Lamps used in greenhouses to provide a lack of light are divided into three categories:

1- Lamps with white light:

White light bulbs produce a lot of heat and have poor light quality. This means that most of the energy used is converted into heat (only 7% of electrical energy is converted into light). These lamps are used for lack of light during the day.


2- Fluorescent lamps:

These bulbs are mostly used in culture media for seed germination. These bulbs are also effective in accelerating the various stages of plant growth. Among fluorescent lamps, cold white lamps and white fluorescent lamps have good efficiency (the conversion efficiency of these lamps is 20% of electrical energy). In the figure below, you can see a greenhouse that uses moonlight. The light of these lamps is close to the blue light spectrum.

Shows the use of white moonlight in the greenhouse.

 

3- Lamps with electric discharge:

These bulbs are made of mercury or sodium at different pressures. These high-intensity bulbs are used to complete the growth cycle of plants in greenhouses.

The grid spectrum of high-pressure mercury lamps is somewhat similar to that of fluorescent incandescent lamps. High pressure mercury and sodium lamps are used to provide light in winter and increase the photosynthesis of plants.

These lamps are less used due to their high cost.