In recent years, energy harvesting has become a popular term in both academic and industrial world, as traditional power generation resources, such as fossil fuels and nuclear fission, are either facing global shortage crisis or simply being quite costly. In contrast, the resources for energy harvesters are usually naturally present, for instance, the temperature gradient from the combustion engine, electromagnetic energy from communication and broadcast, motion from human movement, just to name a few. Currently, areas of research interests mainly consists of piezoelectric energy harvesting, piezoelectric energy harvesting, waste heat recovery, electromagnetic energy harvesting, ambient-radiation energy harvesting, etc. However, current technologies of energy harvesting are capable of producing only enough power to drive relatively low-power electronics. Also, high volume applications of these technologies depend on further enhancement of the energy harvesting efficiencies.
Among all research directions, waste heat recovery (WHR) is most concerned, due to the widespread existence and high accessibility of suitable resources. According to India Bureau of Energy Efficiency , the benefits of WHR includes reduction in the process consumption and costs, reduction in pollution and equipment sizes, and also reduction in auxiliary energy consumption.
According to a survey by WSJ the energy losses in the world are 2.5 times to the energy actually utilized by the humans.
FIG 1- UTILIZATION OF ENERGY IN AUTOMOBILE
FIG 2- TYPICAL TEMPERATURE DISTRIBUTION OF EXHAUST.
1.2 Work Concept
According to the law of conservation of energy ‘ENERGY CAN NEITHER BE CREATED NOR DESTROYED, IT CAN JUST BE CONVERTED FROM ONE FORM TO ANOTHER’.
Thermoelectric generator (TEG) has been utilized in most automotive applications, which are the targets of this thesis. TEGs are devices which convert heat (temperature differences) directly into electrical energy, using a phenomenon called the "Seebeck effect" (or "thermoelectric effect"). Their typical efficiencies are around 5-10%. TEGs are solid-state devices which have no moving parts. Sub-branches of TEG have been developed to cater the needs of specific target applications, such as radioisotope TEG for spacecraft and automotive TEG (ATEG) for automobiles.
A thermoelectric device creates voltage when there is a different temperature on each side. Conversely, when a voltage is applied to it, it creates a temperature difference. At the atomic scale, an applied temperature gradient causes charge carriers in the material to diffuse from the hot side to the cold side.
This effect can be used to generate electricity, measure temperature or change the temperature of objects. Because the direction of heating and cooling is determined by the polarity of the applied voltage, thermoelectric devices can be used as temperature controllers.
Fig-3 SEEBECK EXPERIMENT
CHAPTER-2 PROJECT METHODOLOGY
2.1 Modern methods of power generation
2.1.1 Direct Method
Generating power from waste heat typically involves waste heat utilization from internal combustion engine to generate mechanical energy that drives an electric generator. Electricity generation is directly from heat source such as thermoelectric and piezoelectric generator. A factor that affects on power generation is thermodynamic limitations for different temperature range.. The efficiency of power generation is heavily depended on the temperature of the waste heat gas and mass flow rate of exhaust gas
2.1.2 Piezoelectric Generation
It is used for low temperature range of 100 to 150. Piezoelectric devices convert mechanical energy in the form of ambient vibration to electric energy. This is thin film membrane can take advantage of oscillatory gas expansion to create a voltage output.
2.1.3 Thermionic Generation
It is thermoelectric device operate on thermionic emission. In this system a temperature difference drives the flow of electron through vacuum from metal to metal oxide surface at 1000
2.1.4 Thermo Photo-voltaic
It converts radiant energy to electricity. Heating of emitter emits electromagnetic radiation. All direct electric conversion devices has low efficiency but it can be increased by nontechnology. Advantages in alternate power cycle may increases feasibility of power generation at low temperature. All this direct method of power generation devices are high cost and low efficiency. It can be easily handled and with compact in size. So, require minimum space.
2.2 Automotive Thermoelectric Generator
2.2.1 Construction
An automotive thermoelectric generator (ATEG) is a device that converts waste heat in an internal combustion engine (IC) into electricity using the Seebeck Effect. A typical ATEG consists of four main elements: A hot-side heat exchanger, a cold-side heat exchanger, thermoelectric materials, and a compression assembly system. ATEGs can convert waste heat from an engine’s coolant or exhaust into electricity The generator consists of an array of thermocouples made from two different metals such as copper and strips cut from tin cans or discarded copper and aluminum wire .By reclaiming this otherwise lost energy, ATEGs decrease fuel consumed by the electric generator load on the engine. However, the cost of the unit and the extra fuel consumed due to its weight must be also considered.
