An analysis of reliability in the early stages of photovoltaic systems in Japan

In order to disseminate Photovoltaic (PV) technologies into the energy network, the cost down is not only important, but also improving the performance of the PV system is significant issues. Long-term reliability is one of the most important issues in terms of PV system performance. Previous researches were mainly focused on the reliability of PV modules, but the PV system is composed of a power conditioner, wiring, junction box, and so on. To improve the reliability of PV systems, it is important to accumulate trouble cases focused on all components of PV system. In this paper, we aim at evaluation of the reliability for the PV system on the early stages of PV system's lifetime by using large number of Japanese PV systems' data from the field Test in Japan. New Energy and Industrial Technology Development Organization has been running the “Field test project in Japan” from 1992. In this project, PV system users have cooperated with the collection of monitoring data and reported on the information of maintenance and certain failures of PV systems for 4 years after installation of PV system. Using those reports each year of installation, we evaluated reliability of PV systems by means of parameters such as Mean Time Between Failure, Mean Time To Repair, and the suspension time of PV system. As a result, the main trouble of PV systems was related power conditioner, and a few trouble of PV module was caused by typhoon. Moreover, the trend of the failure rate before FY 2000 of installation was demonstrated as the trend of initial failure in “bathtub curve;” however, the trend of its after FY 2001 of installation was indicated as the accidental failure in “bathtub curve.” Further, the operator simply forgot to restart the power conditioner after maintenance or suspensions of PV system in many trouble cases, and the user did not notice that it had been suspended for a while. These trouble cases can be avoidable easily through the effective alarm such as error message of power conditioner systems with monitoring systems. Thereby, monitoring with the evaluation method of PV systems is one of the important technologies due to the long-term reliability and stable operation. Copyright © 2010 John Wiley & Sons, Ltd.