IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308 _______________________________________________________________________________________ Volume: 04 Issue: 07 | July-2015, Available @ http://www.ijret.org 54 ENERGY AND EXERGY ANALYSIS OF A 250MW COAL FIRED THERMAL POWER PLANT AT DIFFERENT LOADS Soupayan Mitra 1 , Joydip Ghosh 2 1 Associate Professor, Mechanical Engineering Department, Jalpaiguri Government Engineering College, Jalpaiguri- 735102, West Bengal,India 2 Post Graduate Scholar, Mechanical Engineering Department, Jalpaiguri Government Engineering College, Jalpaiguri-735102, West Bengal,India Abstract In this present investigation exergy and energy efficiencies of a coal fired 250 MW thermal power plant operating in eastern part of India are determined both for 100% and 90% load based on actual operating data. The efficiencies are evaluated for the overall plant as well as for different equipments like boiler, turbine, all feed water heaters and condenser. Similarly effectiveness of the feed water heaters is evaluated for both the loads. Exergy destruction % for each of the equipment are also given for clear understandingof the loss of available energy due to irreversibilities involved in the processes for each equipment and the whole plant. It is observed that a major irreversibility or, exergy destruction takes place at boiler though 1st law energy efficiency is quite high. This signifies that there might have further scope of improvement in this equipment. Similar analyses are carried out for other equipments. The results obtained in present analysis are compared with those of other investigators. Keywords: Energy, Exergy, Efficiency, Effectiveness, Exergy destruction, Power plant --------------------------------------------------------------------***------------------------------------------------------------------ 1. INTRODUCTION Exergy or, availability of a system signifies the part of the system energy that can be converted into maximum useful or desired work with respect to immediate surrounding condition, referred to as ‘dead state’. The term Exergy was used for the first time by Rant, Z. in 1956. According to 1st law of thermodynamics energy is conserved, but energy is conserved only quantitatively and not qualitatively. But exergy is a manifestation of quality of energy and unlike energy, exergy is not conserved and in fact, get destroyed due to irreversibility during a process. The energy efficiency or, 1st law efficiency merely implies the ratio of desired or, useful work output against total energy input for a system. But this does not consider the true capability of the system by considering the thermodynamic limitations for which the system is not responsible. Efficiency based on exergy for any system like whole thermal power plant or, say, a turbine reflect the true capability of the concerned system i.e., their actual working capability against their maximum possible capability due to irreversibility present in the system process. Thus unlike, energy efficiency, exergy efficiency gives more insight into the problem and help design, analyse and performance improvement of the energy conversion systems more effectively by identifying the locations and associated irreversibilities. A relationship between energy and exergy is pictorially shown in Fig-1.Of late, many researchers are using exergy methodology for analysing different types of energy conversion systems [1– 6] and in fact, some good books are now available in this arena [8 – 10]. In the present investigation, for a 250 MW thermal power plant energy, exergy efficiency and effectiveness of different equipments as well as for the whole plant are determined based on plant operating data at 100% and 90% load. The results for the loads are compared, analysed and discussed. The present results obtained are compared with those of other investigators. It is believed that present investigation will help understanding the possible improvement locations for a power plant as well as will indicate the priority areas of action for better performance and operation of the plant.