INDOOR VERTICAL FARMING REQUIRES LOW HEAT & POWER EFFICIENCY

Strategies for Sustainable and Cost-Effective Crop Production

Abstract

Cultivating indoors requires an enormous amount of energy. Lighting and HVAC systems make up a majority of the monthly and annual energy consumption, around 38% and 51% respectively. More efficient methods for growing have been discovered through recent technological advancements. Replacing high pressure sodium or metal halide lighting fixtures with light emitting diodes (LEDs) has shown to be more efficient in terms of energy consumption and thermal output. In addition to growing with LEDs, switching from standard alternating current LED drivers to direct current powered LEDs has shown ideal results. Using VDC LED drivers may be the largest shift in vertical farming that growers have ever seen. VDC is nearly 30% more efficient when compared to VAC. It can also remove 40% of the heat from a grow room. Direct current power drivers can extend up to 350 feet away from the light source, while alternating current can only extend about 15 feet away. The need for HVAC systems will decrease as growers integrate VDC LEDs as their primary light and power sources. In addition to lighting and ventilation, transitioning to mobile, vertical racks has been proven to maximize canopy per square foot. Growing vertical has the ability to produce up to 50% more canopy within the same square footage (depending on how many levels are used). By switching to more energy and space efficient options, growers will save substantially on operating costs. The future of growing indoors is growing green.

Keywords

Vertical horticulture, vertical farming, direct current, alternating current, LEDs, HVAC, high pressure sodium, metal halide, photosynthetic active radiation, photosynthetic photonic flux density, quantum response, hydroponics, aeroponics, UL8800, DLC, remote 250v power.


Introduction

Indoor cultivation facilities are becoming the common practice as the industry evolves. With this, comes massive energy consumption and environmental implications. Compared to outdoor or greenhouse cultivation, indoor cannabis production requires an enormous amount of energy. This is mainly due to HVAC and lighting, around 51% and 38%, respectively.

Cannabis was responsible for 1% of the nation’s energy usage in 2011, which amounts to nearly $6 billion annually. In Denver alone, cannabis production has been responsible for up to 4% of Colorado’s total energy usage (2018). From 2012 to 2016, energy production from cannabis has grown an average of 35% annually (2018). The carbon footprint of a typical indoor cannabis facility is anywhere from eight to ten times more than a similar sized office space (Gellerman 2018). It is in grower’s best interest to incorporate energy and space efficient practices in order to drive down operating costs and maintain a baseline level of sustainability.

Indoor vertical farming growing method use vertical racks, and highly engineered LEDs to significantly cut down energy usage and total operating costs.  This technique allows growers to maximize square footage of canopy and even overall biomass yield per grow cycle. This concept can be expanded even further when integrating mobile, vertical tiered racking systems.

Growing with LEDs has a myriad of benefits. One advantage that LEDs have over traditional HPS or metal halide lighting, is that plants can be grown closer to the light source since they radiate less heat. In addition, LEDs have the ability to design customizable spectrums, tailored to specific phases of the grow cycle. LEDs are evolving quickly. However, it’s important to understand that they are not all created equally.

Centralized Remote 250v Power and POE Data

The way in which LEDs are powered makes a significant difference in heat production and energy consumption. Most LED drivers use alternating current (AC) power. Instead, using LEDs with direct current (DC) power drivers is far more energy efficient. DC drivers can be placed up to 300 feet away from the light source, removing excess heat from the grow room. This can be compared to alternating current drivers, which can extend only about 15 feet away from the light. DC power highly reduces and potentially removes the need for HVAC systems. In addition, DC drivers have the ability to be powered fully by solar energy. A conversion of this magnitude will drive down energy consumption and production costs, despite the initial investment.


Peak Roots has designed one of the most energy efficient systems in the world of indoor farming today: growing vertically in mobile racks with direct current centralized powered LEDs controlled by POE. This new method of scaling commercial cultivations is paving the way for a more sustainable future in indoor vertical farming.


Figure 1: A breakdown of energy usage in a standard indoor grow facility (Kolwey 2017). HVAC and lighting contribute to the majority of a grow facility’s energy consumption. Energy consumption from lighting and HVAC can be significantly reduced when converting from VAC to VDC remote centralized powered LED lights.


