Superimposition of elementary thermodynamic cycles and separation of the heat transfer section in energy systems analysis

In a wide variety of thermal energy systems, the high integration among components derives from the need to correctly exploit all the internal heat sources by a proper matching with the internal heat sinks. According to what has been suggested in previous works to address this problem in a general way, a “basic configuration” can be extracted from the system flowsheet including all components but the heat exchangers, in order to exploit the internal heat integration between hot and cold thermal streams through process integration techniques. It was also shown how the comprehension of the advanced thermodynamic cycles can be strongly facilitated by decomposing the system into elementary thermodynamic cycles which can be analyzed separately. The advantages of the combination of these approaches are summarized in this paper using the steam injected gas turbine (STIG) cycle and its evolution towards more complex system configurations as an example of application. The new concept of “baseline thermal efficiency” is introduced to combine the efficiencies of the elementary cycles making up the overall system, which demonstrates to be a useful reference to quantify the performance improvement deriving from heat integration between elementary cycles within the system.