Solar panels after installation need to maintain the output performance guaranteed by the manufacturers for long-term operation of solar power plants at an estimated power generation capacity. The method to check the change in output performance of solar panels is a key point in the O&M (operation and maintenance) services.
Remote systems for respective PV inverters and strings (units for input to combiner boxes) are generally used to check power generation. Power generation data is accumulated by using multiple panels in bundles, and abnormalities in the output are estimated by analysis of aging and other phenomena. In this method, however, the output of each panel needs to be measured to identify the state of each panel including aging.
It is ideal that the measurements performed before shipment by panel manufacturers are done periodically after the start of power generation.
However, some of the measurements are difficult to be done outdoors, and panels have to be removed from the mounting bases and packaged to carry them to companies or organizations that have equipment for performing such measurements. This method is unrealistic when the cost and workload as well as the risk of damage to panels during transportation are considered.
In view of the situation, Chemitox Inc of Ota-ku, Tokyo, which is known for its panel reliability evaluation services, developed a method to perform the same measurements that are done at plants before delivery of panels at power plant sites.
The method incorporates a "movable PV laboratory" mounted on a medium-size truck (Fig. 1).