Lighting

High value crops such as growing cannabis requires high quality light sources and tailored spectrums for various phases in the grow cycle. Traditionally, growers have used high pressure sodium (HPS), metal halide (MH) and fluorescent lights to cultivate cannabis. HPS lights have an emphasis on blue and high red light, which are necessary in the vegetative and flowering phases. HPS, metal halide and fluorescent lights contain full spectrums. However, they have large gaps in many necessary wavelengths that contribute to photosynthesis. Lighting fixtures should closely mimic the sun’s spectrum, which has little to no drop off in energy. Within the visible light spectrum is the quantum response area (400 – 700 nm), which provides active photonic energy. This is also known as PAR light, photosynthetic active radiation. Traditional lighting sources and many LEDs lack necessary PAR wavelengths, while Peak Roots’s LEDs do not.

Through recent technological advancements, the use of light emitting diodes (LEDs) has become increasingly popular. LEDs have the ability to create a customized, full spectrum with little to no drop off in PAR light. Peak Roots LEDs closely mimic the sun’s spectrum. This design delivers precise photonic energy to plants, which drives photosynthesis. In addition, LEDs require much less energy to operate, have a longer lifespan and produce much less heat when compared to their HPS or other traditional lighting counterpart.

Many growers are pleased when making the transition from traditional lights to LEDs, despite their high price tag. When converting to the most efficient LEDs, growers are able to cut their energy consumption down by an average of 50%. This is usually made possible by replacing a 600 watt HPS light for a 300 watt LED light during vegetation. For flower, a 500 or 600 watt light can easily take the place of a 1,000 watt HPS light (Kolwey 2017).


Not only do LEDs reduce energy consumption, but they have a very low thermal output. LEDs have the ability to use a remote power and driver system, automatically redirecting heat away from the plants. With a smaller thermal output, plants are also able to be grown closer to lights. This allows growers to integrate sophisticated vertical racking systems to maximize canopy per square foot (Kolwey 2017). Traditional lighting options lack this capability due to their excess heat production. HPS, metal halide and fluorescent lights require a much larger space between the top of the canopy and the light, so plants don’t get burned or destroyed (Kolwey 2017). Using LEDs in vertical racking systems allows growers to maximize square footage, improve overall cannabis yield and even increase THC percentage in some circumstances (Kolwey 2017). When utilized correctly, LEDs have also shown to expedite the growing process by up to two weeks (2018). Operating costs will also be significantly reduced, considering that using LEDs can cut energy consumption in half. LEDs quickly pay themselves off with monthly and annual energy savings. LEDs have been continually identified as the primary energy efficient opportunity for indoor grow operations moving forward (Remillard & Collins 2017).

Amps

The number of electrons flowing through a specific point per second

Volts x Amps = Watts

Watts

How much energy is consumed per unit of time

Ex. Watts and kilowatts per hour

Volts

Measures how strongly electricity is pushed through a circuit (electrical pressure)

Provided by a + and - charge through a circuit


Direct Current vs. Alternating Current

Alternating current (AC) refers to a back and forth flow of electrons. Direct current (DC) refers to a constant flow of electrons in one direction. DC does not have any drop off in energy, while AC has constant ebbs and flows. Most current LED drivers use VAC (volts alternating current) or a combination of VAC and VDC. Both of these options are much less efficient than using only VDC (volts direct current) power, alone.

One major benefit of choosing VDC power over VAC is heat removal from the grow room. VDC drivers can be placed up to 250 – 350 feet away from the light source, without degradation in the PAR map. Contrarily, AC drivers can only extend about 12 – 15 feet away, which generates enormous amounts of heat. When comparing AC to DC power, the most important thing to consider is how far away the drivers are able to be placed. Using VDC drivers removes roughly 40% of the heat from a grow room, reducing the need for HVAC systems. More lights can be added to the room if less heat is being produced. Using this system also allows for advanced vertical growing. This is because the racks above and below the plants are not getting overheated. Overall, 250V DC rectifiers have shown to be, on average, 30% more efficient than 48V AC LED drivers. Though many factors contribute to efficiency of a grow, direct current power is arguably the biggest technological shift in vertical farming.


Figure 6: Alternating current vs. Direct current. AC power is a back and forth flow in electrons, where power is lost during low points in the wavelength. DC power is a constant flow of electrons, with no drop off in energy. Direct current powered drivers can extend up to 250 – 350 feet away from the light source. Alternating current drivers can only extend about 12 – 15 feet away. Using DC drivers removes a majority of the heat from the room since they have the ability to be located in a different room.

