An analysis of the efficiency and economy of humidified gas turbines in district heating applications

In this article, the performance of gas turbine cycles operating with air/water working fluids, so-called humidified cycles, are examined in district heating applications. The investigated cycles are based on a GTX100 core from ALSTOM Power Sweden AB (ALSTOM)1 and utilise a two-stage flue gas condenser and an inlet air humidifier (pre-humidifier) to provide elevated quantities of district heating. Simulations have shown that electrical efficiencies up to 50% and total efficiencies above 100% can be reached calculated on the lower heating value (LHV) of the fuel. Based on cost data from ALSTOM, humidified cycles have a potential to give much lower (40% per kWel and 60% per kWDH) specific investment costs compared to combined cycles, mainly due to the absence of steam turbine. The humidified cycles are predicted to be cost-effective investments at market electricity prices € 5–8/MWhel lower than the conventional alternatives in district heating applications.