A Humid Air Turbine–Organic Rankine Cycle combined cycle for distributed microgeneration

• Humid Air microTurbine and Organic Rankine Cycle models.
• Micro combined cycle with optimized medium/low temperature heat recovery.
• Thermodynamic analyses of different integrations, fluids and parameters.
• Outstanding performance parameters in the distributed generation power range.
• Economic analyses show the high viability of the proposed concept.

This paper analyses the integration of Humid Air microturbine and an Organic Rankine Cycle in a combined cycle for distributed generation. This integration concept maximizes heat recovery at the exhaust of the micro gas turbine combining the capacities for medium temperature heat recovery of the Organic Rankine Cycle and low temperature heat recovery of the Humid Air Turbine.The integration analysis based on different sets of organic fluids and different recovery temperatures showed that the optimal combination was achieved using toluene and R245fa for medium and low temperature Organic Rankine Cycles respectively. Their combination with the low temperature heat recovery at the Humid Air Turbine saturator maximizes the heat recovery profile from the exhaust gases.The calculations carried out reveal a 25% improvement in net power output of the dual cycle compared to the standalone Humid Air microturbine. Such improvement also affects to global efficiency, increasing it up to 52% in the optimal configuration, above the 41% estimated for the standalone Humid Air Turbine and the 33% rated efficiency of the state of art microturbine Capstone C200. The economic analysis shows that these increases in efficiency and power values make the proposed concept highly competitive, with a 15% reduction in the Levelized Cost of Electricity compared with the standalone Humid Air Turbine and a reduction of 30% compared with the micro gas turbine base case.The presented results show this novel integration as a very promising solution for distributed generation applications at power range under 200 kW, due to its relative simplicity and cost.