<Controlled Environment Agriculture

CEA (Controlled Environment Agriculture) article for improving yields and cropping consistency.

For those of you just tuning in to growing indoors, CEA growing set-ups are "sealed" or "perfect" grow rooms. This means that temperature, humidity and CO2 (carbon dioxide) levels are all very tightly controlled by the grower, and can be maintained at optimal levels at all times for better crop production, regardless of the environmental conditions outside of the growing area. This separates CEA set-ups from traditional in/out style gardens that use an active air intake and exhaust to help moderate the growing environment. While in/out gardens can produce well, they are inconsistent because the environment that can be maintained in the grow room will largely be dependent on the RH (relative humidity) and temperature of the outside air being drawn through the room.

For example, if the outside air in the summer time is 85 degrees F, it will not be very effective for cooling a self-contained growing environment that uses HID (high intensity discharge) lighting. While HIDs can deliver bright light, they generate a tremendous amount of heat that must be managed. Air-cooled lamp reflectors can reduce the cooling requirement of any growing environment, making them a smart investment. However, there will still be some rise in ambient temperature in the grow room, and if outside air is relatively warm to begin with, the grow room will overheat. Overheating in grow room is the number one source of crop failure or disappointing yields for indoor growers.

If you are running centrifugal inline fans for air cooled lamp reflectors, a device like this can really improve the efficiency and operation of your CEA endeavor by continuously adjusting fan speed automatically.
Also, if humidity rises in traditional in/out gardens, the air needs to be exhausted and replaced with outside air. If the RH of the outside air is relatively high, which in most regions is more common than not, the grower loses control over the RH levels in the grow room, leading to poor crop quality and incidence of yield reducing flower and fruit rots, moulds, blights, etc.
Furthermore, increasing CO2 (carbon dioxide) levels in the growing environment can significantly increase yields and reduce cropping time, if properly managed. It is difficult to maintain elevated CO2 levels with in/out gardens because the air is exchanged frequently, if not continuously. The majority of any supplemental CO2 the grower introduces into the in/out grow atmosphere will quickly be exhausted away from the plants when the room is cooling (by exchanging outside air). This reduces the contact time the supplemental CO2 has with the crop, making it less effective if not ineffectual.

Most experienced and knowledgeable growers will maintain that CEA growing set-ups are more productive and easier to work with. A lot of newer growers view the idea of a sealed room with no active in/out fans as alien, and perhaps intimidating. Some smaller and mid-scale experienced growers agree with the CEA concept, but feel that such set-ups are reserved only for the large scale producer due to the additional expense involved versus traditional gardening set-ups.

Well the truth is CEA is more affordable and easier to access than it has ever been before. It can be more economical to upgrade an existing grow room to CEA than it is to create a completely new grow room due to the more frequent, larger and healthier yields that can be achieved. The following will discuss how to setup a hobby sized CEA environment using plug and play technologies available from professional hydroponics retailers or your favorite online sources.

You can also use the information in this article to convert your existing in/out set-up to a more productive and easier to control CEA grow room. Once you make the switch, you won'sealt look back. Do note, however, that CEA growing environments will use about 25 to 30 per cent more electricity versus traditional in/out set-ups. If electrical consumption is a major concern, there are some very energy efficient cooling methods for sealed environments now available, such as water cooling. Just be prepared for a learning curve and additional installation and trial time when taking advantage of water cooling for the first time. The savings in electrical consumption using water cooling can help to recapture some of the initially higher capital outlay in more energy efficient CEA set-ups.

Remember that the principal difference(s) between CEA and traditional in/out grow rooms is that an air-conditioner or chiller will cool temperatures without exchanging air. Humidity can be lowered with a de-humidifier, which typically cycles more often in the dark cycle as the air conditioner operating during the lighting cycle tends to keep humidity levels in the optimal range. Carbon dioxide is supplied via CO2 generators or bottled CO2, and the air is kept purified and free of contaminants with an activated carbon filter and/or HEPA filter scrubbers. The grower sets the desired temperature, humidity and CO2 levels on their control equipment and the perfect growing environment is maintained everyday, consistently for better harvests year round. The level of control offered is every grower's dream; you can manipulate the environmental parameters on a weekly basis to help encourage different traits in the crop throughout the cropping cycle. The colorations of flowers and fruits at harvest in a CEA endeavor can be very dramatic and tantalizing.

