The yellow light of the 15W solar street light mainly considers its economy.

The yellow light of the 15W solar street light is generally high-pressure sodium light, most of the photon wavelength is about 555 nm, which is considered as yellow light by human eyes. Generally speaking, under the high-pressure sodium light, you can see different shades of yellow. But now the commonly used high-pressure sodium light is not a single wavelength, but it can show different colors of objects. Generally, we use the index of color rendering index to characterize this characteristic of the light source. The sunlight and incandescent light have a full score of 100, and the high-pressure sodium light has a score of about 20. Generally, the metal halide light or energy-saving light will have no pressure to distinguish the color of objects above 60. Now there are also high-pressure sodium lights with high color rendering index, such as Philips Cosmo, although their company prefers to classify this light as a metal halide light.

Why use this street light? Because the photoelectric conversion efficiency is high. The common high-pressure sodium light with high luminous efficiency has a light efficiency of more than 140 lumens per watt, and the common incandescent light that has been eliminated has a light efficiency of fewer than 10 lumens per watt. The highest luminous efficiency of the household energy-saving light and the compact fluorescent light is 30 to 40. The higher the luminous efficiency, the brighter the same power, that is, the same brightness can reduce the power and cost Electricity. A 400 Watt street light costs more than 1000 yuan a year. There are more than 70000 street lights in the urban area of the main city.

Besides, a high-pressure sodium light belongs to gas discharge light. Unlike incandescent lights, it can not be directly connected to 220 mains power. It needs an inductive ballast and a high-voltage pulse trigger. The starting current is much larger than the normal working current. It takes 10 to 15 minutes to reach the normal working state after lighting up. After extinguishing, it takes several minutes for the metal sodium of the ionization tube to cool down before relighting It's on, so you can see that although the light has high conversion efficiency, it's not suitable for home use at all.