A. Ohara, Y. Hirose, T. Sugimoto, K. Kajiyama, T. Yokoyama, H. Kawahira, K. Suzuki
In view of the fact that the electricity cost generally has a major influence on the total economy for plant factories, the following technical issues have been investigated.
  1. Improvement in PAR ( photosynthetically active radiation ) efficiency of a light source.
  2. Reduction in thermal radiation of a lighting system.

With respect to (a), PAR(DIN-5031-1978) efficiency of high pressure sodium lamp has been improved by 20% over that of a conventional lamp by optimizing the design parameters of arc tube diameter, sodium amalgam composition and arc potential gradient. Further improvement in PAR efficiency, as well as reduction in thermal radiation, have been observed by a combination of the arc tube with an outer jacket having an infrared reflective coating.

With respect to (b), a newly developed metal reflector, on which a dichroic reflective layer was coated, has proved that the thermal radiation to the illuminated surface from the reflector decreases by approximately 25%.

The lighting system, comprised of (a) and (b), will contribute to reduce the electricity cost and hence, to improve the economy of plant factories.

Ohara, A., Hirose, Y., Sugimoto, T., Kajiyama, K., Yokoyama, T., Kawahira, H. and Suzuki, K. (1988). DEVELOPMENT OF LIGHTING SYSTEM FOR PLANT-GROWTH. Acta Hortic. 230, 349-356
DOI: 10.17660/ActaHortic.1988.230.46

Acta Horticulturae