Lighting in Design

Horticultural lighting is the industry's hottest new market, revolutionising the future of farming with technologies and innovations enabling year-round sustainable crop cultivation.

The revolution in horticulture is a seismic shift that will fundamentally change how we grow plants – and it’s all down to lighting. Thanks to the properties of LED lighting and major advances in our understanding of plants, we are now able to tune light in order to boost yield, customise plant characteristics and maintain plant health.

The growth of horticultural lighting

At a basic level, horticulture is relatively simple. Given the right soil, temperature, moisture, and lighting conditions, horticulturalists should be able to cultivate plants anywhere. The lighting component in this formula is much more complex than replacing natural light with an artificial light source.

Plants require lights with specific spectral characteristics, including concentrations of light within the appropriate wavelength bands to facilitate plant photosynthesis. Green plants require greater amounts of light in blue and red wavelengths, but have other wavelength requirements between those two bands. Before the advent of LED lighting, horticulturalists were unable to generate artificial light that met all wavelength requirements for optimum plant growth.

The use of LED

The power consumed when converting electricity into PAR photons determines the efficiency of the luminaire, and LEDs are the most energy efficient solution available. In addition to most common top lighting applications where luminaires are placed at ceiling level, LEDs can be used closer to plants because of their lower heat radiation. This allows luminaires to be installed much closer to plants to create more dense farms vertically. Mixing different colour LEDs allows better matching of the light spectra for each species and the stage of growth of the plant. With LEDs the luminaires also have a longer lifetime and lower maintenance needs.

Optics, on the other hand, help focus the light/photons onto the plants, allowing either greater crop yield and shorter growing cycles or reduced luminaire bill of materials (BOM) costs. Having uniform light and spectral distribution also helps to produce healthier and more productive plants. Focusing light energy where it is needed gives greater photosynthetic photon flux density (PPFD) with less power. The greenhouse use case for LEDs is primarily as a supplementary light source to the sun, although artificial lighting is increasingly vital during the colder and shorter days of winter.

Cannabis also requires greenhouse-like space where plants can grow vertically. Most legal cannabis growing operations are indoors, and require electrical fixtures as the primary light source. Where LEDs are having the greatest impact, however, is in growing leafy greens and herbs that only reach heights measured in centimetres and that can be grown in layers or racks with each layer having a dedicated set of LED luminaires relatively close to the plants, again enabled by little to no heat radiated by the LEDs. The layering assists so-called urban or vertical farms to occupy relatively small growing spaces inside buildings near population centres, while optimal lighting and technology – including hydroponics – enable faster plant/harvest cycles than can be achieved outdoors.

Challenges in horticultural lighting

There are, of course, challenges in any emerging technology and perhaps even more so in LED-based horticultural lighting where experience with SSL technology is still shallow. Lighting manufacturers based in Asia have targeted the market with what are often affordable but low-end products. However, many of the low-end products on the market lack pertinent certification. Many growers, especially in the cannabis sector, have suffered losses – because of poor fixture performance – in early attempts to deploy LED lighting.

However, documented benefits of LEDs in horticulture continue to grow, and include the Mirai lettuce farm in the city of Tagajo in Japan. GE Lighting developed customised LED lighting for the farm. Mirai worked with GE to develop LED lighting tuned to the lettuce growing cycle. The Japanese Ministry of Economy, Trade and Industry (METI) encouraged the use of technology on the farm, which uses customised sensors and control systems for all aspects of the agricultural environment. The partners say the result is 50% better plant production relative to fluorescent-lit farms along with a 40% reduction in energy usage.

The farm occupies 2300 sqm of floor space and there are 17 500 LED lights in use. The lettuce is grown in cultivation racks to maximise the use of high ceilings. The result is a 10 000-head daily harvest. The success of the project has led to enquiries from interested parties across the globe and has the partners looking to develop other LED-lit farms in Japan.

Key questions to ask when designing horticultural lighting:

Does the light generate enough, and the correct ratio of, photons?

Are the valuable photons going where they are needed, and how efficient is the luminaire at generating those photons?

When it comes to the future of horticulture, LED lighting offers a more robust food supply. And there are no doubt other advantages that have yet to be discovered.

Sources: www.ledil.com; www.ledsmagazine.com; www.specgradeled.com

Horticultural lighting in South Africa

South African lighting manufacturer, Giantlight, is at the forefront of horticultural lighting in South Africa and has recently released two products specifically catered for this market; GrowLED Maxi and Megaledbay GrowLED. The Megaledbay GrowLED offers broad spectrum white LEDs with far red on a separate, switchable circuit with a pendant cable with a clutch for easy suspension and height adjustment.

Specifications include:

  • Body construction: Powder-coated mild steel. Available in SS on request.

  • Lens type: 4 mm Polycarbonate

  • Supply voltage: 230 V ac 50 HZ

  • Total circuit load: 100 W plus 10 W when far red is activated (110 W total). 200 W plus 20 W when far red is activated (220 W total)

  • Lumens: 100 W – 13 600 lumens for broad spectrum white

  • 200 W – 27 200 lumens for broad spectrum white

  • IP rating: IP 65

  • Control type: Standard - no control, on or off 1-10 V control available. DMX control available, DALI control available

  • Power factor: Better than 0,97

GrowLED Maxi specifications:

  • Body construction: Powder-coated mild steel. Available in SS on request.

  • Lens type: 4 mm Polycarbonate

  • Supply voltage: 230 V ac 50 HZ

  • Total circuit load: 408 W

  • 430 W – With far red

  • Lumens: 59 560 (Broad spectrum white)

  • IP rating IP 65

  • Control type: Standard – no control, on or off

  • 1-10 V control available

  • DMX control available

  • DALI control available

  • Power factor: Better than 0,97

 

www.giantlight.co.za

Contact Lighting in Design

Title: Editor
Name: Gregg Cocking
Email: lighting@crown.co.za
Phone: +27 11 622-4770
Fax: +27 11 615-6108

Title: Advertising Manager
Name: Carin Hannay
Email: carinh@crown.co.za
Phone: +27 11 622-4770
Fax: +27 11 615-6108

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