Abstract:
The Brayton cycle’s heat source can be obtained from solar energy instead of the combustion of fuel. The
irreversibilities of the open and direct solar thermal Brayton cycle with recuperator are mainly due to
heat transfer across a finite temperature difference and fluid friction, which limit the net power output of
such a system. In this work, the method of total entropy generation minimisation is applied to optimise
the geometries of the receiver and recuperator at various steady-state weather conditions. For each
steady-state weather condition, the optimum turbine operating point is also found. The authors
specifically investigate the effect of wind and solar irradiance on the maximum net power output of the
system. The effects of other conditions and constraints, on the maximum net power output, are also
investigated. These include concentrator error, concentrator reflectivity and maximum allowable surface
temperature of the receiver. Results show how changed solar beam irradiance and wind speed affect the
system net power output and optimum operating point of the micro-turbine. A dish concentrator with
fixed focal length, an off-the-shelf micro-turbine and a modified cavity receiver is considered.