FIG4 ‘ THERMOELECTRIC GENERATOR CONSTRUCTION
2.2.2 Operation Principle
In ATEGs, thermoelectric materials are packed between the hot-side and the cold-side heat exchangers. The thermoelectric materials are made up of p-type and n-type semiconductors, while the heat exchangers are metal plates with high thermal conductivity.
The temperature difference between the two surfaces of the thermoelectric modules generates electricity using the Seebeck Effect. When hot exhaust from the engine passes through an exhaust ATEG, the charge carriers of the semiconductors within the generator diffuse from the hot-side heat exchanger to the cold-side exchanger. The build-up of charge carriers results in a net charge, producing an electrostatic potential while the heat transfer drives a current. With exhaust temperatures of 700??C (~1300??F) or more, the temperature difference between exhaust gas on the hot side and coolant on the cold side is several hundred degrees. This temperature difference is capable of generating 500-750 W of electricity.
FIG 5 ‘ OPERATING PRINCIPLE OF TEG
2.2.3 Seebeck Co-efficient For different Elements
In Figure, the materials used in the two legs are n- and p-type semiconductors. If we denote their respective Seebeck coefficients to be Sn and Sp, the open circuit voltage Voc generated by this TE couple is then governed by the equation:
If the Seebeck coefficients are approximately constant for the measured temperature range in the TE legs (which is often true), Equation 2.1 can be simplified as:
If the temperature difference ??T between the two ends of a material is small, then the
Seebeck coefficient of this material is approximately defined as:
where ??V is the voltage seen at the terminals.
Thermopower is a collective result of different effects, among which two mechanisms provide major impact, and they are charge-carrier diffusion and phonon drag.
In a TEG where two ends of the n- and p-type legs are at different temperature levels, charge carriers in the leg material tend to diffuse in the direction which can help to reach thermodynamic equilibrium within the leg. That is to say, the hot carriers (charge carriers originally at the end with higher temperature) will move toward the cold side of TEG, and cold carriers move toward the hot side. If temperature difference is intentionally kept constant, the diffusion of charge carriers will form a constant heat current, hence a constant electrical current. Take n- and p-legs of TEG in Figure 2.1 as an example, the heat source, i.e. the side with higher temperature, will drive electrons in the n-type leg toward the cold side, crossing the metallic interconnect, and pass into the p-type leg, thus creating a current through the circuit.
Holes in the p-type leg will then follow in the direction of the current. The current can then be used to power a load.
If the rate of diffusion of hot and cold carriers were equal, there would be no net change in charge within the TE leg. However, we need to take into account the impurities, imperfections and lattice vibrations which scatter the diffusing charges. Since scattering is energy-dependent, the hot and cold charge carriers will diffuse at different rates, which then create a potential difference, i.e. an electrostatic voltage, in the leg. This electric field, on the other hand, opposes the uneven scattering, and equilibrium will be finally reached given enough time. The above analysis brings about the conclusion that the thermopower of a material depends greatly on impurities, imperfections, and structural changes, with the latter affected often by temperature
and electric field.
Another major impact on thermo power is phonon drag. A phonon is a quantum mechanical description of a special type of vibrational motion, in which a lattice uniformly oscillates at the same frequency. Phonons are not always in local thermal equilibrium; they move against the thermal gradient. They lose momentum by interacting with electrons (or other carriers) and imperfections in the crystal. The phonon-electron scattering is predominant in phonon drag in a temperature region approximately defined by equation:
where ??D is the Debye temperature. This temperature is approximately around 200 K. At lower temperatures there are fewer phonons available for drag, and at higher temperatures they tend to lose momentum in phonon-phonon scattering instead of phonon-electron scattering.
