Towards user accepted optimal control of greenhouse climate

Theoretically, using information about crop growth would allow the extensio n of present greenhouse control strategies towards a truly economic optimal control strategy. A brief survey is given of developments in the scientifi c literature. A full solution would require to consider the long-term crop development as well as all relevant short-term dynamics of the crop, the gr eenhouse and the external weather. Obstacles for the acceptance of such sol utions are briefly discussed. One of the key factors is the lack of reliabl e crop development models for the wide variety of crops encountered in prac tice, and the need to leave part of the decision freedom in the hands of th e grower. An analysis is given of simplified approaches resulting from inte grating the crop equations over a day or more. The temperature integral con cept, a specific example of such approach, is gaining popularity, despite t he fact that it lacks exploitation of knowledge about the fast crop respons es. The discussion leads to the concept of separation of responsibilities, where the short-term effects, including photosynthesis and evapo-transpirat ion, are handled by an automated model-predictive optimal controller. while the long-term effects are left to the grower, with support from a flexible decision support system based on crop models whenever they become availabl e. (C) 2000 Elsevier Science B.V. All rights reserved.