Greenhouse automation: cultivating a better future

From precision irrigation and intelligent climate management to conveyance systems, automation and advanced controls technologies aim to optimize resource utilization while minimizing environmental impact.

Resource Innovation Institute (RII) is a not-for-profit, public-private partnership advancing climate resilience by providing resource efficiency education, training and verification services in collaboration with CEA producers, researchers, governments, utilities and the design and construction sector. We uncover and share practical examples and expert insights into seamlessly integrating sustainable practices into CEA operations.

In our first column in Greenhouse Management, we highlight how greenhouse growers can marry technology and sustainability in their facility to improve resource efficiency and cultivate a better future. There is more information at resourceinnovation.org.

Integrating automation & controls: where to start

Integrating advanced controls and automation systems can be scary for greenhouse operators who have relied on their knowledge and experience to make crop decisions. But doing so can have a myriad of benefits on crop quality, resource efficiency and labor demands.

When considering which automation and controls technologies to implement first, it is always best to look at areas with the biggest efficiency impact, which often proves to be irrigation and water circularity systems. Recirculating water and integrating smart irrigation practices can help greenhouse growers achieve “30% water and fertilizer efficiency, a 20% quality and production increase, and 10% labor efficiency,” says Jan Westra, Strategic Business Developer at RII-member organization Priva.

Improving irrigation controls can be as simple as moving from a timer-based system that delivers a preset amount of water and nutrients to the crop toward a sensor-driven system that monitors substrate moisture levels, or even pot weight. By delivering the right amount of water the crop needs, when it needs it, these systems can reduce both water and nutrient waste. It also can help reduce groundwater contamination — by only delivering the nutrients the plants need, greenhouse growers can reduce the leaching volume that is drained to waste.

Citing a 2011 study by former researcher at Wageningen turned independent consultant in New Zealand Elly Nederhoff, Westra highlights the water-saving potential of advanced controlled greenhouses compared to simpler hoophouse structures in tomato production. On average, closed greenhouses with advanced controls and hydroponic systems can see a 90% increase in water efficiency per kilogram of tomato produced.

From a crop production standpoint, stabilizing irrigation and fertigation events can lead to more consistent and resource-efficient yields, even if the crop is not pushed to its maximum potential. “A stable plant performs better overall,” Westra notes. “A lot of growers would settle for 90% of max production as long as it’s a stable output.”

Water circularity systems can also be implemented in a phased way without breaking the bank. For example, irrigation runoff can be collected in a simple plastic gutter directed to a holding area at one end of the greenhouse for disinfection and reuse. As the greenhouse’s business evolves, more advanced water circularity systems can then be built on top of existing processes.

Smart climate and energy systems

Following water circularity and smart irrigation, greenhouse growers can aim to integrate climate and energy systems to function as one cohesive system rather than independently from each other. Doing so can unlock significant energy savings by smoothing out temperature and humidity spikes.

By reducing the frequency competing systems are activated (e.g., opening and closing of vents to let heat and humidity out, only to have to activate heating systems to bring conditions back to target setpoints), facility operators can grow a more stable crop and reduce their energy bills, increasing their greenhouse’s efficiency and efficacy.

For example, “in the Netherlands, we have the APEX, the Amsterdam Power Exchange. And I’m told at 1:30 p.m. the price of electricity is set for the next day,” Westra explains. “Based on that,… software can decide what’s the best way to heat, to cool, to buffer” to maximize efficiency and ensure profitability.

Greenhouses in The Netherlands can also act as energy sinks when grids produce excessive energy that cannot be used elsewhere. “When wind power goes up like crazy, then growers get a signal to the computers to switch on the LEDs,” Westra shares. “The LEDs turn on, even if it’s not necessary, but [utilities] need a sink.” This stabilizes grid energy demand, and growers can also be paid to use this energy. Now, greenhouse operators are looking to leverage electric boilers to convert that excess electric energy into heat stored in buffer tanks that can be used to warm the greenhouse when electricity prices return to their normal rates. While these systems are virtually unheard of in the U.S., their premise is an interesting one as utilities look to manage demand responses.

