An evaporative cooling system, otherwise known as a “wet wall” or a “fan and pad” system, is an easy-to-install structural component used in horticultural production to reduce the temperature in a greenhouse using a cellulose pad, fan ventilation and a water supply.
These systems are simple to use because they run largely on their own, and can be less expensive and rely on less energy than HVAC components, says Brad Gaddy, market manager for SCHAEFER/Pinnacle Climate Technologies.
“The way the system works is, you have water that’s pumped up through a tank, and then the water falls down into a trough [into the cellulose pad wall installed in an opening of the structure] and goes back into the tank so it’s recycled,” he adds. “The way we move air through the system is exhaust fans at the opposite end of the greenhouse or structure, and that [circulates] the air.”
While an evaporative cooling system can be effective in just about any structure that needs to be cooled, the lower the humidity in a geographic region, the better this system will work for a grow structure. “For instance, in a place like Phoenix, Ariz., where the humidity can be 8 to 12 percent, these pads can cool up to 30 degrees,” Gaddy says.
Evaporative cooling been used in ornamental greenhouses for decades, but it’s also used in other applications, such as dairy farming or poultry. “As a matter of fact, [in] the state of Arizona, if you drive around and look at the houses, you’ll see these things on top of the roofs. They’re not air conditioners; they’re evaporative cooling systems because the humidity is so low that they can cool it with water instead of an excessive air conditioning system,” Gaddy says.
Gaddy says that the majority of growers who install evaporative cooling systems can work directly with Pinnacle/Schaefer’s dealers to find a custom solution that will fit their structures. “My customers have dedicated tech service officers where they know how to size the equipment,” he says.
However, to put an installation in perspective, the University of Massachusetts’ Greenhouse Crops & Floriculture Program provides an example calculation to determine the size of an appropriate system:
“Assume a 30' x 100' greenhouse with pads to be located at one end and the fans at the opposite end wall. Total fan capacity, based on 8 cfm [cubic feet per minute] per square foot of floor area is 24,000 cfm (30' x 100' x 8 cfm/sq. ft. = 24,000 cfm). This could be supplied by two 42", ½ horsepower fans. Using a 4" thick cellulose pad with airflow through the pad of 250 cfm/minute, the total pad area needed is 96 sq. ft. (24,000 cfm ÷ 250 cfm/sq. ft. = 96 sq. ft.). A pad measuring 4' high x 24' long would meet this requirement.
Minimum sump capacity required for the system is 72 gallons (96 sq. ft. x ¾ gallon/sq. ft. = 72 gallons). Recommended pump size is 12 gpm [gallons per minute] (24 ft. x ½ gpm/ft. = 12 gpm). The size of the supply piping over the pad will depend on the design of the installation. If the water is piped to one end, it will have to be a minimum 1-1/4" diameter or if supplied from the center, it can be 1". The water supply to compensate for the evaporated water should be a minimum of 1 gpm.”
Gaddy says that proper equipment maintenance can help the system last longer.
^An outdoor view of an evaporative cooling system. Image courtesy of SCHAEFER/Pinnacle Climate Technologies.
“What we recommend is that after every growing season … clean the pads,” he says. “We don’t recommend pressure washing because that will tear them up, but try to get some of the debris out and let them dry. And if [cultivators] can store them somewhere, where they’re not exposed to the outside air, that’s optimal. … We also recommend that while using the system, dependent of how hard the water is, that you bleed the system off every so often to get some of the particulate out of the water, so that you’re introducing water that doesn’t have all that stuff built up. Because what happens is, as the water evaporates, the solids in the water do not, and they get caught in the pads. … [And] you might see your electrical bill go up because fans are trying harder to move the air.”
However, if taken care of, it’s likely that your system will last you up to eight years, he adds.
As a horticulturist with a career history in ornamental plant production, as well as cannabis, David Risley has acquired greenhouse-growing experience with trial and error over the years. Now, as head grower for Euflora in Denver, Colo.—he’s learned much he’d like to share on the topic of evaporative cooling, which is an efficient way to deliver lower temperatures to your cannabis crop when installed and utilized correctly.
Currently, Risley has a wet wall system installed in a 7,200-square-foot greenhouse, but will be building out his grow space much differently in the company’s 17,000 square feet of additions that are currently in the works. Here are his tips on how to make your evaporative cooling system work best for you:
1. Ensure all parties included in planning and construction of greenhouse are in communication - contractor, manufacturer, architects, etc.