2.3 TEG Architecture
The first TEG produced has the architecture similar to the one shown in,with vertical structure and single material within each leg. Later, researchers realized that TE material properties are highly temperature dependent, that is to saytemperature variation influence TEG performance considerably. Hence, innovated design concepts addressing the temperature-dependent issues have been developed along the way. The first improvement in the TEG architecture comes with the concept of segmentation (or stack in some cases) of thermocouple. In this concept, it is suggested that thermocouples should be built with several materials, with each material optimized for the temperature range it is located. With this design philosophy, the TEGs could reach higher overall efficiencies than those built with single material within each leg. Design considerations of segmented thermocouples are discussed in Main concerns are the compatibility of materials and the dimensioning of thermocouple elements.
FIG 6- THERMOCOUPLE CONFIGURATION WITH SEGMENTED LEGS
2.4 Thermoelectric Generation and its Components
The exhaust pipe contains a block with thermo electric materials that generates a direct current, thus providing for at least some of the electric power requirements. In which two different semiconductors are subjected to a heat source and heat sink. A voltage is created between two conductors. It is based on the seeback effect. The Cooling and Heating is done by applying electricity. It is low efficiency approximately (2 to 5%) and high cost.
FIG-7 THERMOELECTRIC GENERATOR WITH ITS COMPONENTS
Thermoelectric devices may potentially produce twice the efficiency as compared to other technologies in the current market. Thermo Electric Generator is used to convert thermal energy from different temperature gradients existing between hot and cold ends of a semiconductor into electric energy This phenomenon was discovered by Thomas Johann Seebeck in1821and called the Seebeck effect”. The device offers the conversion of thermal energy into electric current in a simple and reliable way. Advantages of Thermo Electric Generator include free maintenance, silent operation, high reliability and involving no moving and complex mechanical parts. Recycling and reusing waste exhaust gas can not only enhance fuel energy use efficiency, but also reduce air pollution. Thermal power technology such as the Thermo Electric Generator arises, therefore, significant attention worldwide.
Thermo Electric Generator is a technology for directly converting thermal energy into electrical energy. It has no moving parts, is compact, quiet, highly reliable and environmentally friendly. Because of these merits, it is presently becoming a noticeable research direction. The mathematical model of a Thermoelectric Generator device using the exhaust gas of vehicles as heat source, and preliminary analysis of the impact of relevant factors on the output power and efficiency of Thermo Electric Generator .Analysis of model simulates the impact of relevant factors, including vehicles exhaust mass flow rate, temperature and mass flow rate of different types of cooling fluid, convection heat transfer coefficient, height of PN couple, the ratio of external resistance to internal resistance of the circuit on the output power and efficiency. The results of analysis shows that the output power and efficiency increase significantly by changing the convection heat transfer coefficient of the high-temperature-side than that of low-temperature-side. Pilot program is made to investigate the applicability of thermoelectric generators to the recovery of medium-temperature waste heat from a low-power stationary diesel engine. Experimental investigation to the optimum operating conditions to achieve maximum power outputs from the waste heat recovery system Study on waste heat recovery system by using thermoelectric generator from internal combustion engine reviews the main aspects of thermal design of exhaust-based thermoelectric generators (ETEG) systems Analysis of thermoelectric generator for power generation from internal combustion engine shows results as 20% of energy releasing for the waste heat from engine. It is able to 30-40% of the energy supplied by fuel depending on engine load
CHAPTER-3 Assembling of Module
3.1 Thermoelectric Module Installation
Thermoelectric modules have a large thermal expansion (and contraction) through the range of allowable temperatures -60??C to 300??C. It is vitally important that the mounting system allow for this expansion and contraction while maintaining an even pressure on the module. Please see TEM Mounting. Assembly process is same for TEG and TEC these two comes under TEM
3.1.1 Hot and Cold Side Identification:
Thermoelectric (Seebeck devices or TEGs) generators will only generate electricity if there is a temperature difference across the module. That means that the ‘cold’ side must be at least colder than the ‘hot’ side for there to be any power generation. The hot side is generally attached to a source of heat while the cold side is typically connected to a heat sink that is air or liquid cooled. Keep in mind that the heat from the hot side must travel through the TEG to the cold side in order for there to be electricity generated. It is vitally important that the heat sink on the cold is able to quickly get rid of this heat in order to stay cool. If the cold side cannot get rid of this heat then it will not be the cold side for very long.
ex: Examine the diagram below. The view is seen as if the module is placed on a table in front of you as shown with the wires pointing towards you. The hot side is marked ‘HOT SIDE’.
