URBAN CEA - High-Tech Tactics

May 8, 2008

Erik Biksa

Growing plants in urban areas can be quite rewarding

Introduction

Growers in urban settings face unique challenges when compared to those in rural settings. In high-density urban centers such as Vancouver and Toronto, it’s a safe bet are you are living in an apartment or condo, or at least very close to your neighbors. Your neighbors may share walls with you and even the local foot traffic is close by. You are interested in gardening indoors, but chances are you will find yourself severely constrained by your living situation.

Running large ducts for exhaust through solid concrete and blasting hot air out next to your neighbour’s window isn’t going to win you the tenant of the month award. And you may soon discover that sleeping or having friends over while an exhaust fan blows nearby is a trying experience. The amount of renovation or construction required may also not appeal to you. To permanently modify an urban space for growing purposes demands a real commitment to your endeavour, and the people who live there after you’ve gone may not be impressed by a grow room in their living space. Let’s face it, most people aren’t as passionate about indoor gardening as the readers of this magazine are. Lugging building materials in and out of an apartment or condo is no fun either.

Relax. There are some great solutions to your dilemma that were not available in the not-too-distant past, and they are packaged well for shipping and come with clear instructions. Historically, many urban gardeners had to settle for growing under a few fluorescent lights, perhaps in a spare room or closet. Production levels were very limited; although these gardens could produce nice quality fruit and flowers, there were not enough to make it worth the bother for most people.

Today you can run a small state-of-the-art growth chamber in any spare room in your home and with minimal intrusion on your lifestyle or living space. Don’t expect it to come without a price, but if you are serious about growing a high-yielding garden in an urban setting, there are many options available to you. The trick is to have the right “tools” for the job. Actually, with a lot of plug-and-play technologies, “NO TOOLS ARE REQUIRED FOR ASSEMBLY.”

Putting it to the Test

I decided to test the possibility myself, and I set out to create an experimental indoor garden, with precise environmental control, in an urban living space — essentially a CEA (controlled environment agriculture) growth chamber in a spare room.

As with any growing endeavor there was a need to address certain parameters, but in this case with the constraints of the space also in mind: * Temperature: I needed no, or minimal, exhaust and intake. * Light: I needed it to be as intense as possible with no leaking into the living space. * Humidity: I needed a way to remove the moisture transpired by plants. * Carbon dioxide: I needed no, or minimal, outside air exchange. * Liveability: I needed a way for people to co-exist with the garden in a relatively small space with neighbours to consider.

The Spare Room

The “spare room” I used turned out to be a sun room measuring about 8 ft. (2.5 m) square. It was adjacent to a living room from which it was separated by a frosted (translucent) sliding glass door. The room was near a lot of outdoor foot traffic and appeared to be next to a neighbour’s bedroom. It was also south-facing, with only venetian blinds covering a lot of glass. One of the windows could be opened, so there was a source of passive air exchange. The floor was tiled and level, which was about the only plus the room had to offer as a growing area.

The Growing Enclosure

While at the Indoor Gardening and Hydroponic Expo in Vancouver, BC, I noticed that there were a number of pre-fabricated indoor growing enclosures available. This suited my experiment well. There was no need to renovate my spare room, with all the work that involves: carrying building materials, sawing, hammering, drilling holes, painting, etc. Because the light fixture and shade that I chose were relatively heavy according to the specs, there was a need for something sturdy and light, as well as moisture-tight. It also needed to be easy to assemble and it had to be something that could be dismantled without leaving a trace or causing any damage when it was time to move it out.

The first step, then, was to set up the pre-fabricated enclosure I had chosen. The corner brackets were metal and I deemed them able to support the more than 35-lb. (~16-kg) weight of the reflector I would be installing. I chose the 54.5-in. (138-cm) square model. In this I could set up a respectably productive garden and still have space left for the necessary peripheral equipment — ballasts, chillers, reservoirs, dehumidifier, carbon filters, etc. A space for regular maintenance of plants — pruning, cutting, spraying, etc. — was also required.

There were a number of intake and exhaust, as well as electrical, outlets built into the reflective, light-tight, and waterproof covering of the enclosure. They could be opened or closed with Velcroed port covers. The front and sides could be partially or fully opened with heavy-duty zippered openings; you could open them just a crack or wide enough to slide a flood tray in or out. When closed, they were light tight, preventing light from leaving or entering the enclosure. Being able to maintain a true “dark” period is extremely important, and the grower could still work in the room while the enclosure was in the “dark” cycle.

