Electrical power generation by closed loop Brayton cycle using supercritical CO2 (sCO(2)) as a working fluid has gained significant interest in recent years. Integrating sCO(2) cycle with renewable energy technology (i.e. solar heliostat field) at high temperature ranges has shown promising results. This study highlights the thermodynamic benefits of recompression sCO(2) Brayton cycle and presents a modelling and control strategy to optimize operating conditions for a constant power output utilising solar- and fossil-based heat sources. This optimization maximizes solar field contribution and minimizes the role of auxiliary fossil-fuelled back-up (AFB) heating system. The performances of two common solar heat input (direct and indirect) configurations are compared. It is found that for a specific day, an indirect cycle consumes 19.5% less fossil fuel compared to an equivalent direct cycle. This is mainly attributed to the usage of thermal energy storage (TES) in the indirect Cycle. However, the high capital cost of TES and operability/controllability issues may decrease the merits of the indirect cycle. Although the reliance on fossil fuel contribution in direct cycle is higher by a magnitude of 4.2% or less, this may be economically admissible compared to the substantial reduction in capital cost as in the case of indirect cycle. (C) 2016 Elsevier B.V. All rights reserved.