FIG -8 TEG WITH GRAPHITE FOIL PRE-APPLIED
3.1.2 Temperature Limits:
The Hot Side of the TEG module can work continuously at a maximum temperature of 300??C (572??F). It is important that you only connect the hot side of the TEG module to the heat source. Accidently reversing the module and placing the cold side towards the heat source will cause irreversible TEG damage and failure. The Cold Side of the TEG module can work continuously at a maximum temperature of 160??C (320??F). Do not allow the cold side temperature to exceed this limit or irreversible TEG damage and failure will occur.
3.2 Module Parts
3.2.1 Metal Casing
FIG-9 METAL CASING
It is made up of sheet metal. The desired shape of this casing is got through industrial pressing and folding with machine pressers. The holes and folds in this casing is achieved via hole bearers and are done to create necessary shape casing and provides necessary joining cavities. It also provides with all the necessary rigidity which our whole module requires.
3.2.2 Aluminum Flange
FIG-10 ALUMINUM FLANGE
‘ The flange for holding the exhuast pipe is made of aluminium.
‘ The thickness of the flange of is so selected to provide with necessary rigidity as the exhaust manifold pipe vibrates at a high rate.
‘ Aluminum is selected as flange material due to its following desirable properties:-
o Excellent Thermal Conductivity
o Corrosion resistance.
o Cost Effective compared to rarer metals like titanium, etc.
3.2.3 Thermoelectric module
FIG -11 THERMOELECTRIC MODULE
The generator consists of an array of thermocouples made from two different metals such as copper and strips cut from tin cans or discarded copper and aluminum wire.
It is best to join the metals by soldering or welding, but if that isn’t possible the joints can be made by crimping the metal strips or twisting wire pairs together.
The top surface of the generator is painted flat black to absorb solar energy and heat the top thermocouple junctions. The lower thermocouple junctions rest on a cooling sheet, and there is an airspace between the heating surface and the cooling surface. Thus, the top thermocouple junctions are hot and the lower junctions are cool, and this differential generates a thermoelectric current.
3.2.4 Aluminium Fins
FIG-12 ALUMINIUM FINS
Aluminium fins are used to increase the heat transfer rate and hence help in providing temperature difference between hot and cold side of the thermoelectric module. This causes increase in the output voltage.
3.3 Mounting Techniques
3.3.1 Mounting with Adhesive Bonding
When to Use: When you want to permanently attach the TEM to your heat sink; when mounting with solder is not an option; when the TEM’s need to be lapped to the same height after mounting; when moderate thermal conductivity is required.
Step One: Because of the short amount of time needed for epoxy to set up, be certain to have your TEM’s cleaned and ready to mount before mixing epoxy. Clean and prepare mounting surfaces on both the TEM and heat sink using methanol, acetone, or general-use solvent.
Step Two: Use Marlow Industries Thermally Conductive Epoxy. Follow the instructions on the package carefully. Be certain to mix the two pouches thoroughly or the epoxy will not cure properly.
A. Remove the epoxy pack from the protemtive pouch.
B. Remove the divider.
C. Knead well until thoroughly mixed.
D. Cut a corner and dispense. The epoxy working time is approximately one hour.
CAUTION: Avoid prolonged or repeated breathing of vapor, and use with adequate ventilation. Avoid contact with eyes, skin, or clothing. In case of contact with eyes or skin, flush immediately with plenty of water and get medical attention.
Step Three: Coat the ceramic of the TEM with approximately a 0.05 mm thick layer of epoxy.
Step Four: Place the TEM on the heat sink and gently rotate the TEM back and forth, squeezing out the excess epoxy.
Step Five: Using a clamp or weight, apply pressure (less than 689,465 N/m2), and cure for two hours at 65??C to maximize thermal and physical properties. Curing time at room temperature is 24 hours.
3.3.2 Mounting with the Compression Method
When to Use: When a permanent bond is not desired; when multiple TEM’s are used; or when your TEM is larger than 19mm.
Step One: Prepare heat sink and cold sink surfaces by machining the module area to within +/-0.03 mm.
Step Two: Locate bolt holes in your assembly such that they are at opposite sides of the cooler between 3.2mm to 12.7mm from the sides of the thermoelectric. The bolt holes should be in the same plane line as the heat sink fins to minimize any bowing that might occur.
