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FEATURE ELECTRICAL EQUIPMENT


LED lighting: the unsung hero of indoor vertical farming


and red for special light combinations are also available. And, thanks to the latest technology, efficiency levels as high as 3.779 μmol/J and 3.91 μmol/J can be achieved in vertical farming applications. There is also a good choice of midpower


By Safa Demir, product sales manager Opto at Rutronik I


ndoor vertical agriculture, also known as high-rise vertical farming, is one of the


most promising solutions to one of the biggest challenges our planet face: food insecurity. As food shortages become more likely in the light of climate change and population growth, vertical agriculture can offer a viable alternative to conventional agriculture, using a fraction of the water and land resources. This highly innovative way of growing


crops is made possible by the latest LED lighting technology. As they emit very little heat, LEDs can be placed near plants without burning them, serving as a surrogate for sunlight. This means that crops can be stacked vertically and grown virtually anywhere, including buildings in urban areas. The success of vertical agriculture


largely depends on selecting the correct wavelength spectrum, which ultimately makes photosynthesis possible. Only wavelengths of 450 nm, 660 nm, 730 nm and some green light in 520 to 550 nm affect photosynthesis. And, depending on whether the plants are at the germination, vegetative or fertilisation stage, a different light composition may be necessary. This is particularly true for indoor facilities where natural sunlight is completely absent. The wavelengths must also be adapted to the purpose of the cultivation. This may, for example, depend on whether the plants need to grow quickly or slowly, whether flowers are the focus or whether particularly


20 MAY 2020 | ELECTRICAL ENGINEERING


large or abundant fruit is required. When applied individually many colour spectra do not contain a particularly high proportion of photosynthesising light waves. When combined with other wavelengths


in the correct proportions, the photosynthesis light rate increases. The mixing proportion must resemble the wavelengths found in natural light. For example, as evening draws in, the optimum wavelength is 730 nm (far red) to prepare the plants for their night-time rest, while 450 nm (deep blue) and 660 nm (hyper- red) are required for photosynthesis. Different compositions of the light


spectrum can be achieved simply by varying the number of LEDs in the relevant wavelengths, without changing the design of the Printed Circuit Board (PCB) or the luminaries. However, a controller is required to be able to control the LEDs accurately and alter the mix ratio throughout the day. There is a wide variety of LEDs of many


different wavelengths that can be combined to assemble an individual horticultural board. High-power LEDs give maximum brightness and some of the latest technology offers varying illumination angles (80°, 120° and 150°) and a wide selection of colour spectra. For example, some of the products currently available on the market come in wavelengths of 450 nm (deep blue), 660 nm (hyper-red) and 730 nm (far red) as well as wavelengths of 450 nm (deep blue) and 660 nm (hyper-red). Colour spectra such as blue, true green


The success of vertical agriculture largely depends on selecting the correct wavelength spectrum, which ultimately makes photosynthesis possible


LEDs. Not as bright as their high-power counterparts, midpower LEDs are more affordable meaning they can be a great fit for consumer applications. And their efficiency rates are high enough to enable photosynthesis. Some of the most recent solutions such as purple LEDs provide a space-saving combination of photosynthesising 450 and 650 nm wavelengths. Besides LED emitting visible light, there are also components emitting ultraviolet wavelengths in UV-B (280–315 nm) and UV-A (315–400 nm). The key benefit here is that this technology can kill germs and, therefore, has the potential to extend the shelf life of agricultural products. In addition, they can improve the taste and colour of produce such as fruit. Once the optimal LEDs have been


selected, the next step is tuning the LED drivers accordingly. With large numbers of LEDs installed on horticultural boards, an efficient energy supply is required. A wide voltage range of 200 to 400 V and large breadth of current intensity from 400 mA to 1400 mA allow for a flexible board design layout and a good variety in the number of LEDs. It is also recommended to opt for NFC adjustable current intensity and optimised surge and burst capability at 4 kV. If the LEDs are also fitted with a secondary optic, the colour spectrum and the illumination angle of the light can be controlled more effectively. Depending on the density of the LEDs the light can be focused or scattered, meaning different light intensities can be achieved to meet the specific needs of specific plants. There is a good range of lenses with various illumination characteristics to choose from, which are compatible with many of the standard LED packages. With the global vertical farming market


set to grow tenfold by 2026, this new, sustainable way of cultivating plants is likely to play an important role in addressing some of the major challenges our planet face. LED lighting technology is at the heart of this trend and is will be key to ensuring its success in the future.


Rutronik rutronik.com


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