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Solar cell efficiency

The basic rule of physics is called the law of conservation of energy. It says that we cannot magically create energy or make it disappear in the thin air; all we can do is to convert it from one form to another. This means that solar cells cannot produce more energy than receiving light per second. In fact, as we will see shortly, most batteries convert about 10-20% of the energy they receive into electrical energy. A typical single junction silicon solar cell has a theoretical maximum efficiency of about 30% and is called the Shockley-Queisser limit. This is primarily because sunlight contains a broad mixture of photons of different wavelengths and energies, and any single junction solar cell will be optimized to capture photons only in a particular frequency band, wasting the rest. Some photons hitting a solar cell do not have enough energy to destroy the electrons, so they are effectively wasted, while others have too much energy and the excess is wasted. The best cutting-edge laboratory batteries can use multiple connectors to capture photons of different energies under absolutely perfect conditions, achieving 46% efficiency.

Real-world domestic solar panels can reach about 15% efficiency, giving a percentage point here or there, and this is unlikely to get better. The first generation of single-junction solar cells would not be close to the 30% efficiency of the Shockley-Queisser limit, let alone 46% of laboratory records. Various annoying real-world factors will affect nominal efficiency, including the construction of panels, how they are positioned and angled, whether they are in the shadows, keeping them clean, how hot they are (increased temperature) tends to decrease Efficiency), and whether they are ventilated (let the air flow underneath) to keep it cool.