Micro Humid Air Cycle: Part B — Thermoeconomic Analysis

Part A of this paper demonstrated that the HAT cycle, when applied to small-size gas turbines, can significantly enhance the efficiency and specific work of simple and recuperated cycles without the drastic changes to plant layout necessary in medium- and large-size plants. In this part B a complete thermoeconomic analysis is performed for microturbines operating in a Humid Air cycle. The capital cost and internal rate of return for both new machines and existing microturbines working in an mHAT-optimised cycle are presented and analysed. Three different scenarios are considered. The first scenario reflects a distributed electrical power generation application where cogeneration is not taken into account. Instead, the other two scenarios deal with CHP civil applications for different heat demands. The thermoeconomic results of the integrated mHAT cycle, based on a preliminary design of the saturator, demonstrate that microturbine performance can be greatly enhanced, while specific capital costs, in some cases, can be reduced up to 14%, without significant increase in layout complexity. Moreover, thanks to its operational flexibility (able to operate in dry and wet cycles), the mHAT is financially attractive for distributed power and heat generation (micro-cogeneration), particularly when heat demand is commutated in short period.