Research On Flux Density Measurement Of Concentrated Solar Irradiance In Solar Power Tower Plants

Flux density of concentrated solar irradiance is an important parameter in solar power tower systems. Its measurement is necessary for performance assessment of the receiver and heliostat field as well as supervision and control of the system.Continuous measurement of the flux density distribution facilitates efficient receiver operation and heliostat aimpoint control. For a given receiver, optimization of the system depends on the best receiving location and the uniformity of the flux density distribution. These parameters are modified by changing the tracking parameters of the heliostats and the curvature of the reflecting surface. By optimizing flux density distribution on the receiving surface, the input power of the receiver can be improved, the flux peak can be reduced, thus reducing thermal pressure and possible destruction.The purpose of this research is to study the methods of flux density measurement of concentrated solar irradiance on the basis of domestic and foreign theoretical and practical experiences and to design a system which can be used for the measurement of flux density on receivers of commercial solar power systems.The main studies and contributions included in this dissertation are summarized as follows:1.The current condition of the research of solar thermal power systems and theexisting methods for flux density measurement has been learned.2. The principle of a flux density measurement method based on the“PHLUX”method is investigated and the formulas are derived. A program which is able to process input pictures and data has been written with matlab. A GUI interface which can display the corresponding flux density distribution and other related information has been created.3.The optimal attenuation factors of the demanded neutral density filters in different concentration factor and receiver reflectivity conditions are calculated.Product survey of neutral density filters has been accomplished.4.Experiments have been implemented. The flux density distribution of the concentrated irradiance of a nearly spherical mirror has been measured. The theoretical value of the incident energy of the concentrated irradiance has been calculated. Incident angle of the rays arriving on the mirror is measured with a total station. Consider the deviation of the measured value from the calculated value as a reference, The measurement uncertainty is evaluated.5.The reflection properties of three kinds of diffuse reflectance plate of different materials and prices are compared by experiment, which may provide reference information for future diffuse material selection.6.The possible uncertainty factors are discussed based on the theoretical formula and part of the solutions are proposed.