B-spline Functional Model of Terrestrial Sunshape Based on Measured Data
The function describing the distribution of solar radiative energy received on the ground is called the surface sunshape model.It is important for accurate simulation of the distribution of radiative flux density on the receiver in solar power tower.The percentage of halo radiative energy to the total solar radiative energy is called the CircumSolar Ratio(CSR),which is a key para-meter in the surface sunshape model.At present,the commonly used surface sunshape models have drawbacks of low accuracy,CSR misalignment,discontinuity,and not being integrated analytically.To address these problems,a new sunshape model in terms of tensor product B-spline function is proposed based on observation dataset.Firstly,the two observation datasets are processed via data cleaning,de-noise,normalization,average,and data concatenation.As a result,84 sets of data with different CSR values are obtained.Each set of data corresponds a solar radiative solar energy scanning profile,and varies with incident angle θ.Then,the data set of CSR=O.005 with the most drastic change is chosen as the sample case for constrained B-spline function fitting,whose knot vector and number of control coefficients are determined through differential evolution algorithm and experiments,re-spectively.Then,the other 83 sets of data corresponding to 83 CSR values are fitted using the above knot vector and the number of control coefficients.Finally,the 84 univariate B-spline functions are adopted as inputs,and CSR value is used as variable to per-form B-spline fitting on their control coefficients.The knot vector and the number of control vertices are still determined using the above methods.As a result,a surface sunshape model is obtained,which is in terms of tensor product B-spline function with 12 x15 control coefficients,and variables CSR and θ.Compared with existing models,the proposed B-spline function model is C2 continuous,which has the advantages of CSR alignment,high fitting accuracy,and analytical integration of radiative energy distri-bution.
Sunshape modelCSR alignmentB-spline function fittingQuadratic programmingDifferential evolution algorithm
NETL
NSTL
万方数据
