EFFECTIVE USE OF THE ELECTRIC ENERGY IN PLANT GROWING STRUCTURES
At present, electric energy sources developed for the conventional light-technical practice are being applied for growing vegetable and flower plants under artificial light. These lamps' major drawback is their high heating rate (excessive infra-red irradiation) and low lighting rate. Due to this, different high or low pressure luminescent or mercury lamps are preferably being used. Luminescent lamps have not only more favourable spectrum, which enables growing plants under conditions differing very slightly from natural light, but their emitting of light is three times higher than that of lamps operating according to the heating principle. As regards their technical and economic features, luminescent lamps show a major drawback, i.e. their considerably more complex and costly grid inclusion scheme. This is the main reason for the extensive investigations undertaken in different countries and aimed at developing new schemes and techniques for the inclusion of these lamps into the electric grids and for supplying them with higher frequency electric energy sources. It has been further ascertained that the use of accelerated frequency energy contributes towards bettering the light and technical characteristics of the luminescent lamps.
The first tests aimed at investigating the behaviour of seedlings under the effect of luminescent lamps of higher frequency energy sources were initiated in 1955. Frequences of 0.50, 200 and 500 Hz were tested. No significant effect upon the tomato and cucumber seedlings from the acceleration of the electric current frequency has been determined. However, the 500 Hz grid lamp inclusion schemes have proved superior in simplicity and convenience, as compared to the 50 Hz frequency schemes.
A new commercial-type device for enabling the use of a 2,500 Hz frequency induction generator has been developed at the V.I. Edelstein-TXCA Experimental Station on Vegetable Growing. The general outlook of the scheme and systems proves that accelerated frequency simplifies ballast resistances, decreases their value and the control scheme gains in simplicity of operation and in convenience. The light irradiation of the lamps is raised by 15 to 17 per cent as well.
Comparative results of a number of variants with an additional lighting are the following: with a 100 sqm lighted area, a 480 hour annual use of the device and an energy expenditure of a lighting system furnished with 5–80, 50 Hz lamps being equal to 100 per cent, economically most advantageous has proved the system furnished with 5–80, 2500 Hz lamps - 78 per cent, followed by the ΔP-500 lamps system - 99 per