Maximum Net Power Output of the Recuperative Open and Direct Solar Thermal Brayton Cycle

The small-scale open and direct solar thermal Brayton cycle with recuperator has several advantages. These include low operation and maintenance costs and high recommendation. The main disadvantages of this cycle are the pressure losses in the recuperator and receiver, turbo-machine efficiencies and recuperator effectiveness, which limit the net power output of such a system. Thermodynamic optimization can be applied to address these disadvantages in order optimize the receiver and recuperator and to maximize the net power output of the system at any steady-state condition. The dynamic trajectory optimization method is applied to maximize the net power output of the system by optimizing the geometries of the receiver and recuperator, limited to various constraints. Standard micro-turbines and parabolic dish concentrator diameters of six to eighteen meters are considered. An optimum system geometry and maximum net power output can be generated for each operating condition of each micro-turbine and concentrator combination. The results show how the irreversibilities are spread throughout the system optimally, in order for the system to produce its maximum net power output. It indicates that the optimum operating point of a micro-turbine is at the point where the internal irreversibilities are approximately three times larger than the external irreversibilities.