Other advanced controls systems can take into account outdoor light and temperature conditions to make efficient decisions. For example, “A long time ago I visited a grower [who] wanted to switch on all the HPS lights, but the weather forecast said within half an hour, the sun will come up and then the light would be free,” Westra says. “He was complaining about our software because he wanted the lights on, but then the sun rose as predicted.” Some systems will even take into account average daily light integral levels and use predictive analytics to make changes to supplemental lighting and shading curtains.

Westra cautions against manually adjusting advanced climate control systems too often, thinking their “green thumb” is more sensitive than the army of installed wired and wireless sensors. By constantly changing setpoints, “the system will never get stable because there are so many changes. Advanced climate control systems will have buffered setpoints that minimize system use and slowly bring the environment to the target ranges.

As with most things, experience breeds trust, but growers should remember they purchased and installed these systems for a reason.

Conveyance & processing automation

In addition to water circularity and smart climate control systems, the most automated greenhouses, such as in Oberlin, Ohio’s Green Circle Growers (pictured on pages 26 and 28), will leverage automated conveyance and processing technology to maximize resource efficiency. When it introduced orchids to its commercial production more than 15 years ago, Green Circle Growers also increased the amount of automation and has been growing that technology base across its 150-acre Dutch-style greenhouse since then.

“The more you put in the greenhouse–that goes for automation to equipment — sometimes the harder it gets to manage [natural environments]. It requires more [technical] knowledge,” says Marcel Boonekamp, who joined Green Circle Growers in 2015 as its director of growing. “We look for semi-automated [solutions] as well, if that makes more sense either investment-wise, flexibility-wise, or labor-wise.”

The company’s 5-inch orchid program is the most automated of any crop, Boonekamp says. In addition to rolling benches and automated potting, each pot has a barcode allowing the company to match it to a tray and track its progress from propagation to packing.

The automated potting machine “only requires two persons to put a plant in, but the machine will put the plant into the pot and fill the bark automatically. It also has a unique barcode on the pots. [When a scanner reads the barcode after potting], it links that to the young plant information… So we know at that moment that the plant that we just potted is so old, started as small, medium, large, it’s that variety, and it’s expected to be done by that week,” Boonekamp explains. Once the 5-inch orchids are potted, they only get touched by a human worker one more time during their roughly 48-week development when they are staked.

About halfway through the production cycle, the orchids will go through an automated camera system for evaluation. Using chlorophyll cameras to be evaluated on a 24-point scale.

Orchids that have grown to the company’s large spec get immediately moved to the cooling section of the greenhouse to trigger flowering, while medium and small plants get sorted (via an automated system) to a different table to return to the warmer greenhouse section for further vegetative growth.

This process avoids precious resources being wasted on orchids that are ready for flowering while giving an opportunity to smaller plants to receive the attention they need. “We also grade those [smaller plants] again, and if they’re small again, we even throw those away because … we think those will never grow into a good quality product.”

When leveraging advanced camera systems for grading, Boonekamp stresses the importance of using high-quality cameras and having good lighting. The absence of either (or both) can lead to the system mistaking stakes for spikes, which in turn will lead to more human-worker interactions to correct the automated sorting system.

Once the plants have grown tall enough, they are staked and clipped by hand. Next, the plants run through the camera system. “The camera system looks at the spikes and determines how many spikes, how tall, how many flowers, how many buds, how many branches,” he says. The automated sorter moves each orchid to a different tray based on its rating on the 24-point scale. This allows Green Circle Growers to be able to quickly ship out batches of orchids based on specific customer requests. It also frees up labor to do more creative work that machines can’t do. “We have never reduced our labor force because we invested in automation,” Boonekamp says. “[Automation] enables you to grow. Without automation, we wouldn’t be able to grow as fast as we have.”

The convergence of technology and sustainability in greenhouse operations is not only viable but essential for the CEA industry’s future. The impactful fusion of advanced controls and automation, specifically in irrigation, climate and processing systems, demonstrates profound resource efficiencies. The collaborative efforts within the CEA sector to find creative solutions to climate and resource use concerns underscore the potential for significant enhancements in water and energy utilization, crop quality and labor efficiency. Embracing these technologies is not just an option but a duty as we move toward a more sustainable future.