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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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