DISC Model
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The DISC model was authored by Dr. E. Maxwell. Daryl Myers did the Excel^@ Spreadsheet implementation.The user supplies hourly average measured global horizontal data. The algorithm uses empirical relationships between the global and direct clearness indices (Kt, Kn) to estimate the direct beam component. Computations are based on the solar geometry for the hour and clearness indices. A reference on the performance of the model is:

REFERENCES

• Maxwell, E. L., A Quasi-Physical Model for Converting Hourly Global Horizontal to Direct Normal Insolation, Technical Report No. SERI/TR-215-3087, Golden, CO: Solar Energy Research Institute, 1987

• Skartveit, A., J.A. Olseth, and M.E. Tuft. An Hourly Diffue Fraction Model with Correction for Variability and Surface Albedo. Solar Energy, Vol 63 #2, pp 173-183, 1998.

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