The limitation of energy recourses in the world lead a lot of countries to rethinking in their energy polices and put very strong norms to get rid of waste . As well as this subject makes the scientific community take a look at the energy switch and trying to find a new techniques to face challenges which represent by the limitation of energy recourses. The quantity of energy which related with the first law of thermodynamics affirms that energy cannot be created and destroyed. This law works as an important instrument for the measurement of energy during a process and help the engineer to come over the challenges. On the other hand, the quality of energy deals with the second law of thermodynamics. More specific this law interested with breakdown of energy during process, the entropy generation, and the lost opportunities to do work. As well as it suggests a lot of room improvement. The second law of thermodynamic has works as a very strong role in the encouragement of complex thermodynamic systems. In this chapter, the performance of engineering devices according to the second law of thermodynamics has studied. The discussion starts with the introduction of exergy which means the maximum useful work which could be gained a system at given state and in definite environment and this discussion go on with reversible work which the maximum useful work that can be gained as system from a process between two specific state. Later on, the irreversibility has discussed which means the loss of work or the wasted work potential during process because of irreversibility. Also the second ‘law efficiencies has defined. Then we develop the exergy balance relation and apply it to control volume and close system.
The energy and exergy analysis of Al- Msab power plant which is located in Iraq will presented in this study. The analysis of every component in the system apart is one of the main goals of this paper. As well as we will identify and quantify the sites which have energy and exergy losses. Moreover this analysis will exposed the effect of varying the ambient temperature state. The main loss in energy occurred in the condenser where 140 MW is lost to the environment while the boiler system lost about 15MW to the environment. The percentage ratio of the exergy destruction to the total exergy destruction was found to be maximum in the boiler system (55%) followed by the turbine (8%), and the forced draft fan condenser (11%). Moreover the thermal efficacy calculations depend on the lower heating value of fuel was 28% while the power exergy efficiency was 21%. There is no extreme change in the ambient temperature noticed in the performance of the main components and the main result stayed as it or the same; in the power plant boiler consider the main source of irreversibilities. Chemical reaction consider the most important source of exergy destruction because it can be decrease by preheating the air of combustion and reducing the air ‘fuel ratio in a boiler system.