Why does the horticulture industry need a lighting label?

A horticultural lighting label would make it easier for growers and lighting manufacturers to compare performance metrics among lighting fixtures.

By David Kuack

The lighting facts label found on many residential and commercial lamp and bulb packages was developed by the U.S. Department of Energy. This label provides information on light output, efficiency and lamp life. It can also help consumers calculate the cost to operate a lamp depending on the price of electricity and the number of hours per day the lamp is operating. How could a comparable label on horticultural lighting products help the industry?

Identifying the need for a horticultural label

When university researchers involved with studying horticultural lighting met at conferences one of the regular topics was the need for clarity consistency in the performance metrics for horticultural lighting products.

“The reason for researchers identifying this need was that there really wasn’t anything available to help growers independently compare lighting products from different manufacturers,” said A.J. Both, professor and extension specialist at Rutgers University in New Brunswick, N.J. “If growers talked with a lighting manufacturer, in many cases the company would heavily promote its own products. But growers had no way of comparing lamps from different manufacturers because the companies would use different identifiers or characteristics to promote their products. There was very little independent information to compare the numbers from one manufacturer with those provided by another.

“University lighting researchers felt it was important that there was something that growers could use that was easy to read and understand and would aid in the comparison of products from different manufacturers. The university researchers who worked on the proposed horticultural lighting label had to decide what information would be useful for greenhouse and other controlled environment growers. This is how we settled on the particular label. Our goal was for a label that can be used for all light sources designed for horticultural applications.”

Photos courtesy of A.J. Both, Rutgers University

One of the biggest benefits of the proposed horticultural lighting label is it enables growers to determine how efficient a particular luminaire is at converting electricity into useful light for photosynthesis.

An evolving process

A recent USDA-funded research grant enabled Both and his colleagues at Rutgers University to set up a sophisticated testing program. They have been analyzing commercial horticultural lamps or luminaires for the last three years.

“The horticultural lighting label that has been developed is a proposal,” he said. “The horticultural lighting researchers who developed this label think it contains key information that growers need. But we are open to suggestions for improvements and changes as we gain more knowledge and as new products become available.”

Researchers at Rutgers University have been analyzing commercial horticultural lamps (luminaires) for the last three years.

No approval is required from the Department of Energy for the horticulture industry and lighting manufacturers to use the label.

“I expect the label or something similar to the proposed label will become the industry standard,” Both said. “It will be a voluntary standard. Once the manufacturers start to be pushed by growers to provide information so they can compare products, I expect the label will become the standard and will be used throughout the industry.

“Until that happens, we are trying to promote the label. We talk about it at research and industry meetings. We discuss it with our colleagues and the lighting manufacturers. We really don’t have any way of enforcing the use of the label. It has to be a voluntary process that eventually results in industry-wide acceptance and adoption.”

Benefits for growers

One of the biggest benefits the horticultural lighting label offers growers is they will be able to look at the label and determine very quickly how efficient a particular luminaire is at converting electricity into useful light for photosynthesis.

“The label provides growers with information on the efficiency of a lamp or luminaire,” Both said. “In other words, how many dollars need to be spent on electricity for the amount of light delivered by a particular lamp. This information is going to have a major impact on the operating expenses for running the lamps.

“The PAR (photosynthetically active radiation) efficacy listed on the label tells growers how much of the electricity provided to a luminaire is converted into PAR. By evaluating the PAR efficiency, growers can also assess the amount of electric energy that is converted into heat. The label does not indicate whether this heat is radiant heat or convective heat. These two different kinds of heat are predominantly produced by high intensity discharge (e.g., high pressure sodium and metal halide) or LED lamps, respectively.”

The lighting label will enable growers to assess how easy it is to observe the true color of objects placed under a particular light spectrum. The color rendering index compares the actual color representation under a particular light source to the color representation under natural sunlight.

The label also informs growers about the light spectrum a lamp is producing.

“Hopefully growers will know what a particular plant species or a group of plants need in terms of light spectrum,” Both said. “This will enable growers to determine if a particular lamp provides the right spectrum for the crop or group of crops they’re producing. The label will enable growers to determine for example, how much blue, red or green light is being produced by a particular lamp or luminaire.”

Growers will also be able to assess the uniformity of light distribution from a particular luminaire.

The label will enable growers to determine for example, how much blue, red or green light is being produced by a particular lamp or luminaire.”

Growers will also be able to assess the uniformity of light distribution from a particular luminaire.

