The right intensity, spectrum, and ratio are some of the biggest success factors that make you more likely to reach potential yield in indoor ag, according to HortiPower research. Good lighting design practices remain relevant as well. LIGHTSCRIPT is an approach to sustainable and effective horticultural lighting design, and helps you to grow well.
Understand the success factors that you can evaluate and follow the tips to maximize plant-growth outcomes.
by Jille Kuipers and additional input from Meng Meng Wang
Table of Contents
L is for Luminaire.
Luminaires are designed by a manufacturer for a certain lighting application/ installation. E.g. characteristics such as light output and beam angle are designed for ideal template scenarios and customer requirements. The main criteria for luminaires are output, quality of light, beam-angle, physical dimensions, efficiency, installation method and controllability.
The output should be listed in both lumen and micromole. The quality of light includes metrics such as CRI, CCT, and spectral distribution. Beam-angle and photometric info help to make simulations of lighting design before the actual installation. The efficiency of the luminaire determines to a large extent the efficiency of the overall lighting installation. Installation can be another significant cost factor and should be as fast as possible, with as few steps and tools are possible. The controllability of the fixture refers to dimmability, spectrum control, daisy chain and cloud control.
What are some examples of a ‘wrong’ luminaire choice?
For example, we visited a tissue culture lab in 2019. This lab was using high-end grow lights, however the tissue culture didn’t seem to like it. The problem was that this fixture was made for a much larger ‘free height’ (distance between the cap of the tissue culture to luminaire). This fixture should be installed at a larger height, however the shelves were about 30cm in height to optimize space. And at a lower height, the light effect was too intense and the lighting distribution was poor. A possible solution would be to lower the power and output. In this case, the luminaire didn’t allow for dimmability and it had to be replaced which fixtures that are more modular and flexible.
Choose a luminaire that is designed for your application (i.e. tissue culture, indoor farming, greenhouse etc).
Another common example are green walls. In architectural lighting wall grazers or wall washers are great luminaire choices for illuminating a wall. However a greenwall with plants requires a different kind of lighting effect, with more light on plant leaves. Often with architectural luminaires the plants are likely to die off. The light output and spectrum were not correct, but most importantly the beam angle of the luminaire was too narrow. They should either use a wider beam angle or install at a further distance so that the light can reach further without being blocked by the first row of plants.
The optical design of a luminaire will determine how the light is distributed. Lighting simulations can help visualise and compare alternative proposals.
It is important to distinguish between the lighting effect in the space and the lighting fixtures (aka luminaires). A luminaire is the lighting industry’s term for a light fixture, and it is defined as a complete lighting unit that includes a light source, together with the housing and a connection to a power supply. Lamps or light sources need to be installed in luminaires. With LED, luminaires often have an integrated light source. Sometimes people compare component efficiency such as LED chip vs fluorescent, but it is important to compare on the luminaire level (which includes factors for power loss etc).
I is for Intensity.
The required intensity should be simulated on the plant leaf level. Ideally, the lighting intensity is uniform, without any darker or brighter spots. Uniform lighting helps to achieve uniform crop growth. Different arrangements of luminaires (spacing, height, axis) can make a lighting design more efficient and consistent. Attention should be paid to spill light and reflectance.
Getting sufficient lighting to your plants is essential for photosynthesis and photomorphogenesis. And it should be measured in micromoles.
G is for Goal.
The goal is set by the grower. A facility focused on production requires different lighting compared to one with a focus on research. It is important to understand a bit about the business goals. What crops are grown? Will crop varieties change in e.g. a year's time? What are cultivation challenges? Are there any constraints (e.g. max. energy use, heat gains, cooling). Are there different growth stages? Is the initial price/ budget important? Is the space a productive and comfortable space to work in?
For example: for urban farms marketing is important (either by visual tours around the farm, or photos and live streams). Purple grow lights are therefore not great as they make the produce look dark. We would prefer to propose lights that are great for plants and allow for good visual inspection, staff eye comfort and media use.
The right lighting strategy can help you achieve your business and crop goals.
H is for Hours.
The intensity of a plant is measured in μmol/m2/s. This is a spot measurement and it is important to know the operating hours of the facility. In most cases, lighting should integrate with the normal operating hours of the facility and follow natural sunrise. The photosynthesis and photomorphogenesis of plants are influenced by the duration of lighting hours. For production facilities, it also helps to calculate the DLI (daily light integral). Some plants can also be triggered into earlier or delayed flowering with critical night-time duration.
During the day plants can photosynthesise and at night they need rest and respire. Getting the right operating hours per day can support plant-growth and development.
T is for Type.
