**7. The recovery of exhaust heat from gas turbines**

In this chapter different techniques for recovering the exhaust heat from gas turbines are discussed, evaluating the influence of the main operating parameters on plant performance. A unified approach for the analysis of different exhaust heat recovery techniques is proposed. The methodology is based on relationships of general validity and characteristic plane for exhaust heat recovery, that indicates directly the performance obtainable with different recovery techniques, compared to a baseline non-recovery plant. An innovative scheme for external heat recovery is presented. It envisages repowering existing combined cycle power plants through injection of steam produced by an additional unit consisting of a gas turbine and a heat recovery steam generator.
