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					     Energy Harvesting


 Thomas Vermeer
     3/25/09
Embedded Systems
Agenda

    •   What is Energy Harvesting?
    •   Common Energy Harvesting Systems
    •   Energy Sources
    •   Energy Storage
    •   Optimization Methods
Energy Harvesting
   What is Energy Harvesting?

   • Energy Harvesting is a way of
     powering an embedded system by
     ‘harvesting’ energy from the
     environment
Energy Harvesting
   Common Energy Harvesting Systems
Energy Harvesting
   Common Energy Harvesting Systems
       • Car Tire Pressure Monitors
Energy Harvesting
   Common Energy Harvesting Systems
       • Wireless Weather Stations
Energy Harvesting
   Common Energy Harvesting Systems
       • Implantable Medical Devices
Energy Harvesting
   Common Energy Harvesting Systems
       • Traffic Alert Signs
Energy Harvesting
   Common Energy Harvesting Systems
       • Mars Rover
Energy Harvesting
 Two Design Goals:

 • Choose very low power electronics
 • Harvest and store energy efficiently
Energy Harvesting
  Sources of Energy:
Energy Harvesting
  Sources of Energy:
      • Solar
Energy Harvesting
  Sources of Energy:
      • Mechanical
Energy Harvesting
  Sources of Energy:
      • Thermal
Energy Harvesting
  Sources of Energy:
      • Electromagnetic
Energy Harvesting
   Energy Storage
Energy Harvesting
   Energy Storage
   Option 1:
    Traditional Rechargeable Batteries
Energy Harvesting
   Energy Storage
   Option 1:
    Traditional Rechargeable Batteries
    • Inefficient charging – lots of energy
      converted to heat
Energy Harvesting
   Energy Storage
   Option 1:
    Traditional Rechargeable Batteries
    • Inefficient charging – lots of energy
      converted to heat
    • Limited number of charging cycles
Energy Harvesting
   Energy Storage
   Option 2:
    Traditional Capacitors
Energy Harvesting
   Energy Storage
   Option 2:
    Traditional Capacitors
    • Efficient charging
Energy Harvesting
   Energy Storage
   Option 2:
    Traditional Capacitors
    • Efficient charging
    • Limited Capacity
Energy Harvesting
   Energy Storage
   Option 3 – Best Option:
    Super Capacitors
Energy Harvesting
   Energy Storage
   Option 3 – Best Option:
    Super Capacitors

    • Efficient charging and high capacity
Energy Harvesting

   Super Capacitors
     • Small Size
     • High Efficiency
     • Very high capacity (1-100 Farads)
     • ~20% capacity drop per decade
Energy Harvesting
 Maximizing Energy Stored




  What if our system charges at 5V?
Energy Harvesting
 Maximizing Energy Stored




    We could charge system when
     Vin>5V, or for about 5 hours/day
Energy Harvesting
 Maximizing Energy Stored




    But look at all this wasted energy!
Energy Harvesting
 Maximum Power Point Tracking
Energy Harvesting
 Maximum Power Point Tracking




  Uses buck/boost voltage regulators
Energy Harvesting
 Maximum Power Point Tracking




  Uses buck/boost voltage regulators
   • “Buck” the voltage down at peak times,
     supplying 5V with high current
Energy Harvesting
 Maximum Power Point Tracking




  Uses buck/boost voltage regulators
   • “Buck” the voltage down at peak times,
     supplying 5V with high current
   • “Boost” the voltage up at lower times,
     supplying 5V with low current
Energy Harvesting
 Autonomous Maximum Power Point Tracking
 •   Preprogrammed regulators
 •   Feedback circuits
 •   Inexpensive
 •   Easy to implement
 •   Low power overhead
Energy Harvesting
 Active Maximum Power Point Tracking
 •   Uses MCU or DSP
 •   Difficult implement
 •   High power overhead
 •   Can be counterproductive
Energy Harvesting


        Any Questions?

				
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posted:8/16/2012
language:English
pages:35