Turbomachines for application in LOTHECO powerplants (turbomachines for LOTHECO)

The improvement of the technical and economic performance of electric power generation is a continuous effort. An example is the step from simple-cycle (open-cycle) gas turbines to combined-cycle powerplants. Later, STIG and HAT cycles were introduced and, more recently, the LOTHECO concept was proposed. This concept unites features of the standard combined-cycle powerplant and of the HAT cycle by using low-temperature external heat––and not the exhaust energy of the gas turbine––to humidify the high pressure combustion air. (LOTHECO is the acronym for “combined-cycle powerplant with integrated low-temperature heat”.) An obstacle to the introduction of LOTHECO plants is the fact that in their simplest configuration they require newly designed or at least extensively modified gas turbines. This is because the compressor and the turbine mass flow rates, when adjusted to the LOTHECO conditions, are quite different. To improve this situation, alternatives to the original LOTHECO plant concept must be developed. It is found that combinations of standard gas turbines and expanders are solutions almost equivalent in terms of efficiency and specific work to the original LOTHECO plant with an adjusted gas turbine. Less desirable possibilities appear to be combinations of industrial compressors and expanders because of the relatively low inlet temperature of expanders currently available on the market.