Magazine Articles
This article is reproduced with the permission of GrowerTalks magazine, where is originally appeared in the November 2000 issue on page 88.  For more interesting and informative articles that impact the greenhouse industry, go to GrowerTalks website at www.growertalks.com.

InGear

Outside the Box

by Fred Kaiser


It's natural to think of your greenhouse environmental control system for controlling climate and irrigation.  But what about other uses? Growers tend to be incredibly resourceful, figuring out all kinds of >>
interesting ways to use their tools.  In some cases the application can be so significant that it alone can justify the purchase of a system.  Here are two.
 

Automatic pest control
 If you've ever had to go around your greenhouse before making a pesticide application, turning off fans, closing vents and opening curtains, then re-opening vents and turning on fans for purging, you know what a bad job it is.  A number of HortiMaX customers have found ways to use their environmental control systems to do the job for them.

Kent Belau from Timbuk Farms, Granville, Ohio, was key in the development of a program for HortiMaX's GEM software that let's you program up to four individual application steps: preparation, application, circulation and purge.  You enter the schedule for each of the events.  You pick which day or days of the week, the start time and duration, and whether to make it a permanent or one-time event.  Then you can program the equipment and temperature set point modifications for the following four stages:

Preparation.  This is the period you'd use to prepare the greenhouse for pesticide application.  You can program any zone equipment you want to be overridden for this preparation cycle.

Application.  This cycle is used to activate your sprayer to apply the pesticide.  During this period, the  spraying process is happening,  >>

 


whether from an automated fogger or other method.  Usually the cooling system would be overridden so the pesticide isn't lost to the outside.

Circulation.  The circulation period is used to distribute the pesticide.  You can program the HAF fans to run during this period to circulate the pesticide for even distribution.  You can also use this period to turn off all air-moving equipment to allow the pesticide to settle.

Purge.  This period is used to purge pesticide from the zone in preparation for the re-entry of people.  During this time, the ventilation or cooling equipment is usually activated to allow remaining pesticide to escape outside.

During this portion of the program, there's a real danger of overcooling the house, if the weather is cool.  You can disable the purge if the zone temperature falls a certain number of degrees below your heating target.  It will resume after the temperature recovers.

You can pre-program the computer to automatically control the greenhouse environment in your particular way for each of the steps that you use.  You don't have to use all four stages.  In fact, you can use it to only do purge, if you want.

 

Cutting your energy bill
 Utility companies frequently impose demand charges if your power consumption exceeds a predetermined threshold in any 15-minute interval throughout the day.  In some parts of the country this demand charge can be huge.  Also, some utility companies offer rebates if you utilize energy-saving technology to keep your power below the demand thresholds.  Incidentally, the demand thresholds aren't necessarily fixed.  During peak usage hours, the threshold may be lower than, say, at night or on weekends and holidays.

Some of our customers have significantly reduced their demand charges using their environmental control computer, which is programmed by completing a form for the peak power demand permitted for that month.  A wattmeter is installed, and the computer continuously monitors the power level. >>

Fred Kaiser is chairman, HortiMaX USA Inc., Irvine, California. 		 


If the power level comes close to the threshold, your computer can be set for one of two strategies.  One is to power up the backup generator system.  When the preset kilowatt demand level is exceeded, the generator will take over the electrical needs of the facility until the demand goes back to normal.  Some growers, especially in northern climates, have found that one unseasonably warm spring or fall day can add $1,000 or more to their demand charges.  (A typical demand charge is $10 per kilowatt, so adding 100kW to your demand would do it.)  So you may only need to run your generator for a few hours a month for significant savings.

Another is to do "load shedding," which is having the computer turn off some equipment.  The program can prioritize what gets turned off first, second, etc.  You might give up some cooling, but you can be certain that if you eliminate the demand charge, you'll save yourself a bundle.