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Overview of Energy Harvesting

Overview of Energy Harvesting. EE174 – SJSU Tan Nguyen. OUTLINE. Introduction to Energy Harvesting Limitations on Portable Electrical Energy Discussion of Previous Studies – Energy Conversion – Piezoelectric Materials – Energy Harvesting Circuitry `– Energy Storage

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Overview of Energy Harvesting

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  1. Overview of Energy Harvesting EE174 – SJSU Tan Nguyen

  2. OUTLINE Introduction to Energy Harvesting Limitations on Portable Electrical Energy Discussion of Previous Studies – Energy Conversion – Piezoelectric Materials – Energy Harvesting Circuitry `– Energy Storage – Applications – Energy conversion – Thermoelectric, Radio- Frequency (RF) Future Research Issues

  3. Introduction Energy Harvesting • Energy harvesting (also known as power harvesting or energy scavenging) is the process in which energy is captured from a system's environment and converted into usable electric power. • Energy harvesting allows electronics to operate where there's no conventional power source, eliminating the need for wires or replacement of batteries. • An energy harvesting system generally includes circuitry to charge an energy storage cell, and manage the power, providing regulation and protection. • Energy harvesting can provide “endless energy” for the electronics lifespan. • Ideal for substituting for batteries that are impractical, costly, or dangerous to replace.

  4. Portable Electric Energy Sources Available Batteries – Wide spread availability, high reliability – Low-cost, mature technologies – Replacement/recharging is an issue • Too numerous in the future • Location is unreachable – Sensor size limited by battery size - Relative Improvement in Laptop Technology 􀂃 Battery energy is the slowest trend

  5. Portable Electric Energy Sources Available • Solar Cells • Commercial-off-the-shelf (COTS) energy harvesting • 1cm x 1cm; 0.14 mW (much less inside) • Recent research trend to improve the efficiency, robustness, costdown, etc. • Often limited by the availability of direct sunlight and size.

  6. Sources of Energy • Light (captured by photovoltaic cells) • Vibration or pressure (captured by a piezoelectric element) • Temperature differentials (captured by a thermo-electric generator) • Radio energy (captured by an antenna) • Biochemically produced energy (such as cells that extract energy from blood sugar). Energy harvesting uses unconventional sources to power circuitry.

  7. General Overview of Ambient Energy Sources • Human Body: Mechanical and thermal (heat variations) energy can be generated from a human or animal body by actions such as walking and running; • Natural Energy: Wind, water flow, ocean waves, and solar energy can provide limitless energy availability from the environment; • Mechanical Energy: Vibrations from machines, mechanical stress, strain from high-pressure motors, manufacturing machines, and waste rotations can be captured and used as ambient mechanical energy sources; • Thermal Energy: Waste heat energy variations from furnaces, heaters, and friction sources. • Light Energy: This source can be divided into two categories of energy: indoor room light and outdoor sunlight energy. Light energy can be captured via photo sensors, photo diodes, and solar photovoltaic (PV) panels; and • Electromagnetic Energy: Inductors, coils, and transformers can be considered as ambient energy sources, depending on how much energy is needed for the application. • Additionally, chemical and biological sources and radiation can be considered ambient energy sources

  8. Block Diagram of General Ambient EH systems. • The first row shows the energy-harvesting sources. • The second row shows actual implementation and tools are employed to harvest the energy from the source are illustrated. • The third row shows the energy-harvesting techniques from each source.

  9. Energy Harvesting Block Diagram

  10. Energy Harvesting (EH) • EH uses of ambient energy to provide electrical power for small electronic and electrical devices. • An Energy Harvesting System consists of an Energy Harvester Module and a processor/transmitter block. • Energy Harvesting Module  captures milli-watts of energy from light, vibration, thermal or biological sources. A possible source of energy also comes from RF such as emitted from cell phone towers. • The power is then conditioned and stored within a battery, an efficient quick charging capacitor or one of the newly developed thin film batteries. • The system is then triggered at the required intervals to take a sensor reading, through a low power system. This data is then processed and transmitted to the base station. • This kind of EH System eliminates the dependency of the system on battery power and reduces the need to service the system..

  11. Design Consideration • TI's TMS37157 could also be used to harness the RF energy into electrical energy. TI's MSP430 and Low Power RF parts combined with efficient DC/DC Converters and Battery Management parts are an ideal complement to these low power energy harvesting sources. • With as low as 160 uA/MHz (microamp per megahertz) active power consumption and 1.5 uA standby power consumption, MSP430F5xx MCUs enable longer battery life or no batteries at all for energy harvesting systems that run off of solar power, vibration energy or temperature differences like found on human body.

  12. Energy Storage is a Must • Almost all energy-harvesting scenarios require some sort of energy storage element or buffer. Even if the voltage and current requirements of an embedded application were so low as to be run directly on power captured or scavenged from the environment, such power would not flow in a constant way. • Storage elements or buffers are implemented in the form of a capacitor, standard rechargeable lithium battery, or a new technology like thin-film batteries. What kind of energy storage is needed depends greatly on the application. • Some applications require power for only a very short period of time, as short as the RC time constant discharge rate of a capacitor. Other applications require relatively large amounts of power for an extended duration, which dictates the use of a traditional AA or a rechargeable lithium battery

  13. Industry Applications • Remote patient monitoring • Efficient office energy control • Surveillance and security • Agricultural management • Home automation • Long range asset tracking • Implantable sensors • Structural monitoring • Machinery/equipment monitoring

  14. References: http://www.maximintegrated.com/en/app-notes/index.mvp/id/5259 http://www.ti.com/lsds/ti/apps/alternative_energy/harvesting/overview.page http://institute.lanl.gov/ei/_docs/Annual_Workshops/Overview_of_energy_harvesting_systemsLA-UR_8296.pdf

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