![Page 1: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/1.jpg)
P. Mitcheson, Nov. 2008P. D. Mitcheson, IOM, March 2009
Energy Harvesting for Pervasive Sensing
Paul D. Mitcheson, Eric M. Yeatman
Department of Electronic & Electrical EngineeringImperial College London
![Page 2: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/2.jpg)
P. Mitcheson, Nov. 2008P. D. Mitcheson, IOM, March 2009
Energy Harvesting: what is it?
• Taking useful advantage of power sources already present in the local environment
• This energy would otherwise be unused or wasted as e.g. heat
• “local” being local to the powered device or system
• Extracted power levels generally not limited by source, but by size and effectiveness of generator (“harvester”)
![Page 3: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/3.jpg)
P. Mitcheson, Nov. 2008P. D. Mitcheson, IOM, March 2009
Energy Harvesting: what is it for?
• Normally not as a primary source of power, but for applications where mains power is not suitable, because of:
• Installation cost
• Mobility
• Remote/inaccessible/hostile location
• Usual alternative is batteries:
• Avoid replacement/recharging
• Avoid waste from used batteries
![Page 4: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/4.jpg)
P. Mitcheson, Nov. 2008P. D. Mitcheson, IOM, March 2009
How Much Power?
World electrical generation capacity 4 terawatts
Power station 1 gigawatt
House 10 kilowatts
Person, lightbulb 100 watts
Laptop, heart 10 watts
Cellphone power usage 1 watt
Wristwatch, sensor node 1 microwatt
Transmitted Cellphone signal 1 nanowatt
![Page 5: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/5.jpg)
P. Mitcheson, Nov. 2008P. D. Mitcheson, IOM, March 2009
Cost example:
• Mains electricity: consumer price 15¢ / kWhr
• Alkaline AA battery: 1 € / 3 Whr
• Factor of 2,000
![Page 6: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/6.jpg)
P. Mitcheson, Nov. 2008P. D. Mitcheson, IOM, March 2009
Energy Harvesting Applications
• Key application is wireless sensor networks
• Sensors can be very low power
• Small size often important
• Minimal maintenance crucial if many nodes
• Implementation of WSNs could lead to higher energy efficiency of buildings etc
![Page 7: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/7.jpg)
P. Mitcheson, Nov. 2008P. D. Mitcheson, IOM, March 2009
1 cc wireless sensor node, IMEC
![Page 8: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/8.jpg)
P. Mitcheson, Nov. 2008P. D. Mitcheson, IOM, March 2009
Sensor Node Power Requirements – How much power does our harvester
need to supply?
•Sensing Element
•Signal Conditioning Electronics
•Data Transmission
![Page 9: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/9.jpg)
P. Mitcheson, Nov. 2008P. D. Mitcheson, IOM, March 2009
Sensing Element
Simple signals - temperature, pressure, motion – require electrical power above thermal noise limit.
NT 10-20 W/Hz
For most applications, this is negligible
![Page 10: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/10.jpg)
P. Mitcheson, Nov. 2008P. D. Mitcheson, IOM, March 2009
Signal Conditioning
Likely principal function: A/D Converter
Recent results: Sauerbrey et al., Infineon (’03)
Power < 1 W possible for low sample rates!
![Page 11: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/11.jpg)
P. Mitcheson, Nov. 2008P. D. Mitcheson, IOM, March 2009
Data Transmission: Required Power
Conclusions:
Power independent of bit-rate for low bit-rate
-30 dBm (1 W) feasible for room-scale transmission range
1000100101
50
40
30
20
10
0
-10
-20
-30
-40
-50
Range (m)
Tra
ns
mit
Po
we
r (d
Bm
)
Ideal free-space propagation
Typical indoorLoss exponent(3.5)
Figure: F. Martin, Motorola
![Page 12: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/12.jpg)
P. Mitcheson, Nov. 2008P. D. Mitcheson, IOM, March 2009
Estimated Total Power Needs
• Peak power 1 – 100 uW
• Average power can be below 1 uW
Batteries: Present Capability
•10 Wyr for 1 cm3 battery feasible
•Not easy to beat!