Step Three: The recommended hardware that should be used is: #4-40 or #6-32 stainless steel screws, Belleville or split lock type washers as well as a fiberinsulated washer to insulate the screw head from the heat sink.
Step Four: Remove all burrs. Then, clean and prepare mounting surface with methanol, acetone, or general-use solvents.
Step Five: Apply a thin 0.05 mm layer of Marlow’s Thermal grease to the hot side of the TEM. Place the TEM on the heat sink and rotate back and forth, squeezing out the excess thermal grease until resistance is felt.
Step Six: Repeat step 5 and rotate cold plate back and forth, squeezing out the excess thermal grease.
Step Seven: In a two module system, torque the middle screw first. Be careful to apply torque in small increments, alternating between screws. In general, apply less than 1,034,198 N/m2 (N/m2 = Pascal) per square meter of TEM area.
3.3.3. Mounting with Solder
When to Use: When you need minimal outgassing; when the TEM is smaller than 19mm; when you need a high-strength junction; when high thermal conductivity is required.
IMPORTANT: The device to which the TEM is being soldered should be placed on a thermal insulator. This will allow the device to become hot enough to reflow the solder. If necessary, the device may be placed on a hot plate set at 100??C to help heat it to the solder melting point.
Step One: Clean the surfaces to be soldered with methanol, acetone, or a general use solvent to remove oils and residues which would inhibit soldering.
Step Two: With a soldering iron and a new tip, pre-tin the bottom of the TEM (the side with lead wires) using Marlow Industries’ Solder 96??C or 117??C and General Purpose Acid Flux. Use small amounts. You can heat the soldering iron to a maximum of 150??C, but extreme care must be taken since most TEM’s are constructed with 138??C (min.) solder.
CAUTION: Do not mix solders. Use a separate soldering iron (or a new tip) for each solder.
Step Three: With soldering iron, pre-tin the header or heat sink with the same solder and flux as used in pre-tinning the TEM. Use small amounts.
Step Four: To minimize flux residue, clean both the header and TEM. Rinse them first in hot water, then scrub with Marlow Industries’ Cleaning Solution and rinse again with hot water, brushing away any excess flux residue. Finally, wash with methanol and use forced air to blow dry.
Step Five: Prior to mounting the TEM to the header, add a small amount of Marlow Industries’ Blue Mounting Flux to the mounting site on the header.
Step Six: Hold TEM with tweezers and align on header. While doing this, maintain a steady, downward pressure.
Step Seven: While holding the TEM in place, put the soldering iron to the header near the solder seam. When the solder junction flows, remove the soldering iron. The downward pressure on the TEM will expel excess solder.
REMEMBER: The solder which holds the TEM together flows at 138??C (min.), so if you are using the 117??C solder do not leave the soldering iron on the header surface too long, or you will melt the TEM solder as well.
Step Eight: Continue holding the TEM in place until the solder solidifies.
Step Nine: Check along all four edges of the TEM, looking for voids, cracks, or bubbles. A smooth seam insures proper thermal conduction.
Connecting Lead Wire to Header
Step One: Trim the excess wire from the TEM. Wrap the lead wires 3/4 of a turn around the connector posts on the header.
Step Two: Using solder and Blue Mounting Flux, solder the lead wires to the wire posts. You should be able to see outlines of the wires, but they should be well covered. Wick off any excess solder with the soldering iron.
3.3.4. Final Cleaning and Inspection
Step One: Rinse both the header and TEM in hot water, then scrub with cleaning solution and rinse again with hot water, brushing away any excess flux residue around the pins. Wash with hot water and dry with forced air. To insure complete removal of moisture, dry the entire assembly in an oven for 30 minutes at 60??C. If an oven is not available, the forced-air blower is adequate.
Step Two: Check the solder joints for cracks or bubbles.
3.3.5 Lead Wire Attachment
Some thermoelectric coolers use standard 2.8 mm (0.110) spade lug connectors for lead wire attachment. The spade lugs are easily attached by hand. When designing your wiring harness, we recommend that you design the female spade lug connector into the harness. The AMP part number for this female 2.8 mm spade lug connector is 42398-1.