“Most of the design process of Euflora’s first greenhouse was completed by an architect with no previous experience designing a greenhouse,” Risley says. “The subpar design, combined with an oversimplification of the dynamic nature of a CEA (controlled environment agriculture) structure, led to some costly and completely avoidable blunders, of which I now spend a significant amount of time and energy combating.”
“The biggest mistake by far was locating our mechanical room/head house against the end wall of our veg bay in place of cooling pads. Imagine a 40 x 20-foot shaped L,” he adds. “We now have 10 feet of pad in a 30-feet-wide house. In front of the pad is say, 70 degrees (too cold); in front of the mechanical room is much warmer, 80-plus degrees. And in front of the ‘office’ (turned clone room) is well over 90 degrees and has zero air flow, mostly dead space in summer.”
“Inquire with greenhouse manufacturer about taking tours of already completed projects. Learn what they did and why, then improve and adjust for your project,” Risley says.
2. Ensure proper operation of evap pump and perform routine maintenance.
“Adjust flow to distribution pipe accordingly, and the ensure pump is sized properly,” Risley says. “The goal is to use the least amount of water while maintaining a uniformly wet pad surface; areas where water is running down have reduced rates of evaporation.”
“I like to wash pads down with hose end sprayer and soft brush to remove debris and excess salt,” he adds. “I wouldn’t recommend a pressure washer, as it could damage the pads or strip anti-rot salts off. After rinsing, I clean the pump filter, drain and clean up reservoir, then fill it again with fresh water. I do this monthly in veg. Flower has an adequate bleed-off so draining here is only required seasonally. I recommend contacting Schaefer, and research for more tips relevant to a particular greenhouse for quantity and frequency of bleed-off.”
Also, Risley warns not to pump air from one side of the structure. “If possible, locate the pump and reservoir in the center of the area to be cooled, which will ensure even flow through distribution pipe and a uniformly wet pad surface. If your pads have dry spots, do not attempt to modify distribution pipe by enlarging holes. This was a particularly dumb idea I had at one point,” he says.
Risley also recommends checking the top and bottom of evap frame to ensure air tight (within reason) after installation.
3. Properly seal your facility.
“It didn't take long to figure out that our roof vent was poorly sealed. Turning on our veg bays’ second exhaust fan actually increased temps! With an already higher static pressure from the smaller pad, fan No. 2 sucked down extremely hot air from the gable and outside air from unsealed around doors, outside electrical, partition between bays, etc.,” Risley says. “This is all equates to less air through the pads. Install gaskets around the roof vent, ensure vent motors are closed tight, use weather stripping and door sweep the threshold at base of door to seal it. Silicone and foil tape can be used to seal any other gaps and cracks. Although, it is still mostly unbearable on hot days.”
Also, beware of leaks at aluminum joints. “I highly recommend a PVC system,” Risley says, adding that it’s also important to, “Ensure proper function of evap prior to bringing in plants. Check for leaks and a tight fit between components. Pads have a bit of a break-in period so you likely won't expect the full cooling effect for weeks/months.”
4. Utilize light panels. Select appropriate glazing materials to mitigate excess light and heat build-up.
“The intensity of the sun in Colorado and relatively high light transmission of twin wall poly is more than our veg can handle. Installing diffused light poly will reduce light transmission and eliminate hot spots. This will act like shade paint but without the extra fun and mess of applying shade paint. When it’s hot and the sun is blazing, tender transplants will thank you,” Risley says.
5. Circulate the air.
“Invest in quality HAF (horizontal air flow) fans/circulation fans. In dead zones, or areas where it gets hot, utilize portable evap coolers. They’re efficient, and move a lot of air. So they are very helpful, even if ran with a dry pad,” he says.
6. Consider insect screening and light baffles.
“Installing screening 5x the pad area is ideal to minimize the increase in static pressure,” Risley says. Light baffles (for a light deprivation system) are installed behind cooling pads and exhaust fans to exclude light from entering, and will also reduce flow through pads. “Work with your greenhouse manufacturer, or distributor to appropriately size your exhaust fans to accommodate insect screen/light baffles,” he adds.
7. Don’t skimp on control system and components.
“Just don’t!” Risley warns.
