier.

Capacitor A capacitor is a device that can store electrical charge. In a capacitor equal amounts of positive and negative charges are stored on two separate conductors.

Charging Circuit A super capacitor (0.47F 5.5v) is used to store electric charge. A Zener diode (BZX85-C5V6) is used to protect the super capacitor .

Engineering Principles and Concepts

DC Motor (Speed vs. Voltage) The induced force (F) is perpendicular to the direction of the current (I) and of the electromagnetic flux (B). The speed of the motor is approximately proportional to the input voltage. V e R

Gear Ratio A B driving driven

Gear Train Simple gear train Compound gear train driving idler driven B C A B C D

AC vs. DC In alternating current (AC) the movement (or flow) of electric charge periodically reverses direction. In direct current (DC) the movement of electric charge doesn’t change direction.

Diode Diodes allow the electric current to flow in only one direction. + v - i v i

4 Diode Bridge

The Meaning of Frequency Frequency means the number of times something occurs within a given time period. Frequency for waves is usually measured per second. The unit for frequency is Hertz (Hz), which means per second.

Spectrum Decomposition

Design Trade-offs Two types of testing stations that generate vibrations for the piezo buzzer are designed, with/without a gearbox . The gearbox provides the flexibility to tune the vibration frequency to match the resonant frequency of the piezo buzzer. The more complex the design is, the longer the time and higher the costs it takes to implement it, but the more chance that it should provide better results.

Engineering Design Process Identify the need or problem Research the need or problem Modify to improve the design if needed Develop possible solutions Test and evaluate the prototype Select the best solutions Construct a prototype

Design of a Lateral Saddle1 Gathering information Identify constraints and design variables Preliminary design 1 Freshman Engineering Project. Department of Civil and Environmental Engineering. Polytechnic University of Puerto Rico

Design of Lateral Saddle (cont.) Evaluation and selection of preferred solution Preparation of plan and specification Implementation of the design Test and evaluation

Reflective Problem Solving Strategies define the problem Test, evaluate, and improve the design analyze the problem reflect identify design variables Implement the design propose solutions

Societal Impact Energy harvesting or the process of acquiring energy from the surrounding environment has been a continuous human endeavor throughout history.

Societal Impact Piezoelectric materials, such as the lead zirconate titanate (PZT), are great candidates for energy harvesting using vibrations from the surrounding environment.

Self-powered Wireless Corrosion Sensor Application Areas Wireless corrosion monitoring systems Biomechanical Energy Harvester vehicle vibrating structure frequency Accel. PSD mechanical energy Self-powered Wireless Corrosion Sensor low power wireless transceiver corrosion sensor energy harvester

References M. Raju, “Energy Harvesting, ULP meets energy harvesting: A game-changing combination for design engineers,” Texas Instrument White Paper, Nov. 2008 R.J.M. Vullers, V. Leonov, T. Sterken, A. Schmitz, “Energy Scavengers For Wireless Intelligent Microsystems,” Special Report in Microsystems & Nanosystems, OnBoard Technology, June 2006 Imec, “Design for analog and RF technologies and systems,” www.imec.be Imec, “Micropower generation and storage,” www.imec.be F. Whetten, “Energy Harvesting Sensor Systems – A Proposed Application for 802.15.4f, ” DOC: IEEE802.15-09/0074-00-004f C. Cossio, “Harvest energy using a piezoelectric buzzer,” EDN, pg.94-96, March 20, 2008