Abstract
AbstractDue to high competitiveness in the PV sector, despite the low degradation rate of crystalline silicon PV modules (below 0.5%/year), it is still important for utilities to know its actual value due to its impact on energy yield and hence, profitability, over the lifetime of a PV plant. However, uncertainties related to both the influence of downtime periods due to problems that may appear under normal operation of a commercial PV plant and to the measurement of degradation rates at PV plant level make this a challenging task. In order to obtain a significant value, in this paper, three measuring methods with different uncertainty sources are used for 82 MWp of PV modules on different locations in Spain and Portugal over 10 years. According to the different methods used and PV plants analyzed, excluding PV plants with problems, a range of degradation rates between 0.01 and 0.47%/year has been found. The overall average value observed is 0.27%/year. The findings of this work have also revealed the great importance of good operation and maintenance practices in order to keep overall low degradation rates.
Highlights
The long-term degradation and stability of PV modules has great impact on the economics of PV plants
Measuring degradation rates in commercial PV plants is difficult to achieve experimentally due to the environmental variabilities that arise in consecutive outdoor measurements and due to the small magnitude of the measuring itself
These PV plants have had negligible PV module defects, inverter faults or any other setbacks that may have caused a drop in energy yield
Summary
The long-term degradation and stability of PV modules has great impact on the economics of PV plants. Financial models usually assume a long-term degradation rate for crystalline silicon, x-Si, modules of around 0.5% per year.[1,2] This is in accordance with the results of an extensive compendium of over 200 studies from the open literature up to 2015, which has found median degradation for x-Si technologies in the 0.5%–0.6% per year range,[3] and in accordance with the guaranties offered by manufactures, most typically in the 0.5–0.7%/year range. Difficulties arise from the high accuracy required, well below 1% of repeatability, and from the extrapolation of results to the whole PV plant. Another possibility consists of continuously observing a performance related parameter such as the Performance Ratio, PR
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