09-11-2012, 05:48 PM
Micro Power Systems Overview
1Micro Power Systems.ppt (Size: 1.07 MB / Downloads: 92)
Why Micro Power Now?
Simple example
At an average power consumption of 100 mW, you need slightly more than 1 cm3 of lithium battery volume for 1 year of operation, assuming you can use 100% of the charge in the battery.
Energy density of rechargeable batteries is less than half that of primary batteries.
So, someone needs to either replace batteries in every node every ~ 9 months, or recharge every battery every 3 to 4 months.
In most cases, this is not acceptable.
Two Paradigms In Sensor Nets
Modular
Off the shelf tech fabricated together on one small PCB
Allows for software flexibility at cost of energy
Monolithic
Eliminate layers between radio and sensor
Goal to design hardware quickly around only desired functionality - lower energy needs
Different design paradigms create different power needs
Energy Scavenging Areas
Solar/Ambient Light
Temperature Gradients
Human Power
Air Flow
Pressure Gradients
Vibrations
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
Summary
Primary batteries are not practical given the application area of most wireless sensor systems
A variety of energy reservoir options as well as energy scavenging options exist
Power source chosen depends on the nature of the task and the area of deployment - comes back to modular vs. monolithic