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Inside View on lighting trends October 2016

October 2016 – Greenhouse producers are long familiar with using high-pressure sodium lamps to compensate for reduced sunlight. Not so long ago LEDs started to make inroads into the industry. Because of their ease of maintenance, longevity and energy saving benefits this technology is no longer necessarily cutting edge.

One large producer of bedding and potted crops here in British Columbia installed 600 square Lumigrow fixtures in his new 2.5-acre propagation house. These are a blue-red-white combination of “bulbs,” with additional computer-controlled variable spectrum management. While looking at two to three times the capital cost compared to high-intensity discharge (HID) units, the main benefit is the lower energy usage of LEDs. For this grower, his estimates based on half the electricity consumption of HID lamps yield a quick (two- to three-year) payback period and so he’s looking to extend this lighting option to non-propagation (production) houses.

LEDs have also played a key role in enabling the development and recent expansion of the “warehouse farm” and “urban container” food production models that are popping up faster than a beansprout crop. But are there other benefits?

First off, a study conducted by Wageningen UR Greenhouse Horticulture in 2013 investigated several tomato varieties grown at various intensities of light. They found that tomatoes can contain more vitamin C if exposed to extra light from LED lamps while growing on the plant.₁

Other researchers have found that LEDs may enhance antioxidant levels in leafy crops, have increased carbohydrate and vitamin C content in parsley and dill, can allow management of the volatile profiles (characteristics that affect smell and flavour) of tomato, strawberry and blueberry, and that post-harvest food stored under LED lights improved in appearance and flavour.₂

Growers of indoor crops have known for a long time that the spectrum of light presented to plants can change the physical characteristics of the crop. For example, CubicFarm Systems Corp.™ has demonstrated that LEDs can be used to control the leaf colour of the salad crops they produce.

Matching light spectrum to the normal growing conditions of a plant species allows growth just about anywhere in conditions that closely replicate its natural conditions and can optimize production without wasting energy on non-productive wavelengths. But is it economically feasible?

In his article in 2008, Robert C. Morrow states that “historical and projected evolution of LED performance and wholesale cost is favourable; each decade, LED prices have fallen by a factor of 10 while performance has grown by a factor of 20. This phenomenon is known as Haitz’ Law (Steigerwald et al., 2002). Implementation of mass production for LED lighting arrays will also significantly reduce the cost of building solid-state lighting. As LEDs replace existing lamp technologies in more lighting applications, economy of scale will drive significant cost decreases.”_³

As researchers identify new benefits and applications for LEDs and manufacturers produce lighting arrays that are increasingly not only economical to install and operate but, as the grower at the beginning of the article is finding, can provide costs savings compared to traditional lighting technology, designer lighting is clearly becoming the way of the future.

And who knows – perhaps even our food will be better for it?

1. 1 https://www.wageningenur.nl/en/show/Tomatoes-with-extra-vitamin-C-via-LED-lamps.htm
2. 2 Reported in an article at www.illumitex.com (http://illumitex.com/studies-show-food-grown-led-lights-taste-better-816)
3. 3 Morrow, Robert C., ‘LED Lighting in Horticulture’, http://hortsci.ashspublications.org/content/43/7/1947.full#sec-1

Gary Jones is co-chair of horticulture at Kwantlen Polytechnic University, Langley, B.C. He serves on several industry committees and welcomes comments at Gary.Jones@kpu.ca.