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AmbiMax: Autonomous Energy Harvesting
Platform for Multi-Supply Wireless Sensor
Nodes
Chulsung Park and Pai H. Chou – University of California, Irvine
IEEE SECON 2006
Presenter : Nikos Larisis
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Contents
• Introduction
• System overview
• Operation analysis
• Experimental evaluation
• Conclusion
• Questions
Order of matters addressed
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Introduction
• Empedocles (Ἐμπεδοκλῆς)
Back, back, background theory
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Introduction
• Empedocles (Ἐμπεδοκλῆς) (490 - 430 BC)
Back, back, background theory
• pre-Socratic philosopher from
Agrigentum (Sicily).
• Originator of the cosmogenic theory
of the four classical elements.
fire, air, water, earth(πσρ, αήρ, ύδωρ, γή)
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Introduction
• Energy harvesting
• Definition
• Motivation
• Devices/Sources
• Thermoelectric generator (πσρ)
• Micro wind turbine (αήρ)
• “Eels” (ύδωρ)
• Tidal power generator (γή)
Background theory
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Introduction
• Beyond Empedocles scope…
• Photovoltaic (solar power)
• Piezoelectric devices (pressure, vibration)
• Electromagnetic generator (EM movement)
• p-RFID (ambient radiation)
• many more beyond our scope…
Background theory
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Introduction
• Importance
• Reducing energy
• Energy systems
The “WSN case”
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Introduction
• Importance
• Reducing energy
• Energy systems
• AmbiMax
The “WSN case”
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System overview
• Novel notion
• Maximum Power Point tracking
• Autonomy of harvesting control
• Expandability
Introduction
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System overview
• Architecure
• EH subsystem
• RCA subsystem
• CC subsystem
• Powering principle
Introduction
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System overview
• Solar panel
Solar Panel with Light Sensor
• Solar World’s solar module (4-40-100)
with max: Vout=4V, Iout=100mA
Ambient power sources
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System overview
• Wind generator
Wind Generator with Rotor Speed Sensor
• Joiniff’s wind generator:
500 mW @ 2000 rpm
Ambient power sources
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Operation analysis
• Ambient power source
• PWM switching regulator
- Charge even if Vcap>Voc until batter fully charged
- Emulates diode function preventing….(?)
A. Energy harvesting susystem
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Operation analysis
• MPPT circuitry
1. PWM switching regulator – detects the MPP
2. Comparator – controls the operation the regulator
if Vambi < Vsensor - Vhysterisis then regulator=OFF
if Vambi > Vsensor + Vhysterisis then regulator=ON
A. Energy harvesting susystem
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Operation analysis
• Composition
• Benefits
• volatile ambient power
• main advantage (?)
• avoid battery aging
B. Reservoir capacitor array subsystem
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Operation analysis
• Destination
I. Powering (threshold detector)
if VRCA > Vth then E=RCA
if VRCA < Vth then E=battery
II. Charging (window comparator)
when VRCA > Vth1 && Vbat < FULL
(Vth = 2.7V, Vth1 = 3.4V)
C. Control and charger subsystem
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Experimental evaluation
1. Indoors
A. Experimental setup
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Experimental evaluation
2. Outdoors
A. Experimental setup
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Experimental evaluation
AmbiMax vs Prometheus
• How much time until Vcap=3V
• How much energy harvested for Δt=20sec
B. Solar harvesting efficiency
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Experimental evaluationC. Experimental data on Eco nodes
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Conclusion
+ analog circuitry (autonomy/liberate MCU)
+ multi-supply harvesting
+ MPPT
+ outperforming the “classics”
+ comparing in practice the rivals
- outdoor measurement
- hardware failures/inconsistencies
- cost vs form factor
Pro et contra
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