energy harvesting systems - psma · outline 2 in this presentation we will discuss specific designs...

11

Energy Harvesting Systems

Heath [email protected]

Department of EECSUni ersit of Michigan Ann Arbor

11University of Michigan 111

University of Michigan, Ann Arbor

2Outline In this presentation we will discuss specific designs of energy In this presentation we will discuss specific designs of energy

harvesting systems for two applications:

Intraocular pressure sensor for monitoring internal eye pressure Gregory Chen, Hassan Ghaed, Razi-ulHaque, Michael Wieckowski,

YejoongKim, GyouhoKim, David Fick, DaeyeonKim, MingooSeok, Kensall Wise, David Blaauw, Dennis Sylvester (University of Michigan)

Energy harvesting backpack for powering military radios in the fieldfield Aaron Stein, Heath Hofmann (University of Michigan) Lawrence Rome (University of Pennsylvania, LightningPacks)


Cheng Luo, Guanghui Wang (Penn State University)

3Continuous IOP Monitoring

Optic NerveIris

Cornea

AnteriorChamber

High Intraocular Pressure

Retina

Lens

Implant G Location Glaucoma Second leading cause of blindness affects 60 million people Progress checked by measuring intraocular pressure Progress checked by measuring intraocular pressure

Continuous monitoring with an implanted microsystem Gives doctors a more complete view of disease


Gives doctors a more complete view of disease Faster response time for tailoring treatments

4Intraocular Pressure Monitor

Continuously monitors IOP Continuously monitors IOP Processes and stores medical information Wirelessly transmits data to an external wand


Wirelessly transmits data to an external wand Harvests solar energy to autonomously power circuits

5Intraocular Pressure Monitor

TRx Solar Cells

CDCμP + SRAMμ

PMU

Battery

0.5 mm

2 0

Housing

Pressure Sensor

Two integrated circuit chips

2.0 mm

1.5 mm

Two integrated circuit chips 1mm2 1μAh thin-film solid-state Lithium battery Assembled in a glass housing with pressure sensor (Razi)


Assembled in a glass housing with pressure sensor (Razi) Connected using wire-bonds and through-glass vias (Razi)

6IOP Monitor Block DiagramTop ChipTop Chip

3

Top Power

Management Unit

WirelessTransceiver

Top WakeupController

3

BottomPower

Management

Bottom Wakeup

Controller

Processor Capacitance to Digital ConverterSRAM

Thin-film

Unit

Bottom Chip

Controller ConverterSRAM

Solid-StateLi Battery

CapacitiveBiocompatible Housing

Cross sectional view of microsystem

CapacitivePressureSensor


Cross sectional view of microsystem

7Power Delivery and Management Battery powers CDC and wireless TRx Battery powers CDC and wireless TRx Isolated local TRx power supply prevents catastrophic VDD drop CDC and TRx designed with high-VTH thick-tOX IO devices andCDC and TRx designed with high VTH thick tOX IO devices and

no bias currents for low leakage during standby mode


8Power Delivery and Management 8:1 Switch Cap Voltage Regulator (SCVR) delivers 0 45 V 8:1 Switch Cap Voltage Regulator (SCVR) delivers 0.45 V µP is power gated in standby mode and uses logic devices SRAM and WUC use IO devices for low standby leakageSRAM and WUC use IO devices for low standby leakage SCVR clock is reduced to 50 Hz clock in standby mode


9Power Delivery and Management Solar cell connected when open circuit V exceeds V Solar cell connected when open circuit VSOLAR exceeds V0P45

Check voltage on solar cell with small replica Compare using clocked variable offset comparatorCompare using clocked variable offset comparator

SCVR up-converts solar energy to recharge the battery


10Power Sources30 I 26 A/ 2

15

20

25

30

P = 13.7W/mm2

= 5.48%

A/m

m2

ISC = 26A/mm2

10

15

W/m

m2

0

5

10

15

VOC = 0.54V

Cur

rent

,

0

5

Pow

er,

0.0 0.1 0.2 0.3 0.4 0.5 0.60

Voltage, V

0

0 07 mm2 solar cell Cymbet thin film Li battery 0.07 mm solar cell 0.18 μm CMOS No post-processing

Cymbet thin-film Li battery 1 mm2 custom size 1μAh capacity


No post processing 5% solar efficiency

1μAh capacity 40μW peak power

118:1 Ladder SCVR

0 32 2 ith 35 F MOS fi d 45 F MIM fl i 0.32 mm2 with 35 pF MOS fixed caps, 45 pF MIM flying caps Low switching losses: 1.8 V clocks with level converters Low conduction losses: High switch overdrive and low currents


