Developing Humidified Gas Turbine Cycles

As a result of their unique heat recovery properties, Humidified Gas Turbine (HGT) cycles have the potential to deliver resource-effective energy to society. The Evaporative Gas Turbine (EvGT) Consortium in Sweden has been studying these types of cycles for nearly a decade, but now stands at a crossroads, with commercial demonstration remaining. This thesis binds together several key elements for the development of humidified gas turbines: water recovery and air and water quality in the cycle, cycle selection for near-term, mid-sized power generation, and identifying a feasible niche market for demonstration and market penetration. Moreover, possible socio-technical hinders for humidified gas turbine development are examined. Through modelling salt contaminant flows in the cycle and verifying the results in the pilot plant, it was found that humidification tower operation need not endanger the hot gas path. Moreover, sufficient condensate can be condensed to meet feed water demands. Air filters were found to be essential to lower the base level of contaminant in the cycle. This protects both the air and water stream components. By capturing air particles of a similar size to the air filters, the humidifier actually lowers air stream salt levels. Measures to minimise droplet entrainment were successful (50 mg droplets/kg air) and models predict a 1% blow down from the water circuit is sufficient. The condensate is very clean, with less than 1 mg/l alkali salts and easily deionised. Based on a core engine parameter analysis for three HGT cycle configurations and a subsequent economic study, a steam-cooled steam injected cycle complemented with part-flow humidification is recommended for the mid-size power market. This cycle was found to be particularly efficient at high pressures and turbine inlet temperatures, conditions eased by steam cooling and even intercooling. The recommended HGT cycle gives specific investment costs 3035% lower than the combined cycles and cost of electricity levels were 10-18% lower. Full-flow intercooled EvGT cycles give high performances, but seem to be penalised by the recuperator costs, while still being cheaper than the CC. District heating is suggested as a suitable niche market to commercially demonstrate the HGT cycle. Here, the advantages of HGT are especially pronounced due their very high total efficiencies. Feasibility prices for electricity were up to 35% lower than competing combined cycles. HGT cycles were also found to effectively include waste heat sources. Language: English