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Case study:

Does ETFE greenhouse glazing outshine supplemental LED lights for higher yields and revenue?

In the ever-expanding industry of commercial cannabis cultivation, growers are constantly searching for innovative ways to maximize their yields and deliver premium-quality products to stay competitive in the market. One crucial factor that significantly influences crop productivity for greenhouse growers is the availability and quality (which is dependent on glazing material) of natural sunlight. Cannabis growers who rely on degrading polycarbonate or acrylic glazing for their greenhouses may find themselves facing a dilemma: should they opt for more supplemental light fixtures or consider replacing their greenhouse roof glazing with a higher light transmissive material – such as ETFE (Ethylene Tetrafluoroethylene) – in order to increase their yield?

The choice between these two approaches is not an easy one, as both options offer distinct advantages and considerations. In this article, Ceres Greenhouse Solutions will explore a case study where they calculated what the yield difference would be between the two options. "Whether you are an experienced cultivator or a newcomer to the industry, this discussion aims to shed light on the potential benefits and challenges associated with incorporating supplemental lighting or transitioning to ETFE glazing."

Prioritizing sunlight
When it comes to cultivating cannabis, nature has provided us with an abundant and powerful resource: sunlight. "While supplemental lighting systems can be advantageous in certain situations, harnessing the power of natural sunlight offers numerous benefits for cannabis cultivation. From the full spectrum of light to cost efficiency, environmental sustainability, and enhanced plant health, leveraging the sun's energy can lead to healthier, more flavorful, and more sustainable cannabis crops. By capitalizing on this abundant resource, growers can tap into nature's own recipe for successful cannabis cultivation."

Benefits of ETFE glazing
So how do you increase sunlight to your plants? By choosing the right glazing materials for your greenhouse roof. "At Ceres, we are currently the only North American distributor of a complete ETFE glazing solution – a super durable and high light transmissive glazing system. By incorporating ETFE glazing into greenhouse construction, growers are not only benefiting from increased light transmission (up to 94% for a single layer), they are also reaping the benefits of energy efficiency, durability, and design flexibility. ETFE's self-cleaning capability, lightweight, and environmental compatibility further enhance its appeal. With its ability to provide optimal growing conditions, ETFE glazing is a promising solution for commercial cannabis growers looking to maximize crop yields and create sustainable cultivation environments."

Supplemental lighting
Supplemental lighting is necessary for greenhouse cannabis cultivation in order for plants to get enough light during shorter or more overcast days. "That being said, the type of lights you choose, your fixture layout, and your overall lighting strategy has a significant impact on your energy usage, lighting costs, and yield," the Ceres team says.

Case study
"Now that we've introduced two solutions for increasing light exposure to greenhouse plants, let's take a look at a real-life scenario in which we calculated the yield (and revenue) increases of adding LED lights to a greenhouse environment versus replacing a greenhouse's polycarbonate glazing with ETFE," the Ceres team continues.

The greenhouse considered is 30 ft wide and 98 ft long, with an assumed canopy area of 2,160 ft², and is located in the high desert. This greenhouse uses forced ventilation with outside air, therefore, no CO2 injection is used. Due to budget limitations, artificial lighting is "undersized" for cannabis production. The glazing in this greenhouse is a triple-wall polycarbonate which has a medium light transmission for the crop considered. Using CO2, increasing lighting density, and a better glazing material would significantly increase the yields. The electricity cost paid to the utility company is about 0.06 $/kWh, significantly less than the national average.

"As a disclaimer, there are many other factors that can affect cannabis yield, such as environmental conditions, nutrient delivery, plant genetics, and growing practices (to name a few). Because we are focusing on light measurement, the numbers below represent a conservative estimate of increased crop yield," they add.

Table 1: Current state of greenhouse

This first table shows the monthly light measurements and yield outcome (in pounds) of the cannabis greenhouse with its current setup of supplemental LED lights and polycarbonate glazing. For a quick recap, DLI measures the total amount of light delivered to the plants over a full day (in this case, 12 hours), whereas PPFD measures the intensity of photons hitting a specific area per unit of time. PPFD is measured in micromoles per second per m2. In this graph, "inside DLI" means the amount of sunlight the plants are being exposed to on average per day for every month (excluding artificial lighting). "Total mol of lights" represents the amount of light the plants receive with both natural light and supplemental lights. We can see that in the Summer months of June, July, and August, the grower doesn't run his lights at all because the plants are getting plenty of light from the sun.

Table 2: Greenhouse with 60 more LED light fixtures

This second table is the same commercial grow if the grower were to add 60 LED light fixtures. You can see that the numbers in the "total mol of light" column increased, and therefore, so did the yield. The total yield increased by 248 pounds (112 kg), and in this situation, that amount equates to $148,760 more in revenue per year.

Table 3: Greenhouse with ETFE glazing

This last table represents the scenario of replacing the degrading polycarbonate glazing with ETFE (high light-transmissive) glazing. You can see that the "inside DLI" numbers increased significantly, with the Winter months seeing almost 100% increase in sunlight exposure. By switching to ETFE glazing, this grower would increase his yield by 498 pounds (225 kg) and increase his revenue by $298,641. This is more than double the revenue that scenario one estimates. "It's almost a no-brainer to switch out your glazing, right? Well, let's look at the cost of each."

The economics
"We can estimate the LEDs upfront cost to be around $40,000 ($650 per fixture plus some cost for installation, electrical work, shipping, and taxes), while the upfront cost of ETFE would be closer to $70,000 (installation included)," the Ceres team says.

"Although the upfront cost for the lights is cheaper, the electricity necessary for running the lights would increase the energy usage and cost associated with it (although adding 60 more fixtures will increase the lighting intensity, lowering the overall runtime). We can expect the energy consumption to double (roughly) from 45,000 kWh/year to 90,000 kWh/year. On the other hand, Installing ETFE would also increase the cooling loads due to the increase in solar gain. We estimate a 10% increase to the grower's existing electricity bill for running the fans longer (eventually adding another exhaust fan)."

"This doesn't take into account extra costs associated with increased flower production, such as trimming, pruning, and increased nutrient and water usage. In the table below, we've laid out all cost, revenue, payback period, and ROI (return on investment) considerations for the two upgrade options."

Table 4: Capital Expenditures (CapEx), Operational Expenditures (OpEx), Payback time, and Return On Investment (ROI):

"Increasing supplemental lighting intensity and replacing the greenhouse glazing material are both viable options and will be beneficial for the operation, but ETFE will increase the yields more significantly than adding lights. Both have a very short payback time and very high ROI," according to Ceres.

"Additionally, using ETFE doesn't increase operational cost as much as adding lights. While it will increase cooling costs somewhat because of the increased solar gain, the increased power usage will be much less than running more lighting on a consistent basis. In the end, we believe that the client should install both options over time, but the glazing change should be prioritized as its benefits will be greater."

If you're interested in upgrading your greenhouse glazing to ETFE, you can contact the Ceres team. "You don't have to have a Ceres greenhouse to take advantage of this opportunity to significantly increase your yields."

For more information:
Ceres Greenhouse Solutions
[email protected]