Research on evaluation methods of generated energy and lowering factors of photovoltaic generation system

Despite substantial progress of research efforts in the field of photovoltaic (PV) power generation, some serious problems remain to be solved, including a fairly low energy generated by PV systems in comparison to the expected output, and a broad spread of output values among individual PV systems. The expected level of generated energy is usually evaluated by means of such coefficients as “the performance ratio” which is obtained as the energy actually generated by a PV array over a period of 1 year divided by the calculated output over the same period. However, this method has some limitations, such as the necessity to continuously perform data measurements over a long time, difficulties in the examination of factors reducing the level of the generated energy or improving the system efficiency, and so on. In this study, the authors propose a new method of accurate evaluation of the generated energy. The authors also examined a method for classifying the losses caused by the rise of the PV cell temperature and presented a method of data measurements over a short time period. The proposed method can also be applied to the classification and analysis of losses occurring at the time of the MPPT operation of the system (Pmax operation). © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 154(4): 24–33, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20222