Heating, Ventilation and Air Conditioning

HVAC stands for heating, ventilation and air conditioning. For standard office buildings and cannabis operations, HVAC typically contributes to around half of the total energy usage. HVAC is the largest energy consumer in both residential and non-residential settings. In total, HVAC contributes to nearly 20% of the United State’s annual energy consumption (Perez-Lombard, Ortiz, & Pout 2007).

When using traditional growing methods, HVAC plays an important role in the production of cannabis. These systems reduce outdoor air contamination, help maintain ideal humidity and CO2 levels (Perez-Lombard, Ortiz, & Pout 2007). Controlling for humidity is necessary for ensuring crops don’t grow mold or mildew (Remillard & Collins 2017). It is important to note that temperature and humidity regulation for an indoor grow will vary based on geographic location. For example, Washington state tends to be more humid than Central Oregon. Temperature, humidity and CO2 levels will differ for both of these locations and need to be tightly controlled (Mulqueen, Lee, & Zafar 2017).

Humidity determines how much water plants will consume. Relative humidity is a measure of moisture in the air, compared to what the air can sustain at a given temperature (2005). Most vegetation rooms run roughly 70% relative humidity and flower rooms run around 50% (Kolwey 2017). Typically, growers install one or many rooftop HVAC units, in addition to portable dehumidifiers inside the flower rooms (Kolwey 2017). Designing the room around Vapor Pressure Deficit (VDP) rather than relative humidity can save money and energy consumption long term. VDP is the difference between the leave’s internal vapor pressure and that of the air surrounding the leaves. Ultimately, VDP will determine the rate of transpiration. It will increase with higher room temperatures and lower relative humidity. If VDP is too low, leaves can accumulate condensation. If VDP is too high, plants are easily heat stressed and can dry out (Kolwey 2017).

Growers can save energy and money by choosing a “premium efficiency” dehumidifier. There are a few systems that are recommended for energy savings: plate air to air heat exchange, hybrid desiccant/evaporative systems and chilled water systems. Plate air to air heat exchange dehumidifiers can save up to 30-65% of energy consumed by normal, commercial dehumidifiers. Hybrid desiccant and evaporative systems can save 30-50% of energy. Chilled water systems are effective for grow operations that have larger than a 4,000-6,000 square foot canopy (Kolwey 2017). There are many energy efficient alternatives for HVAC units. However, the need for HVAC is significantly reduced when growing with VDC LEDs. This is due to the reduced thermal output and locating power drivers far outside of the room. Cultivators have also completely removed the use of HVAC systems when growing with a VDC Smart Grow LED system.

Height & Space

One of the best ways to utilize indoor spaces is by installing vertical racking systems. Vertical farming has shown, time and time again, to be a viable solution for increasing crop yield within a given area. Currently, vertical racks are primarily being used for plants in vegetation. At this stage, plants are smaller and require a lower light intensity. This makes using vertical racks a practical option (2018). However, with the right technology, vertical racking systems can be used for both propagation and flower. Vertical systems have been compared with traditional, single level methods and vertical farming has continually produced more crop per unit area.

Indoor vertical farming becomes the most effective when maximizing the grow space between tiers/levels, using specialized VDC powered LEDs. Indoor vertical farming naturally has shorter grow cycles since plants are smaller in size (Typical grow cycle: two weeks clone, two weeks veg, eight-nine weeks flower). This can increase the number of harvests and annual yield. When using VDC LEDs in rack systems, plants can be grown very close to the light. Growing plants closer to the light source maximizes space and increases PPFD, photosynthetic photonic flux density (Kolwey 2017). PPFD is the number of photosynthetic active photons (400 – 700 nm) that fall within a square meter in a given second. It’s important to dose cannabis plants with the proper amount of micromoles during each phase of the grow cycle in order to optimize rate of photosynthesis and plant development.

Indoor vertical farming can be taken to the next level by incorporating a mobile system. Mobile racks can increase cubic space by up to three to four times (depending on how many racks and levels are used). Mobile racks have the ability to be pushed together, creating one giant PAR map. This will ensure an even distribution of light over the grid space, leading to maximum and consistent yields (2018).

Water

Indoor cannabis cultivation is the most water efficient when compared to growing outdoors and in greenhouses. These environments allow for water loss via evaporation. Humidity and total water levels are tightly controlled indoors in a closed system (Mulqueen, Lee, & Zafar 2017). Cannabis plants have a threshold at which they can absorb water. This can lead to serious over watering problems, which is wasteful and detrimental to plant health. Though there are many methods for watering, it has been suggested to hydrate plants in smaller quantities more frequently, versus dumping gallons into the soil every now and again. Automated drip systems are also ideal solutions for precise watering dosages (Fred 2014).

