Environmental Control for Expansion – Cannabis Business Times


The total energy costs of the average indoor cannabis grow operation represent 20-40% of the total operating costs. In comparison, for a typical medium-sized or larger brewery, energy consumption is around 6-12% of total operating costs.

Since energy accounts for a large portion of the costs of operating cannabis, efforts to reduce energy consumption can have a significant effect on the profit margin of a grow operation, as well as on overall competitiveness. of the company. Many states with legalized cannabis markets also have their own energy efficiency goals, prompting state governments to want to work with the cannabis industry to reduce energy use. Additionally, many utilities have programs to help cannabis growers reduce their energy consumption.

For indoor growing, lighting is usually the biggest energy consumer, followed by cooling, dehumidification and ventilation, as shown in Figure 1 (p. 7). For the average indoor grow, the last three together account for around 40% of total energy use, making these mechanical systems an important area to look at. (Note that space heating, normally natural gas, is not included in this breakdown, but typically accounts for less than 10% of total energy use for indoor growing.)

Optimizing energy consumption while maintaining the desired ambient conditions (shown in Table 1) for indoor growing can be difficult. The flowering stage, which requires the most intensive lighting and the longest periods (up to 10 weeks), is often the most difficult due to the narrower window at which you must maintain your humidity levels to limit the growth of molds, fungi and mildew. Flowering is made even more difficult by the fact that you have to account for the dramatic changes in the noticeable cooling load with times of on and off. (The sensible cooling load is the amount of energy required to lower the temperature of the dry bulb, without a change in humidity.)

There are low cost energy efficiency measures, which can be applied to existing installations, and alternative equipment options which mainly apply to expansions or new installations. The following seven tips describe some of these options:

TIP 1: Design and control vapor pressure deficit (VPD) rather than relative humidity. Understanding the importance of VPD can help cannabis companies save upfront capital costs as well as energy during day-to-day operations. VPD is the difference between the internal vapor pressure of a cannabis leaf versus the vapor pressure of the air surrounding the leaf. VPD determines the rate of perspiration, and VPD increases with higher ambient temperatures and lower relative humidity. If the VPD is too low, condensation can occur on the leaves or buds, which can lead to fungal or mildew problems. If the VPD is too high, plants can become too dry or under heat stress.

Data from Zativo’s “Ideal Humidity Level for Cannabis” and “The Cannabis Encyclopedia” by Jorge Cervantes

Many growers try to limit the relative humidity of flower rooms to a maximum of 50 percent, regardless of temperature. By allowing a slightly higher ambient temperature of 75 to 80 degrees Fahrenheit (F) rather than 70 to 75 degrees F, and taking VPD into account, acceptable relative humidity levels in the room can be higher. With these higher set points, the HVAC system (including cooling and dehumidification) can be sized to a smaller capacity, thus reducing the manufacturer’s initial equipment costs. In addition, system power consumption and energy costs during operations will be significantly lower.

TIP 2: Training employees in the proper operating procedures, controls, and good maintenance practices will help save energy.

TIP 3: If the crop relies on rooftop units and electric heating to control humidity, Adding separate dehumidification units in flower rooms will significantly reduce cooling and dehumidification costs.

For crops with less than about 10,000 square feet of canopy, there are two main options for more efficient equipment:

TIP 4: Have separate and efficient dehumidification. When choosing new dehumidification units for flower rooms, choose the most energy efficient model available (for the capacity needed), which can reduce your dehumidification energy costs by up to 15%.

Data source: Energy Trust of Oregon, Resource Innovation Institute

TIP 5: Use high efficiency ductless split air conditioners / heat pumps. Although separate dehumidification units are always necessary (as is the case with rooftop air conditioning units), there is some consensus among experts that using multiple “mini-split” units will be more efficient. and profitable for small crop farms than using rooftop units. There are high efficiency ductless split heat pump / air conditioning systems with Seasonal Energy Efficiency Ratings (SEERs) of 25 or higher, compared to rooftop HVAC units with typical SEERs of 14-15. , split air conditioning units by design use much less fan energy compared to rooftop units.

* Chilled water systems or hot gas reheat systems (HGRH) can be profitable for crops under 10,000 square feet, but these systems tend to require an on-site energy / facility manager more sophisticated to operate and maintain properly, compared to a mini-split system with separate dehumidification units.

For crops with more than 10,000 square feet of canopy, there are at least two options, both of which eliminate the need for separate dehumidifier units:

TIP 6: Consider chilled water systems. A well-designed chilled water system offers several energy-saving advantages, compared to standard or split air conditioning systems with separate dehumidifiers described in the previous tips. Standard rooftop air conditioning units are not designed to remove much latent heat, and the settings available to increase the system’s latent heat capabilities are limited. With a chilled water system, the fan speed can be slowed down and / or the water temperature reduced to achieve greater dissipation of latent heat. So, with a few modifications, a relatively simple chilled water system can control humidity during times of ignition without a separate dehumidifier. Portable dehumidifiers add heat to the space, which increases the cooling load during periods of light.

TIP 7: Consider forced air hot gas reheat systems. These systems are more complex rooftop air conditioning systems with additional hot gas reheating capabilities. This technology adds an additional condenser coil for reheating when needed. Compared to a standard dehumidifier (which has a cooling coil and a condenser coil that heats the cooled and dehumidified air), this system adds an additional outdoor condensing coil in parallel with the reheat coil. This third coil and associated controls allow the system to reject heat to the outdoors when cooling is required in the space (during light periods), or to use the other condenser coil for reheating when sensible cooling needs are minimal (during light periods). – rest periods).

Neil Kolwey is the Industrial Program Director of the Southwest Energy Efficiency Project (SWEEP), where he leads programs aimed at advancing energy efficiency in the industrial sector.

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