During the last year, many states in the USA and Canada have legalized cannabis cultivation, be it for medical use, recreational use, or both. In October 2018, Canada became the first major world economy to legalize recreational marijuana followed by the US in certain states.
Recent cannabis law reforms that have expanded from medical use to now include recreational use. Canadian growers would need to expand their grow areas by 14 to 15 million square feet to meet projected cannabis demand in coming years and the exponential growth all over the world as new product offerings and delivery methods emerge.
In the beginning, many cannabis grow facility managers believed growing spaces required only sensible cooling and that humidity wouldn’t prove problematic once the lights were turned off during the flowering cycle. It was learned later that controlling absolute humidity in the grow rooms was critical not only for quality but both also for productivity.
According to the available statistics, it will be imperative to design integrated humidity and temperature control systems for new as well as retrofit application in existing HVAC facilities for cannabis cultivation in 2020 and beyond, to meet the escalating demand.
Conventional air conditioning is a suitable solution for handling sensible heat loads when the lights are on. However, during the lights off period, these off the shelf conventional air conditioning units can not handle the heavy latent loads. High humidity in the cannabis grow rooms may stunt healthy growth of crops and even damage the entire crop due to mold growth. Many facilities were forced to supplement the conventional HVAC units with portable dehumidifiers, which raised the capital and operating costs further.
Exponential growth of the cannabis industry demands dedicated temperature and humidity control equipment to provide the desired precision and reliability. Availability of such integrated units will enable consulting engineers to specify smaller modular units, versus one large system.
Multiple units can cater to different size facilities and provide desired set points for temperature and humidity, as required for the process.
Cannabis grow room have a significantly high latent load, often not present in any other commercial HVAC application. This latent load comes from the large amounts of water that is used to irrigate the plants on a daily basis. Biological mechanism known as transpiration from the plant leaves releases the moisture which is removed by the dedicated HVAC system. In addition to the above biological process, hydroponic grow rooms have exposed water that must be considered while calculating the total latent load.
To understand the dynamics of latent load we need to know about the plant behavior during its life cycle. The grow house indoor environment conditions must change based on plant behavior and lighting conditions. Successful HVAC designs for the grow space must be able to quickly react to changing needs as well as being able to handle the worst case scenario in regards to the sensible and latent loads.
Some cannabis growers have also experimented with indoor swimming pool dehumidifiers because these are designed to handle large latent loads. These systems recirculate humid air through 6-8 row deep DX cooling coils to remove moisture and then reuse the condenser heat to reheat the cold air to the desired temperature. In a grow facility design, the heat recovery can be used when the lights are off to efficiently reheat the drying coil’s cold discharge air without employing costly gas-fired or electric heat.
In the absence of any guidelines from ASHRAE, consulting engineers have no other option but to specify packaged air conditioner and unitary dehumidifiers, commonly available in the market. Some process control companies have started offering digital control equipment bundled with lighting, irrigation and CO2 control.
In a post-covid-19 economy, growers and production houses and utilities will place an added emphasis on energy efficiency and sustainability. To address these issues Toro Watt Corp., has developed a sustainable, energy efficient HVAC solution for the industry called Dual Path CanPAC.
CanPAC – Based on Climate Appropriate technology to save energy
"None of the existing air conditioning systems used in the Cannabis Grow Rooms are able to take advantage of the very favorable Low ambient temperature and humidity in North America, to optimize the energy use in Indoor farming," Tiger Aster, with Toro Watt, points out.
"CanPAC units are dedicated humidity and temperature control units for Controlled Environment Agriculture (CEA) applications. These modular units are available in 2000, 4000, 6000 and 8000 CFM in single package. They can be located inside or outside the building to distribute air into the space through ducts."
"As many new cannabis production facilities are being built, engineers may find the CanPAC systems to be the most suitable option for specification, especially in new construction."
"CanPAC systems integrate free-cooling, cooling, free-dehumidification, dehumidification and heat recovery system in a single package to reduce the installed refrigeration capacity, reduce refrigerant charge, eliminate leakage possibility by pretesting the unit at the factory before dispatch to the client site. CanPAC runs in a 100% recirculating mode with the ability to bring in fresh air during to maintain required Oxygen levels during human presence."
"These dedicated packaged HVAC units for cannabis grow rooms have IOT controls, fan array, ambient heat sink heat exchangers to reduce the refrigeration capacity and thus smaller refrigeration compressors to ensure built-in redundancy."
"Modular design of CanPAC systems ensure the grow room conditions remain unaffected even if part of the array needs maintenance."
The schematics below show the operating principles of CanPAC unit in various mode to offer enhanced energy saving using the US Patent Pending process.
"CanPAC units save up to 70% energy during lights on period, by using ambient air as the heat sink to control the indoor temperature without using expensive refrigeration process during the favorable ambient conditions," Tiger further explains. "During deep dehumidification also the return air is pre-cooled by the ambient air using dry or wet heat exchange depending upon the season."
Part of the condenser heat is used for reheat during the dehumidification mode and the balance is rejected to the ambient to outdoor either in dry or adiabatic condensing mode, depending upon the season. No electrical or hot water heat is required.
The psychrometric charts shows the favorable ambient conditions and the processes used to control the indoor conditions.
"In connection to the psychrometric chart above, The TORO CanPAC is able to gain considerable advantage and offer significant energy savings and reducing the carbon foot print based on direct and indirect emissions over traditional air conditioning and combined pool dehumidifiers."
The DP CanPAC demonstrate superior energy performance by using the outdoor environment as a heat sink to cool the Indoor space without using paid energy. This patent pending process is a first of its kind solution for the Cannabis Industry to become more sustainable.
CanPAC units leverage free outdoor cooling all through the year.
Industries functioning 24/7 and 365 days of the year, require dedicated and custom designed HVAC systems, Keeping in view, the significant operating cost penalty, the design focus is always on reducing energy use, improving reliability and providing reasonable redundancy.
A similar approach has been used in colder climates for precision temperature and humidity control in Data Centers of Facebook, Google and Microsoft to reduce operating costs.
"CanPAC units are fitted with integral IOT based precision controls to monitor and control the indoor environment from a remote dashboard or smartphone app. Historical data storage , fault alarms and remote factory technician access, all controlled by state of the art security."
For more information:
Toro Watt
+1 416 551 7744
sales@torowatt.com
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