Thermoelectric generator .pptx
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This document discusses thermoelectric generators (TEGs) and their ability to directly convert thermal energy into electric power through the Seebeck effect. It describes how TEGs work using three key elements: a heat exchanger to absorb heat, thermoelectric modules to generate electricity from a temperature difference, and a heat sink to dissipate additional heat. The document also examines common TEG materials like bismuth telluride and challenges like low thermal efficiency around 4%, as well as applications in recovering waste heat from power plants, automobiles, and other systems.
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Thermoelectric generator .pptx
- 1. Thermoelectric generator (TEG) technologies and applications Supervised by : Majeed Abbasalizadeh Prepared by : Ahmed Jassim Khalaf
- 2. Abstract Nowadays humans are facing difficult issues, such as increasing power costs, environmental pollution and global warming.. Scientists are focusing on enhancing energy-harvesting power generators in an effort to lessen their effects. Through the Seebeck effect, thermoelectric generators (TEGs) have proven they are capable of converting thermal energy directly into electric power. Thermoelectric systems have arisen during the past ten years as a possible alternative to existing green energy generation technologies because of the distinctive advantages they provide.
- 3. Introduction In power plants, about two thirds of the energy used to produce electricity is wasted as waste heat that is emitted through cooling towers . The primary cause is that the gas or steam-powered turbine systems, which are responsible for producing the majority of the electrical power, work largely by burning fuel to create heat energy, within the turbine, this thermal energy is transformed into mechanical energy, which is then transformed into electrical energy in a generator Because of this, only roughly one-third of the fuel's energy is actually transferred to the transmission lines that leave the power plant.
- 4. TEG_working principle Mostly, TEG systems consist of three key elements 1- A heat exchanger (HEX); This absorbs the heat and transfers it into the thermoelectric modules. 2- Thermoelectric modules (TEMs); The TEMs generate electricity when a temperature difference exists between their ends. A TEM contains many pairs of thermoelectric couples, 3 - A heat sink; In order to dissipate the additional heat from the thermoelectric modules. The temperature difference between two sides of the generator .
- 5. Seebeckeffect This mechanism, where a temperature differential produces a voltage, is known as the thermoelectric effect or Seebeck effect and it was believed to have been defined for the first time in the 1820s by the German physicist Thomas Johann Seebeck. However, recent evi- dence shows that Alessandro Volta had also observed the Seebeck effect 27 years before Thomas Seebeck.
- 6. Principle of thermoelectric generation
- 7. . Peltiereffect As mentioned earlier, in 1821, Thomas Seebeck, a German physi- cist, carried out numerous tests on electricity and discovered that electricity can function through a circuit comprising two separate conductors, given that the junctions at which these conductors con- nected were kept at different temperatures.
- 8. Power Generation and Electrical Refrigeration (Peltier Effect)
- 9. Thomsoneffect Thomson indicated that as the current passes into unequally heated conductors, the thermal energy is either consumed or formed in the metal structure ,In other words, the Thomson effect is the generation of reversible heat when an electrical current is passed through a conductive material subjected to a temperature gradient,
- 10. Jouleheating The heating effect was first studied and categorised by James Pre- scott Joule, around the year 1840. Joule set out to investigate if the recently invented electrical motor could be more efficient, in terms of cost, than the steam engines in use at the time. This led him to con- duct a series of experiments on the production, transfer and use of energy and mechanical work that ultimately led to the first law of thermodynamics.
- 11. TEG materials, design and optimisation As mentioned above, thermoelectric generators offer a reliable solid-state solution for energy conversion. Devices using advanced thermoelectric materials can become an alternative to traditional power generation heat engines, most notably in lightweight heat recovery systems. The maximum efficiency of the conversion of ther- moelectric energy is typically presented in terms of the temperature of each heat reservoir and the thermoelectric .
- 12. TEG Case Studies and Applications Thermoelectricity, in the form of thermoelectric generators, has a strong capacity for waste heat recovery, and has been researched and demonstrated in a variety of experimental and theoretical works. Through the use of a thermoelectric generator, part of the energy that is usually lost during the production operation can be converted into electricity.
- 13. Types of semiconductors used in thermoelectric generators Three materials are commonly used for thermoelectric generators. These materials are bismuth (Bi2Te3) telluride, lead telluride (PbTe) and Silicon germanium (SiGe). Which material is used depends on the characteristics of the heat source, cold sink and the design of the thermoelectric generator. Many thermoelectric generator materials are currently undergoing research but have not been commercialized.
- 14. Challenges of TEG The primary challenge of using TEG is its low thermal effi- ciency (typically Ztho4%) . Thermoelectric materials effi- ciency depends on the thermoelectric figure of merit, Z; a material constant proportional to the efficiency of a thermoelectric couple made with the material. stated that future thermoelectric materials show the promise of reaching signifi- cantly higher values of the thermoelectric figure of merit, Z, and thus higher efficiencies and power densities can be obtained. Materials such as BiTe (bismuth telluride), CeFeSb (skutterudite), ZnBe (zinc– beryllium), SiGe (silicon–germanium), SnTe (tin tell- uride) and new nano-crystalline or nano-wire thermoelectric materials are currently in development stage to improve the conversion efficiency of TEG.
- 15. TEG in the automotive industry For an automobile engine, there are two main exhaust heat gas sources which are readily available. The radiator and exhaust gas systems are the main heat output of an IC engine . The radiator system is used to pump the coolant through the cham- bers in the heat engine block to avoid overheating and seizure . Conversely, the exhaust gas system of an IC engine is used to discharge the expanded exhaust gas through the exhaust mani- fold. that presently TEG is mostly installed in the exhaust gas system (exhaust manifold) due to its simplicity and low influence on the operation of the engine. Furthermore, TEG system including the heat exchanger is com- monly installed in the exhaust manifold suitable for its high temperature region . Basically, a practical automotive waste heat energy recovery system consists of an exhaust gas system, a heat exchanger, a TEG system, a power conditioning system, and a battery pack .
- 16. Conclusion it has been identified that there are large potentials of energy savings through the use of waste heat recovery technologies. Waste heat recovery entails capturing and reusing the waste heat from internal combustion engine and using it for heating or generating mechanical or electrical work. It would also help to recognize the improvement in performance and emissions of the engine if these technologies were adopted by the automotive manufacturers. T It should be noted that TEG technology can be incorporated with other technologies such as PV, turbocharger or even Rankine bottoming cycle technique to maximize energy efficiency, reduce fuel consumption and GHG emissions. Recovering engine waste heat can be achieved via numerous methods. The heat can either be ’’reused’’ within the same process or transferred to another thermal, electrical, or mechanical process. The common technolo- gies used for waste heat recovery from engine include thermo- electrical devices, organic Rankine cycle or turbocharger system. By maximizing the potential energy of exhaust gases, engine efficiency and net power may be improved. Exergy efficiency is a concept which helps to obviously show the environmental impact by numbers. By increasing the exergy efficiency, sustainability index will increase and leads to less production of pollutants like NOx and SO2 during creating the same amount of power.