Post on 11-Jan-2016
Energy Harvesting
Thomas Vermeer3/25/09
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 HarvestingMaximum Power Point Tracking
Energy HarvestingMaximum Power Point Tracking
Uses buck/boost voltage regulators
Energy HarvestingMaximum Power Point Tracking
Uses buck/boost voltage regulators
• “Buck” the voltage down at peak times, supplying 5V with high current
Energy HarvestingMaximum 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 HarvestingAutonomous Maximum Power Point Tracking
• Preprogrammed regulators
• Feedback circuits
• Inexpensive
• Easy to implement
• Low power overhead
Energy HarvestingActive Maximum Power Point Tracking
• Uses MCU or DSP
• Difficult implement
• High power overhead
• Can be counterproductive
Energy Harvesting
Any Questions?