Low conduction losses: High switch overdrive and low currents Low leakage: Minimum-sized IO power switches

12SCVR Measurements

70

80%

60

ency

,

75% efficiency

40

50

Effi

cie 75% efficiency

30

75% efficiency with 100 nW processor load in active mode

20 40 60 80 100 120 140 160Load Power, nW


75% efficiency with 100 nW processor load in active mode 40% efficiency with 72 pW load in standby mode

13Energy-autonomous Operation0 2 Active

-0.2

0.0

0.2

BA

TT,

ASleep

0 200 400 600 800 1000-0.6

-0.4

3 61

I B

Sl

3 583.593.603.61 Sleep

BAT

T, V

0 200 400 600 800 10003.563.573.58

Active

VB

Time, s Measured battery voltage and current Energy consumed by microsystem is recharged in sleep mode


Energy consumed by microsystem is recharged in sleep mode No net drain of battery energy

14Energy-autonomous Operation16k

12k

14k

16kIndoor Sunny

er D

ay Cloudy

6k

8k

10k 1 per4 mins

3 perminute 10 per minute

emen

ts p

e

0

2k

4k

Mea

sure

0.00 0.01 0.02 0.03

0

Light, suns AM 1.5

Mode Harvesting Discharge RateOne measurement every hour No 20%/year

Idle lifetime No 11%/year


Idle lifetime No 11%/yearUp to 10 measurements per minute Yes 0%/year

15Energy Harvesting BackpackMarines carry large

weightsModern warfare requires electrical energy (batteries)

Large forces cause reduced mobility and

endurance

Disposable batteries add considerable weight (up to 20 lbs) to already heavy

packs (> 80 lbs)

Large forces result in acute and long term

musculoskeletal

packs (> 80 lbs)

Dependence on disposable batteries limit musculoskeletal

injuries

Affects force

pmission duration.

Disposable batteries are Affects force readiness and

retentionvery costly and difficult to

supply and dispose of


16Solution Make the problem work for you!

F 40k * 400 N

Work generated with an 80lb load

Force=40kg*g= 400 NewtonWork=400N*0.05m= 20 JoulesPower=20J* 2step/s=40 Watts


17Energy Harvesting Backpack

Load of backpack attached to f i iframe via springs

Resulting spring-mass resonance frequency tuned to human walking gait

Resulting large displacements of load used to generate Image Copyright 2005 AAAS


electricity • Resonant motion of backpack also has ergonomic benefits

18Energy Harvesting Backpack Circuit

Goal of circuit: to emulate generator load which maximizes


Goal of circuit: to emulate generator load which maximizes efficiency of energy transfer to battery, load

19Resistance-Emulating SEPIC Converter

Buck-boost converter topology Inductor at input allows regulation of input current Input current is regulated to be proportional to input

voltage, Con erter em lates a resistance R at its inp t


Converter emulates a resistance R at its input terminals

20Effects of Resistive Load Emulation Resistive load at Resistive load at

terminals of generator results in a linearresults in a linear damping of the mechanical dynamics. Equivalent mechanical

damping constant bdetermined from resistance R, t / d t ttorque/speed constant ctw of generator, and gearing constant grp of


gearing constant grp of rack-and-pinion gear.

21System Response Resistance R is chosen Mechanical Dynamics: Resistance R is chosen

to satisfy a combination of requirements:

Mechanical Dynamics:

of requirements: Energy harvestingHarvest sufficient power

ErgonomicConstrain displacement of

backpack to a level that is Power harvested at backpack to a level that is acceptable to wearer

Damping

Power harvested at resonant frequency:

Reduction of quality factor Q of mechanical resonant system makes power


harvesting less sensitive to excitation frequency

22Energy Harvesting Backpack Circuit


23Energy Harvesting Circuit Waveforms

Output waveforms, top to bottom:Input voltage and current

waveforms

Output waveforms, top to bottom: battery voltage, battery current,

regulation voltage (with 10Ω load)


G. Wang, C. Luo, L. Rome, and H. Hofmann. “Power Electronic Circuitry for Energy Harvesting Backpack “, ECCE 2009.

24Electricity Generation During Walking

ut (W

)20 2080 lbs

er O

utpu

15 1560 lbs

cal P

owe

5

10

5

1040 lbs

Elec

tric

0

5

0

5

Walking Speed (MPH)2.5 3.0 3.5 4.0


25Questions?


energy harvesting systems - psma · outline 2 in this presentation we will discuss specific designs...

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