What do you need to know before purchasing a lamp for horticultural lighting?

Lamp selection when speaking about plant production in the horticulture or floriculture field is a very important decision. Lamps can be a good investment when we ask ourselves the correct questions. When working with artificial lighting we first need to analyze the requirements of our growing system and our crop.

A clear example are the different needs from an indoor vertical farming system in comparison with top lighting inside a plant factory or a greenhouse. Vertical farming is mostly used for leafy greens production. In vertical farm indoor system plants are grown in a multi layer system where height between plants and lamps allow the use of multiple lamps with a lower photon flux in comparison with the ones required at the top of greenhouses or plant factories where photon flux should be way higher in order to reach plant canopy levels at higher distance and provide enough light per day to optimize plant growth.

Another option in the use of artificial lighting is the use of photoperiodic lighting. In some plants flowering can be triggered by short or long day conditions. Therefore some growers can be interested in the use of artificial lighting to create an artificial photoperiod to promote or delay flowering in different crops. Plants can have a response to photoperiod from very low light intensity levels. Meaning not a lot of light is required in order to promote a photoperiodic response. When your objective is mainly to create an artificial photoperiod for your plants you can go for a more simple lamp which can provide low light intensity levels. This kind of lamp will not have a strong impact in plant growth but will provide enough lighting to induce a photoperiodic response.

Lamps used for indoor vertical farm systems, top lighting and photoperiodic lighting can have very different characteristics and prices. Therefore it is crucial to define which lamp will be the one necessary for you based on the lighting necessities for your plants and your growing system.

Vertical farmingTop lightingPhotoperiodic lighting

Once you define the type of lamp required then comes the most difficult decision. You will encounter several options for vertical farming, top lighting and photoperiodic lighting. How can you decide which is the best option? What should you be looking for in a good lighting system?

A lamp with a good design, can definitely mark the difference in energy savings and overall plant growth and health. But where can you look for information in order to compare different lighting options?

DLC (Design Light Consortium) is a third party verifier of light specs. DLC is a non-profit organization whose mission is to achieve energy optimization by enabling interconnected solutions with a focus on quality for people and the environment. By visiting the DLC website (https://www.designlights.org/horticultural-lighting/technical-requirements/) you can learn the minimum technical requirements for horticultural lighting. Also DLC has tested and reported different LED lamps used in Horticultural lighting and has provided a list of reliable and efficient lighting options for Horticultural lighting included in their DLC Horticultural Lighting Qualified Products List (QPL).

Technical requirements for horticultural lighting include information about: Photosynthetic photon flux, spectral quantum distribution, photosynthetic photon intensity distribution, efficacy, long-term performance, warranty, electrical performance and safety.

Let’s explain why each of these parameters listed by DLC are important and which are minimum requirements stated by DLC:

Photosynthetic photon flux (µmol/s): Will provide you information about the “lamp power”, meaning how is the total output of the product per time including the light within the spectrum that is recognized to be used by plants in photosynthesis (Defined by ANSI/ASABE S640 for PPF: 400-700nm).

Spectral Quantum Distribution (µmol/s•nm): Provides information about how much light are you getting from a lamp but now linked to light quality. Specifically provides information about how photon flux is distributed across the  wavelengths used by the plant for photosynthesis (400-700 nm) and the far-red wavelength (400-800nm) which can also have an impact in plant metabolism.

Comparison of lights, data from DLC

Efficacy (µmol/J):  Is calculated using data about the lamp output (Output of the fixture over the specific range of wavelengths defined by ANSI/ASABE S640) and electrical input. Efficacy will basically tell you how efficiently your lamp is performing. DLC states that in order to consider a lamp reliable and efficient efficacy levels should be 1.81 μmol/J or higher.

Long-term performance: Can be measured by evaluating the ability of the device to maintain its output (Measured in quanta of photons, Q) within the given ranges over time. This can be also called: Flux Maintenance. DLC set a standard to consider a lamp reliable based on their long-term performance evaluation: Q 90 of ≥36,000 hours within the PPF range (400-700nm).

Warranty: Provides a guarantee from manufacturer regarding the condition of its product and can state the reparation or replacement of product during the warranty period. DLC states a good lamp manufacturer should provide at least a warranty of 5 years, including terms and conditions excluding key components such as the LED, driver or optics.

Comparison of lights, data from DLC

Electrical performance:

  • Power factor: Defined as the cosine of an angle between current and voltage of an Ac circuit At lower power factor, higher is the load current and vice-versa. Power factor is important because you may be paying for reactive power that you cannot use to power equipment. DLC states LED lighting for horticulture use must have a measured power factor of ≥0.90 at any rated input voltage and maximum designed output power.
  • Total Harmonic Distortion, current (THDi): Is a measurement that tells you how much of the distortion of a voltage or current is due to harmonics in the signal. Is considered  an important aspect in power systems and it should be kept as low as possible. Lower THD in power systems means higher power factor, lower peak currents, and higher efficiency. Based on DLC technical requirements LED lighting for horticultural practices must have a measured THDi of ≤20% at any rated input voltage and maximum designed output power.

Another important aspect when selecting an option for LED lighting for horticulture is the specific information about the manufacturer: How much experience do they have? How long have been in the lighting business? This information can be linked to how efficient and complete service they can provide. Horticulture lighting can be a high investment, always look for a manufacturer that can provide enough information about their lighting system (All aspects listed above) and can assist you with light spectrum selection and light plans. Light plans will always be a good tool to understand your lighting systems, number of fixtures and light uniformity over your plants.

The more research you can do evaluating all the aspects presented in this article, the more complete lighting system you will be able to acquire. In Hort Americas we offer you a complete service starting from our advice on the best light system from your project, recommendations on light quality, light plans along with all the technical service to support your success.

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