The floor of the unit also had a heavy-duty waterproof liner, for preventing damage in case of spills or overflows. The walls were very reflective, maximizing light efficiency. After setting any type of enclosure up, I recommend the would-be grower allow a week for the canvas to air out before planting anything, as initially they have a strong odour.

I also opted for a controller board mount because I intended to install environmental controls inside. One of the pluses was that the duct flange options were of sturdy metal construction.

Air Intake and Exhaust

I chose the lower left port for air intake from the spare room, and the upper right port for the exhaust. This seemed to offer the most uniform arrangement. Neither intake nor exhaust was connected outside the spare room. The air was exchanged only between the enclosure and the sealed spare room. The spare room, therefore, acts like a lung.

I installed a HEPA intake filter in the intake port to reduce airborne contaminants — spores, dust, dirt, etc. I wanted to ensure that the air was the cleanest possible. A small carbon filter was installed in the exhaust port. This would help keep the room free of odours and further assist in reducing airborne contaminants. It was lightweight and sufficient for a one-1000-W lamp garden.

Although there would be no exhaust leaving the spare room, the air did need to be drawn out of and pushed back into the spare room, continuously recirculating the air through the HEPA and carbon filters. For this I chose a 6-in. (~15-cm) Eco-Plus 440 CFM, in-line, centrifugal fan. It came ready to plug in and featured very sturdy looking (and removable) mounting brackets. A 4-in. (~10-cm) model would have been plenty for the job, but here’s the trick: the 6-in. fan will move more quietly the same volume of air at about a 30 per cent lower fan speed than a 4-in. fan will full-bore. Electricity used by the fan is minimal, especially when running at 70 per cent. Remember that this grow chamber was only feet away from a high-traffic living area, so keeping things quiet was important. Bungee cords are a great alternative for hanging a fan because they dampen any vibrations. The ventilation system was relatively quiet once fully assembled. Little noise could be heard in the adjacent living areas.

Lighting

I stumbled upon my lighting solution at the Indoor Gardening and Hydroponic Expo. It turns out that water-cooled lighting has become a lot more user-friendly and affordable, and it seemed to meet my objectives: near silent; very efficient (less than 200 W of power to keep one-1000-W HID cool); requiring little or no air exchange; and able to achieve very high light levels, for maximum production. When I put my hand to the lamp at the trade show it was the first time I felt an HID lamp cooler than the area surrounding it, so high temperatures would not be a problem in the enclosure. These water-cooled lights are truly impressive pieces of indoor gardening technology.

So, the next thing to go in was the lighting setup. For my enclosure I chose to go with a horizontal reflector with insert. For a stadium-style garden I might choose to go without the horizontal shade. For the purposes of my experiment, the reflector would create a very even light footprint within the enclosure and provide a level of protection to the glass cylinders of the water-cooled system.

The system comprises nine main parts: inner glass tube, outer glass tube, two end caps with hose connections, mogul/lamp holder, and four specialized gaskets. Basically, cooled water is circulated from a pump in a reservoir through a hose manifold, then through the cylinder holding the lamp, then back into the reservoir. The water never touches the lamp itself. The water is circulated continuously. A “no flow, no go” switch is installed in the manifold before the lamp, so if the water flow stops, the ballast operating the lamp shut offs until flow is restored to the fixture.

The lighting unit is relatively heavy, so it was a good test for my enclosure. I found that suspending the unit by four chains, one from each of the top corners, distributed the weight evenly enough for the structure to remain stable. I would not advise suspending anything heavy from anything but the main structural members of whatever enclosure you are using.

For each 1000 W of HID lighting, it is recommended that you maintain a water reservoir for cooling with at least 25 gal. (95 L) of water. Make sure that the water is of the best quality possible. Any particulate could diminish light output from the water-cooled cylinders surrounding the lamps. To keep the water cool, I installed a 1/4 HP water chiller. I set the temperature to 70°F (~21°C). Any time the water temperature begins to rise because of heat being absorbed from the lamp, the chiller will lower it. The chiller consumes less than 200 W of power, and cycles only intermittently. The chiller unit makes a fraction of the noise of an air conditioner or exhaust fan when cycling.

