I would also like to express our gratitude to all faculty members of the school for their timely encouragement and thought provoking suggestion to pursue our work. Last but not he least, we would like to thank all those who were directly and indirectly helped us in completion of this project. CHAPTER: I 1. 0 Introduction Man's constant evolution couldn't have been possible without fuels. Society is putting more emphasis on the mobile transportation sector to achieve future goals of sustainability and on low thermal efficiencies of ICC engine.
About 60% of heat-energy liberated during combustion of fuel is not utilized in producing useful work and getting dumped into the atmosphere daily. To achieve these goals, society needs to jump to a new method to recover the lost part of exhaust energy. The recovering of heat from exhaust gases in automobiles is a typical area of generating steam (or) electricity using W. H. R. B. * (or) Thermoelectric. It depends on the basic principle of 'Speck Effect'.
It would be useful to demonstrate the potential of thermoelectric generation in the automobile industry using Thermoelectric Generator (Tee's). A thermoelectric generator, which can be driven by the temperature difference, incorporates fins into a thermopile to conduct heat toward or away from the alternating spaces between adjacent layers of different types of thermoelectric material. Vehicles are becoming more electrified and the higher electrical demands under nearly all driving conditions are required.
On board electrical energy management and storage systems are more prevalent. TEE'S provides source of additional electrical power without increasing fuel consumption. The study reveals that about 6% of the exhaust energy can be taped from the exhaust there by increasing the thermal efficiency. It can be used to increase the overall efficiency of the engine without increasing the fuel consumption and thus there would be a separate source of the electricity that a vehicle needs for keeping its battery charged and for erring all of its on-board electric circuits. W. H. R. B. = Waste heat recovery boiler 1. 1 Problem Specification To design and fabricate the Thermo Electric Generator and its various components. To test the TAG under various conditions when used on Marti 800 standing engine. 1. 2 Objective To design the TAG and its various components using Silkworms (CAD) designing software and to fabricate the same using various manufacturing processes. Then the manufactured model is tested for efficiency , power output under various conditions when tested with Marti 800 standing engine.
CHAPTER: II 2 Literature Survey 2. 1 Thermoelectric Principle The Thermoelectric principle though established for long back found application only to the field of sensor industry. But recent advances in materials, especially in semi conductors have paved way for applications to the field of power generation. This project studies the application of Thermo electrics as a waste heat recovery solution in vehicles and their potential for the future. 2. 2 Speck Effect The Speck effect is the conversion of temperature differences directly into electricity.
This effect was first discovered, accidentally, by the German-Estonian physicist Thomas Johann Speck in 1821 . He found that a voltage existed between wow ends of a metal bar when a temperature difference AT existed in the bar. Fig. 1. 3 - Speck effect AS and SUB are the Speck coefficients of the metals A and B, and TTL and TO are the temperatures of the two Junctions. The Speck coefficients are non-linear, and depend on the conductors' absolute temperature, material, and molecular structure.
If the Speck coefficients are effectively constant for the measured temperature range, the above formula can be approximated as: Thus, a thermocouple works by measuring the difference in potential caused by the dissimilar wires. It can be used to measure a temperature difference directly, or to assure an absolute temperature, by setting one end to a known temperature. Several thermocouples in series are called a thermopile. This is also the principle at work behind thermal diodes and thermoelectric generators (such as radioisotope thermoelectric generators or Arts) which are used for creating power from heat differentials. . 3 Semiconductor Based Thermoelectric Though the thermo-electric principle was established in the early 19th century, it was only after mid-20th Century advancements in semiconductor technology, however, that practical applications for thermoelectric devices became feasible. Semi- inducting materials, (in conjunction with copper inter-connecting pads), have been found to offer the best combination of Speck coefficient, electrical resistively, and thermal conductivity.
Semi-conducting materials provide another benefit, the ability to use electrons or "holes" (the absence of an electron in a crystal matrix) to conduct current. This last property is useful in assembling many thermoelectric Junctions in series to reduce the overall current flow in the device to manageable levels. 2. 4 Thermoelectric Modules (TEEMS) Bismuth Telluride-based thermoelectric modules are designed primarily for cooling r combined cooling and heating applications where electrical power creates a temperature difference across the module.
By using the modules "in reverse," however, whereby a temperature differential is applied across the faces of the module, it is possible to generate electrical power. Although power output and generation efficiency are presently low, useful power often may be obtained where a source of heat is available. 2. 5 Teems for Power Generation Thermoelectric (ET) energy conversion for power generation is based on the "Speck effect", where a temperature difference, TTS-TTS, across two dissimilar legs of nonconductor material produces a voltage, Avocado.
This voltage is equal to the Speck coefficient of the material, a, times the temperature difference across the device. The dissimilar legs of semiconductor material, one p-type and one n-type, are called a thermoelectric couple. The p- and n-legs are Joined by an electrically conducting material at the p-n Junction. A thermoelectric module consists of a series of p-n couples, which are connected electrically in series and thermally in parallel. Electrically insulating material separates the electrical connectors from the heat source and sink.
When a temperature gradient is applied across the couple, the negatively charged electrons, e-, in the n-leg and the positively charged holes, h+, in the p-leg move from the heat source to the heat sink, conducting heat to the cold base. This flow of electrons and holes causes separation in an initially uniform charge carrier distribution, which results in a current flow, l, in the couple. A thermoelectric module used for power generation has certain similarities to a conventional thermocouple. With no load, the open circuit voltage as measured between points a and b is: V = a.
AT Where: V is the output voltage from the couple (generator) in volts a is the average Speck coefficient in volts/K AT is the temperature difference across the couple in K where When a load is connected to the thermoelectric couple the output voltage (V) drops as a result of internal generator resistance. The current through the load is: 'load = (a . I is the generator output current in amperes RCA is the average internal resistance of the thermoelectric couple in ohms the load resistance in ohms The total heat input to the couple (Sq) is: Sq The . L) - (0. 5. 12 . + (KC .
CAT) Sq is the heat input in watts Kc is the thermal conductance of the couple in watts/K couple in K 2. 6 Module Selection The is the hot side of the The selection of the appropriate module for power generation with required voltage and current output was done on the basis of literature survey and was found that bismuth telluride module best suited to our condition because of its high efficiency and high operating temperature. Bismuth Telluride module was used because of its easy availability, low cost and low operating temperature range with a considerable efficiency.
Material used for fabricating the outer frame is Cast Iron of 5 mm thickness, Cast Iron is used because of its cheap and easy availability. Outer Frame structure made on Solid Works Real time outer frame Full Assembly of the Chamber After the frame was manufactured, it was connected to the main setup as shown low, The setup included the catalytic converter attached to the Marti 800 engine. The inlet to the frame (TAG) is attached to the exit of the catalytic converter and the exit of the frame is to release the final exhaust gas to the atmosphere through a pipe.
Here heat energy is converted into electric energy using thermoelectric module and therefore two plates are used in this experimental setup one is hot which is in direct contact with the exhaust gases flowing through the frame on one side and the other side of hot plate modules are placed and the other plate is cold plate which is assembled with cooling chamber as shown below, Hot plate used here is Aluminum of 5 mm thickness, one of which side is connected to frame exposed to exhaust gases directly.
The picture below is the hot plate when modules are attached to it with the interface pads in between to increase the thermal conductivity and to reduce the thermal resistance between the plate and the module. The cold plate which is assembled with cooling chamber is shown below, After connecting all this plates and module the entire frame structure is made to stand connected to the engine as shown above in one of the figure, and below shows he final completed set up with the exhaust pipe connected to the frame.