10/2021 Lighting and HVACD Part 1 with InSpire
Robbie Batts, Chief Tech Officer, Inspire Transpiration Solutions
The relationship between lighting and HVACD is complex and can have a significant impact on the financial performance of a farm. Smart, up-front decisions can save later frustrations and revenue losses. This topic was discussed in a webinar co-presented by Fluence and InSpire, a San Francisco-based company that delivers cannabis climate control for commercial grow rooms and indoor cultivators.
Casey Rivero, cultivation optimizer at Fluence, kicked off the webinar with her presentation “Key Lighting and HVACD Decisions in New Build Planning.” She included a handy checklist for facility planning:
- Define business goals
- Secure cultivation license
- Identify limitations
- Establish standard operating procedures
- Hire your team
- Educate yourself and your team on key technology terms
- Select your manufacturers
- Execute your plan
These steps are important because they help growers focus on yield, quality, and–most of all–efficiency. Each of these steps impacts financial performance, and each coincides with the choice of lighting. As you design your new facility and consider lighting options, it’s good to ensure you have a handle on the fundamentals of crop lighting. Aaron Fellabom, the director of strategic accounts at Fluence, discussed key terms and metrics in lighting:
- PPF — All the light particles a light source is emitting
- PPFD — Number of light particles arriving on a specific area
- Efficacy — Conversion of electrical energy into photons of PAR
- Wattage — Measure of electrical power
- LPD — Lighting power density
It’s also important to look at the applied financial aspects of your investment:
- $ per PPF
- $ per PPFD
- $ per full room PPF when comparing
- Grams per square foot
- Grams per square foot per year — cycles per year
- Cost per fixture
Putting this data into financial models ensures you are making smart decisions as you design your new build.
Casey emphasized that lighting fixtures don’t grow crops. Individual fixtures and the costs associated with them don’t matter, he said, and what actually matters are the photons. What you’re purchasing is a total amount of photons. While there are plenty of nuanced considerations, growers ultimately should buy the photons–not the fixture.
Plant Vitality and HVACD
Rob Batts, CTO at InSpire, talked about the key parameters of plant vitality that are controlled by HVACD. These paramaters, as he explains, are tied not only to lighting but also to the bottom line.
Among these parameters, CO2 and room temperature are the easiest to control, said Batts. Airflow, however, is a bit more difficult to control (as are humidity and leaf temperature).
The interplay of leaf temperature, room temperature, and humidity is the core of VPD — vapor pressure deficit, which is a measurement of the difference of saturation vapor pressure inside the cells of a plant’s leaves and the vapor pressure of the room’s air at a given temperature and humidity level. VPD is the driving force behind transpiration; essentially, you control water movement through a plant by controlling the VPD. This, in turn, impacts many of the plant’s fundamental processes.
Maintaining constant VPD is crucial, says Batts, and is most easily handled via tools that automate the process. Cultivators should keep in mind that lighting type has a significant impact on VPD.
The fiscal returns on growing potent and desirable cannabis will outstrip the efficiency savings of your dehumidification system. In other words, while you’ll see increased efficiency, you’ll,also see an increase in production, which is even more important.
With carefully managed HVACD, you should experience some OPEX gains, but more critically you should realize huge production gains. “We developed a VPD control algorithm because we know that’s how you make plants thrive,” Rob said. “We modulate every single component inside our devices so we can deliver consistent temperature and relative humidity to happy and thriving plants.” He went on to detail how to turn a flower room into a “star performer.”
Steps for Choosing Lighting
Casey took the mic next and provided a checklist for choosing the right lighting manufacturer:
- Choose your genetics
- Know your facility
- Select your lighting type
- Correctly size your HVCAD
- Understand your lead time
- Purchase and install
Be sure to thoroughly understand the economics of what you’re trying to achieve, he said. A more careful look at the overall picture shows that LED fixtures are indeed more expensive than HPS, but when you factor in HVACD costs you actually come out ahead on CAPEX when using LED technology. Further savings occur when OPEX is evaluated, and even greater savings can be achieved through rebates and incentives.
Rob and Aaron wrapped up the webinar with key takeaways:
Rob: There’s real value in the rules of thumb that legacy growers have developed, but it’s important to also use real data whenever available. Avoid speculation. If you’re making a decision, go as far down the hierarchy of knowledge as you can. Find out why you’re making one decision over another. Mind map all your choices.
Aaron: Get the correct data, then use that data to support your goals. Invest in photosynthetic drivers and focus on revenue in order to optimize the financial performance of your system as a whole.
Following the webinar, the panel took questions from the audience, some of which are below:
Q: If VPD for LEDs is optimal at 82 degrees, or 75 degrees for HID, is there additional overall energy savings by lower cooling load, or is it about the same?
A: The load actually doesn’t change. The transpiration rate in the HPS room and the transpiration rate in the LED room — because we’ve got the same VPD of 1.5 KPA — will be equal. Your dehumidification rate doesn’t go down. What goes down is the amount of energy required to take the humidity out of the room. So, a room that’s warmer at the same relative humidity will need less HVACD and dehumidification in compressor tons than you would otherwise [need] in a cooler room.
Q: How does a grower or a lighting designer know the ideal mounting height of a fixture?
A: Mounting height varies based on the way the light distributes, whether you’re using reflectors, or a secondary lens or what the optic system is. So, depending on whether you’re talking about HID or LED, single-ended or double-ended, they all have different methodologies to spread that light out.
Q: Do you have recommendations for airflow to create a consistent climate across your growth space? Looking at ducted vs horizontal airflow vs vertical airflow fans for an indoor growing environment.
A: The longer the air is moved through a process that will change the humidity or temperature, the less control you’ll have over what those conditions are. So, go through the canopy in the shortest direction possible, either top down or bottom up.