What are HPS, LED and lights?
HPS lights emit light by sending a pulse of high-voltage energy through a pressurized quartz tube filled with vaporized sodium, along with other elements such as xenon and mercury.
As the gases heat, they emit light. Sodium produces an intensely yellow-orange light; this can be mediated by xenon and mercury, both of which emit light in the blue end of the visible spectrum. The final result is whiter light.
LED (light-emitting diode) lights are semiconductors, which allow electrical energy to pass with little resistance in one direction and overwhelming resistance in the other, across a “p-n junction”.
On one side of the junction is a material that has been treated with extra electrons, while on the other side is material that has been treated to lack electrons. When voltage is applied, the extra electrons move across the junction to fill the “electron holes” on the other side. This causes light to be emitted, the colour of which varies according to the material used. Phosphides and nitrides of gallium, aluminium, zinc and silicon are the most commonly-used materials.
The efficacy of different lighting systems
The efficiency (or “luminous efficacy”) of lighting systems can be expressed in a basic equation: output (lumens) divided by total units of power consumption (Watts). High-efficiency lighting is generally accepted to output at least 90 lumens per Watt (lm/W), with some bulbs achieving 150 lm/W or even higher. Increasingly, grow lights are also rated in terms of PAR (photosynthetically active radiation) output, measured in µmol/s (the number of photons per second falling on 1m² of plant matter).
Mmol/s is increasingly seen as superior across the board for horticultural lights, as it is a measure of light usable by plants. Lm/W is a measure of what is visible to the human eye. Thus, it is advisable to get to know how to calculate PAR output measurement. A guide on the concept of PAR can be found here. Currently, the highest-performing HPS bulbs produce around 150 lm/W.
For LED grow lights, lm/W is generally considered less meaningful than the PAR output. This is due to the fact that red-blue systems generally have much lower overall lm/W ratio – as they only provide the most necessary bands for photosynthesis, therefore expenditure of “unnecessary” light energy can be avoided.
However, newer LED lights use multiple bands to create a more complex and full spectrum of light. This is thought to be beneficial to plant growth, and modern LEDS often incorporate white along with reds and purples of the visible spectrum. These new full-spectrum LEDs may or may not list lm/W rating. However, it is generally accepted that the most reputable vendors include both lm/W and the PAR output.
The light spectrum and mimicking daylight
Although improvements have been made in HPS lighting technology, they are still generally considered poorer in their replication of daylight than other modern lighting systems. Without the addition of xenon or mercury, sodium vapour gives off an intensely reddish-yellow light. However, new “full-spectrum” bulbs now exist, and often consist of a dual-arc system comprising both a metal halide and an HPS component.
LEDs are probably the best contenders in terms of spectrum at this stage, with newer full-spectrum models offering up to 11 bands of light wavelengths most needed by plants.
How lighting can affect yields
As light is one of the two most basic foods for any plant (water being the other), it naturally has a big impact on final yield. Annual flowering species follow very strict patterns of temperature, day and light hours, and light spectrum.
As the season changes from summer to autumn, the light spectrum changes, as do the other factors that affect flowering. For this reason, to achieve maximum yields, annual flowering plants should be exposed to different lights at different stages during their growth cycle.
HPS lighting is best used during the flowering stage of a plant’s growth cycle. This is because the spectrum of light emitted is conducive to flower production. LED lighting is also ideal for the flowering stage as they produce a lot of lumens. For most annual flowering species, the summer initiates flowering, a period of the year that is rich with sunlight.
Typically, growers begin a grow cycle with fewer lights. This ensure that seedlings and young plants are not burned by excess light and heat. Growers can increase the amount of light globes as the cultivation process progresses. This also ensures that there is sufficient light once plant size has increased.
The cost of lighting
Aside from the upfront cost of purchasing lights, growers must also consider the cost of electricity. The question of LED vs HPS lights can also be affected by what continent you are living on. In Europe, electricity is more expensive than in the US. This tends to lead to gardeners in the US growing under 1000W bulbs, whereas their European counterparts lean towards 600W or even 400W bulbs.
LED and HPS lights, while emitting the most lumens, are also the most expensive to run. For this reason, many growers will not use LED and HPS in the early stages of plant growth. Fluorescent lights suffice during early growth as seedlings and young plants don’t use as much light as fully matured plants. Another way to decrease the cost of lighting is, as mentioned earlier, to start with fewer lights and increase as the plants mature.
Growers who combine different lighting systems create more complexities in their grow rooms, more room for error, and many more variables to contend with. This is something important to consider when choosing lighting. For “no fuss”, one lighting system should be chosen. Once knowledge increases of different lighting systems and their effects, they can be combined.
The following are the best HPS lights.
- ECO Farm double ended 1000 watt grow light system is a premier choice for your garden. Available in 1,000-Watt versions, the lighting system sets a new standard for others to follow.
- ECO Farm Hood Kit (1000 Watt) This combo can make you control the grow light automatically, plant more conveniently. It not need fans or ducts to cool, which can cool itself, so it can help reduce the energy to save money This set can solve all problems you have in the process of indoor gardening.
- High-frequency dimmable ballast: High frequency digital dimmable ballast 120V-240V designed specifically for double-ended grow lamps 1000 Watt(HPS/MH).
- 1000w HPS bulb: Ultra-bright at 155,000 lumen CCT 2,050k, optimized red & blue spectrum encourages flowering growth. Provides 35% more available energy than the high standard pressure sodium lamp.
- Double-ended adjustable reflector German aluminum layer of 98% reflection and excellent color rendering.
- Delivers an optimal PPFD value over a large footprint. The ballast designed with a high precision microprocessor that makes it super efficient and an exceptionally dependable piece of equipment.
- Being completely silent and lightweight, you will not be disturbed, as this ballast is entirely noise free and can easily be moved if the desire is required.
- Emits a clean, pure light
- Checkerboard with DE HPS or use on its own to produce a quality plant without a loss in yield
- HIGH FREQUENCY DIMMABLE BALLAST: High frequency dimmable ballast 120V-240V designed specifically for Double Ended Grow Lamps 1000W (HPS/MH).
- HIGH REFLECTIVITY RATING: Sturdy reflective hood is made of aluminum rated at 95% reflectivity, with excellent color rendering and outstanding high quality, and the high quality lamp holder.
- Includes a Super HPS Double Ended 1000W HPS Bulb, high PAR output, providing 35% more available energy than Standard HPS Lamp bulb.
ECO Farm 1000W DE HPS grow light kit delivers ultimate light output, superior uniformity and deeper canopy penetration. It is high intensity light and produces noticeably bigger, fuller flowers and overall heavier yields. HPS light has the good spectrum that is best for flowering stage of plant growth.
- High performance dimmable high-frequency ballast with overdrive.
- Glass optical silver-coated reflector with >99% reflectivity.
- 1000W DE HPS lamp has the highest available PAR light outputand maintains results after multiple growth cycles.
- Maximum light efficiency, 25% more grow lights towards crops.
- Support external controlfor multiple lighting fixtures.
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