FIG-13 LEAD WIRE ATTACHMENT
Insertion Procedure: Insert female spade lug over the lead tabs. Use a side-to-side motion to secure the lug on the tab. DO NOT USE an up-and-down motion, for this can damage the tab or the tab solder joint. Insert the lug until it seats onto the tab detent.
3.4 Secondary equipments
3.4.1 Voltmeter
A voltmeter is an instrument used for measuring electrical potential difference between two points in an electric circuit. Analog voltmeters move a pointer across a scale in proportion to the voltage of the circuit; digital voltmeters give a numerical display of voltage by use of an analog to digital converter.
Voltmeters are made in a wide range of styles. Instruments permanently mounted in a panel are used to monitor generators or other fixed apparatus. Portable instruments, usually equipped to also measure current and resistance in the form of a multimeter, are standard test instruments used in electrical and electronics work. Any measurement that can be converted to a voltage can be displayed on a meter that is suitably calibrated; for example, pressure, temperature, flow or level in a chemical process plant.
General purpose analog voltmeters may have an accuracy of a few percent of full scale, and are used with voltages from a fraction of a volt to several thousand volts. Digital meters can be made with high accuracy, typically better than 1%. Specially calibrated test instruments have higher accuracies, with laboratory instruments capable of measuring to accuracies of a few parts per million. Meters using amplifiers can measure tiny voltages of microvolts or less.
FIG-14 VOLTMETER
3.4.2 Thermal Grease
Thermal grease also called thermal gel, thermal compound, thermal paste, heat paste, heat sink paste or heat sink compoundis a viscous fluid substance, originally with properties akin to grease, which increases the thermal conductivity of a thermal interface by filling microscopic air-gaps present due to the imperfectly flat and smooth surfaces of the components; the compound has far greater thermal conductivity than air but far less than metal. In electronics, it is often used to aid a component’s thermal dissipation via a heat sink.
FIG-15 THERMAL GREASE
3.5. Preventing Problems
1. Do not use excessive amounts of solder. This can short the power leads and/or inhibit a good thermal interface.
2. Use the proper solder and flux. Marlow Industries’ General Purpose Acid Flux is recommended. Without it, outgassing or overheating during soldering may occur.
3. Be sure to clean the TEM thoroughly to prevent outgassing.
4. Do not overheat the TEM with the soldering iron. Because of the narrow temperature differential between the mounting solder (117??C) and the solder used in the TEM (138??C min.), care must be taken not to overheat the TEM and reflow the solder.
5. During soldering, be sure the surface on which the soldering is being done is composed of a low thermal conductivity material. This will prevent the solder iron heat from being drawn away, which can cause difficulties with reflowing the solder.
6. When pre-tinning a large area of the TEM, pre-tin in small sections or purchase the coolers
pretinned by Marlow Industries.
7. If a TEM is being soldered to a large header, it may require that the header be placed on a 100??C hot plate. This will minimize heat conduction away from the solder point.
‘
CHAPTER 5-WORKING OF MODULE
5.1 MODULE SPECIFICATION
‘ Hot Side Temperature (??C) 300
‘ Cold Side Temperature (??C) 30
‘ Open Circuit Voltage (V) 8.2
‘ Matched Load Resistance (ohms) 2.93
‘ Matched load output voltage (V) 4.1
‘ Matched load output current (A) 1.4
‘ Matched load output power (W) 5.7
‘ Heat flow across the module (W) ‘ 110
‘ Heat flow density (W cm-2) ‘ 12.2
‘ AC Resistance (ohms)
‘ Measured under 27 ??C at 1000 Hz
‘ 1.2 ~ 2.0
5.2 MODULE COST
‘ TEG module:- Rs 3800/-
‘ Hot side Heat sink:- Rs 1500/-(which includes cutting and machining charges)
‘ M.S Bracket :- Rs 650/-(includes job work charges and powder coating charges)
‘ DC fan:- Rs 50/-
‘ Connector CKT:- 20/-
‘ Insulation material:- Rs 500/-
‘ Screws and wiring:- Rs 200/-
‘ Aluminum Block:- Rs 500/-(includes cutting and machining charges)
‘ Assembly charges:- Rs 500/-
‘ TOTAL =7720/-
CHAPTER 6-EXPERIMENTAL OBSERVATION
‘ The prepared modules of TEG & TEC should be tested once.
