\'Realization of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems_Tan Yen Kheng

1. Realization of Energy Harvesting
Wireless Sensor Network (EH-WSN)
(EH-
- with special focus on the energy
harvesting systems
Presented by
Yen Kheng Tan and A/Professor S.K. Panda
Department of Electrical & Computer Engineering
National University of Singapore (NUS)
tanyenkheng@nus.edu.sg
Research Motivations
Ubiquitous/Pervasive computing (Invisible/Disappearing)
– As people find more ways to incorporate these inexpensive,
p p y p p ,
flexible and infinitely customizable devices into their lives, the
computers themselves will gradually "disappear" into the fabric
of our lives (http://www.microsoft.com/presspass/ofnote/11-02worldin2003.mspx)
– “Will we be surrounded by computers by 2010? Yes, but we
won’t know it.” Bill Gates in ‘The Economist’, 2002
Military Environment Bio-medical Healthcare
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
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2. Research Motivations (cont’d)
Energy Harvesting/Scavenging Technology
– “The pervasiveness and near-invisibility of computing will be
p y p g
helped along by new technologies such as … inductively
powered computers that rely on heat and motion from their
environment to run without batteries.”
Bill Gates in ‘The Economist’, 2002
– “The importance of energy harvesting has motivated the
German federal government to include the topic in its €500
million (about S$1 billion) research support program.”
EE Times article, 2007
Goal: To investigate energy harvesting technologies that can
power tiny pervasive computing devices indefinitely in a smart
environment
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
Architecture of Smart Environment
Reference: D.J. Cook and S.K. Das, ”Wireless Sensor Networks, Smart Environments: Technologies, Protocols
and Applications”, John Wiley, New York, 2004.
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
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3. Design Challenges in Conventional WSN
Sensor node has limited energy supply
Q Hard to replace/recharge nodes’ batteries once deployed, due to
- Number of nodes in network is high
- Deployed in large area and difficult locations like hostile
environments, forests, inside walls, etc
- Nodes are ad hoc deployed and distributed
- No human intervention to interrupt nodes’ operations
=> Restricted resources available for collecting and relaying data
Configure and/or reconfigure sensor nodes into network
Q Network and communication topology of WSN changes frequently
- Addition of more nodes, failure of nodes, etc
Tradeoff between Energy and Quality of Service
Q Limited finite energy and demand for QoS
=> Prolong network lifetime by sacrificing application requirements such
as delay, throughput, reliability, etc
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
Research Issues in WSN
Energy related matter in WSN
- Power management for sensor node
g
- Energy efficient protocols in medium access control (MAC) and
routing layers
Network performance
- Quality of Service (QoS) e.g. data throughput, reliability,
propagation delay, etc
- Network security
- Sensor network deployment
- Real-time location estimation
WSN performances highly dependent on energy supply
=> Higher performances demand more energy supply
=> Bottleneck of Conventional WSN is ENERGY
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
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4. Typical Power Consumption of a Wireless Sensor Node
Compare battery estimated life of a Crossbow sensor
node operating at 1 % and 4 % duty cycles
Duty cycle
=1%
Duty cycle = 4 %
Longer operational lifetime => Require more energy supply =>
Higher energy storage capacity => Larger battery size
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
Energy Harvesting in Wireless Sensor Network
Wireless Sensor Network (WSN) only
Energy Harvesting Wireless Sensor Network (EH-WSN)
Finite
Energy
Energy energy Sensor
manage-
Harvest source nodes
ment
-ing such as in WSN
circuit
batteries
EH + Batteries => prolong energy supply => sustainable
Batteries => finite energy supply => limited WSN lifetime
WSN lifetime
– Network failure occurs after some nodes go into idle state
– Nodes go into idle state after energyusing EH
Recharge batteries in sensor nodes supply exhausted
??? + Batteries => sustainable WSN lifetime$
– Prolong WSN operational lifetime or even infinite life span$
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
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5. Power Aware EH-WSN Considerations
Adapted from MIT, Chandrakasan et al.
