Realization Of Energy Harvesting Wireless Sensor Network (Eh Wsn)   With Special Focus On The Energy Harvesting Systems Tan Yen Kheng
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Realization Of Energy Harvesting Wireless Sensor Network (Eh Wsn) With Special Focus On The Energy Harvesting Systems Tan Yen Kheng

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

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

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  • 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 1
  • 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 2
  • 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 3
  • 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 4
  • 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 5
  • 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 6
  • 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 7
  • 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 8
  • 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 9
  • 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 10
  • 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 11
  • 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 12
  • 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 13
  • 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 14
  • 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 15
  • 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 16
  • 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 17
  • 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 18
  • 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 19
  • 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 20
  • 21. Thank you! Questions and Answers National University of Singapore Yen Kheng Tan tanyenkheng@nus.edu.sg or tanyenkheng@ieee.org Realization Of Energy Harvesting Wireless Sensor Network (EH-WSN) - with special focus on the energy harvesting systems 21