Energy Harvesting From Renewable Resources - MJRET · So in order to meet the power generation...

National Conference-NCPE-2k15, organized by KLE Society's Dr. M. S. Sheshgiri College of Engineering &

Technology, Belagavi, Special issue published by Multidisciplinary Journal of Research in Engineering and

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Energy Harvesting From Renewable

Resources

Charlene Sequeira#1

, Sue Ellen Medeira#2

, Prudelle Fernandes#3

Mugdha Bakhale#4

, Vipul Sardessai#5

Department of Electronics and Telecommunication Engineering Padre Conceicao

College of Engineering, Verna, Goa, India

Abstract: As the sources of conventional energy deplete day by day, resorting to alternative

sources of energy like solar energy, piezo electric energy has become the need of the hour.

So in order to meet the power generation scarcity problem along with resource extinction

drawbacks and pollution problems, scientists have been toiling hard to shift the

dependence onto renewable energy resources. In this research paper, we will be using

solar power and piezo electric energy to charge a battery.

The sun is the ultimate source of energy in the form of light and heat. It will increase

countries’ energy security through reliance on an indigenous, inexhaustible and mostly

import-independent resources, enhance sustainability, reduce pollution, lower the costs of

mitigating climate change, and keep fossil fuel prices lower than otherwise. Light of the

sun is directly converted into electrical energy with the help of a solar cell. The charged

battery can then be used to power the devices that are an essential part of our everyday life

like mobiles phones, mp3, torches, etc. In this paper, the techniques used to harvest solar

energy will be described. It also highlights how to efficiently utilize this energy to charge a

battery so as to serve the various purposes.

Thousands of footsteps land every second around us. A human being takes an average of

7000 footsteps a day. Each footstep produces a large amount of force, a force that is

equivalent to our own body weight. Methods can be developed to use this energy to charge

our phone or any devices. We had an idea of using piezoelectric transducers to harness the

energy from this force.

Key words : Renewable, Solar energy, Solar cell, Harvest, Battery, Piezo electric energy, Piezo transducer

I. INTRODUCTION

Technical innovations have led to the growth of human standards in the present globalized

Journal homepage: www.mjret.in

ISSN:2348 - 6953

http://www.mjret.in/



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world, and thus our electricity utilization has become a mandatory requirement in order to

invent new things, or even to utilize the present technology.

In order to meet the power generation scarcity problem along with resource extinction

drawbacks, we motivated ourselves to create this project which uses natural renewable solar

energy for generating electricity in an efficient manner, thus creating a pollution free world

termed as „GREEN ENERGY‟ power generation concept. In our project we will be

harnessing energy from two resources, namely, Solar Energy and Piezo electric energy.

A.Solar Energy

The sun is the ultimate source of limitless energy in the form of light and heat. This is

directly converted to electrical energy using a solar cell connected to an appropriate circuit.

Our project will allow a solar panel to efficiently recharge a DC battery. The circuitry

monitors the battery voltage level and charges the battery using analog to digital conversion

techniques.

B.Piezo Electric energy

We intend to implement this idea using piezo plates inside the inner sole of the shoe, so that

the force from each footstep can be a step towards changing the dependence on non-

renewable sources of energy.

Piezoelectric transducer takes the mechanical stress as the input and gives an electrical

output. This can be used to charge batteries that are used in everyday life. This output from

the piezo is AC in nature since the input is not constant and therefore we will be rectifying

and then further regulating the output to store the energy in a rechargeable battery.

