THE LIGHT BALANCE IN SEMICYLINDRICAL SHELTERS

While previous studies on this subject by J. Deltour and A. Nisen, centred upon the optic properties of diffusing materials, involved but the material itself and its own influence on the propagation of light, this one is the next step in the agronomic approach of the sub-mentioned theories.
Indeed, the works dealt with the estimation of the luminous balance on the ground, in a semicylindrical tunnel greenhouse covered with different theoretical types of diffusing material (transparent, 50% diffusing, 90% diffusing). This physical problem has been represented by a mathematical simulator.
Thereby, the distribution of light on the ground could possibly be estimated.

The results of the experiments have confirmed some opinions:

• When the sun is low on the horizon, the more diffusing the material, the more luminous the greenhouse and the greater the heterogeneity of the distribution of light intensities within the shelter.
  The luminosity proved to be largely increased in the part of the greenhouse exposed to the "Sun".

• When the sun is high in the sky, which means strong insolution, a rather important shading effect (30 percent) appears.

No focal effect – concentration of the luminous rays onto the geometric centre of a semicylindrical greenhouse – has been noted.

Symposium on Strawberry under Protection

P. Basiaux

https://doi.org/10.17660/ActaHortic.1973.30.20