Relative humidity variation in greenhouses as affected by CO₂ enrichment at high temperatures resulting in energy saving

Research work was carried out in two greenhouses located on the agricultural farm of A.U.Th., in order to study the effect of CO₂ enrichment on greenhouse energy saving.
CO₂ enrichment was applied to C₃ crops under conditions of high temperature with control ventilation.
The better exploitation of solar energy, captured inside the greenhouse, due to reduced ventilation, resulted in energy saving in the experimental greenhouse.
This investigation included three experiments and in the first, the thermal capacity of the greenhouse was taken into consideration.
In the other two, a passive solar system was placed in the greenhouse and its thermal capacity was also considered.
The thermal energy of the experimental greenhouse in relation to the control-greenhouse was 10-25% higher in the first experiment and 35-70% in the other two, as a result of the passive solar system.
Measurements of the relative humidity (RH) during the first and second experiments were used to examine the odd effects of CO₂ enrichment at high temperatures toward the energy saving.
Results showed that the RH is not considered to be a restrictive factor for CO₂ enrichment, when the intervals of this enrichment depend on the air temperature and the solar radiation intensity.
Only in two cases did the RH exceed 80%. The first case appeared during morning enrichments with high temperatures and the cultivation at an advanced stage of growth.
The second case was found with almost a whole day of CO₂ enrichment, since the air temperature did not exceed 30-32°C and the cultivation was at an advanced stage of growth.
Nevertheless, there was no negative effect on the plants.
During the whole investigation these environmental parameters were found to have positive effects on plant growth.

International Symposium on Advanced Technologies and Management for Innovative Greenhouses: GreenSys2019

A. Martzopoulou, D. Vafiadis, V.P. Fragos

carbon dioxide enrichment, high temperatures, relative humidity, greenhouses, energy saving

https://doi.org/10.17660/ActaHortic.2020.1296.19