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PowerPoint Presentation - UT Dallas

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									                        Energy Harvesting Methodologies for Wireless
                                    Sensor Nodes




                                                          Dinesh Bhatia
                                                         Associate Professor

                                                         Abhiman Hande
                                                         Research Associate




                                                 Erik Jonsson School of Engineering
                                                         November 23, 2005


               Embedded and Adaptive                                                  Hande, Nov 2005
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                                                         Outline


               Present power requirements in PANs
               Necessity for alternate sources of energy
               Available alternative energy sources
               Energy harvesting issues
               Energy storage issues
               Power management strategies
               Research at UTD’s EACG




               Embedded and Adaptive                               Hande, Nov 2005
ZigBeeTM Alliance | Wireless Control That Simply Works
               Computing Group
                                                   Technology Trends




                                     Relative improvements in laptop computing technology from 1990–2003.



               Embedded and Adaptive                                                                        Hande, Nov 2005
ZigBeeTM Alliance | Wireless Control That Simply Works
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                                     Feasible Sources of Energy


           Photovoltaic solar cells
                    Amorphous
                    Crystalline                           Power densities of energy harvesting technologies
           Vibrations                                      Harvesting technology            Power density
                    Piezoelectric                         Solar cells (outdoors at noon)      15 mW/cm2

                    Capacitive                             Piezoelectric (shoe inserts)      330 μW/cm3
                                                         Vibration (small microwave oven)     116 μW/cm3
                    Inductive                            Thermoelectric (10oC gradient)       40 μW/cm3

               Radio-Frequency (RF)                         Acoustic noise (100dB)           960 nW/cm3


               Thermoelectric conversion
               Human power
               Wind/air flow
               Pressure variations



               Embedded and Adaptive                                                             Hande, Nov 2005
ZigBeeTM Alliance | Wireless Control That Simply Works
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                     Feasible Devices for Energy Storage


           Batteries
                    Li-ion
                    NiCD
                    NiMH                                VoltaFlex thin film rechargeable lithium batteries


           Ultracapacitors
                    Maxwell
                    Samsung
                    NEC
           Micro-fuel cells
           Micro-heat engines
           Radioactive power sources                          Maxwell 5V 2F 2.7 mAhr ultracapacitor




               Embedded and Adaptive                                                           Hande, Nov 2005
ZigBeeTM Alliance | Wireless Control That Simply Works
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     Energy Harvesting for Wireless Sensor Nodes



                       Energy source                     Energy harvesting and
                                                            energy storage


                                                                                                      VCC
                                                                                                                                                     Antenna




                                       A/D converter                                Microcontroller                         RF communication link

                                                                   Raw data

                                                                                                            Packetized samples




                                         Sensors                                 Program and data flash
                                                                                       memory




    Block diagram of an energy harvesting wireless sensing node with data logging and bidirectional RF communications capabilities


               Embedded and Adaptive                                                                                                          Hande, Nov 2005
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                                        Solar Cell Characteristics


               10-20 % efficiency outdoors
               <1% efficiency indoors
               Needs power management scheme
               Maximum power point might need tracking




                                         V-I characteristics of a Solar World 4-4.0-100 solar panel

               Embedded and Adaptive                                                                  Hande, Nov 2005
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   Solar Cell Efficiencies Under Different Light Conditions




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                                           Vibrations to Electricity




               Embedded and Adaptive                                   Hande, Nov 2005
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 Comparison of Vibrations to Electricity Methods


           Scavenging the power from commonly
            occurring vibrations for use by low power
            wireless systems is both feasible and
            attractive for certain applications.
           Piezoelectric converters appear to be the most
            attractive for meso-scale devices with a
            maximum demonstrated power density of
            approximately 200 μW/cm3 vs. 100 μW/cm3 for
            capacitive MEMS devices.
           Electromagnetic converters provide maximum
            voltage of 0.1 volts


               Embedded and Adaptive                     Hande, Nov 2005
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                                           Piezo Converter Set-up




                                               Piezoelectric converter with rectifier and DC-DC converter




               Embedded and Adaptive                                                                        Hande, Nov 2005
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                                                 Power Management


               Charge energy storage devices
               Route stored energy to sensor node
               Monitor available energy level
               Low power buck/boost converter required

                                                                                                                 VCC to
                                                                                                                 system
                                                           Optional                        Power Management
                                                         rectification


                    Solar panels /                                       Ultracapacitors             Batteries
                    piezoelectric
                      element




                                     Dual energy storage mechanism for a wireless sensor node


               Embedded and Adaptive                                                                                      Hande, Nov 2005
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                                         Research at UTD’s EACG

               CrossbowTM MICAz motes
               2.4GHz, IEEE 802.15.4 compliant ZigBeeTM transceiver.
               Mesh networking protocol
               Potential applications include temperature and light
                monitoring in remote locations, measuring tire pressure,
                monitoring acceleration in automobiles, medical
                applications, etc.




                                   MICAz mote            MICA2 motes


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             Battery Life Estimation for a MICAz Mote

                                        Battery life estimation for a MICAz mote operating at 1% duty cycle
                                                   Processor Currents                Example duty cycle
                                                              Full operation 8 mA          1%
                                                                 Sleep mode 8 A          99 %
                                                     Radio Currents                  Example duty cycle
                                                             Receive mode 8 mA           0.75 %
                                                           Transmit mode 12 mA           0.25 %
                                                                 Sleep mode 2 A          99 %
                                                Logger Memory Currents               Example duty cycle
                                                          Write operation 15 mA            0%
                                                            Read operation 4 mA            0%
                                                                 Sleep mode 2 A          100 %
                                                 Sensor Board Currents               Example duty cycle
                                                              Full operation 5 mA          1%
                                                                 Sleep mode 5 A          99 %
                                              Computed mAhr used each hour
                                                                         Processor          0.0879
                                                                             Radio          0.0920
                                                                  Logger Memory             0.0020
                                                                      Sensor Board          0.0550
                                                                Total mAhr used             0.2369
                                            Computed battery life vs. battery size
                                                         Battery Capacity (mAhr)     Battery Life (months)
                                                                               250           1.45
                                                                              1000           5.78
                                                                              3000           17.35




               Embedded and Adaptive                                                                          Hande, Nov 2005
ZigBeeTM Alliance | Wireless Control That Simply Works
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                                                  Research Challenges

               Set-ups for both solar and vibrational energy
               Dual energy storage scheme
               Power management
               Low power buck converter design

                 Task 1: Develop designs for energy
                 scavenging prototypes

                 Task 2: Develop an appropriate
                 power management scheme

                 Task 3: Identify appropriate
                 components for procurement

                 Task 4: Implement the prototype
                 designs

                 Task 5: Testing and modifications


                         Indicates publications          SP      SU     FA     SP      SU     FA   SP      SU     FA
                                                              2006 (Y1)             2007 (Y2)           2008 (Y3)

                                                                    Tentative research timeline



               Embedded and Adaptive                                                                                   Hande, Nov 2005
ZigBeeTM Alliance | Wireless Control That Simply Works
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                                                         Conclusions


           Acceptable power sources remain perhaps the
            most challenging technical hurdle to the
            widespread deployment of wireless sensor
            networks.
           While significant progress has been made in
            many areas including indoor photovoltaic
            systems, micro-fuel cells, thermoelectrics,
            micro-heat engines, and vibration-to-
            electricity conversion, much more research
            and new approaches need to be pursued.



               Embedded and Adaptive                                   Hande, Nov 2005
ZigBeeTM Alliance | Wireless Control That Simply Works
               Computing Group

								
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