Solar Panel Performance
Each year, solar panel efficiency increases by about 2%. Solar panel performance is tested under standard test conditions (STC), with a solar irradiance of 1,000 W/m² with the panel temperature at 25°C and solar spectrum of AM 1.5.
Solar panel characteristics which are listed on most quality data sheets list the following categories, which are extremely useful for solar system design and testing;
- nominal power (PMAX, measured in W) –
- open circuit voltage (VOC)
- short circuit current (ISC, measured in amperes)
- maximum power voltage (VMPP)
- maximum power current (IMPP)
- peak power
- Watts Peak (Wp)
- Module efficiency (%)
Anti PID Technology
Quality solar panel manufacturers incorporate anti PID Technology to prevent the negative effects of leakage currents. When solar modules are interconnected, voltage differences between the module frame and the active layer can occur. If unchecked, voltage differences can cause leakage currents to develop, which can cause significant power loss within the first few months of operation. This phenomenon called potential induced degradation.
During the manufacturing process of solar panels, certain irregularities may occur such a hairline fractures and deformation of the solar cells and soldering imperfections which in most cases, these defects are not detectable by the naked eye and can only be measured with infrared scanning. These defects can cause extreme localized heat which will reduce power output and in worst cases produce a solar module fire. These are why solar panel imperfections are called hot-spots.
Each solar cell has a unique electrical characteristic, especially in regards to its voltage and Amperage. Positive sorting refers to sorting cells with similar characteristics onto solar modules to decrease overall panel electrical resistance and increase performance and efficiency.
Salt Corrosion Protection
Salt mist is a corrosive agent that can reduce the output of solar modules that are not proven salt-mist resistant. Salt-laden humidity and rain conditions can adversely affect key module components, including the frames, junction boxes and glass surfaces, thus potentially reducing a module’s performance and lifespan.
Most crystalline silicon solar panel manufacturers offer a 25 year warranty, guaranteeing that the solar module will produce 80% of its rated output after 25 years. However, only a handful of solar manufacturers like Kyocera and SunPower that have had more than 25 years of testing history and can confidently guarantee their product for 25 years based on real world conditions.
A solar array must be able to withstand the most extreme climatic conditions, such as torrential rain and hail, fierce winds, ice and snow and extreme heat. Only the best solar panels can withstand these conditions year after year for over 40 years. There is an independent test undertaken by Rheinland TUV which simulates real world conditions of extreme heat, cold and flexing, to see how many cycles a solar panel can withstand before it fails. Kyocera was the first panel to pass the TÜV Rheinland’s Long-Term Sequential Test in 2010.
Kyocera’s modules maintain performance even under very severe environmental conditions and its entire product line of solar modules has passed the Salt Mist Corrosion Test, IEC61701:2011 Edition 2, Severity Level 6, administered by TÜV Rheinland in Tempe, Arizona. Kyocera’s solar panels have evolved over 38 years of product development and pioneering research and are ideally suited in marine and coastal areas for long-term projects.
Kyocera created the world-renowned Sakura Solar Energy Center and is the site of a 43kW Grid-tie System, installed in 1984. This system consists of more than 1,000 Kyocera solar modules which have been exposed to over 45,000 hours of solar irradiation. Performance results have proven that after 25 years, these panels have shown a degradation of only 9.6%.
SunPower expects its modules (panels) have a useful life of more than 40 years, defined as 99% of modules producing at least 70% of their power. This is made possible through fundamental design differences which provide robust protection against real-world stresses. SunPower modules show significantly less degradation than Conventional Modules in the industry standard reliability stresses meant to simulate hot and humid environments and constant thermal cycling. Testing for the dynamic loading affects from shipping, installation, and field exposure also show less degradation. Finally, SunPower modules do not require a diode for safe operation in shaded conditions, removing the potential for a single point of failure.
The degradation modes modeled for solar modules are:
• Cell damage induced by ultraviolet (UV) radiation
• Photo-thermal encapsulant browning
• High-voltage degradation
• Other effects
Unlike degradation modes, failure modes do not cause appreciable degradation in performance until catastrophic failure. Two key failure modes govern the life of solar modules:
• Backsheet cracking due to relative humidity and hydrolysis
• Solder-joint failure due to temperature cycling
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