hal project report

ENERGY HARVESTING USING A THERMO-ELECTRIC GENERATOR MODULE A DISSERTATION SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE AWARD OF THE DEGREE OF

BACHELOR OF ENGINEERING IN ELECTRICAL ENGINEERING

BY

AISHWARYA JAIN (Student ID 08104074) DEPARTMENT OF ELECTRICAL ENGINEERING PEC UNIVERSITY OF TECHNOLOGY CHANDIGARH 160012 January to May, 2012

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CERTIFICATE

This is to certify that the project “ENERGY HARVESTING USING A THERMO

ELECTRIC

GENERATOR

MODULE”

submitted

by

Mr. Aishwarya Jain is a record of bonafide work carried out by him at the Department of Electrical Engineering, PEC University of Technology, Chandigarh under my supervision and guidance in partial fulfilment of requirement for the award of the degree of Bachelor in Electrical Engineering.

Dated:

Guide:

Dr. Darshan Singh Associate Professor Electrical Engineering Department PEC University of Technology Chandigarh

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CANDIDATE DECLARATION I hereby declare that the project work entitled ―ENERGY HARVESTING USING A THERMO ELECTRIC GENERATOR MODULE‖ is an authentic record of my own work carried out at Department of Electrical Engineering, PEC University of Technology, Chandigarh as requirements of six months capstone project for the award of the degree of B.E. Electrical Engineering, under the guidance of Dr. Darshan Singh, during January to May, 2012. The matter embodied in this dissertation has not been submitted by me for the award of any other degree.

(Aishwarya Jain) Date:

Student I D- 08104074

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ACKNOWLEDGEMENT

I would like to express my gratitude to all those who provided me with the possibility to complete this project. I would like to give my heartfelt thanks to Dr. Darshan Singh, Associate Professor, Department of Electrical Engineering, for allowing me to work under his guidance and providing me with this opportunity to work in a very open end field and challenging environment. To devise benefit of his enormous experience, it is a matter of great privilege to me.

I owe sincere gratitude to the whole teaching faculty of PEC University of Technology, Chandigarh for their encouragement and unfailing interest and sincere suggestions from time to time in this work. I also extend my gratitude to Dr. Tilak Thakur, Associate Professor, Department of Electrical Engineering. His valuable inputs and guidance has given me immense support.

I offer my heartfelt appreciation to all my friends and my team in IEEE Student Branch who helped me move ahead with the project. Last but not the least; thanks are also extended to Dr. Balwinder Singh, Professor and Head of Department of Electrical Engineering, PEC University of Technology, Chandigarh for his help and encouragement for carrying out this project.

Dated:

(Aishwarya Jain)

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ABSTRACT Due to the continued exploitation of natural resources, the conventional sources of electric energy, consisting of fossil fuels such as petroleum and coal are getting depleted. The number of countries that are suffering due to the lack of electric energy is increasing every day. Global energy consumption has doubled in the past thirty years and is expected to increase by another 60% by 2030. From the report of International Energy Agency (IEA) and the Organization of Economic Co-operation and Development (OECD), the consumption rose from 5.5 billion toe (tons of oil equivalent) in 1971, to 10.3 billion toe in 2002. By 2030, global energy demand is expected to reach 16.3 billion toe, 1.6 times that of 2002. However, a large portion of this huge energy consumption is dissipated into the air in terms of heat e.g., from power factory, which cannot be efficiently used by human beings. Hence, a technique to collect this huge amount of wasted heat and convert it to electric energy is worth exploring. While new sources of energy such as solar energy, wind energy and hydropower etc. are being explored, an important alternate energy source that is often overlooked is thermal energy. Whenever, a work is done, small to large amount of thermal energy is dissipated into the ambience, which if converted back to electric energy may serve useful purposes. In the project we will focus on the use of Thermo Electric Generators for converting wasted heat into electric energy. One of the applications is a device which generates power from a heat source which is very commonly available in the rural houses such as gas or charcoal grills, oil & alcohol burners, camping stoves of all types including bio-gas, wood stoves. The power generated can be used for charging cell phones. In the project, following contributions will be made. We will investigate an energy harvesting technique to recycle the wasted heat in a cooking utensil into electric energy. We will present measurement results from experiments performed with a commercial TEG and a normal cooking utensil, in order to obtain a realistic estimate of the harnessed energy and determine the prospective applications of the recycled energy.

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INDEX Topic

Page No.

Certificate...........................................................................................................................…...ii Candidate Declaration……………………………………………………………….….…….iii Acknowledgement………………………………………………………………………..…...iv Abstract………………………………………………………………………………..……....v List of Figures………………………………………………………………………………...ix List of Tables…………………………………………………………………………………..x

Chapter (1).

INTRODUCTION…………………………………….…..………….………..1 1.1. Introduction 1.2. Disposition

Chapter (2).

