Articles
THE INRA-CEA SOLAR GREENHOUSE : PHYSICAL RESULTS
The roof is made of a double glass : a normal glass for the upper part, and a special one of the lower, and water is allowed to circulate between the two glasses.
The special glass, made by BOUSSOIS S.A., is a selective filter.
The description of the shape and design of the greenhouse have been analyzed earlier (CHIAPALE et al., 1977; CHIAPALE., 1978).
This paper deals with the results of a set of experiments carried out on tomato plants between March and July, 1980. The energy saving in heating requirement is nearly 100% during this period, but the planting data (March, 5th) may have been too late for the plant to face high heating needs.
The experimental results are in good agreement with theoretical conclusion of VAN BAVEL and DAMAGNEZ (DAMAGNEZ et al., 1980) based on a dynamic simulation of the greenhouse energy balance.
During the night, the plant surface temperature under the solar greenhouse is 2° C higher than under the normal glass.
For the same temperature set point, the microclimatic conditions are better under solar greenhouse.
During daytime, the needs of ventilation are considerably reduced.
When exchanging heat with the underground water table, it is possible to save 100% energy in ventilation needs.
But during daytime, the CO2 concentration under the solar greenhouse is lower than under the normal glass, which may explain the reduction of earliness and yield under the solar greenhouse.