ISHS Acta Horticulturae 711: V International Symposium on Artificial Lighting in Horticulture
SIMULATING DYNAMIC CONTROL OF SUPPLEMENTARY LIGHTING |
| Authors: | O. Körner, A.U. Andreassen, J.M. Aaslyng |
| Keywords: | crop growth, energy saving, greenhouse climate control, light integral, model based control, simulation |
| Abstract:
Supplementary lighting is mainly used with a fixed schedule and switched on when outside radiation falls below a certain threshold. A more dynamic control could increase the crop growth / energy consumption ratio. A daily light integral (DLI) or an average DLI over several days (ADLI) can be used as control. Crop growth could be increased when supplementary lighting is shifted to periods with elevated CO2 concentration. This is typically the case when vents are closed. A simulation study for the period between January 01 and April 15 was performed. We aimed to investigate the effects of the length of the light integration interval (2, 4 and 6 days), the daily light sum set point, and directed supplementary lighting with elevated CO2 (light-on only when vents were closed and CO2 was supplied). A day length neutral pot plant crop was used for the simulations. Regular ADLI basically resulted in the same yield as the control when the light sum was the same. ADLI was better than regular control when assimilation light was concentrated to periods with elevated CO2. The success of the control strongly depended on the season. The simulations showed that crop growth can be increased by up to 12% in February compared to a regular control. In spring, however, there are too few periods with closed vents and elevated CO2 in order to attain the same light sum as the control. The simple ADLI regime can be applied, but needs to be improved regarding the light set point or light-power installation in order to attain the same yield as the reference regime. For model based climate control the investigated ADLI regime founds a good base, but for more advanced light control plant development and quality models are needed and probably have to be combined with economical models. | |
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