Recuperative solar-driven multi-step gas turbine power plants

An analysis on the influence of the recuperator effectiveness in a multi-step solar-driven Brayton engine is presented. The solar collector model includes heat losses from convection and radiation. The Brayton engine includes an arbitrary number of turbines and compressors, regeneration, and several realistic irreversibility sources. It is stated that the combination of both systems makes the evolution of the overall efficiency with the effectiveness of the regenerator not trivial. Such behavior is associated to the losses arising from the coupling of the working fluid with the collector and the surroundings. The overall efficiency admits a simultaneous optimization in regards to the pressure and temperature ratios. When the system is designed to work close to the optimum values of those parameters an increase in the effectiveness of the recuperator is always associated with an increase in the overall optimum efficiency. This holds for configurations from the simplest solarized Brayton up to arrangements with several turbines and compressors.

► Influence of the recuperator efficiency in a multi-step solar-driven Brayton engine.
► Evolution of the combined system efficiency with regeneration is not trivial.
► Pressure ratios over 5 decrease eta when recuperator effectiveness increases.
► This is avoided by using a two-turbines two-compressors Brayton engine.
► Joint optimization of pressure ratios and temperature avoids problems with regenerator.