Evaluation of hourly tilted surface radiation models

• Published in: Solar energy Vol. 45; no. 1; pp. 9 - 17
• Main Authors: Reindl, D.T., Beckman, W.A., Duffie, J.A.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 1990; Elsevier
• Subjects: 140100 - Solar Energy- Resources & Availability; ANISOTROPY; Applied sciences; ARIZONA; CAPTEUR SOLAIRE; COLECTORES SOLARES; DIFFUSE SOLAR RADIATION; DIFFUSION; DIFUSION; ENERGIA SOLAR; ENERGIE SOLAIRE; ENERGY; ENERGY SOURCES; EQUATIONS; EVALUATION; Exact sciences and technology; FEDERAL REGION II; FEDERAL REGION IX; FEDERAL REGION VI; FORECASTING; HOURLY VARIATIONS; INCLINATION; ISOTROPY; MATHEMATICAL MODELS; MODELE; MODELOS; Natural energy; NEW MEXICO; NEW YORK; NORTH AMERICA; PREDICTION EQUATIONS; RADIACIONES; RADIATION; RADIATIONS; RENEWABLE ENERGY SOURCES; SOLAR COLLECTORS; SOLAR ENERGY; SOLAR EQUIPMENT; SOLAR FLUX; SOLAR RADIATION; STELLAR RADIATION; SURFACE INCLINATION; TEXAS; USA; UTILIZABLE ENERGY; VARIATIONS; Diffuse solar radiation; Mathematical model; Performance; Solar radiation; Comparative study; Monthly average; Inclined surface
• ISSN: 0038-092X; 1471-1257
• DOI: 10.1016/0038-092X(90)90061-G

This study investigates the performance of the isotropic and four anisotropic hourly tilted surface radiation models by using monthly average hourly utilizable energy as a standard of measure. Utilizable energy is the radiation above a specified threshold level. Differences between the utilizable energy measured and the utilizable energy predicted are observed for various surface slope/azimuth orientations and critical radiation levels. Normalized root mean square difference and normalized mean bias difference statistics are formed to quantify the ability of each model to estimate the utilizable energy on a tilted surface. The influence of horizontal diffuse radiation on tilted surface model performance is examined by comparing the predicted utilizable energy on a tilted surface using both measured horizontal diffuse and estimated horizontal diffuse found from diffuse fraction correlations. On an overall basis, the isotropic sky model showed the poorest performance and is not recommended for estimating the hourly radiation on a tilted surface. The anisotropic models have comparable performance to each other. There was no significant degradation of tilted surface model performance when the diffuse radiation is estimated from a diffuse fraction correlation rather than obtained from measurements.