What is an indoor grow light?

What is an indoor grow light?

Published:19 Mar 2021

High-pressure lamps (HID) have been used in horticulture for more than half a century. Although LED technology is more recent and more efficient, HID lamps have come a long way in all these years. Today, the use of HID lamps, especially HPS lamps, are the most widely used in technical cultivation. Although the great advantages of energy efficiency and a tailored light spectrum make LED technology an option to consider.

How an indoor grow light works

The operation of grow lights, whether for indoor or greenhouse cultivation, consists of a discharge tube, which contains a mixture of different gases that generate electromagnetic radiation in the form of light when electrons pass through it.

For this to happen, these lamps need a ballast to start the ignition. During ignition, which lasts only a few milliseconds, the lamp receives a discharge of between 2500 and 5000 volts. This discharge converts the gas into a conductor and then drops to the normal operating voltage.

The importance of good lighting for indoor cultivation

In the process of photosynthesis, light plays a very important role. The higher the light intensity, the more nutrition the plant needs in its roots and carbon dioxide in the air. Light is like the accelerator in the development of the plant.

To get the maximum yield from a crop, adequate lighting is required.

A properly designed artificial lighting system adds great value to the production, allowing the chosen variety to be grown all year round.

Correct crop lighting requires consideration of 3 important aspects.

Depending on the type of crop, the lamps should have the right wattage to suit the needs of the plant and the growing area. The requirements for tomatoes are different from those needed for flowers.

In the case of photodependent plants, depending on the number of hours of light of the correct intensity, the phases of the crop will be controlled, from the vegetative stage to the fruiting or flowering stage.

Not all high-pressure lamp technologies are equal in colour. Their different colour spectra condition the morphology of the plant and therefore its production. Choosing the right spectrum for the different stages of cultivation of the plant favours the production and quality of the harvest.

How to light our growing space?

The distribution of the lighting equipment in the growing spaces is a critical point in order to obtain the maximum yield of the harvest.

These growing spaces must be homogeneously illuminated. Avoiding that some plants receive more light than others. To achieve this, the higher the lighting equipment, the greater the homogeneity and the lower the intensity. On the contrary, if we bring the lamps very close to the plants we will obtain a high intensity but there will be less homogeneity where not all the plants will receive the same intensity equally.

How much light does your grow room need?

It is important to note that in agronomy, light intensity is measured in micromoles per second per square metre µmol/s/m² o PPFD.

The amount of PPFD indicates the amount of µmol that a surface of 1 square metre receives every second.

Depending on the type of crop the required intensity is different:
Tomato: 150 – 360 PPFD
Cucumber: 115 – 355 PPFD
Pepper: 115 – 325 PPFD
Roses: 165 – 355 PPFD
Chrysanthemum: 100 – 225 PPFD
Strawberry: 65 – 145 PPFD
Medicinal Cannabis in Vegetative Process: 275 – 575 PPFD
Medicinal Cannabis in Flowering process: 600 – 1000 PPFD

The number of lamps needed in a crop will depend on the surface area of the crop, and the type of lamp used as well as the target harvest yield.

Lighting during growth in indoor cultivation

The vegetative process, also called ‘growth’, in plants with short photoperiods, occurs when the plant receives more hours of light per day than during the flowering process.

As the number of hours is greater, the intensity of light can be lower, hence the lighting equipment used in cultivation allows the intensity to be regulated, so that it can be adapted to the plant’s phases.

Lighting during flowering in indoor cultivation

The flowering or fruiting process of plants with short photoperiods occurs when the number of hours of light is less than the vegetative process.

The photosynthetic process is more demanding and the number of hours of light is lower. Therefore, the intensity requirements are higher.

Types of lamps for indoor cultivation

Lamps can be classified by their technology or by their connection.

HPS. High pressure sodium. They are the most widely used and offer greater intensity with lower energy consumption, they are more efficient. They enhance the flowering processes due to their greater amount of reds.
MH. Metal halide. They are less energy efficient. They are used in seed germination and vegetative processes as they provide a greater quantity of blue.
CMH. Ceramic metal halide. This is the most recent technology, and although it does not reach the energy efficiency of HPS, it does have a balanced spectrum between blues and reds, being suitable for full cycle crops.

DE. Double Ended. These are double ended lamps that use the K12X30s lampholder. Usually used for 1000W lamps that are installed in luminaires.
Conexiones DE
E40. These are lamps with a threaded socket. Typically used for 600W lamps.
PGZX18. Usually used in 315W CMH lamps.

How to choose the best lighting for a crop

Not all growers have the same crop management, nor do they all have the same demands. This conditions the level of economic investment allocated to each project.

Fortunately, there are several technological solutions, with different levels of investment. So there are several options to choose from.

Generally speaking, making the right choice for the best lighting involves choosing the most energy-efficient lamps, reflectors and ballasts, both in terms of energy and design.

At present, 1000W luminaires and Double Ended lamps are the best alternative as they combine all these features with a moderate level of investment.

However, for many reasons, LED lighting equipment has achieved superior results with even lower energy consumption, but with a much higher level of investment.

Best lamps for indoor growing

There are many lamp options. Which will depend on the area, the plant and the harvesting objective.

For use in small growing areas and with low production requirements, CMH is more suitable, although it is less energy efficient than HPS, but offers a better spectrum of light that helps to obtain a higher quality and lighter weight fruit.

For use in large growing areas, where productivity is most important, choosing lighting systems that incorporate more energy efficient lamps is the right solution. In this case, lamps with HPS technology of the Double Ended type are the best option.

Tips and rules for placing the lights for our crops

– Consider the maximum power of your electrical supply point. If necessary, ask your supplier for advice.
– Plan your growing area correctly, without having excessive spaces between plants, lighting an empty corridor costs money.
– Choose the right wattage and type of lamp.
– Install the lamps at the correct height depending on their anchorage points, the area and the type of crop.
– Always choose the most energy efficient lighting systems.