With the increasing interest in distributed power and heat generation, microturbines (mGT) have come to play an important role in small-size energy plants as the most competitive alternative to piston engines, due to their low environmental impact and reduced O&M costs. The Humid Air Turbine (HAT), which has received special attention over the last ten years, can be exploited to enhance thermal efficiency for power generation, although it is still not able to provide more than 30% efficiency for a regenerated cycle. For this reason a micro HAT cycle seems to offer an interesting way to significantly increase thermal efficiency and specific work and easily reduce NOx emissions. This paper presents a general thermodynamic assessment of a micro Humid Air cycle (mHAT), in the range of 100–500 kWe, with cycle optimisation, and a preliminary attempt to integrate existing microturbines and the humid air cycle: the results show that a remarkable increase in efficiency (up to 3–5 percentage points) and specific work (up to 50–70%) can be achieved without any major re-design of the machine, with the exception of the combustion chamber. Moreover, the detailed analysis and design of the saturation tower demonstrates its compactness, one of the overriding requirements for a system for distributed power generation.

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