One of the most effective ways to save water is by growing sea of green with a zero drain to waste system. Smaller sized plants require a shallower soil depth and less water. Sea of green plants are typically grown to be about 18 inches tall versus traditional plants, which are nearly 6 feet tall. The smaller the plant, the less water it requires to stimulate growth. On average, sea of green soil beds are 7 inches deep. Compare this to a traditional growing pot with soil double the depth. Sea of green soil beds will need a smaller quantity of water to reach the root system (Dreier 2014). Growing sea of green has shown to reduce water consumption by up to 60%.

Grow Mediums & Environmental Impact

It is key to find growing mediums that reduce nutrient runoff and water waste. Crops require controlled environments to thrive. Quality, purity, consistency, bioactivity and biomass production can be measured to determine how controlled the environment is. Keeping track of these factors also reduces the risk for pathogens and pests (Hayden 2006).

 There are other methods of growing instead of a traditional soil medium. Hydroponic growing has a system that delivers nutrients in a liquid form, excluding aggregate mediums that would normally anchor the plant. Hydroponics are fairly efficient in terms of water and fertilizer usage (Hayden 2006). They can also be more environmentally friendly, considering they reduce waste from soil run off (2018). Typically, hydroponic systems use mediums such as perlite, rockwool or peat moss. Plants don’t have to work quite as hard in a hydroponic system to obtain nutrients. Therefore, plants will grow easier and develop quickly.

Aeroponic grown crops are suspended in a spray chamber. These systems recirculate nutrient solutions underneath plants and are fairly simple to use. Using aeroponic a-frame structures can allow for up to 1.7 times the amount of growing area that the square footage in the greenhouse would normally allow (372 sq ft of crops in a 216 sq ft space) (Hayden 2006). Both hydroponic and aeroponic systems are becoming more popular grow mediums for cannabis cultivation.

Flood tables are another common grow method. Rockwool cubes are typically used as the medium to anchor the plant’s root system. A flood table has a tray that gets flooded with a water and nutrient solution on a consistent schedule. The rockwool cubes absorb this solution, delivering it to the plant’s roots. Flood tables are said to help speed the rate of growth in plants and overall size as watering intervals increase. Though flood tables are fairly efficient, large amounts of water can potentially be wasted by using this type of system (2018).

Automated fertigation with emitters to coco fiber is a Peak Roots favorite method for growing at scale in the vertical racks.  Typical plant count is one plant for every square foot of canopy area.

Grow Cycles: Perpetual vs. Reset

When designing a flower room, one of the first steps is to decide if you want to grow perpetual or on a reset schedule. Perpetual growing allows for more yields and number of harvests per year. Growing in vertical racks with the SGS DLI dimming controls enables growers have plants in various stages of the grow cycle in different racks. For example, in an flower room with eight racks, one rack could be dedicated to plants in each week of flower (one rack has week 1, the second rack has week 2 plants, and so on). A major downfall of perpetual growing is that it requires intensive labor due to frequent transplanting and harvesting. For this reason, growing on a reset schedule is more common. A reset grow is when all veg plants are transplanted to flower at once and then harvested at the same time.

The Peak Roots 24” vertical canopy line recipe consists of two weeks clone, two weeks veg and eight-nine weeks flower. Growing throughout the entire year gives growers 4 to 4.5 annual harvests. A perpetual grow done correctly could result in a minimum of one additional harvest per year. And of course, more harvests results in more income.

Cost Analysis

High pressure sodium and metal halide lights have a fairly cheap initial cost when compared to LEDs. As stated earlier, HPS and MH consume an enormous amount of energy and produce excessive amounts of heat. LEDs have an higher initial cost but quickly pay themselves off with monthly and annual savings. Standard LEDs are rated for 50,000 hours, which typically last up to 10 years on a 12:12 flower schedule (2018). In most cases, HPS bulbs need to be replaced once or multiple times a year (2018). Considering up to 50% of total costs in a grow operation come from energy, it is worth investing in more expensive alternatives that will pay themselves off quicker (Kolwey 2017).

For example, Yerba Buena in Hillsboro, Oregon converted their veg room to 1,270 tubular LEDs from standard HPS lights. They run nearly 6,570 hours a year. The conversion from HPS to LEDs cost just under $30,000. However, it will be paid back within just 9 months due to energy savings and reduced operating costs. Yerba Buena is saving 258,600 kWh/year just by switching to LEDs and reducing their annual operating costs by $22,000.

