Plasma lighting is turning heads in the indoor gardening community. Many growers are praising these lights for their energy efficiency, low heat output and full-spectrum light outputs containing both UVA and UVB rays. But the relatively high price of plasma fixtures has deterred many people from trying them. Let’s take a closer look at this technology’s origins, how it works and its applications so you’re able to make a decision for your own garden.

What Makes Plasma Lighting Unique?

In 1894, Nikola Tesla discovered he could use radio waves to ionize different gases into a high-energy state called plasma, in which light photons are released. Plasma is often referred to as the fourth state of matter, as it is neither a solid, liquid or gas. Recently, radio frequency chip technology has advanced to the point where we can now produce radio waves in a solid-state form, as opposed to using a magnetron, making the technology more reliable and efficient.

Unlike high-intensity discharge (HID) lights, a plasma bulb doesn’t have a metal filament that’s used to carry an electrical charge through the bulb. The lifespan of traditional bulbs are limited because the thin metal that composes a filament eventually breaks due to heat fatigue. Plasma lights use a small quartz bulb about the size of the tip of your index finger, which contains a proprietary blend of gases. The bulb is then housed in a resonator, which concentrates the radio waves towards the bulb. In this way, plasma technology can produce light reliably and efficiently, without any electricity passing through the bulb.

Plasma Benefits: Energy, Economics, and Spectrum

Growers who have tried plasma lights may have done so to extend their facilities’ power capacity, which brings us to one of plasma’s greatest assets: energy efficiency. Depending on electricity and lighting costs, people may earn back the cost of a plasma fixture through energy savings in less than a year. Plasma grow lights require up to 50% less electricity than conventional lights to cover the same growing area, and the basis for that savings is in the spectrum. The spectral output from plasma lights is more concentrated in the wavelengths where photosynthesis occurs, rather than wasting energy on excessive infrared radiation, green and yellow light.

This spectrum optimization has a few important implications. First, it allows plasma lights to potentially produce the same plant growth as HID systems, but with less energy. Second, less infrared radiation means plasma lights produce less heat, which saves money on cooling costs. Finally, even though plasma lights might register a slightly lower micromole (PPFD) intensity, they can still perform as well as lights with higher micromole intensities, which have more yellow and green light in the spectrum. Furthermore, plasma lights have a high color-rendering index (CRI), which means users can more easily differentiate objects in the grow environment. Having the full power of your sight is critical to seeing small objects, such as unwanted pests.

If you’re not considering plasma lights for their energy savings, you’re probably interested in their sun-like spectrum that includes UVA and UVB rays. Plants have evolved for 400 million years under ultraviolet light from the sun, and a plant’s natural defense mechanisms generally produce characteristics that people enjoy. Ultraviolet light brings out more colors, tastes, aromas and other beneficial properties in plants. Plasma lights allow growers to receive all the benefits of natural sunlight, while maintaining the flexibility and control of an indoor environment. The fact that plasma lights produce UV along with a balanced PAR spectrum reduces the need for complicated facility designs incorporating supplementary UV light sources.

Growers are also beginning to realize the labor-saving trick of using UVB to control unwanted pathogens, such as powdery mildew. A recent study completed by researchers from Cornell and the Norwegian University of Life Sciences showed a significant reduction in powdery mildew after plants were exposed to UV. The UV method works like this: unlike plants, powdery mildew spores do not have the pigments necessary to protect themselves from UV light. While the chlorophyll in plants provide good protection, exposure to UV light quickly breaks down cell membranes in powdery mildew, destroying the spores. Researchers saw spores reduced from 90% coverage on leaves to only 5% after UVB exposure. Continual foliar applications to prevent powdery mildew can significantly increase labor costs. Alternatively, plasma lights can help control this for you.

Choosing a Plasma Fixture for Your Hydroponics System

Now that you know a little more about plasma fixtures, you’ll want to know the right questions to ask so you’re able to choose between fixtures for your particular application. The main differences are total output, bulb orientation, bulb replacement and the amount of red light in the spectrum.

