MICROPOWER

SYSTEMSBy:____________________________________________________________________________________________________________

Topics

• Driving forces for micro power systems

• Energy scavenging/ collecting systems

• Energy reservoir/ power generation systems

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.

Why Micro Power Now??

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

Energy Scavenging Areas

1.Solar/Ambient Light

2.Temperature Gradients 3.Human Power

4.Air Flow 5.Pressure Gradients 6.Vibrations

Solar and Ambient Light

• Sources– Noon on a sunny day -

100 mW/cm2

– Office Lights: 7.2 mW/cm2

• Collectors– SC Silicon

• 15% - 30% efficient– Poly-Silicon

• 10% - 15% efficient– Photoelectric Dyes

• 5% to 10% efficient

Solar Powered Pico Radio Node

• 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

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

Solar PV Arrays

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

• 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 module attached to this bracelet and powered by the thermoelectric generator

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

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

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

• 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

Solar PV Arrays

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

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

• 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 module attached to this bracelet and powered by the thermoelectric generator

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

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

Energy Reservoirs/Power Generation

BatteriesFuel CellsCapacitorsHeat EnginesRadioactive Sources

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

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)

Stanford University

Fraunhofer

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

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

Radioactive Approaches!!

• High theoretical energy density

• Power density inversely proportional to half life

• Demonstrated power on the order of nanowatts

• Environmental concerns

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

REFERENCES• terrain.org• powerconnect.com• micropower-connect.org• the-infoshop.com

THANK YOU