How do you calculate the power and quantity of supplemental grow light required for a greenhouse?

The following detailed methods will help us determine the power and quantity of additional grow light needed for a greenhouse, guaranteeing that plants receive enough light at various stages of development.

 

 

You first have to grasp the size of the greenhouse. Based on the greenhouse's height, width, and length, find the area accessible for more lighting. Should the greenhouse be a basic rectangle, the area comes out as follows:

M², the greenhouse area： length * breadth

Should the greenhouse be another form, the area can be computed using the relevant geometric formula.

 

 

 

Different light needs exist during various phases of plant development. Usually expressed in photosynthetic active radiation (PPFD, photoactive photon flux density), the power of the additional light should be chosen depending on the plant's light requirements. In μmol/m²/s, PPFD is the count of photons reaching the plant per second per unit area.

 

Requirements for PPFD at every level of development:

Germination of seeds: 100–200 μmol/m²/s

200–400 μmol/m²/s is vegetative development.

400–600 μmol/m²/s is flowering/fruiting.

500–800 μmol/m²/s for fruit ripening

 

The target PPFD in the greenhouse could change depending on the plant species and stage of development. Assume we have a target value, say 400 μmol/m²/s, which is what most vegetables and certain fruits in the vegetative development stage need.

 

 

Selecting a light source fit for greenhouse supplementary lighting takes spectrum, light efficiency, heat generation, and other considerations in addition to power and economy. The right light source will maximize plant development, lower energy use, and enhance illumination benefits. LED additional lighting is extensively applied in greenhouse farming. Several important considerations should guide your decision on a light source:

1) Choice of spectrum

Distinct wavelengths of light call for distinct requirements from different plants. Blue light (40–500 nm) and red light (600–700 nm) are the primary spectral areas for plant photosynthesis; they most influence plant development and flowering. Thus, selecting LED lamps with full or tailored spectra will enable plants to obtain the necessary light at several phases of development.

 

Full-spectrum LED bulbs replicate natural sunshine, usually offering several wavelengths from blue to red light. The ideal option for greenhouses is either full-spectrum LED lamps or a tailored spectrum (optimized depending on plant development requirements).

 

2) Light efficacy (μmol/J).

Measuring the efficiency of light sources-the quantity of photosynthetic active radiation (PAR) produced per watt of power input-requires consideration of light efficiency. Usually higher than conventional light sources (such as high-pressure sodium lamps, fluorescent lamps, etc.), LED lamps with the same power can produce more photosynthetic active radiation, supplying enough light for plants and saving energy.

 

Common ranges of LED light efficiency span 2.0 to 3.5 μmol/J. Selecting LED lights with a power of more than 2.5 μmol/J will help guarantee the effective use of light sources for greenhouse fill-in lamps.

 

3) Energy efficiency ratio and choosing of power

Varying plants need varying light intensities and exposure times. Hence, it is imperative to select lights with the correct power. Usually expressed in watts (W), LED fill-in lights have a common power range spanning tens to hundreds of watts. While lamps with lower power are fit for smaller greenhouses or certain areas, lamps with more power can cover more areas.

 

Generally speaking, the area of the greenhouse, the necessary PPFD, and the light source's light efficiency should determine the wattage of greenhouse fill-in lamps that one chooses. For instance, if you require more light, you can select 600W–1000W bulbs, often with better light efficiency and appropriate for covering more planting areas.

 

4) Heat control and dissipation

The performance of LED bulbs depends critically on their heat management. Although LED lights produce less heat than conventional bulbs, their light efficiency and service lifetime may drop if they are kept in high temperatures for an extended period. Consequently, selecting LED bulbs with effective heat dissipation designs is crucial. Standard heat dissipation techniques are air cooling systems and aluminum alloy heat sinks. These heat dissipation systems extend the lamp's life by helping to maintain its temperature within the normal range.

 

An efficient LED bulb, for instance, generates 2.7 μmol/J light efficacy, meaning that 2.7 micromoles of photosynthetic active radiation are produced for every 1 watt of consumed power.

 

 

Determining the overall power needed calls for weighing the lamp's light efficacy, goal PPFD, and greenhouse area.

Steps for computation:

Assuming:

Area of greenhouse: 100m²

Needed PPFD: 400 μmol/m²/s

Lamp's 2.5 μmol/J lighting efficiency

PAR output, per watt of power: 2.5 μmol/J

 

Required total photosynthetic active radiation:

PPFD (μmol/m²/s) = Total Photo Synthetic Active Radiation (μmol) × m2, the greenhouse area × illumination time (seconds)

 

If the lighting time is 12 hours daily-that is, 43200 seconds-then:

400×100×43200=1,728,000,000 total photosynthetic active radiation

 

Then, figure the total electricity needed (W):

Calculate the required total power (W) as well.

Total photosynthetic active radiation (μmol) / (lighting efficiency of lamp (μmol/J) × light source efficiency (J/W)) determines the required power (W).

If the lamp's illuminating efficiency is 2.5 μmol/J, its total power

 

If the lamp's illuminating efficiency is 2.5 μmol/J, its total power is 1,728,000,000μmol/(2.5μmol/J x 3600J/W)≈192 kW.

 

 

Knowing the overall power needed helps the lamp.

Each LED lamp has 600W of electricity, so one would need 600W of lamps overall.

The needed number of lamps is total power (W) / power of each lamp (W) = 192,000/600≈320 lamps.

 

 

Consider power, number, lamp dispersion, and light homogeneity when designing a greenhouse lighting system. To guarantee that every part of the greenhouse receives sufficient light, the lamps should ideally be equally spaced on the top or side.

 

One customizes the layout and light count based on the lamps' radiation angle-usually 60 degrees, 90 degrees, or 120 degrees-and the greenhouse's height.

 

 

Environmental aspects include light transmittance and greenhouse light loss. For instance, the transmittance may be lowered if the greenhouse has a sunshade net or glass, so the power of the additional light must be raised in line.

 

Winter or overcast days may call for additional light time for the greenhouse.

 

 

 

Accurate calculation of the necessary lamp power and quantity depends on knowing elements such as the greenhouse area, the plants' light needs, the lamp light efficiency, and the radiation angle. Usually, the light intensity should be changed depending on the stage of growth, and the number and power configuration of the additional light should be changed depending on the real surroundings.

 

JT Grow Light boasts a strong background in greenhouse supplemental lighting. We have effectively offered one-stop solutions for clients in the United States, Canada, and other countries. If you are unsure about selecting greenhouse supplementary lighting, contact us immediately so your plants can benefit from a highly efficient lighting source.

 

Learn More Information

https://www.china-growlight.com/led-grow-lights/led-grow-lights-for-weed/