Micro Power Stations

MICROPOWER
SYSTEMS
By:
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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 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

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 moduleattached 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 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

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 moduleattached 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
Batteries
Fuel Cells
Capacitors
Heat Engines
Radioactive 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)
Fraunhofer
Stanford University

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

Micro Power Stations

by Mayank Vora

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