We discussed this with one of our commercial growers in Phoenix, and he does not think that this is a viable standalone metric. Not only do yields vary significantly by strain, but there are so many other factors that make this number unreliable for any comparison except for within a single facility (grower skill, nutrients, lighting schedule, grow style, room temperature, number of plants per square foot, etc.). For example, he has some strains that produce 1.25lbs per light (HPS) and others that produce 3+lbs under the same light.
What you are really looking for is intra-facility results with everything constant except the light. He has been doing just that with 4 strains using our Dragon XL1200 against a couple different types of lights. They just harvested and the average dry weight was 12% greater than those strains grown under HPS. When converting this to pounds-per-light, the HPS strains ranged from 1.4 to 2.6 pounds per light where the strains grown under the Scynce lights ranged from 2.0 to 3.4 pounds per light.
This question needs to be answered in two ways, as there is much confusion and misunderstanding on this topic.
- The light itself has a certain efficiency rating. Our Dragon LP250 has a 47% efficiency rating which means that 53% (or 133 watts) of the energy does not get turned into light. The formula to convert watts to heat energy (BTUs) is 1 watt = 3.41 BTUs/hour. This would mean that the Dragon LP250 produces 451 BTUs/hour of heat energy that it does not convert into light.
- The other way to look at this is that energy in = energy out. That means that a 250 watt luminaire would create 853 BTUs/hour. This would be the same for any type of light.
The untold story here lies in a couple of factors. First, LEDs have virtually no infrared (IR) light as compared to HID lights that have quite a bit. IR light is what restaurants use to heat food and it is also what will heat up and burn plants. Second, it is impossible to fully quantify how much of the light is absorbed by the plants. This means that some of light energy is used by the plant in photosynthesis which does not create direct heat but heat through transpiration, which is ultimately what we are looking for when plants are healthy and growing. Third, because LEDs don’t create as much heat on the leaves it is recommended to keep the ambient temperature of the grow room 8-10℉ warmer than when using HID or HPS lights.
Generally speaking an engineer planning out a cultivation will need to understand the total watts of the lights and their efficiency rating to be able to calculate non-light energy that gets turned into heat (BTUs/hour). As a rule of thumb, every 12,000 BTUs requires 1 ton of cooling. In a 12’x12’ room (144 sq. ft.) Scynce recommends using six (6) of our Dragon XL1200s. These lights are 44% efficient and thus create 2,291 BTUs/hour of heat energy each. In total, all six lights create 13,748 BTUs/hour. This would typically require a 1.5 ton air conditioning unit to handle the heat abatement.
XL1200 = 2,291 BTUs/hour
XL600 = 1,146 BTUs/hour
LP250 = 451/BTUs/hour
Raging Kush 600 = 1,084/BTUs/hour
LED lifespan is based on the manufacturer provided LM80 data. We use the XPG3 from Cree, in 3 different shades of white. The warm white (3000K) is going to be the worst performing, where the L90/L80/L70 is a % of what the output of a new LED is, in percentage. According to that datasheet, the warm white LED’s will maintain at least 80% of the new output to 81,600 hours.
This testing is according to IES accepted testing standards. It isn’t realistic to test all new LED’s for 7-10 years of continuous use so this is how LED lifespan is determined. On top of that, our lights are all thermally protected with software to ensure that they always run cool. If something fails, or the temp runs away in a room, the software will kick in and protect the light from any overheating damage. Everything else electronic in the unit, including the power supply and fan’s, are all rated for at least 100,000 hours based on the temperatures we are running them at.
One major benefit of LED technology is the ability for manufacturers to custom tune the spectra of light to provide to your crop. The first versions of LED-based horticulture lighting systems mainly consisted of red (660 nm) and blue (450 nm) diodes to achieve the highest photon efficacy possible. While red LEDs have the highest photon efficacy,plants did not evolve in nature under narrow band wavelengths, so they are not always the most efficient spectra with regards to optimizing plant growth and development. This is especially true in situations where lighting systems are used for sole-source lighting, as compared to supplemental greenhouse lighting.
One problem that growers complained about was inconsistent plant morphology during different growing seasons due to varying percentages of total red/blue light provided when the amount of ambient sunlight changes. On cloudy days plants receive a much higher percentage of light from a supplemental light source, and narrow band wavelengths can cause plants to have varying morphological responses during production, as you are significantly changing the spectra of light from day to day. Read More
Initial studies by a Wisconsin group demonstrated the need to supplement high-output red LEDs with some blue light to get acceptable plant growth ( Hoenecke et al., 1992 ). Subsequent studies at the Kennedy Space Center showed wheat seedlings germinating under 500 μmol·m−2·s−1 of red LED light failed to develop chlorophyll but that supplementation with only 30 μmol·m−2·s−1 of blue light, or just reducing red PPF to 100 μmol·m−2·s−1, restored chlorophyll synthesis ( Tripathy and Brown, 1995 ). Further studies have confirmed that some blue light is typically necessary to improve growth and minimize shade avoidance responses, including excessively elongated stems (Snowden et al. 2016). Blue light activates the cryptochrome system and matches chlorophyll and carotenoid absorption spectra, thus having significant effects on green vegetable morphology, growth, photosynthesis, and antioxidant system response ( Olle and Viršilė 2013 ).
Green light also has valuable physiological effects ( Olle and Viršilė 2013 ). In several studies, 510–530 nm LED light (Johkan et al. 2012; Son and Oh 2015), comparably to green fluorescent lamps, supplemental for red and blue LEDs (Kim et al. 2004), promoted growth. Snowden et al. (2016) and Bugbee (2016) explained that green light penetrates deeper into leaves and canopies, thereby altering plant growth and development (128 A. Viršilė et al.). Green is characterized by better transmission through leaf tissue, as compared to red or blue light wavelengths (Massa et al. 2015).
