energy harvesting systems - psma · outline 2 in this presentation we will discuss specific designs...
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11
Energy Harvesting Systems
Heath [email protected]
Department of EECSUni ersit of Michigan Ann Arbor
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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)
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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
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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
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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)
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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electricity • Resonant motion of backpack also has ergonomic benefits
18Energy Harvesting Backpack Circuit
Goal of circuit: to emulate generator load which maximizes
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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
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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
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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
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harvesting less sensitive to excitation frequency
22Energy Harvesting Backpack Circuit
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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)
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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
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25Questions?
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