Micro-energy harvesting

1. Micro-energy harvesting • Testing the feasibility of indoor harvesting from routine motion in the environment. • A comparison of three energy harvesters gathering from linear motion produced by a sliding door. • Looking at piezo elements, stepper motor generator and faraday induction.

2. What is energy harvesting?+ Energy harvesting (also known as Power harvesting or energy scavenging) is the process by which energy is captured and stored. Frequently this term is applied when speaking about small autonomous devices, like those used in sensor networks. A variety of different sources exist for harvesting energy, such as solar power, thermal energy, wind energy, salinity gradients and kinetic energy.

3. Piezo electric elements • It is the inherent property of piezo electric material to produce an electrical potential, high voltage - low current, when put under strain, either deflection or compression. • Used both micro-fiber composite (mfc) and traditional ceramic types.

4. Stepper motor generator • Produce power at low rotation rates • Produces twice as much power as a dc motor • Common and easily available

5. Electro-Magnetic induction (Faraday’s law) • Passing a magnetic field through a conductive coil produces an electrical potential. • Utilized a commonly available “shake flash light” and circuit.

6. Early trials • We initially worked on testing the feasibility of piezo energy harvesting to find a method of capturing the energy, rectifying it, storing it and measuring it.

9. MFC piezo transducer • - A woven fiber composite piezo - • produces three times the current • compared to a standard piezo. • needs to be adhered well to a • flexible substrate for optimal output • produced a cater lever with a counter • weight for optimal deflection and • energy output

11. Data Logging: processing->graph->text->movie

12. Piezo solution:

14. Stepper solution:

17. Graphing with mySQL + php- Each Harvester has an xbee radio checking the charge of the capacitor from its analog i/o pin and sends the byte value and address in an api packet to a base station every 60 sec.- The base station, running processing, pulls apart the api packet and logs the data by address into amySQL database running on a server.- A php script grabs the analog data, converts them into volts and then into joules and graphs them online.

18. Xbee transceiver communication Setup: base station joules1/2/3 atid 1955 1955 atmy 0 1/2/3 atdl 1 0 atir 0x32 0xEA65 Atit 0x1 0x1 Atd0 - 0x2 Atd2 0x3 0x4 Atio 0x03 - Atic 0x18 - Atia - 0x00

19. FlashLite phone app • Pulls the last value from the • mySQL database via a php scipt • graphs the three values as volts • as related to the xbee ref • if a cap reaches the xbee max: • 1023==3.3, • app allows the user to press a • button that places a call to the • asterisk server. • acts as a testing management • tool

20. Flashlite -> Asterisk -> Processing FlashLite places a call to the asterisk server asking them to enter the extension. User enters the dial plan where text to speech introduces them and explains the interface. A shell scipt then launches a Java file: JEAGIClient, which grabs the call data. 4. JAEAGIServer.java runs on the server handing data back and forth between asterisk and processing. 5. Processing parses the key values from the server that then trigger an api at command to the local xbee.

21. Writing api AT commands to the xbee //api packet to be sent out HIGH port.write(0x7E); //start byte port.write(0x0); //MSB int dataLength = 4; // set this to whatever your data length is currently port.write(0x1 + dataLength); //LSB=data length + API id + frame id + two command bytes int checksum = 0; port.write(0x08); // send API command identifier checksum = checksum + 0x08; port.write(0x01); // send frame ID (set to 0 if no response is required) checksum = checksum + 0x01; port.write(0x49); // at command i checksum = checksum + 0x49; port.write(0x4F); // at command pin2 checksum = checksum + 0x4F; port.write(0x08); //set pin high checksum = checksum + 0x8; println("Pre-checksum: " + checksum); checksum = 0xFF - checksum; println("checksum: " + checksum + " <-- this must be a single byte!"); port.write(checksum); //checksum println("sending api packet to xbee!!!");

26. General Conclusion Indoor energy harvesting is both feasible and necessary. It is also very inexpensive and readily available. All indoor environments have objects in routine motion, such as doors opening and closing that can be converted to electrical potential.

27. Conclusion: piezo harvesting Piezo harvesting was the least effective form that we tested. The frequency of deflection necessary to produce a usable amount was not possible from installation on a door. Effective Piezo transducers and costly: $160+ per They produce very high voltage spikes and very low current, thus, a perf- board was required rather than a bread broad due the instantaneous rate of change. Reasonable deflection was not possible from vibration so flicking became the preferred means results in noise.

28. Conclusion: stepper motor generator The greatest amount of energy was attained via the motor as linear motion was transferred to circular. Quickly 5volts was able to be stored in a . 33F cap. Leakage of the cap was a problem as energy stored and released are both exponential. 4. Cheap and readily available, small package and no extra noise.

29. Conclusion: electro-magnetic Great potential to produce electricity, but a door was not the right environment due its requirements for linear motion and high frequency. Very cheap and easily produced.

30. Link to resource wiki