Evaluation of the change in photosynthetic active radiation of the LED light source depending on the operating time

Modern LED light sources make it possible to create the necessary values of photosynthetic irradiance both for growing seedlings and for growing vegetable crops in greenhouse conditions. It is LED light sources that in the near future will replace sodium lamps, which are used in most greenhouses, The area of these greenhouses in the Russian Federation is more than three thousand hectares, with electricity consumption for lighting one hectare of the greenhouse being at least 1 MW per hour. The paper presents the results of experimental studies of the photonic characteristics of LED lamps. Lighting characteristics of LED lamps were measured; light values were recalculated into energy values in accordance with GOST R 58461-2019. Research tests of LED lamps were carried under normal climatic conditions for 10,000 hours, with an intermediate test running time of 5,000 hours. It was found that the arithmetic mean value of photosynthetic irradiance decreased by 1.9 times. In the process of operation, a spectral component in the blue region of the optical spectrum grows from 0.35 to 0.6 relative units, while the spectral component in the yellow-red region of the optical spectrum decreases with time of operation. The decrease in photosynthetic irradiance is caused with the degradation of the phosphor composition over time. The results of these studies can be used by developers of LED light sources in order to improve the preservation of photonic characteristics over time, and in particular, to improve the phosphor composition that provides photosynthetic irradiation of the light source over time.