1. MICROPOWER SYSTEMS By: ________ ___________________ __________________________________________________________________ _______________
2. Topics Driving forces for micro power systems Energy scavenging/ collecting systems Energy 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.
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
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8. Solar PV Arrays Solar Photo Voltaic (solar PV) is the direct conversion of solar energy into electricity They are formed using semi-conductor materials like Si Light energy bounces the electrons away from their atoms † flow of electrons † current
9. Solar PV Arrays Solar Photo Voltaic (solar PV) is the direct conversion of solar energy into electricity They are formed using semi-conductor materials like Si Light energy bounces the electrons away from their atoms † flow of electrons † current
10. Temperature Gradients Exploit gradients due to waste heat / ambient temp Maximum power = Carnot efficiency 10˚C differential = (308K –298K) /308 = 3.2% Through silicon this can be up to 110 mW/cm2 Methods Thermoelectric (Seebeck effect) ~ 40µW/cm2 @ 10˚C Piezo 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 forces Thermal energy scavengers that use Seebeck effect to transform the temperature difference between the environment and the human body into electricity Generators are mounted on a bracelet - 150μW Bismuth telluride thermoelectric block, consisting of about 3000 thermocouples Flexible wireless sensor moduleattached to this bracelet and powered by the thermoelectric generator
12. Air Flow Power output/ efficiencies vary with velocity and motors Applications exist where average air flow may be on the order of 5 m/s At 100% efficiency ~1 mW MEMS turbines may be viable
13. Pressure Gradients Using ambient pressure variations On a given day, for a change of .2 inches Hg, density on the order of nW/cm3 Manipulating temperature Using 1 cm3 of helium, assuming 10˚C and ideal gas behavior, ~ µW/cm3 No active research on pressure gradient manipulation
14. Micro Heat Engines MEMS scale parts for small scale engine 1 cm3 volume 13.9 W Poor transient properties Micro size heat engine ICE’s, thermoelectrics, thermoionics, thermo photo voltaics via controlled combustion Meant for microscale applications with high power needs
15. Solar PV Arrays Solar Photo Voltaic (solar PV) is the direct conversion of solar energy into electricity They are formed using semi-conductor materials like Si Light energy bounces the electrons away from their atoms † flow of electrons † current
16. Temperature Gradients Exploit gradients due to waste heat / ambient temp Maximum power = Carnot efficiency 10˚C differential = (308K –298K) /308 = 3.2% Through silicon this can be up to 110 mW/cm2 Methods Thermoelectric (Seebeck effect) ~ 40µW/cm2 @ 10˚C Piezo thermo engine ~ 1 mW/mm2 (theoretical) Piezo thermo engine
17. Human Power Burning 10.5 MJ a day Average power dissipation of 121 W Areas of Exploitation Foot Using energy absorbed by shoe when stepping 330 µW/cm2 obtained through MIT study Skin Temperature gradients, up to 15˚C Blood Panasonic, Japan demonstrated electrochemically converting glucose
18. Autonomous nodes can only become reality when research on ultra-low-power electronics and micro-power generators join forces Thermal energy scavengers that use Seebeck effect to transform the temperature difference between the environment and the human body into electricity Generators are mounted on a bracelet - 150μW Bismuth telluride thermoelectric block, consisting of about 3000 thermocouples Flexible wireless sensor moduleattached to this bracelet and powered by the thermoelectric generator
19. Air Flow Power output/ efficiencies vary with velocity and motors Applications exist where average air flow may be on the order of 5 m/s At 100% efficiency ~1 mW MEMS turbines may be viable
20. Pressure Gradients Using ambient pressure variations On a given day, for a change of .2 inches Hg, density on the order of nW/cm3 Manipulating temperature Using 1 cm3 of helium, assuming 10˚C and ideal gas behavior, ~ µW/cm3 No active research on pressure gradient manipulation
22. Batteries Macro Batteries - too big Zinc air (3500 J/cm3), Alkaline (1800 J/cm3), Lithium (1000 - 2880 J/cm3) Micro Batteries - on the way Lithium (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 Cell Current Generation Toshiba 1 cm3 hydrogen reactor Produces 1watt Next Generation Planar Arrays Fraunhofer - 100 mW/cm2 Stanford - > 40 mW/cm2 (more room for improvement) Fraunhofer Stanford University
24. Capacitors Capacitors Energy density too low to be a real secondary storage component Ultra capacitors Energy density on order of 75 J/cm3 Work being done to shrink them
25. Micro Heat Engines MEMS scale parts for small scale engine 1 cm3 volume 13.9 W Poor transient properties Micro size heat engine ICE’s, thermoelectrics, thermoionics, thermo photo voltaics via controlled combustion Meant for microscale applications with high power needs
26. Radioactive Approaches!! High theoretical energy density Power density inversely proportional to half life Demonstrated power on the order of nanowatts Environmental concerns
27. CONCLUSION Produce high quality competitive R&D Micropower: The Next Electrical Era Emergency Micro-Power Systems Squeezed every wasted kilowatt-hour or leaking calorie of heat out of our homes and businesses
