Department of Mechanical and Aeronautical Engineering, University of Pretoria, Private Bag X20, Hatfield, Pretoria 0028, South Africa
Le Roux, W.G., Department of Mechanical and Aeronautical Engineering, University of Pretoria, Private Bag X20, Hatfield, Pretoria 0028, South Africa; Bello-Ochende, T., Department of Mechanical and Aeronautical Engineering, University of Pretoria, Private Bag X20, Hatfield, Pretoria 0028, South Africa; Meyer, J.P., Department of Mechanical and Aeronautical Engineering, University of Pretoria, Private Bag X20, Hatfield, Pretoria 0028, South Africa
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. © 2012 Elsevier Ltd.
Brayton; Direct solar; Dish concentrator; Environmental conditions; Finite temperature differences; Fluid friction; Focal lengths; Heat sources; Micro turbine; Modified cavity receiver; Operating points; Optimum; Optimum performance; Power out put; Solar; Solar beam; Solar irradiances; Surface temperatures; System net; Total entropy; Weather conditions; Wind speed; Brayton cycle; Concentration (process); Entropy; Fuels; Geometry; Meteorology; Receivers (containers); Recuperators; Solar heating; Thermoelectric power; combustion; environmental conditions; error analysis; geometry; irradiance; optimization; performance assessment; power generation; renewable resource; solar cycle; steady-state equilibrium