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
Research Issues in EH-WSN
1. Quality of service (QoS) under constrained energy supply
– Trade-off between energy consumption in sensor node &
gy p
QoS in WSN
– Determine optimal operating point e.g. optimal sleep and
wakeup strategy => achieve highest system utility
2. Optimization of energy usage based on EH device
behaviour
– Harvested energy largely depend on ambient conditions
– Optimize energy usage to satisfy Q constraints under
p gy g y QoS
varying energy supply
3. Cross-layer optimization
– Energy optimization in WSN using EH in cross-layer fashion
e.g. energy-aware routing and MAC protocols
4. Integration with new wireless technologies
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
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6. Design and Development of EH-WSN
Objective: Integrate energy harvesting systems into
wireless sensor nodes target for specific applications
g p pp
– Investigate on various energy harvesting (EH) sources
– Model and characterize the performances of energy
harvesters
– Develop suitable power/energy management circuits
between energy harvester and load
– Validate EH sensor nodes in practical applications
p pp
Energy
Finite Power/
harvest
Energy energy Energy Sensor
-ing
harvest source manage- nodes in
sources
ers such as ment EH-WSN
i.e.
batteries circuits
wind
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
Energy Harvesting Sources and their Energy Harvesters
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
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7. Existing Research Works
EH-WSN research
– Indoor Solar EH (SEH) wireless sensor node for smart
environment
– Outdoor Solar EH for military portable computing system
– Vibration EH (VEH) wireless sensor node for condition
based maintenance of large equipment
– Thermal EH (TEH) from human warmth for wireless
body area network
– Wind EH (WEH) wireless sensor node for remote
sensing and management of disasters
Other energy related research
– Wireless energy transfer
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
Indoor SEH Wireless Sensor Node
Example of indoor testbed in
Cables
Pavoda
Issue on battery duration for
non–cabled nodes
→ even worst for large
numbers of nodes (100-1000)
Michele Zorzi, 2008
Introduce indoor solar energy
gy
harvesting for indoor nodes
Bulky size and heavy weight
Large area required by Solar panels
nonocrystaline solar panels
Dallas IEEE, 2007
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
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8. Indoor SEH Wireless Sensor Node (cont’d)
Resistance Emulation using DCM boost converter to
achieve MPPT during impedance matching
g p g
i1 (t ) Conversion ratio, M
Battery-powered
Ts Emulated Resistor, R e
+ 2
d (t )Ts V 1 + 1 + 4d 2 / K
sensor node v1 (t ) T M= =
i1 (t ) T = v1 (t )
2
s
s
2 Ts Vg
Indoor Solar 2L 2L V 1 + 1 + 4 R / Re
- Re (d ) = 2 = 2 f s =
powered sensor node d Ts d Vg 2
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
Indoor SEH Wireless Sensor Node (cont’d)
Voltage waveforms of DCM DC-DC boost converter
PFM from VCO
(C1)
Vsolar (C4)
1
Vinductor (C3)
2
3
V (C2)
DCMswitch DC-DC converter
boost
1 2 3
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
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9. Indoor SEH Wireless Sensor Node (cont’d)
Evaluate power harvested from solar panel with MPPT for
various loading conditions (Vref = 0.93 V)
Pharvested Pharvested Difference in
Rload Vload harvested power
w/emulator@Rload w/Rload
180 Ω 1.510 V 12.67 mW 8 mW 58.4 %
270 Ω 1.836 V 12.48 mW 6 mW 108 %
470 Ω 2.412 V 12.38 mW 3 mW 312.7 %
680 Ω 2.907
2 907 V 12.43
12 43 mW 2 mW 521.5
521 5 %
1200 Ω 4.1 V 14.00 mW 1 mW 1300 %
3900 Ω 6.906 V 12.23 mW 0.32 mW 3721.9 %
Significant increase in power harvested with resistor emulator
Q Rload // Re matches with Rsolar → fs changes, Re changes
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
Outdoor SEH Portable Computing System
Deployment testbed and experimental results
Experimental Testbed
Courtesy of DSO & NUS research team
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
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10. Maximize VEH Using SCE Technique
Illustration of synchronous charge extraction circuit
Primary Circuit Secondary Circuit
Piezoelectric
generator
Switch S closed
Primary Circuit: Accumulated charges Secondary: Open-circuit
extracted from piezoelectric generator Circuit
transferred to transformer, L
Switch S Open
Primary Circuit: Open-circuit & Secondary: Stored energy in L
generated charges accumulated in Circuit gets released to
generator Cr & RL
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
Maximize VEH Using SCE Technique (cont’d)
Piezoelectric generator
Vibration
SCEC energy source
Bootstrap Circuit
Latching Circuit
Accumulates sufficient energy power
Allows applications with higherin storage
Buck Converter operated intermittently, Vibration
cap, which then be
consumptions toprovide the initial startup
Regulatescontinuously voltage @5V
rather than the output
power to the control circuit. energy source
Shaker
Power consumption of control circuit ~300 μW
(60μA @5V)
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
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11. Maximize VEH Using SCE Technique (cont’d)
Performance of SCE technique
Theoretical results 8.8 mW
Simulation results 6.7 mW
Experimental results 5.6 mW
Y.K. Tan, J.Y. Lee and S.K. Panda, “Maximize Piezoelectric
Energy Harvesting Using Synchronous Electric Charge
Extraction Technique For Powering Autonomous Wireless
Transmitter”, IEEE International Conference on Sustainable
Energy Technologies (ICSET 2008), 1254-1259, 2008.
