Solar Cell Modules' solar panel efficiency is a measure of the amount of sunlight (irradiance) that falls on the surface of a solar panel and is converted into electrical energy. Due to the many advancements in photovoltaic technology in recent years, the average panel conversion efficiency has increased from 15% to over 20%. The significant increase in efficiency has resulted in an increase in the power rating of standard-size panels from 250W to 370W.
As explained in detail below, the efficiency of a solar panel is determined by two main factors; photovoltaic (PV) cell efficiency, based on cell design and silicon type, and overall panel efficiency, based on cell layout, configuration, and panel size.
Cell efficiency depends on the cell structure and the type of substrate used, usually P-type or N-type silicon. The cell efficiency is calculated from the so-called fill factor (FF), which is the maximum conversion efficiency of the photovoltaic cell at the optimum operating voltage and current.
Cell design plays an important role in panel efficiency. Key features include silicon type, busbar configuration, and passivation type (PERC). Panels made from high-cost IBC cells are currently the most efficient (20-22%) because it uses a high-purity N-type silicon substrate and is immune to busbar shadowing. However, panels developed using the latest monocrystalline PERC cells and more advanced heterojunction (HJT) cells have achieved efficiency levels well above 20%.
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Solar panel efficiency is measured under Standard Test Conditions (STC) with a cell temperature of 25°C, solar irradiance of 1000W/m2, and air quality of 1.5. The efficiency (%) of a panel can be effectively calculated by dividing the STC's maximum power rating or Pmax (W) by the total panel area measured in square meters.