The even growing demand for electric energy, the limitation of energy resources, and the increasing power generation costs necessitated the very well established optimal economic dispatch operation in most power uitilites. This is simply stated as "operate with minimum fuel cost and keep valid all system operating constraints ". That was a firm binding strategy in all power utilities up to the end seventies of the last century. Since then, environmental awareness, and then after, the environmental policies have forced electric utilities to restructure their operational practices to account for their emissions impact. Thermal power plants are contributors to air pollution , specifically ,pollutants like, carbon oxides (COx) ,sulfur oxides (SOx) , and nitrogen oxides (NOx) . These emissions led to green house gases concentration in the atmosphere leading to global warming. Minimization of the adverse and catastrophic effects of global warming forced the utilities to adopt emission reduction measures. The emerged new operation philosophy led to the power utilities to a conflicting reality fact. That is, to minimize fuel cost, emissions are at maximum value and vice versa.