  • Total Output – In terms of output, some fixtures are designed to supplement HID lights, while higher-output plasma fixtures can directly replace a 1,000-W HID light or provide more intense supplemental light.
  • Bulb Orientation – With plasma lights, you’ll also notice there are both vertically oriented and horizontally oriented bulbs. Vertically oriented bulbs generally have a better coverage area.
  • Bulb Replacement – Some bulbs are easier and less expensive to replace than others. Plasma bulbs that are fixed to the resonator might not even be replaceable by the consumer, so check with your retailer before purchase.
  • Spectrum – Lastly, always remember to check the PAR spectrum graph. Plasma fixtures designed to supplement HPS or red LEDs generally have less red light in their spectrum.

All plasma lights have a relatively slow spectrum degradation compared to other technologies, which makes for a longer lifespan. Bulb life is long—up to 50,000 hours. When comparing the lifespans of different plasma fixtures, it is important to note at what degradation level the manufacturer suggests a bulb replacement.

One may recommend users replace a bulb after 10,000 hours, because the bulb has degraded by 8%, while another may suggest replacing after 50,000 hours, because a bulb has lost 30% of its output. To decide when to replace a bulb, users will have to understand the degradation and lifespan hours.

Bulb replacement should be determined by the cost of a replacement compared to the risk of the potential loss in revenue attributable to a decreased harvest over the lifespan of the bulb.

Applying Plasma Lighting in the Garden

Plasma technology has some unique best practices when used in the growroom. Most indoor growers have adapted their growing formulas and environmental controls to HPS lights, so it’s natural that changing your light source may affect other variables in your operation.

The first variable you’ll need to pay attention to is temperature. Rooms solely using plasma lights can be kept at higher ambient temperatures because there is less heat radiating directly onto plants’ leaves. The allowance for higher temperatures encourages a sealed room design, creating more efficient CO2 supplementation conditions. The lower amounts of direct heat from plasma means the fixture can be hung closer to the plant canopy, allowing you to grow in more compact spaces, such as vertically stacked grow beds.

Plants grown under plasma lights also tend to require more calcium and magnesium because photosynthesis is occurring more efficiently. Growers may need to speed up production cycles because of faster propagation, as well as quicker and closer node site development. Lastly, because of plasma’s similarity to the sun, you can use the same light from beginning to end, and seamlessly transition from indoor to outdoor environments. In fact, users generally see better results when phenotypes are selected from plants grown with plasma from germination. You’ll quickly notice the difference between HID lights and plasma once you have tweaked your growing, especially on the second harvest.

Some growers use a combination of HPS and plasma fixtures to maximize yields and quality, and to reduce the up-front costs of transitioning to an all-plasma facility. Depending on the wattage of the HPS fixture and the ratio of plasma-to-HPS fixtures, it is still possible to save significant amounts of energy. By strategically arranging HPS and plasma fixtures, plants will get the outright photon intensity of an HPS fixture as well as critical parts of the light spectrum that plasma provides.

Growers who feel unconstrained by electrical consumption may even add plasma lights alongside their existing lighting arrangement or add plasma watt-for-watt to replace their existing HID lights. In general, a 500-W plasma fixture is equivalent to a standard 1,000-W HPS fixture inside a 4- by 4-ft. growroom. Use this as a rule of thumb when planning lighting arrangements.

The Bottom Line

Plasma is widely regarded as having the best light spectrum in the industry. Some people even say it’s better than the sun. These qualities are things every grower desires, and the industry needs to grow sustainably.

While some may believe the initial cost of plasma lights is high, a closer look at the lifetime cost will usually show a savings. Additionally, depending on the manufacturer and your local utility, a plasma light may qualify for an energy conservation rebate, which will pay for a substantial proportion of the fixture’s cost.

An investment in plasma lighting is often the right choice for the serious grower who is invested in improving their facility and harvests for the long term. Now is the time for innovation, to be more responsible about our energy consumption, and to improve our harvests.