Maximizing greenhouse efficiency with LEDs

It’s natural for Allison Driskill and Colin Brice to put themselves in the shoes of produce growers who cultivate crops under cover because they’ve worn them before.

They know firsthand how challenging it is to decide between various and necessary upgrades in a controlled environment greenhouse and weighing which one to tackle first.

Before they became key account managers on the Philips Horticulture LED solutions team at Signify, Driskill launched and operated a leafy greens business in North Carolina, and Brice's microgreens company supplied restaurants in East Tennessee.

They know upgrading to light-emitting diodes (LEDs) is just one of many choices business owners confront each season. They also know how even a small increase in supplemental lighting at just one stage of plant growth can help transform operations.

Signify has conducted research and case studies to determine the ideal light levels for myriad varieties, whether the grower’s goal is to increase yield, save on energy costs or steer the plant toward a specific color or shape.

“Every facility and every operation is its own puzzle,” Driskill says.

Then they dig into questions: What are they struggling with? What is the desired outcome? And what’s the best way to get there?

Goal: Increase yield

Adding light strategically can help growers maximize yield in an existing facility without having to increase space. It can also help them offset seasonal lighting fluctuations in greenhouses, especially in leafy greens varieties, which can thrive in higher light levels.

“For a greenhouse grower, they need to have consistent high output for their buyers that’s of consistent quality,” Brice says. Adding LED lighting to a facility with HPS or without supplemental lighting can help them achieve those goals. “And they get a price premium (for leafy greens) in the winter oftentimes.”

Every operation is different, but in general, a 1% increase in light will result in a 1% increase in yield, as long as other environmental controls are properly dialed in, Brice says. While head lettuce crops don’t necessarily require more light, leafy greens can get to daily light integral (DLI) ranges on par with light-loving tomato and cucumber crops.

And often, there are either prescriptive or custom rebates available from energy suppliers that can cover a significant portion of the cost, making a large capital investment like lighting possible.

Goal: Maximize consistency

Consumers don’t necessarily appreciate the effort it takes to grow the same crop the same way every time. What they want is consistency in their bagged lettuce or pints of tomatoes, 52 weeks a year, Driskill says. The same goes for restaurants. But that takes sophisticated technology to have “seasonally agnostic crops,” she says.

LEDs can help operations achieve peak consistency and efficiency year-round, helping to meet the expectations of customers, whether they are grocery stores, restaurants or consumers.

“When we start a project with someone, we take the data from the natural light in your region and identify the times of year you are going to see less-than-ideal light levels to maintain the certain mols of DLI per day that you need to create a quality crop that meets your spec,” Driskill says. “And here’s what we need to supplement to make sure that you can maintain that quality and consistency year-round.”

Goal: Achieve a specific color or leaf architecture

“LEDs give you spectral control, where you can manipulate your blue light, for example, to keep your crop more compact,” Driskill says. “Or you can manipulate far red and elongate the plant or have your full heads (of lettuce) open up more.”

Brice adds that even if you don’t necessarily need supplemental light, you can use LEDs to extend your photoperiod or keep it more consistent to get those improvements in color and shape.

Goal: Reduce energy consumption and costs

Cost is often the chief concern for investing in LEDs. But Driskill says it’s important to factor in not only the capital expense but the operating expense and the ROI for adding energy-efficient lighting.

“If you can add X amount in lighting, how much yield uplift could you expect? And then how long does it take to pay off?” Driskill says, noting key questions for growers to consider. “If you’re talking to someone investigating the retrofit, we ask do you want to increase light and keep the same wattage install? Or do you want to cut your energy bill by 50% and keep the same light levels? And what does that look like for you? Is there a rebate involved that could help pay for this, and does that change the ROI calculation?”

Goal: Start small and ease into LEDs

To benefit from LED systems, an entire facility conversion or retrofit isn’t necessary. Some growers prefer to start in a single bay, and benefits can be seen even when starting with one stage of plant growth.

Researchers at Signify are discovering that even adding supplemental lighting in just one phase of a crop, especially when plants are young, can result in higher yields and better quality once plants mature.

“You can put more lighting strategically on the young plant phase of a crop and have it pay dividends at harvest,” Driskill says. “An important calculation that we do is light-use efficiency. We have quite a lot of customers who are growing in vertical farms. So, we have a lot of data on how effectively a plant is going to take those photons and convert them into mass. And from that research, we realized that lighting more intensively during the young plant phase ends up resulting in higher yields at harvest, regardless of if you continue that high intensity throughout until harvest.”

Goal: Work with an LED provider where support and resources are available

Like Driskill and Brice, many people on the Signify team are former growers or have horticultural backgrounds and can offer support based on real-word experiences and results-driven research.

Research and case studies have been a focus for Philips since the beginning, when in 2006, the company began working with growers and universities to better understand crop-light interactions, which led to its advancements and developments in LED technology.

“We base everything around the grower. With every project, you have three points of contact that are supporting you,” Driskill says. “The key account manager, application engineers and plant specialists. Our plant specialists of course advise on light, but they understand that everything is holistic and lighting is not in a vacuum. You have to have your climate dialed in as well.”

At the Philips GrowWise Research Center in the Netherlands, the team continues to conduct trials to keep enhancing their LED products and recommendations to growers.

As Driskill notes, “We’re constantly researching on our own, taking what we’re learning and then using that to benefit growers.”