An Estimation Method of Irradiation Data for Evaluating PV Systems

Photovoltaic (PV) systems have been introduced around Japan, and expected to diffuse more and more. As well as a lot of PV systems are installed; all of them have not been taken care after established. In fact, there are some troubles about PV operations behind owners of PV systems even if they are very few cases. It seems to be difficult to identify characteristics of PV systems such as the ideal output energy. Therefore, it is very important to evaluate the characteristics of them. For evaluating them, equipments of measuring are required, and they, especially pyrheliometer, are expensive as much as owners of the PV system cannot equip with main systems as usual. Consequently, an evaluation method which can reveal the performance of operation such as the performance ratio with a very few kinds of data is necessary. As for evaluation, irradiation data are absolutely imperative item. An estimation method of irradiation by using external data is one of the essential studies. Therefore, developing the estimation method of irradiation is intended in this study.

In Japan, there are the weather observation stations which are Automated Meteorological Data Acquisition System (AMeDAS) and surface weather observation administered by Japan Meteorological Agency (JMA). In this method, it is essence that the irradiation data is alternated by estimated data from AMeDAS and actual measuring data from JMA. The data of them are appropriately each weather condition. Irradiation is estimated by AMeDAS data on fine days, and JMA data are alternated on the cloudy days. As a result, the proposed method can estimate irradiation less than 10% of error.