II. SOLAR PANEL

A solar cell, or photovoltaic cell, is an electrical device that converts the energy of light

directly into electricity by the photovoltaic effect. It is a form of photoelectric cell, defined as

a device whose electrical characteristics, such as

current, voltage, or resistance, vary when exposed to light. Solar cells are the building blocks

of photovoltaic modules, otherwise known as panels. They are electrically connected and

mounted on a supporting structure (more commonly known as a solar panel), which can then

be grouped into larger solar arrays. The solar panel can be used as a component of a larger

photovoltaic system to generate and supply electricity in commercial and residential



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applications. The cells also all have one or more electric field that acts to force electrons

freed by light absorption to flow in a certain direction. This flow of electrons is the current,

and by placing metal contacts on the top and bottom of the PV cell, we can draw that current

of for external use. PV modules are generally made by connecting several individual cells

together to achieve useful levels of voltage and current, and putting them in a sturdy frame

complete with positive and negative terminals.

A. Structure

Photovoltaic cells rely on substances known as semiconductors. Semiconductors are

insulators in their pure form, but are able to conduct electricity when heated or combined

with other materials. A semiconductor mixed, or "doped," with phosphorous develops an

excess of free electrons. This is known as an n-type semiconductor. A semiconductor doped

with other materials, such as boron, develops an excess of "holes," spaces that accept

electrons. This is known as a p-type semiconductor. A PV cell joins n-type and p-type

materials, with a layer in between known as a junction. Even in the absence of light, a small

number of electrons move across the junction from the n-type to the p-type semiconductor,

producing a small voltage. In the presence of light, photons dislodge a large number of

electrons, which flow across the junction to create a current. This current can be used to

power electrical devices, from light bulbs to cell phone chargers.

B. Operation

An electrical current is created by the movement of free electrons, which carry a negative

charge. Normally, electrons are entangled in an orbit around the nucleus of an atom, which is

made of protons and neutrons. These atomic particles are the building blocks of matter and

can be found in absolutely everything. Some matter holds its electrons more tightly than

others, but given enough energy, an electron can be knocked loose from its orbit. Photons

from sunlight carry enough energy to remove these electrons from their orbit in the element

silicon, which is the material used in most solar cells. The photon's ability to disentangle

electrons is called the photoelectric effect.

An imbalance between positively charged and negatively charged particles is created within

the silicon by adding the impurities boron or phosphorus. This imbalance creates an electrical



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field in the silicon. When photons strike the material and break electrons free from their

orbits, this electrical field pushes them towards the front of the solar cell, which creates a

negatively charged side. The protons left behind on the other side of the cell surface create a

positive charge .When these two sides are connected using an external load, an indirect

circuit like the terminals of this solar battery charger will be formed, and the electrons flow

into the load and create electricity. Since a single solar cell only produces one or two watts of

electricity, multiple cells are combined to form modules that work together to produce

enough power to charge a battery.

Figure1: Operation of a PV cell

Solar panels are a great way to use sustainable, natural resources to create energy. No matter

where you live, home solar panels can be installed by first professional fitters. Even if you

don‟t collect enough sunlight for all of your electricity, you can collect enough of it to

significantly reduce what you do use. Solar energy is a renewable, sustainable resource. Oil

on the other hand, is not renewable or sustainable. Solar cells are totally silent. They can

extract energy from the sun without making any noise. Solar energy is non-polluting. Of all

the advantages of solar energy over those of renewable sources, this is perhaps the most

important.

III. . CHARGING OF THE BATTERY

The solar panel as per specifications provides an output of about 8V and 2.5mA. This after

regulation to 5V can be used to charge AA rechargeable batteries that are available easily.

A.. How Batteries Work

Batteries do not actually store electricity, although it is true that electricity can be put into a



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battery and then taken out again. When a battery is placed inside an electrical circuit, the

chemical reaction goes forward and transforms chemical energy into electrical energy. There

are several different chemicals that release electricity when they are combined in the right

way. One of the primary ways batteries vary is in which chemical reaction is used.

B. Difference between Rechargeable and Non Rechargeable Batteries

The main difference between the rechargeable and non rechargeable batteries is in the type of

chemical reaction used. In Non- Rechargeable batteries, the chemical reaction involved is

one way and cannot be reversed by any means. But in Rechargeable batteries the reaction can

be reversed bypassing electricity through them. So these batteries can be used again after

charging.

