Exergy Analysis of Coal Fired Power Plants Cogeneration System

Capturing and making use of waste heat is critical to the improvement of thermal power plant technology. A typical coal fired power plant converts only one third of the input energy into electricity; the remaining twothirds are lost as waste heat. In contrast, a cogeneration system generates electricity and can utilize the ‘waste’ heat for example for water heating, comfort heating, pool heating and drying. Such a system can reduce both energy consumption and fuel costs by utilising up to 80 per cent of the fuel’s energy. In addition such systems has the overall beneficial effect of not only reduction of CO2 emission but also all kind of pollution associated to the use of fossil fuel such as Cox, Nox, So2 and ete. The use of waste heat recovery systems, in conjunction with high efficiency power plants is becoming increasingly important despite their high cost, mainly because the combined cycle efficiency thereby obtained is greater than that of a traditional steam plant. Since the bulk of the power produced is taken as electricity, most previous research has focused on the electricity generation. However, improvement in the heat-rejection part of the Rankine cycle can make a significant contribution to the overall plant efficiency. This paper describes the novel use of waste heat from power cycles specifically the use of waste heat to drive an absorption cooling cycle. The objective of the work was to investigate this proposal using an exergy model. The paper describes the development of the model and presents results, which demonstrate the overall importance of the use of waste heat for heating and cooling.