The chiller discharges the heat removed from the reservoir via a fan. Although this increases the air temperature in the spare room, it also helps to dehumidify the air. This is advantageous because maturing crops can transpire significant volumes of moisture. The chiller does not need to be in the spare room. If the heat from the discharge becomes excessive, it can be placed elsewhere, where heat discharge won’t be an issue or might even be welcome, especially in damper and colder winter months. It is relatively simple to run 1/2-in. (~1-cm) hose from the water-cooled light and reservoir to the chiller. Great distances are possible, and for my setup I could easily drill a 3/4-in. (~2-cm) hole through baseboards to run the hose out of sight.

To keep everything circulating I installed an Eco-Plus 633 GPH submersible, magnetically driven pump into the reservoir. The pump is powerful enough to lift the water to the required height for the water-cooled fixture — in my case, near 7 ft. (~2 m). It uses a minimal amount of electricity and looked to be of reliable construction. It also came with an assortment of hose connections. The hose circulating the chilled and return water in the water-cooled lighting system was a consideration. I wanted to be able to see that the water was flowing in the lines, but did not want to start an algae population in the cooling water, because it would diminish the light output from the fixture. As luck would have it, there was a translucent blue hose available that blocks the light wavelengths that algae require. It was relatively inexpensive, easy to work with, and fit standard 1/2-in. (~1-cm) hose connections. In short, perfect for the application.

Environmental Controls

The proper growing environment in the enclosure was a priority: temperature, humidity, and CO2 needed to be maintained at optimal levels. There was a lot of choice on display at the Vancouver show and I was able to have a good look at the various models.

To control the environment in the enclosure, I would need, at a minimum, to be able to remove heat and humidity. Since the grow space was small, the need for the garden to be very productive was high, so carbon dioxide levels also required a degree of control. Because the internal air volume was relatively small, bottled CO2 tanks could be used; they are safe and will not increase the heat in the area like gas-fired CO2 generators do. Another advantage in using bottled CO2 was that it would be more likely to stay at the crop level. Gas-fired generators would heat the gas and it would tend to rise away from the crop.

A number of different controls, monitors, and configurations will be tested throughout the course of my experiment with the indoor garden, to determine what will work best for the application. I will report the results in subsequent issue(s) of Maximum Yield. I will keep changing things until everything is 100 per cent optimal and efficient.

To start, I installed a CO2-2 (CAPS) atmospheric controller on the controller board. The device is plug-and-play and very user friendly. I simply set the temperature to 85°F (~29°C), set the relative humidity to 70 per cent, and plugged in the exhaust fan — and it did all the rest. A great feature is the remote temperature probe; this allows temperature control at the plant canopy rather than the growing enclosure in general. There can be a 15°F (~9°C) degree difference between shade and light within a growing setup.

The CO2-2 atmospheric controller also features a cycle and duration timer for bottled CO2 enrichment. They are integrated into the dehumidistat and cooling thermostat of the unit. So, when the exhaust function is active due to a rise in either, it will deactivate the CO2 injection until the fan turns off. This ensures that CO2 is used efficiently. If I had a limited budget, this would be all the control I would probably need. However, as this is an experiment, I will go a few steps further to determine what is optimal rather than practical.

To measure and enrich the exact amount of CO2 in the environment, an infrared CO2 monitor was required. There are many units in the marketplace from which to choose. The CO2-2 can be integrated with an infrared monitor but must be of the same brand, though there is a level of compatibility between some units. Make sure you do your research. Using the cycle and duration timer on the CO2-2 unit, the monitor is activated only intermittently and will not activate if the exhaust function is on due to temperature or humidity rise. The infrared CO2 monitor has another excellent feature for growers using gas-fired CO2 generators: in the event of a malfunction and the burner cycles continuously, generating excessive CO2, an exhaust fan plugged into the unit will kick, removing the heat generated and keeping CO2 levels within a safe range. Both the CO2 enrichment and evacuation levels and differentials can be adjusted on the unit within seconds.

For purposes of my experiment, and to create an environment that is optimal at all times, one objective is to be able to maintain separate day and night temperature and humidity levels within the environment.

Testing of current lighting technologies will be discussed in future installments of MY. Stay tuned to the next issue to see how the preliminary setup functioned. I’ll give you a hint — it appears to be the easiest and most efficient setup possible. Until next time….

Written by Mike · Filed Under Hydroponics Articles