Step 1: Seal the Room
The growing environment needs to be well sealed in order to be effective and efficient. The easiest way to accomplish this is to purchase a pre-fabricated grow tent or hydro hut; they are available in a multitude of sizes, anywhere from as small as two feet by two feet to beyond 10 feet by 10 feet. Look for manufacturers that have a history of standing behind their product when making a selection. Pre-fabricated grow tents and hydro huts are completely sealable, and usually have multiple zippered openings to contain light and air, while maintaining complete darkness for the dark phase, which is absolutely essential. They are easy to clean and relatively water-proof, allowing people to set-up a high quality grow room in any space that fits without making any significant alterations to existing rooms. You can usually have one completely assembled using minimal or no tools in less than one hour. Note however that they are not well insulated, so the area you set them up in should be, ideally.

If you already have a grow room, make sure to seal up any cracks and leaks. Go through the following checklist:

>Remove and seal off previous intake and exhaust ports, you may choose to keep them for use with air-cooled lighting however.
>Seal off any cracks with expanding foam, available in cans. Make sure to wear gloveswhen applying.
>Ensure that any duct work, i.e. air cooled reflectors, is well sealed using aluminum tape.
>Make sure that the doorway does not leak air. This can be accomplished by using a sheet of durable and reflective poly sheeting with some heavy duty adhesive zippers or Velcro strips.
>Retain your carbon filter and fan; you will need this for "scrubbing" the air within the CEA growing set up.
>Ensure that the grow room itself is well insulated to improve efficiency and reduce noises that can be disturbing outside of the growing area.

Step 2: Equipment Checklist: (Environmental Control)
You will need:
>cooling thermostat
>high temperature kill-switch
A high-temp kill switch is a relatively simple device: if the temperature gets too high due to equipment failure or other problems, it shuts off the HID lights until temperatures go back to normal or until the problem is remedied. This device can save your crop.

Fan speed controllers are also recommended for use with air-cooled lighting and carbon scrubbers. For air-cooled lighting, a high quality fan speed controller will reduce your cooling requirements by more energy intensive equipment such as air-conditioners. The controller featured in this article allows the air-cooled lighting fan(s) to remain at a constant speed and decibel pre-set by the grower. If temperatures increase, fan speed increases and vice versa. Also, if the temperature becomes too cool, the device will shut-off the air-cooling fans allowing for the growing environment to maintain the optimal temperature. If you use centrifugal fans for any kind of cooling purposes, get one of these controls

Carbon Dioxide Gear
One of the benefits of running a CEA grow room is that you can effectively supplement and maintain increased levels of CO2 in the growing environment for faster growth rates and bigger yields. CO2 can increase your yields by as much as 30 per cent, assuming all other growing parameters are optimal, which is achievable in a CEA set-up.

You will need:
>either a CO2 generator (propane/natural gas) or a tank (bottled CO2)
>an infrared CO2 monitor/controller (pricey, but worth it) or a timer.

Note: if going with a REG (regulator, flow meter and solenoid) system for bottled CO2, you may choose an IR monitor/controller or a timer. If going with a CO2 generator, only an IR monitor/controller is recommended for safety and accuracy.

Environmental Control
Air Conditioner
The AC or chiller unit is at the heart of all successful CEA operations. ACs are energy intensive, although they can keep a sealed room at the perfect temperature when sized correctly for the number of lamps and other sources of heat like gas fired CO2 generators. The rule of thumb is to allow for about 4500 BTUs of cooling for every 600 to 1000 watts of light. The exact BTU rating required is somewhat dependent on how well the room is insulated; if the ballasts are in the room or not; if air cooled lighting is being used; as well as if a gas fired CO2 generator will be. Again, usually 4500 BTUs is a good rule of thumb. It's better to get a unit that's a little bit of overkill than to have a unit that can't keep up, forcing the grower to shut down individual lamps.

For most hobby sized, one to two light endeavors and a portable upright style AC will do the job and they are relatively inexpensive and easy to find. They are commonly available in 9500 to 12,000 BTU ratings for cooling. They also have the benefit of being able to plug into common 110/120 volt household circuits, although an entire circuit (breaker) should be dedicated to the AC unit.

