Automatic temperature and humidity regulation – High and low temperature alternate
Patent
1980-06-11
1982-07-13
Wayner, William E.
Automatic temperature and humidity regulation
High and low temperature alternate
47 17, A01G 900, G05D 2300
Patent
active
043390749
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method and an apparatus for controlling the temperature in greenhouses, the nominal value of the temperature being adjusted between a higher daytime temperature and a lower night temperature.
Generally, such adjustment between different temperatures is controlled by a timer which at suitable times in 24 hours at the change from day to night and from night to day, respectively, switches the regulator for the heating unit of the greenhouse from a preset daytime temperature to a preset night temperature, and vice versa. In this connection, it is of course of interest from an economical point of view that there is not maintained in the night a temperature in the greenhouse, which is higher than that necessary in order that the plants will get on therewith and the growth, flowering or fructification thereof shall not be stunted.
However, it has been found that the night temperature which is ideal to the plants during a major part of the year, during another part of the year when the conditions in the daytime are most favourable to the plants, in a remarkably high degree stunts the plants. It has turned out that this is due to the fact that in the daytime a considerable amount of sunlight energy has been supplied to the plants; the change-over from daytime conditions to night conditions in the greenhouse as a consequence thereof represents a shocklike reduction of the total energy supply to the plants if the control is strictly tied to the maintenance of a predetermined nominal value of the temperature in the greenhouse in the daytime and a predetermined lower nominal value of this temperature in the night if the energy-economical aspect only is taken into consideration as far as a suitable difference between these two nominal values is concerned.
Bearing the aforementioned in mind and in order to eliminate the shock effect for which the plants-as has been found-may be exposed during sunny and warm days, and to obtain optimum economy with regard to the energy consumption as well as the result of the growth a method and an apparatus for working said method are proposed according to the invention, having the characteristics appearing from claims 1 and 4, respectively.
In order to illustrate the invention some embodiments thereof as presently preferred will be described in more detail below reference being made to the accompanying drawings in which
FIG. 1 is a diagram illustrating the variation of the sunlight intensity over the time,
FIG. 2 is a diagram illustrating the adjusted nominal value of the temperature in the greenhouse at different times,
FIG. 3 is a block diagram of an embodiment of the apparatus according to the invention,
FIG. 4 is a diagram illustrating the relationship of the adjusted nominal value of the night temperature and the incident sunlight energy, and
FIG. 5 is a block diagram of another embodiment of the apparatus according to the invention.
In the diagram according to FIG. 1, the intensity of the light inciding into the greenhouse is indicated in lux on the ordinate of the diagram, the time being indicated on the abscissa of the diagram. The light intensity in lux is indirectly related to the sunlight power in cal/cm.sup.2 /min. In the daytime the light intensity increases successively from a value at or close to zero to reach a maximum at the middle of the day and then decreases again to a value at or close to zero, said latter value then being maintained in the night. The area defined below the graph in FIG. 1 represents the total sunlight energy supplied in cal/cm.sup.2. In controlling the nominal value of the temperature one has not so far taken into account the sunlight energy quantity supplied to the plants in the daytime. The control apparatus of the greenhouse heating unit has been set on a predetermined temperature for the daytime, the temperature then being set on a predetermined lower nominal value in the night for economical reasons. This is illustrated in FIG. 2 which indicates the nominal value of the temperature in the greenhouse on the ordinate o
REFERENCES:
patent: 3905153 (1975-09-01), Enter
Nissmo Jim A.
Sjostrom Lars B.
Sundin Jan A.
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