The authors showed that traditional sodium greenhouse irradiators are being replaced by more efficient LED ones. (Research purpose) To conduct a comparative assessment of the main characteristics of sodium and LED greenhouse irradiators with an equal photosynthetic photon flux. (Materials and methods) The authors collected a database of 79 sodium irradiators (34 irradiators with electronic ballasts and 45 – with electromagnetic) and 118 – LED. A comparative assessment was carried out in two stages. At the first stage mathematical models of the power, mass, area and cost of irradiation facilities dependence on the photosynthetic photon flux generated by them were obtained. At the second stage the system of equations of sodium and LED greenhouse irradiators for each characteristic were solved. (Results and discussion) The consumed active power of LED irradiators is on average 33 percent less compared to sodium. The area of LED illuminators is 2.5 times larger than sodium irradiators with electronic ballast and 44 percent more than sodium irradiators with electromagnetic ballast. The LED irradiators mass is 3.5 times more than sodium with electronic ballast and 20 percent more than sodium with electromagnetic ballast. The cost of LED illuminators is 3.5 and 4.3 times higher. (Conclusions) LED irradiators are more energy efficient compared to sodium ones. However, due to the high cost, their implementation requires a feasibility study, including additional evaluation criteria: service life, operating costs, electricity price and others.
The aim of the work is to determine the permissible load factors of step-down transformers when powering various types of greenhouse irradiators. All examined irradiators have nonlinear volt-ampere characteristic and generate upper current harmonics. The object of research are greenhouse illuminators with high pressure sodium lamps, induction and light-emitting diodes greenhouse illuminators (LED) with active and passive power factor. The permissible load factors of transformers are calculated using obtained data: for high-pressure sodium lamp light is 0.95 max; for LED lamps with active power factor corrector – 0.76 max; for LED lamps with passive power factor correction – 0.59 max; for electrodeless lamp light – 0.98 max. To reduce current harmonics in systems with LED lamps and to increase the load factor of transformers, it is necessary to apply special devices – active or passive harmonic filters. For greenhouse irradiators with sodium lamps and induction irradiators, the use of harmonic filters is not required.
The thermal regime of plants determines the temperature of the environment, the evaporation of moisture by plants, and the heating of plants by radiation from irradiation plants. Today, induction and LED greenhouse irradiators are promising for replacing irradiators with sodium lamps in terms of energy efficiency. Experimental studies were performed to assess the possibility of proximity of irradiators with induction lamps and LED irradiators to plants to increase their level of irradiation, in comparison with sodium radiation sources. When setting up the experiment, a complex was used, including a Fluke ti32 thermal imager, PHO-250-2-M linear autotransformer, 220V power supply, and a greenhouse irradiator. Processing of the measurement results was carried out in the Fluke SmartView 3.1 program. The heating temperature was determined when reaching the nominal mode, with the nominal mode of operation of the irradiators, with a change in the supply voltage level. Sodium and induction irradiators heat up to a maximum temperature 10 times faster than LED ones. The heating temperature of optical radiation sources with sodium lamps is 5 times higher than LED and 2.5 times higher than induction. A change in the supply voltage level affects the heating temperature of the sodium irradiator with electromagnetic ballasts, the heating temperature of sodium and induction irradiators with electronic ballasts, as well as LED irradiators, remains unchanged and equal to the nominal value at a supply voltage level of ± 10% of Unom.. Low heating temperatures of induction and LED irradiators can reduce the height of their suspension and bring them closer to plants, which will increase the irradiation of plants by increasing the level of illumination or reduce the power of irradiators, that is, increase the energy efficiency of irradiation systems
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