Calculating LED Grow Light Energy Savings:

kWh Savings = lighting kWh savings + HVAC interactive

Lighting kWh savings = (HID wattage – LED wattage) x Annual Operating Hours

HVAC interactive = lighting kWh savings x 3,412 BTUs/kWh + 12,000 (tons/BTU) x HVAC kW/ton 

(BTUs = British Thermal Units. The amount of thermal energy required to change the temperature of one pound of water by one degree in one hour (2018)).

Conclusion

Indoor cannabis facilities will be built as the industry continues to grow. It’s important for growers to migrate away from traditional growing methods in order maintain a baseline level of sustainability. Old grow methods use an enormous amount of energy, space, water and other resources. Growing cannabis can be more eco-friendly by using VDC powered LEDs, mobile vertical racks and zero drain to waste systems. LEDs powered by 250V DC remote power can significantly cut down energy consumption. Using VDC LEDs produces nearly 40% less heat. Ultimately, this transition reduces the need for HVAC systems, which contribute to half of a standard grow’s energy consumption. LEDs have a very small thermal output compared to traditional HPS or MH lighting systems. In addition, 250V DC LEDs are twice as efficient as 48V AC LEDs and up to four times as efficient as traditional HPS lights.

To maximize space within a grow area, using mobile and vertical rack systems has shown to be the most effective method. Mobile racks can be moved together, creating one giant PAR map over the canopy area. They also allow for up to three to four times more canopy within the same square footage. Vertical farming in combination with sea of green has shown to produce the highest yields. There are many metrics that can be measured to determine how sustainable a grow facility is. Peak Roots recommends keeping track of kWh/pound, grams/watt and grams/square foot. Running these numbers helps growers understand their costs, yields and income more precisely. In order for the cannabis industry to sustain itself, growers must transition towards more energy efficient alternatives. Ultimately, the goal is to maximize canopy while saving energy and money with the Peak Roots integrated remote centralized power and data solutions.

References

Cannabis Environmental Best Management Practices. Denver Public Health and Environment, Oct. 2018.

“Cannabis Humidity Management.” Conviron, Conviron Environments Limited, July 2005, www.conviron.com/cannabistechtalk.

Everything about Flood and Drain Systems for Growing Cannabis. Cannabis.info, 16 Oct. 2018, www.cannabis.info/en/blog/flood-drain-systems-growing.

Fred, Dreier. “Cultivation & Conservation: Easy Ways for Marijuana Grows to Cut Water Usage.” Marijuana Business Daily, 2 June 2014.

https://mjbizdaily.com/easy-ways-to-cut-water-usage/

Gellerman, Bruce. How Green Is Your Weed? Mass. Limits Energy Usage for Marijuana Growers. Wbur, 29 June 2018, www.wbur.org/bostonomix/2018/06/29/marijuana-energy-usage.

Hayden, Anita. “Aeroponic and Hydroponic Systems for Medicinal Herb, Rhizome, and Root Crops.” Native American Botanics Corporation, vol. 41, no. 3, Jan. 2006, pp. 536–538.

“Hydroponic Systems 101.” Full Bloom Hydroponics , 2018, www.fullbloomhydroponics.net/hydroponic-systems-101/.

“Is the Cannabis Boom Jeopardizing Our Electrical Grid?” Deschutesgrowery.com, Deschutes Growery, 16 Oct. 2018.

Kolwey, Neil. A Budding Opportunity: Energy Efficiency Best Practices for Cannabis Grow Operations. Southwest Energy Efficiency Project, Dec. 2017.

“Managing a Run to Waste (RTW) Hydroponic Crop from a Nutritional Perspective.” Science in Hydroponics, 5 Apr. 2017, scienceinhydroponics.com/2017/04/managing-a-run-to-waste-rtw-hydroponic-crop-from-a-nutritional-perspective.html.

Mulqueen, April, et al. Energy Impacts of Cannabis Cultivation. California Public Utilities Commission Policy and Planning Division, 20 Apr. 2017.

Perez-Lombard, Luis, et al. “A Review on Buildings Energy Consumption Information.” Science Direct, vol. 50, 9 Mar. 2007, pp. 394–398.

Remillard, Jesse, and Nick Collins. Trends and Observations of Energy Use in the Cannabis Industry. ACEEE Summer Study on Energy Efficiency in Industry, 2017.

GROW MORE, EARN MORE FASTER WITH VERTICAL FARMING
Increase a faster investment pay period for with better cap x strategies