Solar radiation incident on tilted flat surfaces in Barcelona, Spain

Monthly averages of hourly irradiances upon a surface tilted toward the south in Barcelona, Spain, have been calculated from the global and diffuse average hourly solar irradiance on a horizontal surface computed over a period of three years (1973–1975). Similarly, daily irradiation on a monthly average and total annual irradiation for several inclinations were computed. Optimum slopes corresponding to a maximum incident energy were calculated from the annual average of daily solar irradiation, summer and winter, in the same way as the values of the inclination for which annual irradiation is maximum and minimum.