LED Grow Lights Guide

Indoor Plant Lights: Device and Working Principle

Before we start thinking about how efficient LED lighting is, let us review different types of plant grow lights and their working principles. Lights for growing plants can be in various form factors, but the main difference is the way of heat dissipation from LEDs, i.e. cooling method. Any type of LED plant lights has their advantages and disadvantages. No matter what form factor and cooling method, any plant grow lights working principle is same.

Let’s see what modern LED Grow Light consist of:

LEDs

As a rule, LED grow light consist of several dozens, or even hundreds of LEDs. The more LEDs there are in a LED light, the higher its power and more efficiently it lights the plants beneath. LEDs may vary in power, PPF, efficiency, as well as spectrum.

LED modules

LEDs assembled onto PCBs are called LED modules. During a production of professional LED grow lights manufacturers usually use metal core PCBs, mainly having aluminum or copper core. This is done to effectively transfer heat from LEDs to a cooling system.

Cooling system

The application of the cooling system is to transfer heat from an LED. This is a very serious issue in LED industry. The top side of LED emits almost no heat, whereas the heat is transferred through heat slug to heat sink. LED light housing can serve as a heat sink, or heat sink may be placed into LED grow lights housing. Aluminum works as a heat sink, as it has high thermal conductivity and has excellent heat dissipation characteristics. Let us look at what kinds of heat sinking methods exist now.

We can point out several cooling methods in LED grow lights:

• Passive Cooling. LED Lights for growing plants with passive cooling have a number of advantages compared to active cooling. The first and most obvious advantage is longevity and simplicity. With passive cooling, while developing an LED luminaire for plants engineers do thermal simulation for LED housing. To passively cool high power LED grow lights the housings must have very large surface and sometimes intricate form.
• Active Air Cooling. LED luminaires with active cooling are more complex. To dissipate heat into the air usually aluminum heat sinks are used together with fans, This kind of heat dissipation has both pros and cons. Low weight and small size of high power LED grow lights are the biggest advantages of this kind of cooling. The disadvantage is the higher complexity of the system, and if the fan goes out of order your system worth several hundred dollars may be ruined.
• Water Cooling. This type of cooling allows us to get very high power and photon flux in extremely compact size. To dissipate heat from a very high power LED light, housing alone is not enough. Water is a good solution for this. The disadvantage of this type of system will be the complexity of the system, as alone with electrical issues, plumbing tasks have to be tackled. This requires a whole plumbing work, pumps to make water circulate, chiller to cool the heat. Nonetheless, this type of cooling is a great solution in contained environments like climate chambers, or trendy now shipping containers for growing vegetables, as it allows to get most compact luminaires with high power and decrease degradation of LEDs.

Power supply and control systems

All LED components of a plant lamp are assembled onto a circuit board and connected to power supply. To control spectrum, different channels of the circuit are dimmed or switched off. Power supplies may be either built-in or remote.

Secondary optics

LEDs have a quite wide emission angle, usually 120deg, although some exotic angles like 80 or 150deg also produced by some manufacturers. Secondary optics are used in LED grow lights only in the case when the manufacturer wants to focus the beam on a certain surface thus increasing PPFD. This is not good on a large scale project, as uniformity and cost of the project will be compromised.

What to Pay Attention to When Choosing LED Plant Lights?

While choosing LED Lights one should take into consideration plant needs and specifics. If light loving plants are given insufficient light then its fruiting activity is greatly reduced. Same situation with shade-loving plants. The plants can be categorized into groups:

• Long day plants;
• Short day plants.

In the first case, the lighting should last at least 12 hours a day, while in the second case 8-10 hours. It should be noted that plant development stage should also be considered, as seedlings do not need as much light as for example flowering plant.

LED Grow Lights for Growing Cannabis

What is the best light for growing cannabis? How to chose LED grow light for growing cannabis from the wide variety on the market? This is the question many beginner growers ask. Let us find out what LED lights are best for cannabis cultivation.

Every grower wants his plant to look healthy and have good yields. For this, cannabis should not only be supplied with the needed amount of heat, humidity, and fertilizers, but also with optimal lighting. Light is one the key factors of successful plant growth, photosynthesis directly depends on the amount of light and its quality.

It’s a fact that different strains of marijuana require different light duration. To make photoperiodic strains of marijuana transfer from vegetation to flowering stage, lighting mode should be changed. Traditionally in the vegetation period, the lights are supplied with 18 hours of lighting. In theory, if light deprivation is not used, then photoperiodic marijuana will not go to the flowering stage. In natural conditions, cannabis will flower at shortening daylight. If you grow cannabis indoors, it will flower after you change lighting mode to 12 hours light and 12 hours of darkness.