In greenhouse environments, the impact of supplemental light quality seems to be diminishing, especially when background solar irradiance provides sufficient photosynthetically active photon flux (Mitchell et al. 2015). It is likely that there is a threshold background solar daily light integral (DLI) or a relative level of supplemental DLI that requires the additional blue photon flux through supplemental lighting (Hernández and Kubota 2012; 2014a, b; Mitchell et al. 2015).
New questions continue to arise when considering LEDs for horticultural lighting in view of recent studies, such as what levels/proportions of red, green, and blue light will be required for particular crops? This has prompted a few horticulture lighting companies to implement white LEDs (which are blue LEDs with a yellow phosphor coating). Better productivity generally is seen with the additional wavelengths and broadening of the spectrum achieved with white light. LEDs used as supplements to sunlight or other types of lighting in greenhouses or growth chambers could modify crop growth or development in a desired direction without depriving crops of necessary wavelengths (Massa, 2008).
The use of LED technology is commonly assumed to result in significantly cooler leaf temperatures than high pressure sodium technology. If plants are not water stressed, leaves… were typically within 2°C of air temperature. As water stress increases and cooling via transpiration decreases, leaf temperatures can increase well above air temperature. In a near-worst case scenario of water stress and low wind, leaves can increase [up to 12° C], [however] because LED fixtures emit much of their heat through convection rather than radiative cooling, they result in slightly cooler leaf temperatures than leaves in greenhouses and under HPS fixtures, but the effect of LED technology on leaf temperature is smaller than is often assumed.
Compared to sunlight and HPS lamps, LED fixtures emit almost no near infrared radiation (NIR; 700–3000 nm), but this radiation is not well absorbed by plant leaves. Photosynthetic (400 to 700 nm) and longwave (3,000 to 100,000 nm) radiation are about 95% absorbed, but non-photosynthetic solar NIR is only about 20% absorbed, and has a smaller effect on leaf heating. Unabsorbed radiation is either transmitted or reflected. A recent analysis showed that the conversion efficiency of electricity to photosynthetic photons of the most efficient commercial scale LED fixtures was equal to the most efficient HPS fixtures at 1.7 μmol photosynthetic photos per joule of electrical input (Nelson and Bugbee 2014). They thus generate the same amount of thermal energy per photosynthetic photon. LED fixtures, however, dissipate much of their heat away from the plane they illuminate, while HPS fixtures dissipate more heat toward the plane they illuminate.”
Bugbee, B. (2016). Toward an optimal spectral quality for plant growth and development: The importance of radiation capture, 9-10.
One thing we hear quite a bit is, “I can’t get the same readings on my PAR meter that you show on your simulations.” That is absolutely correct! Because all of our lights utilize custom (patented) optics, the bulk of our light exceeds the critical angle of the light sensor. “What is the critical angle” you ask? In simple terms it is when the measurement sensor can’t absorb the light that hits it at too great of an angle. Instead of getting measured, it reflects off and results in total PPFD readings that are lower than the true energy reaching the plants. Read More
True lighting science requires cutting edge tools in order to quantify data and provide real-world application insights. Many lighting manufacturers only test their lights in a sphere, instead of a gonio. While this may look amazing on a spec or data sheet, they are only providing total energy. Sadly, this ignores the more important light patterns and intensities, which are all that plants care about at the end of the day. Light is a necessary and very expensive component of indoor horticulture. Giving botanists, farmers and growers the data they need to make informed decisions is imperative. At Scynce, we have a Goniospectrophotometer in-house, allowing our R&D team to test an unlimited amount to ensure that all of our lights are top quality and perform as promised. Read More
If we look to mass market, inexpensive and mostly foreign made lights it almost impossible to take their stated specifications and marketing claims at face value. One claim we see quite often is about how many watts a particular light fixture is. This is the equivalent power vs. actual power conundrum.
What science has taught us is that a watt is a watt, no matter the voltage, amps, light source, whether it has optics or any other possible differentiating factor. When you strip out the hyperbole and fairy tale marketing claims, you end up with a 540 watt LED light fixture. Read More
Another topic many people are misguided on is Photon Efficacy, which is typically measured in uMol/j (micromoles per joule). Because Scynce’s products utilize optics on every light, we take an efficiency hit in regards to the overall energy (quantity) emitted from the light fixture. This is compensated for because our optics take all of the remaining light energy and focus it 100% on the plants. This is why PAR Maps are so important as an actual depiction of the intensity and focus, not just quantity. Read More
There’s a big debate in the grow community about Smart LED grow lights and if they are as effective as some claim. The real truth here remains elusive but LEDs lights are finally starting to shed their negative reputation of not being able to flower cannabis.
As we move into the next era of grow lights where energy consumption matters but so does a strong yield, it will take more than just the ability to flower at the top of the canopy. At Scynce, we’re continually developing technologies around one goal: Getting the Best Yields Ever! This is where the optics play a key role.
Read More Part 1
Read More Part 2
For the record, in our Dragon XL products we use a combination of 7 watt white and 5 watt red LEDs manufactured by Cree and Luminous Devices, respectively. Just like a car, you have to start with a good engine to build a quality vehicle! The three most popular consumer diesel trucks all have engines made by somebody else: Cummins (Dodge and Nissan), International (Ford) and Isuzu (Chevy). The engine is the base, but it doesn’t make the truck. Just as LED’s are important but they don’t define the light! LED chip size can be anything between 0.1 and 30 watts for each individual chip. Using a quality LED with good efficiency from a known manufacture will contribute more than size ever will matter. What you do with the light matters 1,000% more than what size chips they are. Read More