C. Working of a Rechargeable Battery

Figure 2: Rechargeable Battery Diagram Convention

These types of batteries have two electrodes namely the cathode and the anode. Voltage

difference between the anode and cathode causes a current to flow between them through an

electrolyte. Batteries these days are made up of plates with the help of reactive chemicals that

are separated by barriers. These barriers are polarized so that all the electrons gather on one

side. The side where they gather becomes negatively charged and the other side becomes

positively charged. When we connect a device, it creates a current and the electrons flow

through the device to the positive side. At the same time, an electrochemical reaction takes

place inside the batteries, which cause the electrons to replenish. The result is a chemical

process that creates electrical energy. A rechargeable battery, however, can efficiently reverse

the chemical changes that occur during the discharge process. In this manner, it is restored to



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full charge and is fit for use repeatedly. It must also be able to undergo the reverse reaction

both efficiently and safely multiple times.

D. Procedure

Figure 3: Procedure of charging a battery

The solar panel provides the output of 8V when placed in the sun. But this voltage is too high

to charge a normal battery. The batteries required in this circuitry are mainly AA (NiMh Or

Li - ion) rechargeable batteries with an output of 1.5V. In this case we need to step down the

high voltage of 8V to lesser value of about 5V using a voltage regulator IC. The input

provided to this IC is 8V from the panel and it efficiently brings down the voltage to 5V to

satisfy the requirements.

The output of this regulator is then given to the batteries and then the batteries get charged.

These batteries can then be used to power up power banks, torches etc. The power banks are

easily available and can be used to charge mobiles, mp3 players etc.

IV. WORKING OF THE CIRCUIT

The output of the solar panel being used is 8V and 2.5ma. The voltage required for our

application is a voltage around 5V. To achieve this we need to regulate the voltage to 5V.

This 5V is given to either the “POWER BANK (external battery)” or to the “INTERNAL

BATTERY”.

A. Charging the Power Bank

When the external power bank is connected to the pins of the micro controller, the controller

will sample the voltage of the battery, by performing an ADC conversion. If the charge of the



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mobile phone is below the set threshold value, the micro controller will generate an interrupt

and provide a path for the energy from the solar panel to move to the battery for charging

through a relay.

B. Charging the internal battery

If the external power bank is full and does not require to be charged any more, the micro

controller will switch the position of the relay and the solar energy will be used to charge the

internal battery. This internal battery is used to power up the micro controller and other

internal circuitry being used.

Figure 4: Basic block diagram of the working.

V. WORKING OF PIEZO ENERGY HARVESTING

A. Operation of Piezo Disc

Figure 5. A Piezo Disc

A piezo disc is a thin metal disc with the top surface being coated with piezoelectric material

which has a naturally occuring electronic charge. This top surface acts as an anode while the

metal surface is cathode. When a piezoelectric material is strained in one direction in open

circuit, the resulting charge displacement causes a force which tries to move the material

back to an unstrained state, and some work is done in straining the material.

Longitudinal effect



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The amount of charge produced is strictly proportional to the applied force and is

independent of size and shape of the piezoelectric element. Using several elements that are

mechanically in series and electrically in parallel is the only way to increase the charge

output. The resulting charge is

Cx= dxxFxn (1.1)

where dxx is the piezoelectric coefficient for a charge in x-direction released by forces

applied along x-direction in pC/N). Fx is the applied Force in x-direction [N and n

corresponds to the number of stacked elements.

Shear effect

The charges produced are strictly proportional to the applied forces and are independent of

the element‟s size and shape.

For n elements mechanically in series and electrically in parallel the charge is

Cx=2 dxxFxn (1.2)

where dxx is the piezoelectric coefficient for a charge in x-direction released by forces

applied along x-direction (in pC/N). Fx is the applied Force in x-direction [N].

