As light emitting diodes (LEDs) become more efficient and more affordable, an increasing number of greenhouse and plant factory growers will consider installing LED luminaires to light their crops. In the case of greenhouse growers, these luminaires would provide light to supplement natural sunlight. For plant factory growers, production depends entirely on the light provided by an artificial light source including LEDs, high pressure sodium or metal halide luminaires.
According to University of Georgia horticulture professor Marc van Iersel, the electricity for supplemental lighting in a greenhouse accounts for 20-30 percent of variable costs. In the case of plant factories which rely solely on artificial light, the electricity cost accounts for 50-60 percent of the variable costs.
van Iersel is heading up a $5 million, four-year research project that will focus on enabling growers to maximize the return on their lighting investment. Funding for the Lighting Approaches to Maximize Profits (LAMP) project is being provided by the USDA National Institute for Food and Agriculture Specialty Crop Research Initiative. The team that has been assembled to work on the project includes 15 university researchers, an advisory panel of greenhouse and plant factory growers and industry consultants.
“The job of the advisory grower panel is to make sure that the research that we do is actually what they need,” van Iersel said. “These are growers who will directly benefit from the research. We are also working with consultants who represent a big section of the industry. We are looking to them to help disseminate the information generated by the research to the industry.
“The research is looking to determine how growers can maximize their return on investment. There has been a lot of research done on how to grow plants with LED lights. We know growers can produce plants with lights. But what we don’t really know is how can growers make the most money doing it.”
FOCUSED ON LEDS
van Iersel said most of the project’s research will focus on the use of LEDs with some economic comparison to high pressure sodium (HPS) lamps.
“LEDs are clearly the lights of choice for the future,” he said. “Where we are interested in comparing LEDs and HPS is in regards to the economics. LEDs are more efficient, but they are also more expensive. Is the extra cost of LEDs worth it or are some growers actually better off paying less in capital expense for HPS lamps and more for the electricity to operate them? That is not a simple question to answer.
“There really hasn’t been a big price drop in LEDs. What LED manufacturers have done is rather than lowering the price, they have focused on making the LEDs better. Newer LED lights have hundreds of individual diodes in them. That is one way to help make the lights more efficient. But obviously they are putting more hardware in the lights. In older LED lights there were fewer individual diodes that went into a single light. The diodes were expensive. Now that the diodes are relatively cheap the manufacturers are putting in more of them so that the lights are more efficient. There seems to be a race among manufacturers to try to make the most efficient LED light possible. Right now it seems like the focus is more on creating a more efficient light than on creating a cheaper light.”
van Iersel said LED light manufacturers can easily match the light intensity of HPS lamps.
“What the LED manufacturers typically do with more diodes is run the diodes at only a fraction of their full power,” he said. “That makes the diodes more efficient. If an LED operates at 50 percent of its maximum power, it is substantially more efficient than running it at full power.”
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