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04/12/2023 WI-PIE 1
WI-PIE: ENERGY HARVESTING IN MOBILE ELECTRONIC DEVICES
PRESENTED BY,
APARNA VIJAYAN K.M
ROLL NO: 16GUIDE:Mr. MUHSIN K.A
04/12/2023 WI-PIE 2
INTRODUCTION
• Number of mobile phones in use around the world at an
astonishing 5 billion.
• Overall energy consumption increases.
• World moving towards an energy crisis.
• An alternate method to power these mobile electronic devices.
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OBJECTIVE
• How we can harvest energy in mobile devices by using piezoelectric
material and dipole antennas.
• To reduce e-waste .
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WHY ENERGY HARVESTING IS USED?
• To reduce Total Cost of Ownership(TCO).
• To eliminate disposable battery waste.
• To increase life time and reliability.
• Charging the device during power failure.
• Minimizing the use of external chargers thereby reducing e-waste
and eventually making these devices charger-free
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Fig.1: Proposed energy harvesting model
WI-PIE MODEL
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TECHNIQUES FOR ENERGY HARVESTING
• Energy harvesting in mobile devices involves 2 techniques:
1. Piezoelectric energy harvesting.
2. RF energy scavenging.
• These provide an alternative method of powering mobile electronic
devices.
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PIEZOELECTRIC ENERGY HARVESTING
• Energy obtained from piezoelectric materials.
• Placing the piezoelectric crystals beneath the keys of a mobile
phone.
• Harvest the energy generated from the pressure of a key-press.
• Identify the average energy generated during every key press and
then utilize it by storing it in a secondary storage device.
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PIEZOELECTRIC HARVESTING MODEL
• Piezoelectric material is used to harvest energy and accumulate it
into an secondary storage until an level.
• Piezoelectric transducers are: MFC, PZT and Quick pack.
• Capacitor can be used as a secondary storage devices- in small
wireless sensors or for wearable medical appliances.
• Successfully model the energy harvesting system .
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SPECIFICATION OF PIEZOELECTRIC TRANSDUCER
• Piezoelectric transducer considered here is a std PSI-5A4E single layer
disk (.0075” thick) piezo ceramic sheet
• The material under consideration is a .125" (3.2mm) diameter disc and
is suitable for placing beneath the keys of a mobile phone.
• This material is chosen because of its high motion to volt sensitivity in
the order of 390 x 10-12 meter/volt and -190 x10-12 meter/volt.
• Direction of force under consideration here is parallel to the
polarization axis.
• Nickel electrodes are provided for electrical contact
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Fig.2 Dimension of T107-A4E-073 piezo ceramic sheet
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Fig.3 Layers in the Piezoelectric Model Phone
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PIEZOELECTRIC DESIGN
• Longitudinal effect is considered, so independent on the size and
shape of the material
• Piezoelectric crystals placed beneath the keys of a mobile phone and
connected electrically in parallel.
The resulting charge is
Cx = dxxFxnWhere;
dxx - piezoelectric coefficient (in pC/N).
Fx - applied force in x- direction
n - number of stacked elements.
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CAPACITORS vs THIN FILM BATTERY
Limitations of Capacitors:
* Inability to provide continuous source of power.
* Exhibits sharp bursts of charge and discharge - use voltage
regulator.
* Limited by their voltage level.
* Unstable discharge. Capacitor charging and discharging. Secondary storage device:
* Charge by using the trickle voltage from the key-press and
discharges only at the time of full charge.
* Thin film or battery cell .
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THIN FILM BATTERIES FOR SECONDARY STORAGE
• A thin film Li-ion battery with high charge density.
• Charge using the trickle voltage and discharge 5V to charge primary
battery.
• Protection circuits employed.
• A common protection circuit is used.
• Rechargeable, hence last longer.
• An efficient low loss interface circuit that could effectively transfer the
energy to the battery.
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RF ENERGY HARVESTING
• Circuits can be included to harvest the known and the unknown RF
energy in the environment.
• By using this circuit, the received radio energy can be converted to
DC and supplied to the battery.
• Since the technology is in its inception, the power generated would
be low.
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RF ENERGY HARVESTING MODEL
• Signals transmitted by mobile phone antennas are electromagnetic
radiation in the radio frequency spectrum.
• A large portion of this radiation is wasted as stray energy in the
environment.
• This radiation can be captured using power generating circuits with
a suitable antenna and can be converted to useable DC voltage.
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SPECIFICATION OF HARVESTING MODEL
• A micro strip size printed dipole antenna and additional power
conditioning circuitry.
• Power output varies with the distance from the source of the
radiation.
• Power densities from 0.1mW/m² to 1.0mW/m² can be obtained at
distances of 25m to 100m
• This can be increased by a factor of up to 3 by using an array of
these antennas.
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Fig.4 A model of the printed dipole antenna
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RF ENERGY HARVESTING MODEL DESIGN
• During heavy mobile traffic, the power generated is significantly high.
• A floating gate transistor at the output of the patch dipole antenna in
order to convert the obtained RF energy into useable DC power.
• In the case of a mobile phone, a higher power is required for the
purpose of charging.
• A capacitor can be linked to the drain of the transistor and an
additional transistor may also be used in order to generate that
required power.
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ADVANTAGES
• The energy of stray radiation in the vicinity of the phone utilized.
• Efficient fold-back mechanism.
• Ability to charge the device during power failure.
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APPLICATIONS
• Used in mobile phones as an alternative charging method.• For wearable medical appliances.
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FUTURE SCOPE
• Advancement of MEMS technology and micro-sensor applications
this could be developed in to an efficient control and interface
circuit model to improve the power harvested from ambient
vibrations.
• The reducing size of all devices will make this model implementable
in all commercial electronic devices.
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CONCLUSION
• From the environment perspective, this model could also reduce the
amount of e-waste .
• Integration of the two energy harvesting techniques has the potential
to make these devices entirely battery-free
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REFERENCE
• Guru Karthik Balasubraminan, Shivaraman Shankar, Aditya
Subramanyan, “Wi-Pie: Energy Harvesting in Mobile Electronic
Devices”, In. Proceedings of IEEE Global Humanitarian Technology
Conference, 2011.