•Useful energy reservoir for energy harvesting
![Page 13: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/13.jpg)
P. Mitcheson, Nov. 2008
Fuel-Based Power Sources
• Energy density much higher than for batteries, 10 kJ/ cm3
• Technology immature, fuel cells most promising
Micro fuel cell, Yen et al.Fraunhofer Inst.
![Page 14: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/14.jpg)
P. Mitcheson, Nov. 2008
Energy Source Conversion Mechanism
Light
Ambient light, such as sunlight Solar Cells
Thermal
Temperature gradientsThermoelectric or Heat Engine
Magnetic and Electro-magnetic
Electro-magnetic waves
Magnetic induction (induction loop)
Antennas
Kinetic
Volume flow (liquids or gases)
Movement and vibration
Magnetic (induction)
Piezoelectric
Electrostatic
Energy Scavenging : Sources
![Page 15: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/15.jpg)
P. Mitcheson, Nov. 2008
Solar Cells
• highly developed
• suited to integration
• high power density possible:
100 mW/cm2 (strong sunlight)
• but not common:
100 W/cm2 (office)
• Need to be exposed, and oriented correctly
Solar cell for Berkeley Pico-Radio
![Page 16: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/16.jpg)
P. Mitcheson, Nov. 2008
Solar Cells in Energy Harvesting Applications:
• Cost not the main issue
• Availability of light is key
![Page 17: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/17.jpg)
P. Mitcheson, Nov. 2008
Thermal
• need reasonable temperature difference (5 – 10C) in short distance
• ADS device 10 W for 5C
• even small T hard to achieve
Heat engine, Whalen et al,
Applied Digital Solutions
![Page 18: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/18.jpg)
P. Mitcheson, Nov. 2008
Seiko Thermic (no longer in production)
![Page 19: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/19.jpg)
P. Mitcheson, Nov. 2008
Ambient Electromagnetic Radiation
Graph: Mantiply et al.
10 V/m needed for reasonable power: not generally available
![Page 20: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/20.jpg)
P. Mitcheson, Nov. 2008P. D. Mitcheson, IOM, March 2009
Motion Energy Scavenging
• Direct force devices
• Inertial devices
![Page 21: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/21.jpg)
P. Mitcheson, Nov. 2008P. D. Mitcheson, IOM, March 2009
Direct Force: Heel Strike
Heel strike generator: Paradiso et al, MIT
![Page 22: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/22.jpg)
P. Mitcheson, Nov. 2008P. D. Mitcheson, IOM, March 2009
Direct Force: larger scale
East Japan Railway Co.
• Energy harvesting ticket gates
![Page 23: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/23.jpg)
P. Mitcheson, Nov. 2008P. D. Mitcheson, IOM, March 2009
m
z o
y = Y cos( t)o
dam per im plem ents energy conversion
Inertial Harvesters• Mass mounted on a spring within a frame
• Frame attached to moving “host” (person, machine…)
• Host motion vibrates internal mass
• Internal transducer extracts power
![Page 24: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/24.jpg)
P. Mitcheson, Nov. 2008P. D. Mitcheson, IOM, March 2009
m
z o
y = Y cos( t)o
dam per im plem ents energy conversion
• Peak force on proof mass F = ma = m2Yo
• Damper force < F or no movement
• Maximum work per transit W = Fzo = m2Yozo
• Maximum power P = 2W/T = m3Yozo/
Available Power from Inertial Harvesters
![Page 25: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/25.jpg)
P. Mitcheson, Nov. 2008P. D. Mitcheson, IOM, March 2009
0.1
1
10
100
1 10 100
frequency (Hz)
pow
er (
uW)
How much power is this?
