PhD candidate Fatemeh Sheibani looks through a vertical farm plot for her research.
(Courtesy of Purdue Agricultural Communications)
Researchers at Purdue University have designed two simple LED lighting strategies to increase yield and reduce energy costs for indoor, vertical farms.
The work is part of a project called OptimIA led by Michigan State University with collaborators at Purdue, University of Arizona and Ohio State University. It is sponsored by the USDA’s Specialty Crop Research Initiative.
PhD candidate Fatemeh Sheibani said the use of LEDs allows for vertical farms to take advantage of the light source’s unique properties and save costs on energy.
“LEDs are cool at the emitting surface, we can place them closer to the canopy without any damage to the plants,” she said. “And the second one is that they are dimmable, since they are current driven as we dim them down, less energy will be applied. In other sources of lighting, when you dim the lights down, the energy wouldn't be cut down.”
Vertical farms, in which plots of crops are stacked on top of one another, are a growing industry worldwide, with the U.S. being a leader in research and development. These types of food production systems hold many potential benefits for consumers.
“In areas that they do have limitations for outdoor production, specifically in urban areas, that demand for local fresh produce is high,” she said. “A vertical farm is one of the choices that people would go to. And also, when you're thinking about all those fossil fuels that are used for the transportation from long distances away, those are all eliminated in a vertical farm setting.”
In vertical farms, LEDs are the sole light source for the plants and account for a minimum of 30% of operational costs. Close-canopy lighting works because LEDs shine in all directions, like the sun. At standard plant/light separation distances, significant light streaming at wide angles over the plants misses them entirely. But with reduced separation distances, the plants absorb light that would otherwise go to waste.
Figuring out how to make the most of light sources as cheaply as possible is part of the aim of Sheibani’s research, with the goal being to help more vertical farms become profitable.
“Based on two-years-old data, only 37% of vertical farms are to be profitable,” she said. “So this is one of the issues that they have. And there might be different approaches, one of which is the reducing of electricity costs for LEDs.”
Sheibani and professor Cary Mitchell also are testing an energy-saving, focused-lighting approach that relies on a custom-made LED system with selective controls.