THERMO-ELECTRIC GENERATOR……………………………………….3 2.1. Introduction 2.2. Thermocouple 2.3. Principle of Operation 2.3.1. Laws for Thermocouple circuits 2.4. Practical Use 2.4.1. Temperature- Voltage relationship 2.4.2. Cold- junction compensation 2.5. Types of Thermocouples 2.6. Thermo-Electric Generator 2.7. Conclusion

Chapter (3).

DESIGN OF OUTPUT CIRCUIT…………………………………………11 3.1.

Introduction

3.2.

DC-to-DC Convertor

3.3.

Boost Convertor 3.4.1. Circuit Analysis 3.4.2. Applications

3.5.

Conclusion

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Chapter (4).

Chapter (5).

DESIGN OF HARDWARE MODEL……………………………………….15 4.1.

Introduction

4.2.

Temperature Sensor

4.3.

LM 35 Temperature Sensor

4.4.

AVR 8-bit Microcontroller

4.5.

Conclusion

LABORATORY VIRTUAL INSTRUMENT ENGINEERING WORKBENCH (LABVIEW)…………………………………………..……21 5.1.

Introduction

5.2.

Features of LabVIEW 5.2.1. Data Flow Programming 5.2.2. Graphical Programming

5.3.

Benefits of using LabVIEW 5.3.1. Interfacing 5.3.2. Code Compilation 5.3.3. Large Libraries 5.3.4. Code Re- Use

Chapter (6).

5.4.

Software Architecture- VISA

5.5.

Serial Communication

5.6.

Conclusion

RESULTS AND SNAPSHOTS OF THE PROJECT…………………..……29 6.1.

Significance of the Project

6.2.

Circuit Diagram of Hardware Model

6.3.

Heat Sink mechanism

6.4.

Flowchart for Notification system in LabVIEW

6.5.

LabVIEW Programs

6.6.

Applications

Chapter (7).

CONCLUSIONS AND FUTURE SCOPE OF WORK……………..……….39

Chapter (8).

REFERENCES……………………………….………………………………41

Chapter (9).

ANNEXURES………………………………………………………………..43 10.1. LabVIEW Technical Details 10.2. Source Code 10.3. LM 35 Datasheet 10.4. ATMEGA 16 Datasheet

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LIST OF FIGURES Figure 1.1: Global primary energy consumption, 1971-2030

1

Figure 2.1: A Thermocouple measuring circuit

4

Figure 2.2: When heat and cold are applied, the device then generates electricity

9

Figure 3.1: The basic schematic of a boost converter

12

Figure 4.1: The Sensing Process

15

Figure 4.2: Connections of LM35

17

Figure 4.3: Working of ADC

18

Figure 4.4: Pin configuration for ADC system of Atmega16 microcontroller

19

Figure 5.1: The LabVIEW Environment

21

Figure 5.2: Virtual Instrument Software Architecture

25

Figure 5.3: Serial Communication

26

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LIST OF TABLES Table 2.1: Polynomial Coefficients 0-500 °C

6

Table 2.2: Thermocouple Comparison

8

Table 5.1: RS 232 Cabling

27

Table 10.1: Windows System Requirements

43

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1. INTRODUCTION 1.1.

INTRODUCTION

Energy harvesting devices, which convert mechanical energy into electrical energy, have attracted much interest in both the military and commercial sectors. Some systems convert random motion, such as that of ocean waves, into electricity to be used by oceanographic monitoring sensors for autonomous operation. Future applications may include high poweroutput devices (or arrays of such devices) deployed at remote locations to serve as reliable power stations for large systems. All of these devices must be sufficiently robust to endure long-term exposure to hostile environments and have a broad range of dynamic sensitivity to exploit the entire spectrum of wave motions. Typical power densities available from energy harvesting devices are highly dependent upon the specific application and design of the harvesting generator.

The number of countries that are suffering due to the lack of electric energy is increasing every day. Global energy consumption has doubled in the past thirty years and is expected to increase by another 60% by 2030. From the report of International Energy Agency (IEA) and the Organization of Economic Co-operation and Development (OECD), the consumption rose from 5.5 billion toe (tons of oil equivalent) in 1971, to 10.3 billion toe in 2002. By 2030, global energy demand is expected to reach 16.3 billion toe, 1.6 times that of 2002.

Figure 1.1: Global primary energy consumption, 1971-2030 Source: Energy White Paper 2005 Japan.

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While new sources of energy such as solar energy, wind energy and hydropower etc. are being explored, an important alternate energy source that is often overlooked is thermal energy. Whenever, a work is done, small to large amount of thermal energy is dissipated into the ambience, which if converted back to electric energy may serve useful purposes. In the project we will focus on the use of Thermo Electric Generators for converting wasted heat into electric energy. One of the applications is a device which generates power from a heat source which is very commonly available in the rural houses such as gas or charcoal grills, oil & alcohol burners, camping stoves of all types including bio-gas, wood stoves. The power generated can be used for charging cell phones.

1.2.

DISPOSITION

In the project, following contributions will be made. We will investigate an energy harvesting technique to recycle the wasted heat in a cooking utensil into electric energy. We will present measurement results from experiments performed with a commercial TEG and a normal cooking utensil, in order to obtain a realistic estimate of the harnessed energy and determine the prospective applications of the recycled energy.

