The most common use of supplemental lighting in greenhouses is to extend the photoperiod for plants during the winter months. Turning on the lamps for a few hours in the evening gives the plants as much free sunlight as possible, while at the same time providing a supplement of light.
Although its use is common in the winter season, there may be cases where it is also used in summer for greenhouses with intensive production programs. E.g; A cloudy summer evening can sometimes leave plants without light as much as in winter.
The main purpose of supportive lighting is to increase the sun exposure time when the plants cannot sunbathe naturally; to increase crop quality and shorten the harvest time. Thus, it will be possible to meet the planned production targets in greenhouses.
What Types of Supplementary Lights Are Used in Greenhouses?
Supporting lights commonly used in greenhouse cultivation; Compact Fluorescents are HPSs and LEDs. These three different types of light; light qualities (the wavelengths they produce), light intensity, efficiency (how much light the lamp produces for each unit of energy consumed in watts), lifetime; and investment cost (preliminary cost) over variables such as comparatively.
Compact Fluorescent (T5)
Compact fluorescents (CFLs) are the bulbs we usually use in our homes. As grow lights, these are often referred to as T5. The T is tubular - long skinny bulbs - and the number represents the diameter of the tube. The larger the number, the larger the bulb size. T5s are the latest and most efficient of fluorescent bulbs (previous versions were T8s and T12).
The primary advantage of fluorescents is that they have a low upfront cost and are readily available. However, they typically have lower light intensity and lower efficiency than other types of lighting. This situation makes them rather than commercial production greenhouses; makes it suitable for growers looking to add some light to their garden or indoor growing environment.
Another disadvantage is the fixtures to which they are attached. These fixtures are often large and create unwanted shadows in a greenhouse during the day. This is why many growers use fluorescents only to germinate seeds. When plants are just starting to grow, they need less light intensity and fixtures (which don't produce as much heat as other types) can be placed very close to them.
After a few months or a year of use, the bulbs become less efficient and need to be replaced, making fluorescents more expensive in the long run.
With the innovations brought by the developing technologies in the lighting sector; compact fluorescents are no longer used in greenhouse lighting.
High Density Discharge (HPS)
As the name suggests, HPS lights produce very high light intensities. These are a larger investment used by commercial growers who often rely on artificial lighting. HPS lamps give yellow/orange light and growers generally prefer HPS lamps in environments where people do not need to work intensively.
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To better understand how intense light HPSs produce, we can make the following comparison: A 400-watt HPS lamp produces the same light intensity as ten 54-watt T4 lamps. Therefore, HPSs are rarely used for horticulture or indoor cultivation, except for certain crops that require high light levels.
HPS lights come with a few extra components, including a ballast to power the light, a reflector that directs the light towards the plants, and a fan to reduce the heat above the plants.
Light Emitting Diode (LED)
LEDs are the latest technology to enter the market among other types of lights. There may be cases where it is more expensive than others in terms of cost. Many types of LEDs offer much greater efficiency (they use less energy to produce equivalent light intensities).
There are several misconceptions about LEDs. One of them is that it produces lower light intensity than HPS lamps. The truth is they can produce equivalent light intensities but; they usually cost much more. Therefore, LEDs may not be the best option if light intensity is of primary concern. On the other hand; As a category, it is more efficient than HPSs, although it varies between certain types.
One disadvantage of LEDs is hot spots with intense light concentrations in the middle. Depending on the type, they may have difficulties in scattering the light homogeneously.
Unlike HPS lamps, LEDs produce almost no waste heat, so fans or vents are not needed. Also; they last longer and maintenance costs are lower.
Which Light Should I Use For My Greenhouse?
The answer to this question will of course vary for each greenhouse and for each enterprise. The best choice depends on your budget, spatial and climatic conditions, and most importantly your goals.
HPS systems have been used by breeders for a long time. Therefore, we can say that it has been tested and approved. They provide the highest light intensity.
Fluorescent systems would be ideal for small-budget businesses or gardeners or small spaces. It can also be used to germinate seeds. But as we mentioned earlier, this technology is no longer used today.
LEDs are above Fluorescents and below HPSs in terms of light intensity. Although they have a high price tag, they are more profitable because they consume less energy in the long run. On the other hand; Since they emit less heat, cooling costs will also be lower.