‘ Take the TEG module and bisect the clamps by unscrewing the screws.
‘ Select the exhaust pipe area which is in perfect shape without any ducts and bends. By taking emery paper make the exhaust pipes surface smooth and without any rust.
‘ After the surface finishing is complete clean the dust particles with dry cloth.
‘ Apply TIM material on the exhaust it is because in order to avoid air space and better transfer of Thermal inter face between exhaust pipe and TEG equipment
‘ Clamp the TEG Equipment on the exhaust manifold and tighten the screws make sure the clamp should not be loose.
‘ Plug the pin into the power output connector in this one is positive and other is negative connect it to the volt meter.
‘ Start the engine and keep it for the initial warm up condition for 5 min.
‘ Arrange the digital thermometer setup to the engine exhaust (T2) and at heat sink of TEG (T1).
‘ By using stop watch note the readings of T1, T2 and voltage and time for every one min of interval.
‘ The obtained power is used to turn on the led lights for indication
‘ The power generated is stored in the battery (12V)
‘ The stored energy is used to run the TEC the positive and negative wires connected to the battery
‘ If the Led of TEC is glows then the circuit is in perfect condition
‘ With the peltier effect the temperature difference is obtained this works as a heat pump. the heat pumps from the cold side to hot side of TEC with the help of heat sink the hot side is contincestly cooling with this effect the cold side temperature rapidly decreases and cabin gets cooled.
Experimental table readings
THERMO ELECTRIC GENERATOR:
COLD SIDE TEMPERATURE(T1) HOT SIDE TEMPERATURE(T2) TEMPERATURE DIFFERENCE(??T) TIME(min) VOLTAGE(v)
36 105 69 6 0.58
36 112 76 7 1.0
37 120 83 8 1.38
37 124 87 9 1.69
38 126 88 10 1.76
38 127 89 11 1.80
39 129 90 12 2.5
40 132 92 13 2.8
40 135 95 14 3.2
41 138 97 15 3.8
42 152 110 16 4.4
43 154 111 17 4.8
44 156 112 18 5.2
44 160 116 19 5.8
TABLE 1-OBSERVATION TABLE
CHAPTER 7-RELATED WORKS DONE IN THIS FIELD
7.1 Heat recovery technology used in BMW
FIG 16- SYSTEM OF RECOVERING HEAT EMPLOYED IN BMW
The Heat Recovery Technology is used by Bmw in X5 to utilize the waste heat from the exhaust of the automobile. It comprise of Thermoelectic modules(TEG) mounted on exhaust with hot side connected to the exhaust and cool side above in connection with the coolant lines.
Electric pump is utilized to to transport the coolant from the radiator to the cooler side of TEG. This increases the temperature difference between hot and cold side of TEG which causes the electrons from N-side to flow from P-side causing the current to flow.
The bypass valve is connected with the coolant lines to control the flow and pressure of the coolant flow.
This entire arrangement increases the efficiency of the automobile by 15-20% with affordable cost from industrial point of view.
FIG 17-TEG ASSEMBLED ON EXHUAST
The Thermoelectric device comprising at least one thermoelectric module for generating electrical energy from thermal energy of the exhaust comprises of thermoelectric device having a high temperature side and a low temperature side, and being shaped and placed around the perimeter of a portion of the exhaust gas flow path with the high temperature side of the thermoelectric device in heat transfer contact with the flowing exhaust gas stream
A body of thermally conductive material contained and interposed around the perimeter of the exhaust gas flow path and between the exhaust gas and the high temperature side of the thermoelectric device, the contained thermally conductive material providing the heat transfer path between the exhaust gas and the high temperature side of the thermoelectric device, the body of thermally conductive material having a mass and a melting point or melting range such that heat transferred from the exhaust gas melts a portion of the body of material, the latent heat of the partially melted body of material reducing the temperature at the high temperature side of the thermoelectric device as it is heated by the exhaust gas.
CHAPTER 8-APPLICATIONS
There are many possible applications which includes :-
‘ Charging and re-charging of battery
‘ Providing current to another circuit
‘ Providing an alternate circuit to the system of ALTERNATOR
‘ Providing power to engine fan
‘ Increase in Output Power and Torque