A review on the thermodynamic optimisation and modelling of the solar thermal Brayton cycle

Many studies have been published on the performance and optimisation of the Brayton cycle and solar thermal Brayton cycle showing the potential, merits and challenges of this technology. Solar thermal Brayton systems have potential to be used as power plants in many sun-drenched countries. It can be very competitive in terms of efficiency, cost and environmental impact. When designing a system such as a recuperative Brayton cycle there is always a compromise between allowing effective heat transfer and keeping pressure losses in components small. The high temperatures required in especially the receiver of the system present a challenge in terms of irreversibilities due to heat loss. In this paper, the authors recommend the use of the total entropy generation minimisation method. This method can be applied for the modelling of a system and can serve as validation when compared with first-law modelling. The authors review various modelling perspectives required to develop an objective function for solar thermal power optimisation, including modelling of the sun as an exergy source, the Gouy-Stodola theorem and turbine modelling. With recommendations, the authors of this paper wish to clarify and simplify the optimisation and modelling of the solar thermal Brayton cycle for future work. The work is applicable to solar thermal studies in general but focuses on the small-scale recuperated solar thermal Brayton cycle.