CANNABIS CULTIVATION: THE EARLY YEARS

For years, dwelling in the realms of criminality, the cannabis growers supplied a potent product that was more recognised for its ability to create euphoria than its medicinal effect. This plant is cultivated outdoors, in glasshouses and indoors with artificial lighting replacing the gentle rays of the sun.

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MEDICINAL CANNABIS AND HIGH-TECH HORTICULTURE

But now medicinal cannabis has been legalised and afforded a semi-decriminalised status in many countries including Australia, it has led to an influx of companies trying to cash-in on this “cash crop”. 

The “green oil rush”, “gold in them there greenhouses”, “high-tech horticulture” are some of the terms being used to describe the interest in a plant that for many years existed solely in the shadowy confines of the black market.

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THE SOLAR ENERGY CONNECTION

So what is the connection between horticulture, specifically the cultivation of medicinal or pharmaceutical grade cannabis and renewable energy?

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PROPAGATION AND ENERGY

The answer is energy and lots of it! A normal horticultural business growing, say tube stock in 2 inch pots (50 mm), uses energy in the form of heated beds, irrigation cycles, automated environmental HVAC (Heating Ventilation Air Conditioning) etc.

Cuttings are “struck” in a variety of propagating mixes, then pots or trays are subjected to ideal conditions to stimulate root growth. Then, when plants are showing signs of adventitious roots, they are moved to an area that has changed environmental conditions. These effectively artificial climates require energy inputs, usually in the form of electricity, natural and/or LPG (Liquified Petroleum Gas).

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ADDRESSING SITE LOADS

From an electrical point of view daytime loads can be addressed by solar, photovoltaics and nighttime loads addressed by energy storage and the grid. So a standard nursery will benefit greatly from a renewable energy source by itself or in conjunction with storage (see link to Energy Storage Blog).

So what’s different about these cannabis “grows”? In a nutshell these facilities not only have environments more rigorously controlled with optical growth recognition technology and other high-tech approaches  but there is the added electrical load from artificial lighting.

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GROWING MEDICINAL CANNABIS = HUGE ELECTRICITY BILLS

Even in an outdoor greenhouse setting artificial lighting is used to extend the vegetative light cycle during the shorter days of the year. And when it comes to flowering, it is used to increase the available light intensity to speed up maturation, maintain short nodal length and maximize the floral to vegetative biomass ratio. In other words, maximise the medicinal part of the plant, minimise the rest in the shortest space of time.

Production output is measured by grams per metres squared, closely tempered by how long it takes to get a crop to fruition.

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CLIMATE, ENERGY, CONSUMPTION PROFILE

Now, in a totally indoor grow the light is completely artificial. This light is provided by either H.I.D. (High Intensity Discharge) lighting in the form of Metal halide, High Pressure Sodium or a combination of both and/or colour corrected L.E.D. (Light Emitting Diode) lighting.

The pros and cons of these lighting systems can be discussed by others more knowledgeable but the important point is that lots of light for many hours for lots of plants = lots of electricity that can be provided by renewable energy, namely photovoltaics, solar.

For example, consider an indoor grow with full automation and environmental control. There are four designated areas all requiring lighting. In no particular order, the clone room for a minimum of 18 hours/day; the “mother room” for say 16 - 18 hours/day; the vegetative room, again 18 hours/day; and finally the flowering room for potentially 12 hours/day. 

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LED HID MORE ELECTRICITY

The system is continuous in that the flowering room is always producing. Without going into too much detail let’s say the: 

• Vegetative room is 50 metres x 10, so 500 m2. 
• Lighting is 600 watts per m2 (those that know can argue about the merits of higher light intensities, H.I.D. versus L.E.D.) 
• So a total of 500 x 600 watts = 300,000 watts or 300 kW.

Now the cycle is: 

• 18 hours/ day x 300 kW = 5400 kWh/day. 
• Will assume we get a levelised cost of electricity at $0.15/kWh.
• Per day we are using $810, per year this equates to $295,650/year

And we haven’t even accounted for the clone, mother, flowering room and HVAC or irrigation energy usage, let alone the historical rise in electricity costs!

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CONCLUSION

High-tech horticulture’s reliance on energy is all part of an energy management system where renewable inputs not only make financial sense but environmental sense. A prudent approach to the costs and benefits of any site energy usage is vital for the successful profitability of any business. And with commercial solar achieving 4 - 5 year paybacks with traditional businesses, the choice is obvious.