Improving the efficiency of greenhouse climate control: an optimal control approach

A method to improve the efficiency of greenhouse climate control based on the framework of optimal control theory is described. By exploiting a dynamic model of the greenhouse crop production process, information on auction price, operating costs of the climate conditioning equipment and outdoor climate conditions, the optimal greenhouse climate control scheme balances basic costs against revenues for operating the equipment. In a greenhouse experiment (using lettuces) the behaviour of conventional greenhouse climate control by the grower was measured. Then, in simulation experiments, optimal control strategies were calculated for the same conditions (outdoor climate, auction price, energy price). The results support the conclusion that a considerable improvement in the efficiency of greenhouse climate management is possible. This improvement may well exceed 15%.

Download Full-text

Microclimate Prediction for Dynamic Greenhouse Climate Control

HortScience ◽

10.21273/hortsci.42.2.272 ◽

2007 ◽

Vol 42 (2) ◽

pp. 272-279 ◽

Cited By ~ 21

Author(s):

Oliver Körner ◽

Jesper Mazanti Aaslyng ◽

Andrea Utoft Andreassen ◽

Niels Holst

Keyword(s):

Confidence Interval ◽

Energy Saving ◽

Climate Control ◽

Climate Conditions ◽

Potted Plants ◽

Greenhouse Climate ◽

Save Energy ◽

Heat Of Evaporation ◽

Greenhouse Control ◽

Greenhouse Climate Control

Greenhouse energy-saving and biocide reduction can be achieved through dynamic greenhouse climate control with computerized model-based regimes. This can be optimized when next to greenhouse macroclimate (i.e., the aerial environment) also, the crop microclimate is predicted. The aim of this article was to design and apply a simple deterministic microclimate model for dynamic greenhouse climate control concepts. The model calculates crop temperature and latent heat of evaporation in different vertical levels of a dense canopy of potted plants. The model was validated with data attained from experiments on dynamic or nondynamic (regular) controlled greenhouse cultivation. Crop temperature was with a 95% confidence interval of 2 °C or 2.4 °C for sunlit or shaded leaves, respectively, accurately predicted in a simple greenhouse with predefined climate set points. With a more dynamic greenhouse control also including assimilation lighting and screens, the prediction quality decreased but still had a 95% confidence interval of crop temperature prediction of 3.8 °C for sunlit leaves. Simulations showed that controlling greenhouse temperature according to the predicted crop temperature rather than according to the air temperature can save energy. Energy-saving is highest during winter and 12% energy saving was attained during January under Danish climate conditions.

Download Full-text

A Daylight Climate Chamber for Testing Greenhouse Climate Control Strategies and Calculating Canopy Carbon Dioxide Exchange

HortTechnology ◽

10.21273/horttech.16.2.0191 ◽

2006 ◽

Vol 16 (2) ◽

pp. 191-198 ◽

Cited By ~ 4

Author(s):

Lise T. Jensen ◽

Jesper M. Aaslyng ◽

Eva Rosenqvist

Keyword(s):

Carbon Dioxide ◽

Air Temperature ◽

Control Strategies ◽

Day Length ◽

Small Scale ◽

Carbon Dioxide Exchange ◽

Climate Control ◽

Climate Chamber ◽

Greenhouse Climate ◽

Greenhouse Climate Control

A daylight climate chamber was designed with the aim of testing new greenhouse climate control strategies on a small scale. Precise control and measure ment of the chamber climate and long-term measurement of canopy carbon dioxide (CO2) exchan ge was possible. The software was capable of simulating a climate computer used in a full-scale greenhouse. The parameters controlled were air temperature, CO2 concentration, irradiance, air flow, and irrigation. The chamber was equipped with a range of sensors measuring the climate in the air of the chamber and in the plant canopy. A chamber perfor mance experiment with chrysanthemum (Chrysanthemum grandiflorum `Coral Charm') plants grown in perlite was carried out over the course of 3 weeks. Five air temperature treatments at a day length of 13 hours were carried out, all with the same 24-hour mean temperature of 20 °C, but different day temperatures (18.0 to 25.1 °C) and night temperatures (14.0 to 22.4 °C). Rate of canopy CO2 exchange in the chambers was calculated. In the range of day temperatures used, rates of canopy photosynthesis were almost equal. The results showed that leaf area and plant dry weight after 3 weeks were not significantly different among temperature treatments, which is promising for further investigations of how climate control can be used to decrease energy consumption in greenhouse production.

Download Full-text

Decision support for dynamic greenhouse climate control strategies

Computers and Electronics in Agriculture ◽

10.1016/j.compag.2007.05.005 ◽

2008 ◽

Vol 60 (1) ◽

pp. 18-30 ◽

Cited By ~ 31

Author(s):

O. Körner ◽

G. Van Straten

Keyword(s):

Decision Support ◽

Control Strategies ◽

Climate Control ◽

Greenhouse Climate ◽

Greenhouse Climate Control

Download Full-text

Active Control of Greenhouse Climate Enhances Papaya Growth and Yield at an Affordable Cost

Agronomy ◽

10.3390/agronomy11020378 ◽

2021 ◽

Vol 11 (2) ◽

pp. 378

Author(s):

Irene Salinas ◽

Juan José Hueso ◽

Julián Cuevas

Keyword(s):

Active Control ◽

Skin Color ◽

Natural Ventilation ◽

Control Strategies ◽

Soluble Solids ◽

Growth And Yield ◽

Climate Control ◽

Tropical Fruit ◽

Greenhouse Climate ◽

Solids Content

Papaya is a tropical fruit crop that in subtropical regions depends on protected cultivation to fulfill its climate requirements and remain productive. The aim of this work was to compare the profitability of different climate control strategies in greenhouses located in subtropical areas of southeast Spain. To do so, we compared papayas growing in a greenhouse equipped with active climate control (ACC), achieved by cooling and heating systems, versus plants growing in another greenhouse equipped with passive climate control (PCC), consisting of only natural ventilation through zenithal and lateral windows. The results showed that ACC favored papaya plant growth; flowering; fruit set; and, consequently, yields, producing more and heavier fruits at an affordable cost. Climate control strategies did not significantly improve fruit quality, specifically fruit skin color, acidity, and total soluble solids content. In conclusion, in the current context of prices, an active control of temperature and humidity inside the greenhouse could be a more profitable strategy in subtropical regions where open-air cultivation is not feasible.

Download Full-text