A PV module may be producing reduced output for reversible reasons. It may be subject to shading, for example, by a tree which has grown in front of it. The front surface may be soiled (PV modules will generally experience up to 10% loss of output due to front surface soiling). One module may have failed, or the. Degradation mechanisms may involve either a gradual reduction in the output power of a PV module over time or an overall reduction in power due to failure of an individual solar cell in. By-pass diodes, used to overcome cell mismatching problems, can themselves fail, usually due to overheating, often due to undersizing 1. The problem is minimised if junction temperatures are kept below 128°C. UV absorbers and other encapsulant stabilizers ensure a long life for module encapsulating materials. However, slow depletion, by leaching and.
