Originally published in Issue 7
Scientists and growers are excited about the potential of LEDs for plant growth. Researchers advise growers that not all LEDs are created equal and that they should do their homework before investing in this new technology.
Light emitting diodes (LEDs) are gaining the attention of horticulture researchers and commercial growers.
“There is always an interest in lighting regardless of how new or old the technology is,” said Michigan State University horticulture professor Erik Runkle. “Combining lighting with an emerging technology like LEDs, which are continuing to evolve, there is a natural attraction and an element of curiosity. Many LEDs emit a pinkish-purplish spectrum that makes them intriguing to people. People also want to be on the cutting edge, so they may be considering LEDs before they know all of the advantages and challenges with using them.”
Purdue University associate horticulture professor Roberto Lopez said growers are very excited about LEDs and he receives a lot of questions about them and their applications.
“It’s a new technology and the growers see their potential,” Lopez said. “Growers who are using incandescent bulbs for photoperiodic lighting have to look at alternative light sources since incandescent bulbs are being phased out of production. Some growers are looking at compact fluorescents as replacements and others are looking at using LEDs.”
Utah State University professor Bruce Bugbee said much of the interest in LEDs comes from the promotion they are receiving.
“Venture capital is funding many of the lighting companies,” Bugbee said. “There is considerable interest in LEDs because of the promotion and advertising on the part of the LED manufacturers. People naturally get excited about new technology.”
Funding LED research
While LED manufacturers may be spending money to promote their products to the horticulture industry, few are providing researchers with the funding to study the lights.
“Each lighting company is looking at research from its own business perspective,” Runkle said. “There isn’t a whole lot of cash coming from these companies, but often times they’re helping to subsidize the cost of the LEDs.”
Runkle said the funding for LED research is coming from a variety of sources.
“Some of the lighting companies have a lot of good data, but they also want to see some independent testing,” Runkle said. “Some growers are supporting the research because they realize the importance of generating unbiased, research-based data.”
Lopez said he has received funding from companies including Philips Lighting and Hort Americas, a horticultural distributor.
“I haven’t received funding from other lighting companies,” Lopez said. “Most of the companies are willing to donate the lights. But I explain to them that I have to pay the graduate students to do the research.”
Runkle and Lopez are part of a team of university researchers who have received a $2.4 million grant from USDA to study LED lighting for greenhouse applications. An additional $2.5 million in matching funds was provided by the universities and private companies for the research.
“Funding is coming from the government including the Specialty Crop Research Initiative from USDA,” Runkle said. “These are quite competitive proposals and a good team of scientists has to be put together in different areas of study. The researchers have to come up with a compelling case for why the research is needed and how it will benefit horticulture crop producers.
“In the case of the Specialty Crop Research Initiative proposals, there was a required matching component. For every dollar the researchers received from the government, they had to match it with a dollar from academia or private industry. This matching component could be either through direct cash or through in-kind contributions such as providing lights, plant material or industry time. This coming year, matching funds will not be required.”
Bugbee said the money he has received for LED research came from NASA, but the funding from this federal agency has been limited in recent years.
Learning more about LEDs
Runkle said research projects are generally funded based on a variety of factors.
“There has to be some short to intermediate term impact in a positive way to the specialty crops industries,” he said. “Looking at the potential advantages of LEDs, whether they are realized this year or in two to four years, I expect most people would agree that we should understand the technology as it develops rather than letting the technology develop and then kind of figuring things out later.”
Runkle advises growers to be cautious about investing in LEDs until they have examined how LEDs compare to other lighting technologies.
“Until recently commercial lamps used in agriculture were developed for human application,” he said. “They weren’t developed for agriculture, they were developed for people. With the new LED technology there is the ability to develop LED arrays that emit light that are very effective on plants. Many LED fixtures emit deep red and deep blue light, which humans poorly perceive and so they appear relatively dim. But from a plant perspective, they are intense.”
Lopez said growers need to be wary of some of the claims being made about the energy efficiency of LEDs.
“What I tend to see is the “supposed” claimed efficiencies of LEDs or claims that the LED intensities are equal to high pressure sodium, when in fact there not. It really depends on the manufacturer,” Lopez said.
Bugbee and graduate student Jacob Nelson recently published the results of a study on the economic analysis of greenhouse lighting. Their study compared 22 lighting fixtures, including LEDs, two types of high pressure sodium (HPS), metal halide and fluorescent fixtures. The best LEDs and high pressure sodium lamps were equally efficient, but the cost of the technologies varied widely.
“Per photon, LEDs are considerably more expensive than the new double-ended fixtures, but there are specific applications where LEDs are useful,” Bugbee said. “LEDs are more focused than HPS fixtures and this is valuable in some applications. LEDs are like spotlights and they can be focused right on the plants.
“LEDs probably aren’t the best choice for a large greenhouse full of plants. They need to come down in price by about a factor of 10 to be comparable in price with high pressure sodium lamps for uniformly lighting large areas.”
Bugbee, who uses LEDs in his research greenhouses, said LEDs are cost effective in many commercial applications.
“We are studying the effect of colors of light on plant shape,” he said. “We cannot get unusual color ratios with other lighting technologies.”
For more: Erik Runkle, Michigan State University, Department of Horticulture, (517) 355-5191 Ext.1350; firstname.lastname@example.org; http://www.hrt.msu.edu/erik-runkle.
Roberto Lopez, Purdue University, Department of Horticulture and Landscape Architecture,(765) 496-3425; email@example.com; https://ag.purdue.edu/hla/lopezlab/Pages/default.aspx.
Bruce Bugbee, Utah State University, Plants, Soils & Climate Department, (435) 797-2765; firstname.lastname@example.org; http://cpl.usu.edu/htm/about-us/directory/memberID=5316.
David Kuack is a freelance technical writer in Fort Worth, Texas; email@example.com.