Introduction to Energy Harvesting

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Introduction to Energy Harvesting

• EE174 SJSU
• Tan Nguyen

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OUTLINE

• Introduction to Energy Harvesting (EH)
• How does EH work?
• Sources of Energy
• Energy conversions
• EH Components
• EH system and EH Circuit
• Energy storage is a Must
• Application
• Future Research Issues

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Introduction Energy Harvesting (EH)

• Energy Harvesting (EH) also known as power
  harvesting or energy scavenging, is the process
  in which energy is captured from an ambient
  energy and converted into usable electric power.
• Energy harvesters provide a very small amount of
  power for low-energy electronics.
• EH allows electronics to operate where there's no
  conventional power source, eliminating the need
  for wires or replacement of batteries.
• EH systems generally includes circuitry to charge
  an energy storage cell, and manage the power,
  providing regulation and protection.
• EH-powered systems need reliable energy
  generation, storage and delivery
• Must have energy storage as EH transducer energy
  source is not always available (solar at night,
  motor vibration at rest, air-flow, etc.)
• EH can provide endless energy for the
  electronics lifespan.
• Ideal for substituting for batteries that are
  impractical, costly, or dangerous to replace.

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Ultra Low Power uController
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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
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How Energy Harvesting works?
An energy harvester comprises one or more
transducers, power conditioning, and energy
storage. These technologies work together to
collect energy and deliver power to the device.
On the other hand, the device which uses the
energy needs to be designed to work with energy
harvesting as the power source.
(Sources of Energy)
(Devices)
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How Energy Harvesting works?

• The transducer converts energy from one energy
  type to a another energy type, usually
  electricity.
• Power conditioning is necessary because the
  natural output of the transducer can be
  intermittent, and at the wrong frequency, voltage
  and current to directly drive the device. A
  specialised DC-DC converter microchip takes in
  power from the transducer and convert to voltages
  which can then be stored or used.
• Energy storage is needed to balance the energy
  supply and energy demand. For applications where
  energy is used as soon it is collected (e.g. RFID
  and wireless light switches), no storage is
  needed. Usually however a rechargeable battery,
  capacitor, or supercapacitor is used. Batteries
  degrade over time, and so the lifetime of the
  storage device can often be the limiting factor
  in the overall lifetime of the harvester.

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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 Frequency (captured by an antenna)
• Biochemically produced energy (such as cells that
  extract energy from blood sugar).

Energy harvesting uses unconventional sources to
power circuitry.
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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

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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.

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Energy Harvesting Block Diagram
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• 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..

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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.

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Biochemical Energy Production

• Catabolism metabolic reactions in which large
  molecules are broken down into smaller molecules
  Usually produce energy (but not always)
• Anabolism metabolic reactions in which smaller
  molecules are joined to form larger molecules
  Usually consume energy

Metabolism
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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

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Li-Ion Battery Thin Film Battery Super Cap
Recharge cycles Hundreds Thousands Millions
Self-discharge Moderate Negligible High
Charge Time Hours Minutes Sec-minutes
Physical Size Large Small Medium
Capacity 0.3-2500 mAHr 12-1000 µAHr 10-100 µAHr
Environmental Impact High Minimal Minimal
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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

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• 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.

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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_Worksho
ps/Overview_of_energy_harvesting_systemsLA-UR_8296
.pdf http//chipdesignmag.com/lpd/blog/2009/07/17
/energy-scavenging-and-storage-must-work-together/
http//scholar.lib.vt.edu/ejournals/JOTS/v35/v35
n1/yildiz.html http//www.msm.cam.ac.uk/teaching/
partIII/courseM19/M19H.pdf file///C/Users/test1
/Downloads/Energy20harvesting20(1).pdf http//h
ealth.uml.edu/horta/23Energy.pdf