“This information will help growers in consultation with a lighting designer to lay out a particular grid of lamps or array of lamps in a facility for maximum uniformity of the light distribution,” Both said.

One piece of information that will not be on the label is the life expectancy of the luminaire.

“Life expectancy is not so easy to determine,” he said. “A researcher would have to run many lamps or in the case of LEDs, would have to run the lamps for many hours because they last much longer than traditional lamps. They would have to be run for tens of thousands of hours. Many of the lamps would have to be run in order to achieve a statistical assessment.

“The lighting industry has developed a different test that can be done in less time to come up with an estimate for life expectancy. This is isn’t easy to do so we have opted to not include this information on the label. The life expectancy is something that manufacturers can opt to add themselves.”

The horticultural lighting label can be used for the most common lamp types used by growers, including LEDs, high pressure sodium and metal halide lamps.

“The one difference between LED fixtures and the other lamps is we want to determine the temperature of the surface to which the LEDs are attached,” Both said. “That surface temperature has an impact on the output of the LEDs. If the LEDs are run warmer there is a different output then if the LEDs are run cooler. On the lighting label there is a box for this temperature measurement that is specific for LED lamps. This is not something that is typically done for other types of lamps mostly because it is more challenging to determine the operating temperature of a high pressure sodium or metal halide lamp.”

The lighting label will allow growers to assess the uniformity of light distribution from a particular luminaire which will help in determining lamp layout for maximum uniformity of light distribution.

Another benefit the label will provide growers interested in using LEDs is related to the color spectrum of the light produced.

“Many LED luminaires use a combination of red and blue diodes to create a magenta or purplish color of light,” Both said. “Plants are most sensitive to and most efficiently use red and blue light. However, this color of light makes it very difficult for humans to assess the color of the plants. When plants experience a specific nutrient deficiency, there is typically a color change in the leaves or the veins of the leaves. Those types of changes are very difficult to observe under the magenta light from combinations of red and blue LEDs.

“The lighting label will enable growers to assess how easy it is to observe the true color of objects placed under a particular light spectrum. The label includes the color rendering index (a number less than or equal to 100). This number compares the actual color representation under a particular light source to the color representation under natural sunlight. The closer the color rendering index is to 100, the easier it will be to assess color changes in a plant’s leaves.”

Benefits for lighting manufacturers

Both said that one of the benefits for the manufacturers is the label would help to distinguish between quality-made products and cheap knock-offs.

“The serious lighting manufacturers regularly complain about the cheap lighting fixtures that are produced by companies that don’t have high manufacturing standards,” he said. “As a result the cheaply-made lighting fixtures don’t deliver based on the claims published in their documentation. The serious manufacturers feel that these cheaper lighting fixtures typically don’t perform as well, are not as reliable, don’t produce the required spectra and don’t have the longevity that they sometimes claim.

“Having a label and voluntarily asking for compliance, serious manufacturers can use the label to present product performance information that is important to growers. By using the label manufacturers will know their products have been rated based on a fair scale that is used by the industry and the label information can be used by growers to make smart purchasing decisions. Hopefully the label will help to create a self-regulating system.”

Another benefit from using the label is that it will offer manufacturers an opportunity to show growers the differences between their own products and the products of other manufacturers.

“Manufacturers will have some bragging rights based on the numbers on their labels,” Both said. “If one manufacturer’s label numbers are better than a competitor’s, this information can be shown to growers trying to decide which product is best for their particular production needs. This type of product comparison is very useful when a technology is still developing and improvements continue to be made.

“It seems like every few months we read about a new lamp that is available that is even better than the previous iteration or better than the competitors’ lamps. The label could be the standard that all manufacturers follow and could allow them to claim that their lamp is significantly better than other lamps manufactured by competitors.”

Educating the growers

Both said even if lighting manufacturers don’t use the label or don’t provide this product information, the label should help growers to ask key questions when they are considering changes to their lighting strategies.

“I’m not only hoping that the industry is moving in the direction of adopting this label, but I also hope that the label can help educate growers as to the type of product information they should have before deciding which products to buy,” he said. “As growers become more informed about the lighting products, I’m hoping the manufacturers will become more incentivized by all the questions they are receiving from potential buyers to use the label or something very similar in their marketing strategies.”

For more:A.J. Both, Rutgers University, Department of Environmental Sciences; (848) 932-5730; both@sebs.rutgers.edu; http://horteng.envsci.rutgers.edu.

David Kuack is a freelance technical writer in Fort Worth, Texas; dkuack@gmail.com.

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