Energy Harvesting

1. Energy Harvesting Thomas Vermeer 3/25/09 Embedded Systems

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

3. Energy Harvesting What is Energy Harvesting? • Energy Harvesting is a way of powering an embedded system by ‘harvesting’ energy from the environment

4. Energy Harvesting Common Energy Harvesting Systems

5. Energy Harvesting Common Energy Harvesting Systems • Car Tire Pressure Monitors

6. Energy Harvesting Common Energy Harvesting Systems • Wireless Weather Stations

7. Energy Harvesting Common Energy Harvesting Systems • Implantable Medical Devices

8. Energy Harvesting Common Energy Harvesting Systems • Traffic Alert Signs

9. Energy Harvesting Common Energy Harvesting Systems • Mars Rover

10. Energy Harvesting Two Design Goals: • Choose very low power electronics • Harvest and store energy efficiently

11. Energy Harvesting Sources of Energy:

12. Energy Harvesting Sources of Energy: • Solar

13. Energy Harvesting Sources of Energy: • Mechanical

14. Energy Harvesting Sources of Energy: • Thermal

15. Energy Harvesting Sources of Energy: • Electromagnetic

16. Energy Harvesting Energy Storage

17. Energy Harvesting Energy Storage Option 1: Traditional Rechargeable Batteries

18. Energy Harvesting Energy Storage Option 1: Traditional Rechargeable Batteries • Inefficient charging – lots of energy converted to heat

19. Energy Harvesting Energy Storage Option 1: Traditional Rechargeable Batteries • Inefficient charging – lots of energy converted to heat • Limited number of charging cycles

20. Energy Harvesting Energy Storage Option 2: Traditional Capacitors

21. Energy Harvesting Energy Storage Option 2: Traditional Capacitors • Efficient charging

22. Energy Harvesting Energy Storage Option 2: Traditional Capacitors • Efficient charging • Limited Capacity

23. Energy Harvesting Energy Storage Option 3 – Best Option: Super Capacitors

24. Energy Harvesting Energy Storage Option 3 – Best Option: Super Capacitors • Efficient charging and high capacity

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

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

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

28. Energy Harvesting Maximizing Energy Stored But look at all this wasted energy!

29. Energy Harvesting Maximum Power Point Tracking

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

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

32. 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

33. Energy Harvesting Autonomous Maximum Power Point Tracking • Preprogrammed regulators • Feedback circuits • Inexpensive • Easy to implement • Low power overhead

34. Energy Harvesting Active Maximum Power Point Tracking • Uses MCU or DSP • Difficult implement • High power overhead • Can be counterproductive

35. Energy Harvesting Any Questions?