001Have you had a chance to see Disney’s animated film Zootopia? Rated one of the top 10 films of 2016 by the American Film Institute Awards, Zootopia follows the devious plot of the Assistant Mayor of Zootopia, a sheep named Bellwether, to overthrow the city’s Mayor, a lion named Lionheart. Bellwether orders her henchmen to inject a serum made from Night Howler flowers into the city’s predators, causing them to become violently aggressive. As intended, panic ensues, and the villainous Bellwether nearly achieves her goal of usurping power.

002But wait a moment — did you happen to notice how Bellwether and her cronies grew the Night Howler flowers? It turns out that the writers and producers at Disney knew about one of the latest advances in horticulture: LED-powered “plant factories”. In Zootopia, Bellwether secretly turns an abandoned subway car into an underground plant factory powered by LED lights to grow the Night Howlers.

So how exactly did this LED-powered plant growing technology work?

As we all know, plants undergo a process called photosynthesis in order to obtain energy to grow — and different types of plants often need different amounts of light to survive. In turn, this means that different plants and growing conditions may require different types of artificial light sources. So what does it take to design effective LED-based grow lighting systems? Let’s take a closer look:

1. Light Spectrum Quality

004Compared to other organisms, plants are the most sensitive to light exposure. The wavelength range in the light spectrum that most plants need to survive roughly corresponds to the visible light spectrum of humans —around 400 to 700 nanometers (nm) — and this is precisely the range in which photosynthesis occurs. In other words, plants will absorb any photons within this range and then undergo photosynthesis. However, not all wavelengths can be absorbed, and certain wavelengths are more readily absorbed than others depending on a plant’s particular pigment type.

In terms of practical applications, a suitable illuminating light source must be selected that meets the specific growth, wavelength range, and peak wavelength requirements of each plant type and also accounts for different growth cycles and light spectrum absorption rates for a single plant type.

So, how do we identify a plant’s particular wavelength range and peak wavelength in order to choose a suitable illuminating light source? These parameters can be identified in a laboratory, but an even better option is to conduct an on-the-spot test using your very own handheld spectrometer.

2. Optical Density and Irradiation Time

005When it comes to lighting for plants, is more always better? On the contrary, going to one extreme can lead to the opposite effect! Just as humans are satisfied on a full stomach, plants only need a certain amount of light before becoming satiated.

There is a limit to how much optical density a plant needs —this is known as its “light saturation point”.

When optical density reaches a plant’s light saturation point, the plant’s ability to undergo photosynthesis will hit a peak. Likewise, when optical density exceeds a plant’s light saturation point (a phenomenon known as oversaturation), the plant’s ability to undergo photosynthesis will decline rather than increase; this causes the plant to begin a reverse process called photoinhibition.

In traditional lighting applications, light energy is generally measured by luminous flux and luminance, whereas irradiance or photosynthetic photon flux density (PPFD) correspond to the optical density of lighting for plants.

PPFD values can be measured in real-time at the site of a plant growing operation to tell us whether a plant is receiving enough light.

A specific irradiance period can be designated for an LED plant growing light which matches the plant’s growth requirements, and the overall lighting cycle can be controlled automatically at the flip of a switch. This is where the Lighting Passport — the world’s first smart spectrometer — comes in. The Lighting Passport features specially-developed smartphone apps for agricultural lighting applications, giving users total control over the lighting parameters for the entire growing process.

In contrast to traditional measuring instruments, a smart spectrometer is capable of remotely collecting statistical data through the convenience of a smartphone setup.

In addition to being able to take multiple readings 24 hours a day which are used to calculate daily light integrals (DLIs), the Lighting Passport can also generate daily “Smart Logs” for tracking plant growth.

3. Optical Uniformity in Lighting Designs

006In buildings, optical uniformity is a fundamental part of lighting design to help prevent irregular lighting. In the case of plant growing operations, it turns out that optical uniformity is also critical.

LEDs have a strong directional nature which can result in sharp contrast between illuminated and non-illuminated areas as well as uneven fluctuations in color temperature. Because plants can’t reposition themselves, optical uniformity is a critical element of lighting design for any plant growing operation. Evenly distributed light ensures that plants will, regardless of their position, absorb an equal quality and quantity of light. Optical uniformity also helps prevent discrepancies in terms of size, rate of growth, and rate of photosynthesis of a single plant type.

When it comes to the optical uniformity design of a lighting system, there are two important factors to consider. First is the consistency of the colorimetric characteristics of the LED light source (i.e., consistency in the radiation spectrum). Second is the light distribution of the LED (i.e., irradiance uniformity). Together, these two factors will result in a high degree of optical uniformity, ensuring that plants grow together at a consistent and uniform pace.

Now that we know about the numerous features and benefits of the Lighting Passport, only one question remains: how do we get our hands on one? The Lighting Passport may be purchased from any genuine Asensetek distributor and, as always, we encourage potential customers to contact us directly for more information.

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Zootopia : They “plant” out with lights!
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