A Basic Study on Estimation of Solar Irradiation for Photovoltaic Power Generation

Abstract

The photovoltaic power generation has a weak point that its power output is unstable according to the weather conditions. In order to realize the optimum control of a diesel-photovoltaic hybrid generation system, this paper describes a novel method to estimate daily/hourly amount of solar irradiation. The outline of the proposed method is as follows; (1) solar irradiance is observed and maximum and minimum values of “atmospheric transmittance” are obtained, (2) maximum and minimum values of daily/hourly solar irradiation are theoretically calculated using the values of the atmospheric transmittance, (3) a ratio of the sunshine time is also estimated by the observed solar irradiation, (4) the daily/hourly amount of solar irradiation is finally estimated using the ratio and the maximum and minimum values of the daily/hourly solar irradiation. The data of solar irradiance for one year, 355 days in 2000, were analyzed by the present method, and the values of daily (9 to 17 o'clock)/hourly (12 to 13 o'clock) solar irradiation were estimated. The result shows that the estimated values agree very well with the observed values on more than half of the days in 2000.