Plot assumes:
• Si proof mass (higher densities possible)
• max source acceleration 1g (determines Yo for any f)
10 x 10 x 2 mm
3 x 3 x 0.6 mm
![Page 26: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/26.jpg)
P. Mitcheson, Nov. 2008
Achievable Power Relative to Applications
0.001
0.01
0.1
1
10
100
1000
10000
100000
0.01 0.1 1 10 100 1000
volume (cc)
pow
er (
mW
)
f = 1 Hz
f = 10 Hz
Sensor node
watch
cellphone
laptop
Plot assumes:
• proof mass 10 g/cc
• source acceleration 1g
![Page 27: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/27.jpg)
P. Mitcheson, Nov. 2008P. D. Mitcheson, IOM, March 2009
Implementation Issues: Transduction Mechanism
Piezoelectric?• Difficult integration of piezo material• Reasonable voltage levels easy to achieve• Suitable for miniaturisation
![Page 28: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/28.jpg)
P. Mitcheson, Nov. 2008P. D. Mitcheson, IOM, March 2009
Typical Inertial Generators
Piezoelectric
Ferro solutionsWright et al, Berkeley
![Page 29: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/29.jpg)
P. Mitcheson, Nov. 2008P. D. Mitcheson, IOM, March 2009
Implementation Issues: Transduction Mechanism
Electromagnetic?• Dominant method for large scale conversion• Needs high d/dt to get damper force ( = flux)• d/dt = (d/dz )(dz/dt )• Low frequency (low dz/dt) needs very high flux gradient• Hard to get enough voltage in small device (coil turns)• Efficiency issues (coil current)
Variant: magnetostrictive
![Page 30: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/30.jpg)
P. Mitcheson, Nov. 2008P. D. Mitcheson, IOM, March 2009
Typical Inertial Generators
Magnetic
Southampton U. CUHK
![Page 31: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/31.jpg)
P. Mitcheson, Nov. 2008P. D. Mitcheson, IOM, March 2009
Implementation Issues: Mechanism
Electrostatic?• Simple implementation, no field gradient problem• Suitable for small size scale• Damping force can be varied via applied voltage• But needs priming voltage (or electret)
![Page 32: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/32.jpg)
P. Mitcheson, Nov. 2008
Typical Approach: Constant Charge
Input phase Output phase
inputinputVCQ outputoutputVCQ
inputoutput
inputouput V
C
CV
222
2
1
2
1
2
1outputoutputinputinputouputoutput VCVCVCE
inputoutput VV
![Page 33: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/33.jpg)
P. Mitcheson, Nov. 2008
Assembled generator Detail of deep-etched moving plate
Prototype MEMS Device
![Page 34: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/34.jpg)
P. Mitcheson, Nov. 2008P. D. Mitcheson, IOM, March 2009
Device Operation
po
siti
on
tim e
tim e
trajectory of m oving plate
vo
ltag
e
t2 t3t1
voltage on moving plate
upperlim it
lower lim it
moving plate/ proof mass
fixed plate
discharge contact
charging contact
Output > 2 W
![Page 35: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/35.jpg)
P. Mitcheson, Nov. 2008P. D. Mitcheson, IOM, March 2009
Other Options: Rotating Mass
Example : Seiko Kinetic
![Page 36: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/36.jpg)
P. Mitcheson, Nov. 2008P. D. Mitcheson, IOM, March 2009
Large Inertial Generators
Backpack: U Penn
• 7 watts!
![Page 37: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/37.jpg)
P. Mitcheson, Nov. 2008P. D. Mitcheson, IOM, March 2009
Pervasive Sensing for Energy Generation
![Page 38: P. Mitcheson, Nov. 2008 P. D. Mitcheson, IOM, March 2009 Energy Harvesting for Pervasive Sensing Paul D. Mitcheson, Eric M. Yeatman Department of Electronic](https://reader035.vdocuments.mx/reader035/viewer/2022070415/5697bfa01a28abf838c95575/html5/thumbnails/38.jpg)
P. Mitcheson, Nov. 2008P. D. Mitcheson, IOM, March 2009
Conclusions
• Power levels in the microwatt range are enough for many wireless sensor nodes
• Small energy harvesters can achieve these levels
• Help enable pervasive sensing by eliminating maintenance burden
Contact: [email protected]
Review Paper: Mitcheson, Yeatman et al., “Energy Harvesting From Human and Machine Motion for Wireless Electronic Devices”, Proceedings of the IEEE 96(9), 1457-1486 (1998).