Whether cannabis growers choose to convert their High Pressure Sodium (HPS) lighting systems to light-emitting diode (LED) technology, to a different type of lighting, or choose to build a new facility with LEDs, the The growing environment must be adjusted to accommodate the light source.
The temperature, humidity and nutrition of plants are among the environmental parameters that must be evaluated and potentially taken into account. Many lighting manufacturers, such as Fluence by OSRAM, work with growers to help them manage their grow rooms to adapt to LEDs.
Retrofit with LEDs
Abhay Thosar, director of horticultural services at Fluence, says he often sees growers struggling with changes in temperature and humidity when converting from HPS lighting to LED lighting. HPS lights give off more heat than LEDs, he says, and growers who switch to LEDs could see a temperature drop of up to 8 degrees Fahrenheit, which in turn affects humidity.
“The humidity needs to be adjusted because, remember, when you use the HPS, there is so much radiant heat,” says Thosar. “Most of the time you don’t have high humidity in the room, and the reason is the heat of the HPS. . . Usually dried up that humidity, and you could have 50% or 55% humidity, and that was easy. But, now, moving to LEDs, it’s a spectrum that optimizes photosynthetic activity. . . and the plant will have higher transpiration as well. . . this will increase the humidity in the room.
Thosar says growers need to increase their dehumidification and airflow to avoid bacterial and fungal diseases that can affect plants exposed to higher than ideal humidity levels. “You have to have much better air circulation in the room – around the crop – in order to maintain that rate of perspiration and also to have better airflow to avoid places where there is a little bit of moisture. humidity, again, to avoid some of the fungal or bacterial diseases that might occur in the plant.
Temperature and humidity are also closely related to vapor pressure deficit (VPD) – the difference between the amount of moisture in the air and the amount of moisture the air can hold when saturated. Thosar says many growers use VPD to optimize plant growth.
“Most growers like to run the crop with VPD,” he says. “They’re trying to be in a great location, and that’s why it’s important to maintain the temperature and humidity.”
Higher photosynthetic activity also means that plants will have increased metabolic activity, he adds, which will lead to increased water and nutrients.
Growing media may also need to be evaluated and adjusted, Thosar says, as plants make more active use of irrigation and fertilizers. For example, if a farmer is using rock wool, the size of the rock wool block may need to be increased.
Thosar and the rest of the Fluence Horticultural Services team are working with growers to help them fine-tune their environmental parameters after installing LED lighting to optimize their crops for their unique cultivars, growing media, etc. their light intensity, their infrastructure, etc.
“We work closely with growers throughout the first two or three flowering cycles, so that they can understand how to optimize their use of LEDs and achieve optimum crop production,” says Thosar.
Fluence is also conducting trials with growers using side-by-side comparisons of HPS and LED lighting to help them decide if LEDs are right for them and what environmental parameters will need to be adjusted when switching on a large scale.
Overall, Thosar says the biggest mistake he sees growers making with LEDs is maintaining the same environmental settings they used with their HPS fixtures.
“They’re used to growing under HPS, and that’s exactly where these mistakes come in, just because sometimes they still manage the crop as if it’s grown under HPS,” he says. “These are the pitfalls they must avoid. . . Now they have changed the light source, [and] they have to change their way of thinking and make sure they recognize the fact that it is not grown under HPS. If they keep that in mind, I think they can avoid most of the pitfalls.
On the other hand, one of the biggest opportunities for growers when using LEDs is to have better control over their environment as a whole.
“It gives us a lot more control over how we want to increase the light and not worry about the heat part,” he says. “You can compose the crop however you want. “
The HPS luminaire emits much more radiant heat than the LED luminaire. This would be 50 to 55% radiant heat, against 15 to 20% radiant heat from LEDs. So when we separate the heat and light component of the lights, we can orient the environmental or climatic conditions to optimize crop productivity. During certain stages of the cultivation, if we can manipulate the environmental conditions while still wanting to provide high light intensity, it would be possible to work with LEDs and not with HPS.
Designed with LEDs in mind
Growers who choose to install LED lights early on when building their grow facilities must also adjust their environmental settings to accommodate the lighting.
Michael Ward, CEO and founder of the Michigan-based company Harbor farm, built its 11,000 square foot vertical growth with LED lighting because it says “the benefits outweigh the costs” when you consider the energy efficiency and discounts available from many power providers .
Ward and his team worked with mechanical, electrical, and plumbing (MEP) experts, who were able to perform load calculations based on Harbor Farmz’s decision to use LEDs.
“All of these calculations should be done before you even buy the HVAC system,” he says. “If you’re late to the party and you’ve already installed your HVAC, your equipment will be less loaded if you opt for LEDs over HPS. “
Ward decided to build his facility around LED lighting due to the low power consumption of the fixtures, as well as the improved yields and terpene profiles in the crop. Harbor Farmz typically produces between 2.5% and 4.5% terpenes on all the flowers it grows under its LEDs, says Ward. Additionally, the company typically produces between 50 grams and 65 grams per square foot at their facility, with yields increasing with each harvest.
After selecting LED lighting, the Harbor Farmz team set up their air conditioning and dehumidification system based on the number of plants and the transpiration rate.
“We are different from others when it comes to farming because of the fact that we are vertical farmers,” says Ward. “We grow 22 feet in the air, we have three levels, [and] we are not just one big room. We’re small and narrow rooms, and I can grow up to 324 plants per room on three levels, so 108 plants per level on three shelves. . . The actual room setup will decide which HVAC system you are going to use.
With the Harbor Farmz facility up and running, continuous adjustments were made to temperature set points as the crew pushed the lights to maximum intensity.
“When you dial [photosynthetic photon flux density] (PPFD) and the settings in the room and grow the lights and grow the plants, you’re going to drive them in a direction that is going to maximize your yields, maximize your potency, and maximize your terpene levels, ”says Ward.
Harbor Farmz is successful when it comes to implementing LEDs and adjusting the many variables throughout the growing process. Fluence continues to work closely with similar growers who want to push the boundaries of what is possible with plants.