Most upright portable ACs will use a discharge hose to vent heat away. This means discharging heat to the outside, along with a small volume of air from the grow room. The air volume discharged is relatively small versus fan cooling rooms and cycles on and off rather than constant, so CO2 supplementation still remains relatively efficient. Also, since a carbon or HEPA scrubber operates 24/7 in the growing area, offensive odors are not released to outside of the growing area through the AC discharge. Sometimes growers need to lengthen the hose for discharging warm air away; this will likely void warranties although it can be accomplished with duct booster fans and insulated flexible ducting.

An alternative method to create a small CEA environment is to install a window air conditioner in a spare room. The air in this room is kept cold at all times and can be vented into the CEA growing area to cool the air as necessary via intakes and ducting; the air from the growing area can be vented into the spare room, which now acts as the "lung" for the growing endeavor, keeping it cool and fresh. In these instances you may want to retain the duct ports from your existing grow room.

There are specialty air conditioners available that are better suited to CEA endeavors, although they usually need to be obtained from specialty suppliers. These types of units exchange absolutely no outside air with the air inside of the growing environment. "Split" ACs are an example of this, as well as units that utilize an exclusive air intake and exhaust to the AC unit itself. The intake and exhaust never touch the air from the growing environment; they are used exclusively to keep the AC blowing cold air into the grow room when activated by the cooling thermostat. In this method the AC itself is acting as a sealed unit.

Water cooled ACs are the ultimate for CEA endeavors. All of the heat is discharged down the drain with water, and no hot air needs to be discharged anywhere. Typically a flow rate of 1.5 gallons per minute is required to effectively operate water cooled air-conditioners, so access to large volumes of cold water is required.

However, as stated previously for most small hobby sized CEA endeavors, a portable upright AC is inexpensive, easy to find and relatively efficient.

This will help to keep humidity from climbing to excessive levels in a tightly sealed room, as the crop transpires water through the leaves that was absorbed through the roots. Excessive humidity levels encourage stretchy low yielding growth and often promote diseases such as rots and mildews. A de-humidifier will add a bit of heat to the growing environment, and will discharge condensed humidity through a drain hose. You can save this water and use it for other purposes. The de-humidifier is controlled by the de-humidistat, which operates 24/7, although the de-humidifier will cycle most often during the dark cycle when the AC cycles are infrequent. If you use water chillers/fan units to cool the growing environment, you will really need to step-up your de-humidification capabilities. For most applications, count for about 25 to 30 pints per 24 hour period of de-humidification capability per 1000 watt lamp of garden.

Carbon/HEPA Scrubber (with fan)
You may already have one or several of these if you are converting your existing grow to CEA. Otherwise, you will need to size-up an appropriate activated carbon filter or HEPA filter. In fact, the best solution is to use both. Have your fan draw the air from the grow room through the activated carbon, then discharge and re-circulate it through the grow room through a specialty inline HEPA filter. This will keep the air smelling fresh and clean, while reducing insects, spores, dust and pollen in the growing area. This equals healthier air yields, healthier plants and fewer problems. Usually for an area with two to four HID lights, a six inch inline centrifugal fan with the correct sized carbon filter and the six inch fan mount HEPA will keep the air perfectly fresh for you and your garden.

Well, that should give you enough to do between the time you read this article and the continuation that will appear in the next edition of this magazine. Besides, you may already have a crop in progress, and will have to wait until you harvest to make the switch to CEA from your existing in/out growing set-up. Start to take note of which pieces of equipment you already have that can be used to make the upgrade, while researching and sourcing any other controllers, appliances, etc you will require to make the change-over complete and effective.

The extra time and expense that you put into this will be worth it when you are able to realize exacting and complete control over the temperature, humidity and CO2 levels in your growing environment. Not only will you potentially yield more at harvest due to improved CO2 levels, you will be able to bring out delicious and eye pleasing qualities in your plants that can best be achieved through precise temperature manipulation made possible by running a sealed and air conditioned environment. In the next installment we will discuss putting it all together and how to make the most of your modern day CEA growth chamber, including crop feeding, for the biggest and tastiest yields you have ever had.