The solar panel efficiency is the ability of the panel to convert sunlight power to usable electrical power, for example, if the solar panel efficiency is 16%, that means only 16% of the sun light hits the panel will be converted to usable electricity. Actually in the market, the average solar panels efficiency ratings vary in the range 15% up to 20%.
The question is: Will the solar panel loses some of its efficiency over its operation life? The answer is: Yes, the solar panel can lose more than 30% of its rated power and it can reach to 90% loss. The power loss is caused due to Potential Induced Degradation phenomena which is discovered recently, and confirmed by tests conducted in German Institutes. However, this phenomenon is still under final tests.
The potential Induced degradation phenomena occurred due to chemicals reactions between solar cell surfaces and panel glass under certain circumstances, causing a leakage current flow between the solar panel frame and the solar cells. So, the intensity of such degradation depends on some factors, like: ambient environmental conditions, module type, and the solar panel power inverter location in the array string. However, for high voltage solar array like 700V or above, the high surrounding humidity will lead to some moisture on the solar panels surfaces, and this will increase the degradation reactions between solar panel surface and the glass. So, it’s very important to check the potential Induced degradation performance for the solar panel before purchasing it, to see if the solar panel will keep its original efficiency for long time or Not. There are many entities in the world doing such potential degradation tests and provide accurate performance results, like Fraunhofer laboratory and TUV testing laboratory in Germany.
There are many well manufactured solar panels brands over the world providing very good performance and perfect test results related to Potential Induced Degradation phenomena, and those are what we have to use in our new solar photovoltaic installation to make sure We will get the maximum harvest (electricity) over the solar system expected life time.