Development of strategies for model-based control of CO₂ supplement in greenhouse

Supplement of carbon dioxide (CO₂) positively improves leaf photosynthesis and thus productivity for greenhouse crops.
However, cost-efficient control of CO₂ supplies is necessary since it is expensive.
This study aimed to develop strategies for model-based control of CO₂ supplement.
The control strategies are based on the prediction of the amount of CO₂ taken up by the crop and ventilated CO₂ loss.
Equations have been employed to estimate photosynthetic rate, ventilation rate, ventilated CO₂ loss, and current internal CO₂ concentration.
Strategies for model-based control of CO₂ supplement are as follows: i) a step to set the target CO₂ concentration (C_g), ii) a step to input predicted values (PV) of leaf temperature (LT), greenhouse air temperature (DT), relative humidity (RH), and measured internal radiation (IR) and CO₂ concentration (C_i) prior to the first supplement of the day to estimate net assimilate rate, ventilation rate, and ventilated CO₂ loss, iii) a step to calculate the first amount of supplemental CO₂ from the PPFD level higher than 400 µmol m^‑2 s^‑1 level, and to supply the first CO₂ fertilization (if the C_i is lower than C_g, the CO₂ is supplied, or if it is higher than the C_g, the CO₂ is not supplied), iv) a step to predict current CO₂ concentration (C_t) inside greenhouse after t time (after calculating the net assimilate rate and ventilated CO₂ loss from the first supplement of the day, the CO₂ concentration become the C_t), v) a step to decide a further supplement (if C_t is lower than C_g, the CO₂ is supplied, or if it is higher than the C_g, the CO₂ is not supplied). The validation experiment performed to compare the calculated with measured C_t showed a correlation coefficient of r²=0.82 (n=98). A future study will implement the algorithm into a commercial integrated environmental control system.

International Symposium on Models for Plant Growth, Environments, Farm Management in Orchards and Protected Cultivation – HorchiModel2023

S.H. Choi, Y.H. Woo, D.C. Jang, Y.A. Jeong, S.A. Yoon, E.Y. Choi

equations for model-based control, greenhouse CO₂ concentration, net assimilate rate, ventilated CO₂ loss

https://doi.org/10.17660/ActaHortic.2025.1425.24