Lighting in Design Q1 2019

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 evenmore so in LED-based horticultural lighting where experience with SSL technology is still shallow. Lighting manufacturers based in Asia have tar- geted 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 per- formance – in early attempts to deploy LED lighting. However, documented benefits of LEDs in horticulture continue to grow, and include the Mi- rai lettuce farm in the city of Tagaj ō 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

Horticultural lighting terms Photosynthetic photon flux (PPF): This comes from the total amount of photosynthetically active radiation (PAR) that has the most effect on how strong plant growth will be. More PPF means more photons and more power, and this value is easily measured and used as a parallel to lumens. Photosynthetic flux density (PPFD): How many of the photons hit their target, and this can be related to lux levels. Top lighting – Greenhouses: Illumination of the hall and plants from ceiling level. Top lighting – Vertical farming: Illumination from the top of the plants at a close distance.

Intra-canopy: Illumination on the side or in-between the plants.

(METI) encouraged the use of technology on the farm, which uses customised sensors and control systems for all aspects of the agricultural environ- ment. 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 m 2 of floor space and there are 17 500 LED lights in use. The lettuce is

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LiD Q1 - 2019