Why are solar panels only 20 efficient?

Solar panels are typically only about 20% efficient due to several factors:

1. Material Limitations: Most solar panels are made of silicon, which can only convert a certain portion of sunlight into electricity. Silicon absorbs photons (light particles) and releases electrons, but not all the photons that hit the solar cell have enough energy to generate electricity.
2. Energy Loss as Heat: A large part of the sunlight that hits a solar panel is lost as heat. Only photons with the right amount of energy can free electrons to generate electricity, and photons with too much energy create heat instead of electrical energy.
3. Reflection: Some of the sunlight that hits the panel is reflected off the surface, reducing the total amount of energy available for conversion into electricity.
4. Electrical Resistance: In the wiring and connections within the solar panel, there is some resistance that causes a small amount of energy to be lost as heat.
5. Spectral Limitations: Sunlight is composed of various wavelengths (colors) of light, and not all of these can be used by the solar panel. For example, infrared and ultraviolet light aren’t absorbed as efficiently as visible light.

Although research is ongoing to improve the efficiency of solar panels, these physical and material limitations keep the efficiency relatively low at around 20%. Some specialized panels can achieve higher efficiencies, but they tend to be more expensive.