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
TEH from Human Warmth for WBAN
Overview of WBAN and its TEH system
Human wrist
TEH system
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
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12. TEH from Human Warmth for WBAN (cont’d)
Circuit design and video demonstration
D.C. Hoang, Y.K. Tan and S.K. Panda, “Thermal Energy Harvesting From Human Warmth For
Wireless Body Area Network In Medical Healthcare System”, The 8th IEEE International Conference
on Power Electronics and Drive Systems, 2009, in-progress
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
WEH Wireless Sensor Node
System-level problems to be addressed
- Fluctuating wind energy source → load energy requirement
- Min and max wind speeds available → voltage regulation and
Wind
turbine
energy storage
- Portability of wind energy harvester system → size and
Scheme 1
Scheme 2
weight
- Energy consumed by wind speed sensing and wireless
communicating
Power management
Motivation transmitter
and RF
circuits
- Self-sufficient and sustainable by wind energy source
- Compact and miniature wind energy harvester
=> Two WEH schemes implemented to power remote area wind
speed sensor in disaster management application
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
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13. WEH Wireless Sensor Node (cont’d)
Video demonstrations on the wind turbine and wind piezo
harvesting systems$
g y
Scheme 1: Wind turbine Scheme 2: Wind piezo
R.J. Ang, Y.K. Tan & S.K. Panda, “Energy harvesting for Y.K. Tan & S.K. Panda, “A Novel Piezoelectric Based Wind Energy
autonomous wind sensor in remote area”, 33th Annual IEEE Harvester for Low-power Autonomous Wind Speed Sensor”, 33th Annual
Conference of Industrial Electronics Society, pp.2104-2109, 2007. IEEE Conference of Industrial Electronics Society, pp.2175-2180, 2007.
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
MEH through Inductive Coupling for WSN
Magnetic energy harvesting based on Ampere’s law and
Faraday’s law
y
Gauss
meter
AC power
source
Magnetic energy
harvesting circuit
Resistor
load Magnetic energy
bank harvesting circuit
Y.K. Tan, S.C. Xie and S.K. Panda, “Stray Magnetic Energy Harvesting in Power Lines through
Inductive Coupling for Wireless Sensor Nodes”, The Proceedings for the 2008 nanoPower Forum
(nPF’08), Darnell Group, Irvine, Costa Mesa, California, 2008.
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
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14. Wireless Transmission of Power with
Magnetic Resonance 80
70
Efficiency (%) vs Inductance (H)
60
Source Transmitting
g Receiving Load
g
y )
n y(%
50
Coil Coil Coil Coil
fficie c
40
30
E
20
10
0
1.00E- 1.00E- 1.00E- 1.00E- 1.00E- 1.00E- 1.00E- 1.00E+0
07 06 05 04 03 02 01 0
Inductance (H)
Efficiency (%) vs Capacitance (F)
80
70
60
ffic n y )
E ie c (%
50
40
30
20
10
Transmitting Receiving 0
1.00E-15 1.00E-13 1.00E-11 1.00E-09 1.00E-07 1.00E-05 1.00E-03
end end Capacitance (F)
Efficiency (%) vs Conductor radius (m)
Efficiency (%) vs Distance (m)
100
120
90
100 80
70
ffic n y )
E ie c (%
ffic n y )
E ie c (%
80 60
50
60
40
40 30
20
20
10
0 0
0 0.5 1 1.5 2 2.5 0 0.002 0.004 0.006 0.008 0.01
Conductor radius (m)
Distance (m)
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
Case Study Example
Wind Energy Harvesting Wireless Sensor Node
– Modeling and Analysis
– Design considerations
– Implementation and hardware prototype
– Live Demonstration
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
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15. Wind Speed Distribution
Fire behavior on the Bor Forest Island under the FIRESCAN
fire research program
p g
Nominal daily wind speed in the deployment location over a
period of one month
Wind speed high, wind energy harvester harvests energy for
electronic circuitries and charge supercapacitor
Wind speed too low, supercapacitor acts like DC power
source to power electronic circuitries
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
Functional Model and Power Equations of
Wind Turbine
Pwind = FA v =
1
ρAv 3 Pmech = Paeroη gear
2
1