B. Implementation

We are using 3 piezo discs in parallel with each other. This model is placed in between the

inner and outer sole of a shoe. The source of pressure will be from the weight of a person

walking over it. The output of the piezoelectric material is not a steady one. It is in the form

of discrete pulses. A bridge circuit is required to get the output into a steady AC signal. We

need the output to be a DC signal for the charging of batteries, therefore we use a rectifier to

convert the AC into a constant DC output. These two functions are incorporated using ICs

from Linear Technology. The circuit along with these ICs can be implemented using a circuit

simulator by Linear Technology called LTspice. The two ICs being used are LTC-3588-1 and

LT-3009-5.

VIN (Pin 4): Rectified Input Voltage. A capacitor on this pin serves as an energy reservoir

and input supply for the buck regulator. The VIN voltage is internally clamped to a maximum

of 20V (typical).

SW (Pin 5): Switch Pin for the Buck Switching Regulator A 10μH or larger inductor

should be connected from SW to VOUT.



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VOUT (Pin 6): Sense pin used to monitor the output voltage and adjust it through internal

feedback.

Figure 6. Output of a single piezo disc

C. LTC 3588-1

The LTC3588-1 integrates a low-loss full-wave bridge rectifier with a high efficiency buck

converter to form a complete energy harvesting solution optimized for high output

impedance energy sources such as piezoelectric, solar, or magnetic transducers. An ultralow

quiescent current under-voltage lockout (UVLO) mode with a wide hysteresis window

allows charge to accumulate on an input capacitor until the buck converter can efficiently

transfer a portion of the stored charge to the output. In regulation, the LTC3588-1 enters a

sleep state in which both input and output quiescent currents are minimal. The buck

converter turns on and off as needed to maintain regulation.

Figure. 7. 100mA Piezoelectric Energy Harvesting Power Supply

1)Pin Functions

PZ1 (Pin 1): Input connection for piezoelectric element or other AC source (used in

conjunction with PZ2).



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PZ2 (Pin 2): Input connection for piezoelectric element or other AC source (used in

conjunction with PZ1)

CAP (Pin 3): Internal rail referenced to VIN to serve as gate drive for buck PMOS switch. A

1μF capacitor should be connected between CAP and VIN. This pin is not intended for use

as an external system rail.

VIN2 (Pin 7): Internal low voltage rail to serve as gate drive or buck NMOS switch. Also

serves as a logic high rail for output voltage select bits D0 and D1. A 4.7μF capacitor should

be connected from VIN2 to GND. This pin is not intended for use as an external system rail.

D1 (Pin 8): Output Voltage Select Bit. D1 should be tied high to VIN2 or low to GND

to select desired VOUT (see Table 1).

D0 (Pin 9): Output Voltage Select Bit. D0 should be tied high to VIN2 or low to GND

to select desired VOUT (see Table 1).

Figure8: Internal Block Diagram of LTC 3588 PGOOD

(Pin 10): Power good output is logic high when VOUT is above 92% of the target

value. The logic high is referenced to the VOUT rail.

GND (Exposed Pad Pin 11): Ground. The Exposed Pad should be connected to a continuous

ground plane on the second layer of the printed circuit board by several vias directly under

the LTC3588-1.

D. LT 3009 series

The LTR3009 Series are micro-power, low dropout voltage (LDO) linear regulators. The

devices supply 20mA output current with a dropout voltage of 280mV. No-load quiescent

current is 3μA. Ground pin current remains at less than 5% of output current as load

increases. In shutdown, quiescent current is less than 1μA.



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The LT3009 regulators optimize stability and transient response with low ESR ceramic

capacitors, requiring a minimum of only

1μF. The regulators do not require the addition of ESR as is common with other

regulators. Internal protection circuitry includes current limiting ,thermal limiting,

reverse-battery protection and reverse current protection.

