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WI-PIE: ENERGY HARVESTING IN MOBILE ELECTRONIC DEVICES

PRESENTED BY,

APARNA VIJAYAN K.M

ROLL NO: 16GUIDE:Mr. MUHSIN K.A

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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.