8. Get to know your community.
“Build a good relationship with your fire department and regulatory agencies. Request pre-inspection and take advantage of resources to ensure your building and accessory parts are up to code,” Risley says, adding that Euflora recently received a code violation in May, during their peak production period, for having a shade hung at the top of the veg bay. The negative effects from the increase in temps were immediate, and production ground to a halt. “At the beginning of June, we applied shade paint and have moved more plants in the last two weeks than in the previous month,” he adds.
Maryland medical marijuana regulators took steps Monday to deny a license to one of the 15 companies picked to grow the drug, saying there was a "reasonable likelihood" the firm would not properly safeguard the medicine.
In voting to tell MaryMed LLC that it would not receive a final license, the Maryland Medical Cannabis Commission cited concerns about MaryMed LLC's former parent company Vireo Health, which operates medical marijuana businesses in two other states. The commission also faulted MaryMed for not cooperating with Maryland investigators.
The concerns stem from the February indictment of two former Vireo executives, who face felony charges in Minnesota for allegedly smuggling a half-million dollars worth of cannabis oil across state lines in December 2015.
Maryland regulators said MaryMed mentioned those two executives by name in its November 2015 application to grow the drug here, and the firm "emphasized that its operations in Minnesota and New York, and the experience gained thereby, demonstrated its ability to successfully operate medical cannabis operations in Maryland."
MYM Nutraceuticals Inc. announced that it has signed an exclusive deal with the Municipality of Weedon, Québec to build a 1.5 million-square-foot cannabis production facility consisting of fifteen 100,000-square-foot greenhouses. Once the entire project is completed and licensed, it would be one of the largest growing operations in the world, with the potential to produce over 150,000 kilograms of cannabis per year or $750,000,000 annually.
This is a first-of-its-kind partnership where a municipality has partnered with a cannabis company to build a major production facility. The agreement is unique as Weedon will purchase the 329 acres of land for MYM to build the project on.
The Weedon agreement was signed by a subsidiary of MYM, CannaCanada Inc., a Montréal-based cannabis company of which MYM has purchased 75%. By the completion of the project, MYM will own 90% of CannaCanada Inc. CannaCanada's strong ties with Weedon city officials allowed MYM to also obtain full exclusivity regarding the future development of any cannabis or hemp-growing facilities within the municipality.
The municipality of Weedon, which is approximately two hours east of Montréal, is actively involved in the project. Weedon has already identified the land on which the facility will be built and has signed an option to purchase it. The subject to certain requirements, Weedon will exercise that option and then donate the land to the project.
MYM anticipates that the project will advance quickly as Weedon's planning department has already approved the preliminary construction designs for the initial portion of the facility. The detailed plans for the first 100,000-sq-ft greenhouse and a 20,000-sq-ft warehouse are now being drawn up by the MYM's architects, Latimer Hu. MYM has engaged Factotum Consultants, who have successfully obtained two Licensed Producer licenses for other clients to manage the ACMPR application process and expects to submit its application to Health Canada this Friday.
"This is an important and significant deal for MYM and its shareholders," said Rob Gietl, MYM's CEO. "The sheer scope and exclusivity of this project will bring MYM global attention and propel the company into its next stage of growth. We have all of the architects, engineers, and consultants in place, and with the full support of the municipality of Weedon, we are moving ahead at an accelerated pace."
MYM has committed to manage and fund the project and will pay $75,000 and issue 250,000 common shares to CannaCanada or its principles, with a further 250,000 shares six months later. When the project's ACMPR application reaches pre-license inspection stage, MYM will issue CannaCanada or its principles an additional 500,000 shares. When the application is approved by Health Canada and a license is granted, MYM will issue a further 1,000,000 shares, and another 1,000,000 shares one year later. In exchange for these milestones, MYM's ownership of the project will grow from 75% initially, to 85% when the license is granted, then to 90% one year later. MYM will also pay a 10% finder's fee, in common shares, to the person who brought the deal to management's attention.
Yann Lafleur, the President of CannaCanada Inc. commented, "CannaCanada's bond with the municipality of Weedon, Quebec will create sustainability that will reflect on the entire industry of cannabis leading to incredible future projects involving many other aspects of the industry. MYM Nutraceuticals will supply us with the necessary resources and tools in order to establish this deed and transmit this heritage. Creating an alliance with MYM Nutraceuticals enables our enterprise to expand into the U.S. and European territories in order to spread this wealth of information and experience for generations to come. MYM Nutraceuticals and their entire team will be a divine asset to establishing a patrimony of cannabis in this country. Our joined network of leading cannabis experts will pave the way to the continuity of results, remaining leaders in this new industry."
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