Figure 9: IC LT3009-3.3

SHDN (Pin 1/Pin 5): Shutdown. Pulling the SHDN pin low puts the LT3009 into a low

power state and turns theoutput off. If unused, tie the SHDN pin to VIN.

The LT3009 does not function if the SHDN pin is not connected. The SHDN pin cannot be

driven below GND unless tied to the IN pin. If the SHDN pin is driven below GND while IN

is powered, the output will turn on. SHDN pin logic cannot be referenced to a negative rail.

GND (Pins 2, 3, 4/Pin 6): Ground. Connect the bottom of the resistor divider, that sets

output voltage, directly to GND for the best regulation.

IN (Pin 5/Pin 4): Input. The IN pin supplies power to the device. The LT3009 requires

a bypass capacitor at IN if the device is more than six inches away from the main input

filter capacitor. In general, the output impedance of a battery rises with frequency, so it

is advisable to include a bypass capacitor in battery-powered circuits. A bypass

capacitor in the range of 0.1μF to 10μF will suffice. The

LT3009 withstands reverse voltages on the IN pin with respect to ground and the OUT pin. In

the case of a reversed input, this occurs with a battery plugged in backwards, the LT3009 acts

as if a large resistor is in series with its input. Limited reverse current flows into the LT3009

and no reverse voltage appears at the load. The device protects both itself and the load.

OUT (Pin 6/Pins 2, 3): Output. This pin supplies power to

the load. Use a minimum output capacitor of 1μF to prevent oscillations. Large load transient

applications require larger output capacitors to limit peak voltage transients. See the



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Applications Information section for more information on output capacitance and reverse

output characteristics.

Figure 10: Output from combination of LTC ICs

Figure 11: Final Block Diagram

Figure 12: LTSpice Simulation of block diagram in figure 9



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VI. IMPLEMENTATION

The circuit shown in Fig. 4 can be implemented by using the software, LTspiceVI. It is a high

performance Spice III simulator, schematic capture and waveform viewer with enhancements

and models for easing the simulation of switching regulators. The enhancements by Linear

Technology made to Spice have made simulating switching regulators extremely fast

compared to normal Spice simulators, allowing the user to view waveforms for most

switching regulators in just a few minutes. Included in the software is Spice, Macro Models

for 80% of Linear Technology's switching regulators, over 200 op-amp models, as well as

resistors, transistors and MOSFET models.

ACKNOWLEDGMENT

We are immensely grateful to our project guide Mrs. Reena Fernandes (Asst. Prof. at Padre

Conceicao College of Engineering) for her guidance and continuous support. A big thank you

to the Head of the Electronics and Telecommunication Department Dr. K. R .Pai and Mr. Evy

for clearing many of our doubts. Our thank you also goes out to Mr. Suhaas Sadekar for

providing us with the solar panel without which our project would not be possible. Thank

you.

REFERENCES

[1] Aladdin Solar, LLC, 2008

[2] Raymond T. Fonash, “Solar cell”, April 2014

[3] V. Ryan, “Advantages and disadvantages of solar power”, 2005-2009

[4] Zachary Shahan, “Advantages and disadvantages of solar power”, October 2013

[5] Shivananda Pukhrem, “How Solar Cells Work — Components & Operation Of Solar Cells”,May 2013

[6] Komp, Richard J., “ Practical Photovoltaics” , Aatec Publications, 1984

[7] Murray, Charles J. "Solar Power's Bright Hope," Design News. March,1991,30.

[8] Jain and Jain, “A textbook of Engineering Chemistry”, Dhanapatrai

Publications, New Delhi.

[9] en.wikipedia.org, “AA battery”, “Nickel Metal Hydride Battery”..

[10] “MSP-430” data sheet, Texas Instruments, United states of America.

[11] “LTC 3588-1” Datasheet, Linear Technology, United States of America

[12] LT 3009” Datasheet, Linear Technology, United States of America.

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