1. Power from motion - alternative energy
for microelectronics
Pit Pillatsch
Research Postgraduate
Imperial College London
Supervisors: Prof. E.M. Yeatman, Prof. A.S. Holmes
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2. Contents
Introduction
Piezoelectric Impulse Excited Generator
Experimental Set-Up
Results
Comparisons
Key advantages
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3. Energy Harvesting
Solar: very high achievable power outputs (1500 μW/cm2), however
only outdoors
Thermal: limited by the Carnot efficiency, which is dependent on
the temperature difference, commercially available for industrial
applications
Radio Frequency: in use for wireless power transfer with a
dedicated source, tissue attenuation can be high
Inertial Energy: available as vibrations, fluid flows, etc., highly
dependent on external excitation, commercially available for
industrial applications
With an increased number of wearable and implantable body sensors,
power supply needs to be addressed
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4. Inertial Devices
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5. Rotational Devices
Operation under any orientation,
independent of gravity
Rotational and linear external
acceleration due to eccentric mass
No inherent displacement limit for the
proof mass travel, i.e. continuous
rotation
Power limit in a purely rotational case:
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6. Piezoelectric Impulse Excited Generator
Plucking of a piezoelectric beam
Beam vibration at natural frequency
enhances electro-mechanical
coupling over large frequency range
No gears necessary
No mechanical contact due to
magnetic coupling, good for long
lifetime
Small number of parts, reduced cost
Convenient for miniaturization
Suitable for wearable and
implantable applications
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7. Experimental Setup
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8. Comparisons
Seiko Kinetic watch: (-) many moving parts,
(-) prone to wear, (-) electromagnetic means lower
voltages
Mitcheson 2004: electrostatic, (-) voltages are
very high , (-) operation only at resonance
frequency and in one linear direction
Pillatsch 2011: piezoelectric, (+) large frequency
range but only one linear direction, (-) gravity
can cause difficulties depending on orientation
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9. Comparisons
Pozzi 2011: piezoelectric, (+) large bandwidth,
(-) only one rotational direction, (-) needs two
attachment points, (-) direct impact on piezo
when plucking can damage the brittle material
Gu 2011: (-) only one linear
direction, (-) direct impact on piezo
can damage the brittle material
Galchev 2010: (-) only one linear direction
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10. Key Advantages
Taking the best from all the other devices and getting rid of limitations
No mechanical impact/contact on piezo when plucking
Piezo allows very useful voltages
Large frequency range
Only one moving part
Only one attachment point
Operation under linear and rotational motion
Independent of orientation and gravity
Current status:
Maximal power output of 2.6 μW at 1.45 Vrms
Best effectiveness of conversion currently around 5.8%
Future work on optimal parameters for magnetic beam plucking
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