Articles
ENERGY SAVING CLIMATE CONTROL REGIME FOR CUT CHRYSANTHEMUM
Article number
633_61
Pages
489 – 496
Language
English
Abstract
The ability of crops to tolerate temperature deviations from the average set point could play an important role in energy saving greenhouse climate control regimes.
For that, temperature integration (TI) is often applied.
Regular temperature integration algorithms (RTI) use fixed maximum and minimum temperatures.
Our aim was to increase energy savings by modifying TI (MTI) with more freedom for temperature fluctuations.
The same quality and yield as common climate control (CCR) should be achievable fixed set points.
In MTI, TI was applied with two nested control cycles.
Long-term TI was applied over a 6-day period and optimum temperature was calculated in a short-term TI (24-h) with the aid of weather forecasting.
In the short-term, temperature was optimised every 5 minutes by maximising crop gross photosynthesis and a temperature dose-response for temperature extremes.
To avoid overruling TI by humidity control, a process based humidity regime (HR) was implemented.
Ca-deficiencies, plant water stress, crop growth, crop development and airborne fungus diseases were taken into account.
Computer simulations were performed to compare the regimes in different seasons. RTI or MTI in a 12-week cultivation period in spring reduced energy consumption by 22% or 26% compared to CCR. MTI combined with HR resulted in up to 40% reduction in energy consumption when CCR was applied with a set point of 80% RH. In a greenhouse experiment, crops which performed well and with 39% higher total dry weight could be achieved when MTI was combined with HR.
For that, temperature integration (TI) is often applied.
Regular temperature integration algorithms (RTI) use fixed maximum and minimum temperatures.
Our aim was to increase energy savings by modifying TI (MTI) with more freedom for temperature fluctuations.
The same quality and yield as common climate control (CCR) should be achievable fixed set points.
In MTI, TI was applied with two nested control cycles.
Long-term TI was applied over a 6-day period and optimum temperature was calculated in a short-term TI (24-h) with the aid of weather forecasting.
In the short-term, temperature was optimised every 5 minutes by maximising crop gross photosynthesis and a temperature dose-response for temperature extremes.
To avoid overruling TI by humidity control, a process based humidity regime (HR) was implemented.
Ca-deficiencies, plant water stress, crop growth, crop development and airborne fungus diseases were taken into account.
Computer simulations were performed to compare the regimes in different seasons. RTI or MTI in a 12-week cultivation period in spring reduced energy consumption by 22% or 26% compared to CCR. MTI combined with HR resulted in up to 40% reduction in energy consumption when CCR was applied with a set point of 80% RH. In a greenhouse experiment, crops which performed well and with 39% higher total dry weight could be achieved when MTI was combined with HR.
Authors
O. Körner, H. Challa
Keywords
greenhouse, humidity, temperature integration, fungal diseases
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