Synthesis and optimization approach for integrated solar combined cycle systems based on pinch technology. Part I. Heat recovery pressure levels

Integrated solar combined cycle systems (ISCCS) represent, both economically and energetically, a promising alternative for the conversion of solar energy while offering a guarantee of a minimum power supply independent of the level of solar radiation. Their performances are, however, strongly dependent on the intensity of the solar input. The approach proposed in this paper allows, from the characteristics of the turbines (gas turbines and steam turbines) and of the solar field, to rationalize the choice of the pressure levels and of the massflows of a steam cycle with multiple pressure levels. It is based on the coupling of a pinch technology approach with a thermodynamic modelling, allowing an optimisation with deterministic algorithms. Results are applied to a dual pressure steam cycle and account for the respect of the 'cone law' for steam turbines. It is shown that an increase of the exergetic losses linked to heat transfer in the steam generators is inevitable at certain operational regimes and depends directly on the level of solar supply. The variations of the main steam cycle parameters as a function of the thermal supply (combustion gases + solar thermal oil) are shown for an 80 to 120 MWe power plant equipped with two gas turbines and one steam turbine train. (C) Elsevier, Paris.