Micro power systems generate small amounts of electricity from sources near the point of use to eliminate transmission grids. They exploit various forms of ambient energy including solar, temperature gradients, human power, airflow, vibrations, and pressure gradients using technologies like solar cells, thermoelectrics, and MEMS turbines. Energy is stored using micro batteries, fuel cells, capacitors, or heat engines to power autonomous wireless sensor nodes. Further research is needed to improve energy scavenging and storage methods to enable micro power systems to provide reliable off-grid power.

1. MICROPOWERSYSTEMSBy:____________________________________________________________________________________________________________

2. TopicsDriving forces for micro power systemsEnergy scavenging/ collecting systemsEnergy reservoir/ power generation systems

3. What is Micro Power??Generation of small amounts of electricity from sources close to where it's used. Eliminates the need for both excess production by the traditional generating stations powered by coal, oil or nuclear power, and transmission grids to deliver that power.

4. Why Micro Power Now??

5. Why Micro Power ??renewable, on the site energy and reducing greenhouse gas emissions plan not to replace the traditional electrical grid providing reliable service in remote communities waste energy scavenger concepts

6. Energy Scavenging Areas 1.Solar/Ambient Light 2.Temperature Gradients 3.Human Power 4.Air Flow 5.Pressure Gradients 6.Vibrations

7. Solar and Ambient LightSourcesNoon on a sunny day - 100 mW/cm2Office Lights: 7.2 mW/cm2CollectorsSC Silicon15% - 30% efficientPoly-Silicon 10% - 15% efficientPhotoelectric Dyes5% to 10% efficientSolar Powered Pico Radio Node

8. Solar PV ArraysSolar Photo Voltaic (solar PV) is the direct conversion of solar energy into electricity They are formed using semi-conductor materials like SiLight energy bounces the electrons away from their atoms † flow of electrons † current

9. Solar PV ArraysSolar Photo Voltaic (solar PV) is the direct conversion of solar energy into electricity They are formed using semi-conductor materials like SiLight energy bounces the electrons away from their atoms † flow of electrons † current

10. Temperature GradientsExploit gradients due to waste heat / ambient temp Maximum power = Carnot efficiency10˚C differential = (308K –298K) /308 = 3.2%Through silicon this can be up to 110 mW/cm2MethodsThermoelectric (Seebeck effect) ~ 40µW/cm2 @ 10˚CPiezo thermo engine ~ 1 mW/mm2 (theoretical)Piezo thermo engine

11. Autonomous nodes can only become reality when research on ultra-low-power electronics and micro-power generators join forcesThermal energy scavengers that use Seebeck effect to transform the temperature difference between the environment and the human body into electricityGenerators are mounted on a bracelet - 150μW Bismuth telluride thermoelectric block, consisting of about 3000 thermocouplesFlexible wireless sensor moduleattached to this bracelet and powered by the thermoelectric generator

12. Air FlowPower output/ efficiencies vary with velocity and motorsApplications exist where average air flow may be on the order of 5 m/sAt 100% efficiency ~1 mWMEMS turbines may be viable

13. Pressure GradientsUsing ambient pressure variationsOn a given day, for a change of .2 inches Hg, density on the order of nW/cm3Manipulating temperatureUsing 1 cm3 of helium, assuming 10˚C and ideal gas behavior, ~ µW/cm3No active research on pressure gradient manipulation

14. Micro Heat EnginesMEMS scale parts for small scale engine1 cm3 volume13.9 WPoor transient propertiesMicro size heat engineICE’s, thermoelectrics, thermoionics, thermo photo voltaics via controlled combustionMeant for microscale applications with high power needs

15. Solar PV ArraysSolar Photo Voltaic (solar PV) is the direct conversion of solar energy into electricity They are formed using semi-conductor materials like SiLight energy bounces the electrons away from their atoms † flow of electrons † current

16. Temperature GradientsExploit gradients due to waste heat / ambient temp Maximum power = Carnot efficiency10˚C differential = (308K –298K) /308 = 3.2%Through silicon this can be up to 110 mW/cm2MethodsThermoelectric (Seebeck effect) ~ 40µW/cm2 @ 10˚CPiezo thermo engine ~ 1 mW/mm2 (theoretical)Piezo thermo engine

17. Human PowerBurning 10.5 MJ a dayAverage power dissipation of 121 WAreas of ExploitationFootUsing energy absorbed by shoe when stepping330 µW/cm2 obtained through MIT studySkinTemperature gradients, up to 15˚CBloodPanasonic, Japan demonstrated electrochemically converting glucose

18. Autonomous nodes can only become reality when research on ultra-low-power electronics and micro-power generators join forcesThermal energy scavengers that use Seebeck effect to transform the temperature difference between the environment and the human body into electricityGenerators are mounted on a bracelet - 150μW Bismuth telluride thermoelectric block, consisting of about 3000 thermocouplesFlexible wireless sensor moduleattached to this bracelet and powered by the thermoelectric generator

19. Air FlowPower output/ efficiencies vary with velocity and motorsApplications exist where average air flow may be on the order of 5 m/sAt 100% efficiency ~1 mWMEMS turbines may be viable

20. Pressure GradientsUsing ambient pressure variationsOn a given day, for a change of .2 inches Hg, density on the order of nW/cm3Manipulating temperatureUsing 1 cm3 of helium, assuming 10˚C and ideal gas behavior, ~ µW/cm3No active research on pressure gradient manipulation

21. Energy Reservoirs/Power Generation Batteries Fuel Cells Capacitors Heat Engines Radioactive Sources

22. BatteriesMacro Batteries - too bigZinc air (3500 J/cm3), Alkaline (1800 J/cm3), Lithium (1000 - 2880 J/cm3)Micro Batteries - on the wayLithium (i) Thin film Li (1-D micro scale, 2-D macro scale ) (ii) 3-D Lithium Ion (in initial stages)Ni/ NaOH /Zn

23. MEMS Fuel CellCurrent GenerationToshiba 1 cm3 hydrogen reactorProduces 1wattNext GenerationPlanar ArraysFraunhofer - 100 mW/cm2Stanford - > 40 mW/cm2 (more room for improvement)FraunhoferStanford University

24. CapacitorsCapacitorsEnergy density too low to be a real secondary storage componentUltra capacitorsEnergy density on order of 75 J/cm3Work being done to shrink them

25. Micro Heat EnginesMEMS scale parts for small scale engine1 cm3 volume13.9 WPoor transient propertiesMicro size heat engineICE’s, thermoelectrics, thermoionics, thermo photo voltaics via controlled combustionMeant for microscale applications with high power needs

26. Radioactive Approaches!!High theoretical energy densityPower density inversely proportional to half lifeDemonstrated power on the order of nanowattsEnvironmental concerns

27. CONCLUSIONProduce high quality competitive R&DMicropower: The Next Electrical Era Emergency Micro-Power SystemsSqueezed every wasted kilowatt-hour or leaking calorie of heat out of our homes and businesses

28. REFERENCESterrain.orgpowerconnect.commicropower-connect.orgthe-infoshop.com

29. THANK YOU