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One of the greatest problems encountered in greenhouses and buildings with large glazing is control of the internal atmosphere. The inherent characteristic of these buildings to act as solar collectors is to be used effectively for collecting and storing the excess solar energy. A new type of glazed roof, a Solar Climate Control roof system, was designed as a means to cool the interior environment of the greenhouses during the daytime and to heat during the nighttime or on overcast days. / A heat exchanger-storage system, using water as a thermal mass is included in the design of the Solar Climate Control system. A film of water flows on the inner surface of the roof and absorbs the direct solar heat radiation, acting then as a cooling agent. The energy absorbed may be reused for nighttime heating. / An efficient water dispersion pipe for the Solar Climate Control system was developed. The use of a soap solution rather than water alone for the Solar Climate Control water film system permitted a significant reduction in pumping rate and improved uniformity of the film. / A computer simulation model was run to determine the energy loads for both a conventional (double glazed roof) greenhouse and one equipped with the Solar Climate Control system. The Solar Climate Control system shows low operating cost and very good efficiency in heat removal.

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Call number: LD2668 .T4 1961 B34

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M.Ing. / This research project is dedicated to the automation of environmental control within greenhouses. To create an optimal climate in the greenhouse, the main environmental parameters that need to be controlled are temperature, humidity and light intensity. As a result of process dead times and the extreme interdependence of these parameters, the control problem can be classified as non-linear and multi-variable. In the past, most greenhouse environmental control systems depended on the decision making of an experienced human operator. This often gave rise to trial and error, especially when new species were established. With the current advances in "intelligent" control systems and high accuracy sensors, more and more of the decisions involved in greenhouse control can be automated. In this way more emphasis can be placed on emulating the abilities of an expert operator, by means of a computerbased automatic control system. In this research project, "intelligent" as well as "non-intelligent" control techniques, for addressing the problem of automated climate control in a greenhouse, are investigated. These include PID-control as a "non-intelligent" technique, and rule-based fuzzy logic control and self-learning fuzzy logic control as two "intelligent" control techniques. These techniques are all applied to experimental greenhouse which is equipped with management mechanisms, such as fans, heaters, sprinklers and lights. The results of the experiments are evaluated according to two performance parameters: the Control Performance Index (CPI) and the Mean Square Error (MSE). The three techniques are not only assessed for their efficiency, but also for their applicability to the greenhouse environmental problem. Each of the control techniques has a unique characteristic response to the non-linear, non-stationary, multi-variable problem of environmental control and are subsequently addressed in the respective chapter.

The purpose of a greenhouse is to maintain desirable growing conditions for plants during the different seasons of the year. The glass-covered greenhouse has been found to be suitable for this purpose through many yeara of use and improvement. It has been very popular for providing a controlled environment in which out-of-season crops can be grown and also as a research house for the study of plant growth. The sturdy construction required to support the weight of glass involves a high initial cost. With the development of plastic sheeting suitable for use as a glazing material, a new type of greenhouse has evolved. Greenhouses covered with plastic do not require the sturdy structure necessary to support glass, although a permanent construction may be used. To date the plastic greenhouse has found its greatest use as a temporary low cost structure. The possibility of growing crops intolerant of frost during the winter months in the southwestern United States where mild winters keep heating costs low, has increased interest in plastic greenhouses. Since high temperatures occur during the summer months in the Southwest, cooling as well as heating have to be provided if the greenhouse is to be operated through the entire year. This study was designed to measure the modification of the environment within a plastic greenhouse and to evaluate the growth response of tomatoes under these conditions. Studies were conducted to determine the temperatures which could be maintained in a plastic greenhouse during the summer, winter and spring seasons. The growth response of tomatoes under plastic was studied using winter and spring variety trials.

M.S.

No description available.

No description available.