Autoflowering breeds of cannabis do not depend on photoperiod and will flower according to their genetic data. Growing autoflowering sorts indoors, most growers prefer to stick to 18/6 lighting mode during the whole life cycle. Despite autoflowering breeds do not depend much on lighting mode, there is data proving spectrum is crucial for them. With blue shifted light during vegetation, vegetative growth is stimulated. On flowering stage, more shift should be done on the red part of the spectrum, this will enhance flowering and you will end up with more generous yields.

Mistakes that people make in cannabis lighting.

It’s a fact that light is important for plants, however, it needs within certain limits that are called DLI (daylight integral). Excess or deficiency of light is harmful to plants.

In the first case, the plants will stretch, bend and warp. As a result, long and weak stems cannot bear the weight of the buds and spend extra energy for delivering water to leaves, although they could spend that energy on extra flowers. As a result, 30-40% of crops are lost.

In the case of light oversaturation, the plants will have light burns. At light burn, part of chlorophyll is decomposed and leaves turn yellow and dry, the plant growth and development slows down or stops. This is most common when light sources are placed too close to plant tips.

Grow Lights for Seedlings

We should point out that supplemental lighting is crucial for seedlings in greenhouses.

• Firstly, special models of lights that are designed for quick young plant development allows obtaining more sturdy seedlings within a shorter period of time.
• Secondly, it’s easy to control LED assimilation lighting so it’s easier to control daylight integral.
• It is very important that LED grow lights do not emit much heat, so there is no risk of damage to plants owing to high temperature.

Cost of LED Grow Lights

Among the technologies that are used for greenhouse lighting LED technology is most economic. LED grow lighting cost a lot, but they break even quickly due to several reasons:

• LEDs consume up to 60% less electricity.
• Their lifetime is several times longer than other technology.
• They are very robust and hard to break, which is not true with conventional lamps.

Why Should You Use LED Grow Lights?

Artificial lighting can control plant development, accelerate or hinder flowering, shift harvesting time. Once you extend daylight the long day plant development will accelerate, which means the crops can be earlier delivered to the market. On the contrary, extending daylight will slow down flowering of short day plants. LED grow lights are perfect for these tasks.

LED lights for plants will allow to maximally mimic sunlight. This can be done during all life cycle of your plants.

The thing is, that LED luminaire spectrum for plants is very similar to sunlight, therefore up to 96% of light is used by the plants. An additional advantage is that harmful wavelengths are not emitted by the luminaire.

And the main advantage of LEDs is that they provide the plants with needed spectrum. It’s best for their development and growth.

Advantages of LED Lighting

The advantages of LED grow lights are:

• Lower power consumption compared to MH or HPS;
• Low heat emission;
• Full spectrum available;
• Longevity- up to 50K hours;
• Possible to use as supplemental lighting;
• Low weight and size;
• Easy to install;
• Can be automatically controlled;
• High energy efficiency;
• Environmentally friendly- no mercury or other harmful or hazardous substances.

Disadvantages of LED Grow Lights and Application Peculiarities

Still, although the advantage list is so long, LEDs are not commonly used for greenhouses.

What is the reason?

• The first disadvantage is the high capital cost of LED grow light equipment. LED luminaires cost 3-5 times more than similar products with alternative technologies, and not so many companies are ready to such investments.
• The second disadvantage- LEDs still degrade by up to 10% within 2-3 years.
• If you need to do large area supplemental lighting, e.g. greenhouse, you will need more lamps.
• Heat dissipation is problematic, and in closed surroundings, like climate chambers, you still have light emission for LED grow lights, and this heat needs to be transported from the chamber outside.

Full Spectrum LED Grow Lights

We should separately mention Full spectrum Grow Lights. These lights have optimal spectrum for plant growth, flowering and fruiting. Full spectrum LED grow lights are assembled with modules that have an optimal amount of light in PAR spectrum.

Advantages of Full Spectrum LED Grow Lights:

• The transition from narrowband LEDs to full spectrum LED in the range 400-740nm, that looks closer to sunlight.
• Full spectrum is good for all stages of plant growth which was not the case with narrow band LEDs.
• The problem with the simultaneous growth of plants in the different development stage is solved.

These advantaged of full spectrum LED grow lights afford us to come close to sun light quality.

Effect of Wavelength on Plants

Sunlight spectrum consists of different wavelengths, and the plants use some of them