Paero = Pwind C p (λ , θ pitch ) = ρπR 2v 3C p (λ ,θ pitch )η gear
2
1
= ρπR 2 v 3C p (λ , θ pitch ) Pelec = Pmechη generator = VI
2
v − v2 1
C p = 4a (1 − a ) 2 , a = = ρπR 2v 3C p (λ ,θ pitch )η gearη generator
2v 2
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
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16. Characteristic of Wind Turbine
AC electrical power generated by wind turbine vs voltage
and current under varying wind source
y g
MPPT pt MPPT pt
Does not exist any voltage or current reference point for
maximum power harvesting over the range of wind speeds
di λv
Q V = I s R s + L s + k φω , where ω =
dt r
Fixed reference V and I MPPT approaches are not applicable
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
Characteristic of Wind Turbine (cont’d)
AC electrical power generated by wind turbine vs load
resistance under varying wind source
y g
Maximum power extraction at optimal load resistance of 100Ω
– Low optimal resistance => high output current EH source
Deviate away from optimal loading, either very light or heavy
loads, will result in significant drop in output power harvested
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
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17. Overview of WEH Wireless Sensor Node
Power
management
electronic
circuits
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
Resistance Emulation Approach
Resistance Emulation (RE) is based on the concept of
impedance matching
p g
RE = REmulated by converter // RLoad
2
Vin Vo2
=
Rin Ro
Rin ⎛ 1 ⎞
=⎜⎜ (1 − D ) 2 ⎟
⎟
Ro ⎝ ⎠
where Rin = Rs ⇒ Ro b, D b
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
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18. Performance of Resistance Emulator
Performance of resistance emulator for matching source
Rs = 150 Ω with dynamic load (
y (charging supercapacitor)
g g p p )
DC electrical power (mW)
urce resistance (Ω)
Ropt = 150 Ω Pmppt = 7.5 mW @3.5 m/s
Sou
Load resistance (Ω) e Duty cycle
Supercapacitor is initially uncharged, i.e. Rload = 0 Ω
As supercap is charged, Rload changes => dynamic load
Ropt = 150 Ω remains and Pmppt = 7.5 mW @3.5 m/s achieved
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
Performance of Resistance Emulator
Performance of resistance emulator for matching source
Rs = 150 Ω with dynamic load (
y (charging supercapacitor)
g g p p )
ource voltage (V)
Load voltage (V)
1
Vl =
So
L
Vi
(1 − D)
Load voltage (V) Duty cycle
As supercap is charged
– Vcap increases, but Vsource remains at Vmppt = 1.07 V
– Rload changes, D changes to maintain Ropt = 150 Ω
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
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19. Performance of Resistance Emulator
Performance of WEH w/ and w/o resistance emulator in
charging supercapacitor (act like a dynamic load)
g g p p ( y )
t
−
Vcap (t ) = Vcap ,max (1 − e τ )
Vmax =
For Vcap ,max = 5.5V ,
2.14 V
w/ MPPT control
1) Vcap (t = 500 sec) = 2.14V
Vmax = τ w / mppt = 1015 sec
w/o MPPT control
0.66 V 2) Vcap (t = 500 sec) = 0.66V
τ w / o mppt = 3911sec
⇒ τ w / mppt << τ w / o mppt
where τ is the charging
time constant
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
Performance of Resistance Emulator
Demonstrate the effects of MPPT and WEH on the
operation of a sensor node i.e. 1 sec per transmission
p p
@ 3.6 m/s wind speed
Vo, boost
Vi, boost
Ii, boost
w/o MPPT w/MPPT w/o MPPT
w/WEH w/WEH w/o WEH
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
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20. Live Demonstration
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
Conclusions
Challenges and research issues in a sustainable
WSN – energy supply is the bottleneck
Integration of energy harvesting wireless sensor
network
Design considerations for energy harvesting
systems in practical applications
Maximize energy harvesting with dedicated power
management solutions
Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems
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21. Thank you!
Questions and Answers
National University of Singapore
Yen Kheng Tan
tanyenkheng@nus.edu.sg or tanyenkheng@ieee.org
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