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ISHS Acta Horticulturae 245: Engineering and Economic Aspects of Energy Saving in Protected Cultivation

MODELS FOR GREENHOUSE CLIMATE CONTROL

Author:   P.D.H. Tantau
DOI:   10.17660/ActaHortic.1989.245.53
Abstract:
The capacity of microcomputers is continuously increasing and the costs are steadily decreasing. Therefore the numbers of microcomputers which are used for greenhouse climate control is growing. The task of greenhouse climate control is to maintain optimal growing conditions for the plants. As greenhouses are covered with thin materials which must have a high light transmissivity, the greenhouse climate is influenced very rapidly by changes of outdoor weather conditions. This makes good control of the greenhouse climate very difficult.

The use of microcomputers offers the chance of using better control algorithms. The computer control algorithms usually originate from analogue control systems with added capability, incorporating logical decisions and data monitoring. The use of adaptive control algorithms can not improve the control precision of a well tuned controller (Udink ten Cate, 1983).

In practice feedforward control is used to improve feedback control. For feedforward control the use of process models is necessary. These models should be physical models based on heat balances of the greenhouse. For control purposes these models should not require too much computing time. Therefore simple models are used, describing idealized physical components.

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