International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 06 Issue: 04 | Apr 2019 www.irjet.net p-ISSN: 2395-0072 © 2019, IRJET | Impact Factor value: 7.211 | ISO 9001:2008 Certified Journal | Page 801 Thermoelectrical Generator for Waste heat Recovery- Review Kunal B. Saykar 1,* , D.S. Patil 1 , Dr. R.R. Arakerimath 1 1 Department of Mechanical Engineering, G. H. Raisoni College of Engineering and Management, Pune, India-412207 ---------------------------------------------------------------------***---------------------------------------------------------------------- Abstract – Nowadays, an increasing environmental issues of emission due to discharge of engine exhaust and industrial waste heat. The Thermo electrical Generator can produce clean energy conversion and are environmental friendly. Thermo electrical power generators have emerged as a promising alternative green technology. Thermo electrical power generators provide a potential application in the direct conversion of waste heat energy in to electrical energy. The purpose of this paper is to review on different cooling systems, thermal uniformity of exhaust heat exchanger, and various operating conditions. Key Words: Heat Exchanger, thermo electrical generator, Thermal uniformity, Waste Heat. 1. INTRODUCTION Approximately 30% of the energy generated by the combustion of fuel in the engine cylinder will be converted by the cylinder piston motion into the brake force of vehicles (5% of it will be neutralized by friction loss of machine members). In addition, about 70% of it cannot be converted into mechanical energy, but disperses to the environment as waste heat [1].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 [2]. Over the last 30 years, there has been growing interest in applying this thermoelectric technology to improve the efficiency of waste heat recovery, using the various heat sources such as geothermal energy, power plants, automobiles and other industrial heat-generating process [3].The power generation of exhaust TEG (thermoelectric generator) depends on heat energy and thermoelectric conversion efficiency. High efficiency heat exchanger is necessary to increase the amount of heat energy extracted from exhaust gas[4]. Thermoelectric Module (TEM) offers thermoelectric energy conversion in a simple and reliable way along with advantages of not involving moving or complex parts, silent in operation, maintenance free and environmental friendly [5]. Owing to these advantages, there have been considerable emphases on the development of the small TEGs for a variety of aerospace and military applications over the past years. More recently, there is a growing interest for waste heat recovery TEG, using various heat sources such as combustion of solid waste, geothermal energy, power plants, and other industrial heat-generating processes. In the case of TEG for waste heat recovery power generation, there have been many conceptual designs of a power conversion system which are potentially capable of obtaining application in this area [6].In general, the cost of a thermoelectric power generator essentially consists of the device cost and operating cost. The operating cost is governed d by the generator’s conversion efficiency, while the device cost is determined by the cost of its construction to produce the desired electrical power output [7]. 2. THERMOELECTRIC THEORY Thermoelectric modules are devices which can convert heat or temperature different directly into electrical energy. A two element of semiconductor bismuth telluride (Bi2Te3) is a common material used in thermoelectric modules. Bismuth telluride has high See beck coefficient such as the efficiency of generated voltage per unit temperature different is high thermoelectric elements are made from P- type and N-type semiconductors that are connected by metallic interconnect. When there is temperature gradient on the two sides of the semiconductors, a voltage is created. Current will flow through the N-type element, cross a metallic interconnect and passes into P-type element as shown in Fig.1. The current can then be used to power a load. The thermoelectric module converted the thermal energy into electrical energy. Every P-type or N-type of thermoelectric element is a single power generation unit. As shown in Fig.1, the P-type and N-type semiconductor elements are configured thermally in parallel, but electrically in a series circuit. The total output electrical voltage from the thermoelectric module is series-adding of the voltage of each semiconductor. In a truly thermoelectric element, many such P-type and N-type semiconductors are employed to bring the See beck voltage up to useful levels. Fig.2. shows a two coupled thermoelectric element [5]. The total output electrical voltage from the thermoelectric module is series-adding of the voltage of each semiconductor. In a truly thermoelectric element, many such P-type and N-type semiconductors are employed to bring the See beck voltage up to useful levels. Fig.2. shows a two coupled thermoelectric element [5].