Evaluation of hourly solar radiation on inclined surfaces at Seoul by Photographical Method

• A Photographical Method (PM) is proposed for predicting solar irradiance.
• 5 solar radiation models and 4 albedo models are evaluated with PM.
• Prediction accuracy of solar irradiance with PM was improved in all cases.

Generally, a proper solar radiation model considers nothing more than the angle of inclination of a slope, without considering the influence of obstacles and surrounding buildings. In this study, we proposed a Photographical Method, which can increase the prediction accuracy of solar radiation on an inclined surface, with considering the shape of obstacles in the sky view. This paper evaluated twenty cases (5 solar radiation models in each of 4 albedo models), by the new method of the Photographical Method (PM). The following conclusions were drawn: (1) The prediction accuracy of solar radiation on an inclined surface was improved in all twenty cases with the PM. (2) The new method showed a higher degree of improvement of prediction accuracy in the low range of solar radiation (a high proportion of diffuse solar radiation). (3) The prediction accuracy of solar radiation with the PM improves with increasing tilt angle from the horizontal to the vertical. Applying the Photographical Method is more suited to an urban region with a forest of buildings, than a region of wide grasslands and sunny climate.