Each crop variety or type can have slightly different preferences and lighting needs. These needs also evolve during the crop lifecycle. For common crops, we have lighting guidelines. It is recommended to run A/B experiments and trials. Over time these incremental adjustments and improvements can help you increase the profitability and consistency of your indoor growth facility. This brings us to our next factor.
Each crop and growth stage might need a slightly different kind of light. E.g. in some stages lighting could focus on vegetative growth, in other stages on flowering, fruiting, elongation etc.
S is for Spectrum.
Plants see light differently compared to humans. The photoreceptors of the plants are very sensitive to red wavelengths, blue wavelengths and to a lesser extent green/ yellow wavelengths. Different spectra can help you achieve different outcomes such as compact growth, or elongation, more flowering, better rooting (and nutrient intake), etc. The spectrum ranges from 350 to 780nm. Note that the human eye is most sensitive to light around 550nm (which is the green area) whereas plants are least sensitive to light. Hence light that appears bright to the human eye, might not be bright for plants and visa-versa.
In most cases, it is important to have a large amount of deep red in your spectrum. Note that pure 'white' lights often feature very little of deep red, which makes them a suboptimal choice for plant-lighting. Use plant-centric lights.
C is for Color.
With color we refer to the color as defined by CIE that the human eye perceives. As mentioned under the Goal, it is important to have good or excellent light for visual tasks such as crop inspection, harvesting and more. In some countries there are increasingly guidelines for a minimum percentage of green light, so that grow lights do not appear too purple. Pure purple lights can lead to dry eyes and discomfort. When we design an indoor grow facility we would like to know about staff presence and the tasks that they perform so that we can design proper lighting for plants and people.
Well-designed grow lights can be good for plants and visual comfort of people.
R is for Ratio.
With ratio, we mean the ratio of colors within the spectrum. Optimizing this factor can increase yield and support plant development and growth in the way that you would want. In some cases, less light with a better ratio between colors can lead to a superior effect. In natural daylight, the ratio’s between colors is very even around noon-time. However in the early morning and late afternoon, there are big variations in colors, for example in the far-red region.
Optimising the ratio is recommended for greenhouses, farms and laboratories that are leading in their field or aspiring to lead.
I is for Installation.
Space in indoor facilities is scarce. Installation should be easy, fast and long-lasting without too many separate or moving parts or parts that can generate heat or trap dust and insects. Sleek, smooth and slim surfaces help to avoid dust collection. The unboxing is also part of the installation and it should be as fast as possible. We prefer master box packaging for professional projects rather than individual packaging as it saves material and labor time.
Installation should be hassle-free and ideally within seconds with minimal use of tools and packaging. For tissue culture and indoor farming, check the height of the luminaires including cables. For greenhouses, check the width of the luminaires and if it blocks natural daylight from coming in.
P is for Power.
It is important to check the total power consumption of the whole installation and to check if the building's electricity connection can support this. Power consumption should be as energy efficient as possible as energy cost is a substantial operational cost item.
Use luminaires that are energy efficient. And a lighting design that is energy efficient. Note that luminaires tend to be more efficient if the wattage is higher than e.g. 40watts. However these fixtures often require an installation height that is higher to spread the light. Therefore light can be hanging in the air and using a fixture that uses less power and can be installed close to the plants might be more energy efficient.
And external power supply and cabling can also lead to inefficiencies.
Another important factor is the heat gain of lights. While the light beam of an LED is cool, the LED chips dissipate heat to the housing or internal heatsink. A luminaire that is well designed takes this thermal management into account. Another point to note here is the Law of Conservation of Energy which simply states that energy is not created or destroyed but can change its form. Hence it is important to calculate the cooling capacity that is required with the amount of wattage that you bring into the room.
Efficiency of the luminaire should be ≥ 1.9 µmol/J according to DLC and other norms. Check the total power that is used in the whole installation. Take potential heat gains into account.
T is for Tried & Tested.
Every grower and growth environment is slightly different. We therefore recommend doing a pilot or A/B trial so you’ll know what result you are getting with your crop. We often recommend an A/B trial between current lights and e.g. HortiPower lights so the grower can see what difference it makes. Using your own growth data and observation is more trustable and relevant than what somebody else can grow in a completely different setup.
Try out before your roll out. In particular if you're growing (or planning) on a large scale it is recommended to make a mock-up installation and see how your plants respond to a new lighting plan.
Well, that wraps up our LIGHTSCRIPT approach. If you have specific questions feel free to let us know.
Below is a lighting plan, if you're thinking of expanding your farm or replacing your current lights feel free to reach out to us by email or arrange a zoom/ teams meeting with us.