The project report begins with the introduction of the project with an overview of the problem statement in consideration. It is followed with separate chapters dedicated to each major topic of the project. To start with, first of all the concept of thermo-electric generators is explained. The next chapter describes the role of dc-to-dc convertor in the output circuit and importance of the same. Analysis of the hardware model is done with the theoretical description of each of the major components used in the circuit. A separate chapter is dedicated to LabVIEW describing its usefulness and ease of use. A notification system is put in place to make the feedback system of the project responsive. Results and snapshots of the project are followed. The report then concludes giving conclusion and future scope of the work done followed by the references to the project.

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2. THERMO-ELECTRIC GENERATOR MODULE 2.1.

INTRODUCTION

TEGs are made from thermoelectric modules which are solid-state integrated circuits that employ three established thermoelectric effects known as the Peltier, Seebeck and Thomson effects. It is the Seebeck effect that is responsible for electrical power generation. Their construction consists of pairs of p-type and n-type semiconductor materials forming a thermocouple. These thermocouples are then connected electrically forming an array of multiple thermocouples (thermopile). They are then sandwiched between two thin ceramic wafers. Their typical efficiencies are around 5-10% [1].

2.2.

THERMOCOUPLE

A thermocouple is a device consisting of two different conductors (usually metal alloys) that produce a voltage, proportional to a temperature difference, between either ends of the two conductors. Thermocouples are a widely used type of temperature sensor for measurement and control and can also be used to convert a temperature gradient into electricity. They are inexpensive, interchangeable, are supplied with standard connectors, and can measure a wide range of temperatures. In contrast to most other methods of temperature measurement, thermocouples are self-powered and require no external form of excitation. The main limitation with thermocouples is accuracy and system errors of less than one degree Celsius (C) can be difficult to achieve.

Any junction of dissimilar metals will produce an electric potential related to temperature. Thermocouples for practical measurement of temperature are junctions of specific alloys which have a predictable and repeatable relationship between temperature and voltage. Different alloys are used for different temperature ranges. Properties such as resistance to corrosion may also be important when choosing a type of thermocouple. Where the measurement point is far from the measuring instrument, the intermediate connection can be made by extension wires which are less costly than the materials used to make the sensor. Thermocouples are usually standardized against a reference temperature of 0 degrees Celsius; practical instruments use electronic methods of cold-junction compensation to adjust for

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varying temperature at the instrument terminals. Electronic instruments can also compensate for the varying characteristics of the thermocouple, and so improve the precision and accuracy of measurements.

Thermocouples are widely used in science and industry; applications include temperature measurement for kilns, gas turbine exhaust, diesel engines, and other industrial processes.

Figure 2.1: A Thermocouple measuring circuit with a heat source, cold junction and a measuring instrument

2.3.

PRINCIPLE OF OPERATION

In 1821, the German–Estonian physicist Thomas Johann Seebeck discovered that when any conductor is subjected to a thermal gradient, it will generate a voltage. This is now known as the thermoelectric effect or Seebeck effect. [2] Any attempt to measure this voltage necessarily involves connecting another conductor to the "hot" end. This additional conductor will then also experience the temperature gradient, and develop a voltage of its own which will oppose the original. Fortunately, the magnitude of the effect depends on the metal in use. Using a xiii

dissimilar metal to complete the circuit creates a circuit in which the two legs generate different voltages, leaving a small difference in voltage available for measurement. That difference increases with temperature, and is between 1 and 70 microvolts per degree Celsius (µV/°C) for standard metal combinations.

The voltage is not generated at the junction of the two metals of the thermocouple but rather along that portion of the length of the two dissimilar metals that is subjected to a temperature gradient. Because both lengths of dissimilar metals experience the same temperature gradient, the end result is a measurement of the difference in temperature between the thermocouple junction and the reference junction.

2.3.1. Laws for Thermocouple Circuits

The properties of thermoelectric junctions with varying temperatures and compositions can be summarized in three laws describing the behavior of thermocouple circuits.

Homogeneous material A thermoelectric current cannot be sustained in a circuit of a single homogeneous material by the application of heat alone, regardless of how it might vary in cross section. In other words, temperature changes in the wiring between the input and output do not affect the output voltage, provided all wires are made of the same materials as the thermocouple. No current flows in the circuit made of a single metal by the application of heat alone.

Intermediate materials The algebraic sum of the thermoelectric emfs in a circuit composed of any number of dissimilar materials is zero if all of the junctions are at a uniform temperature. So if a third metal is inserted in either wire and if the two new junctions are at the same temperature, there will be no net voltage generated by the new metal.

Successive or intermediate temperatures If two dissimilar homogeneous materials produce thermal emf1 when the junctions are at T1 and T2 and produce thermal emf2 when the junctions are at T2 and T3, the emf generated when the junctions are at T1 and T3 will be emf1 + emf2, provided T1