The Results of Performance Measurements of Field-aged Crystalline Silicon Photovoltaic Modules

摘要

This paper presents the results of electrical performance measurements of 204 crystalline silicon-wafer based photovoltaic modules following long-term continuous outdoor exposure. The modules comprise a set of 53 module types originating from 20 different producers, all of which were originally characterized at the European Solar Test Installation (ESTI), over the period 1982-1986. The modules represent diverse generations of PV technologies, different encapsulation and substrate materials. The modules electrical performance was determined according to the standards IEC 60891 and the IEC 60904 series, electrical insulation tests were performed according to the recent IEC 61215 edition 2. Many manufacturers currently give a double power warranty for their products, typically 90 percent of the initial maximum power after 10 years and 80 percent of the original maximum power after 25 years. Applying the same criteria (taking into account modules electrical performance only and assuming 2.5 percent measurement uncertainty of a testing lab) only 17.6 percent of modules failed (35 modules out of 204 tested). Remarkably even if we consider the initial warranty period i.e. 10 percent of P_(max) after 10 years, more than 65.7 percent of modules exposed for 20 years exceed this criteria. The definition of life time is a difficult task as there does not yet appear to be a fixed catastrophic failure point in module ageing but more of a gradual degradation. Therefore, if a system continues to produce energy which satisfies the user need it has not yet reached its end of life. If we consider this level arbitrarily to be the 80 percent of initial power then all indications from the measurements and observations made in this paper are that the useful lifetime of solar modules is not limited to the commonly assumed 20 year.