Apparatus and method for controlling a greenhouse environment

Abstract

A method of controlling an environment in a greenhouse, the method comprising: periodically venting air from inside to outside the greenhouse during first periods while drawing air from outside to inside the greenhouse and heating drawn in air with heat extracted from the vented air; during second periods between the first periods, drawing in air from outside to inside the greenhouse and heating the air as it is drawn in; and initiating first periods when the relative humidity becomes greater than a predetermined relative humidity.

1 . A method of controlling an environment in a greenhouse, the method comprising:
 periodically venting air from inside to outside the greenhouse during first periods while drawing air from outside to inside the greenhouse and heating drawn in air with heat extracted from the vented air;   during second periods between the first periods, drawing in air from outside to inside the greenhouse and heating the air as it is drawn in; and   initiating first periods when the relative humidity becomes greater than a predetermined relative humidity.   
     
     
         2 . A method according to  claim 1  and comprising switching between first and second periods at regular intervals. 
     
     
         3 . A method according to  claim 1  and comprising determining a same duration for a plurality of consecutive first periods. 
     
     
         4 . A method according to  claim 1  and comprising initiating second periods substantially at times when first periods end. 
     
     
         5 . A method according to  claim 1  wherein an average flow rate at which air is drawn in from outside to inside the greenhouse during the second periods is substantially proportional to the greenhouse volume. 
     
     
         6 . A method according to  claim 5  wherein the flow rate is greater than about 2,500 m 3 /hr per 3,000 m 3  of greenhouse volume. 
     
     
         7 . A method according to  claim 5  wherein the flow rate is less than about 3,500 m 3 /hr per 3,000 m 3  of greenhouse volume. 
     
     
         8 . A method according to  claim 7  wherein the flow rate is equal to about 3,000 m 3 /hr per 3,000 m 3  of greenhouse volume. 
     
     
         9 . A method according to  claim 1  wherein first periods have duration less than or equal to about 10 minutes. 
     
     
         10 . A method according to  claim 1  wherein first periods have duration greater than or equal to about 5 minutes. 
     
     
         11 . A method according to  claim 1  wherein first periods have duration equal to about 6 minutes.