As the cost of electrical energy costs continue to rise,
growers are
increasingly drawn to technologies that will allow them to operate at
greater energy and life span efficiencies while maintaining or even
improving upon crop qualities and times to harvest. It is up
to lighting
manufacturers to be responsible and provide the end user with factual
statements of values and not exaggerate or misstate their products
capabilities. To sum it up if the manufacturer is stating that
they
have the 'Greatest Indoor Grow Light' there is a pretty good chance that
it is not any such thing.
LED grow light manufacturers tend to advertise aggressively and make claims that their lights can deliver better crop results for far less energy than all other technologies, including induction lighting. When a manufacturer makes these types of revolutionary product claims it pays to be skeptical and to really research the data to see if the claims are even remotely believable. To that end you'll find an in-depth analysis at the bottom of this page where we examine the product information sheets of several leading LED grow light manufacturers to see how their claims measure up to the science.
This is simply not true. Consider that only about 20% of an LED lamps energy is utilized for actual plant growth the rest is trapped as heat within the lamp housing. That heat has to be removed from the housing or electronic components that drive the LED's will burn up. Also the amount of heat generated by an LED is also directly proportional to the LED power levels. If you want to prove this to yourself try taking a Low Power 5mm LED array, wrap them in a towel and see how will quickly they’ll heat up since the heat would have nowhere to go. So while an LED won’t run as high a temperature as an HID lamp that creates both convection and radiant heat an LED does create convection heat and that heat still contributes to increased ambient room temperatures.
Considering that sunlight is
the broad spectrum light source and it has supported a variety of plant
species for nearly 4 billion years, it would be reasonable to assume
that the plant/sun relationship is both a dynamic and an intimate
one. As a result of LED's being narrow spectrum, LED lighting
manufactures tend to reduce the importance of the natural symbiosis that
occurs between broad spectrum lighting and plants by reducing the
importance of certain spectrums or worse, eliminating them
altogether.
LED manufacturers who rely solely on Chlorophyll Absorption Charts and don’t reference Net Photosynthetic Action Spectra data, or accept the Emerson Effect, do so because it’s not in their best commercial interest's to do so. To illustrate this point you will see by the Emission and Sensitivity Curve chart on the right we show a plant sensitivity curve in black that shows the regions this plant would be absorbing energy in the wavelengths it requires for optimum growth. Next you can see by the regions the HPS lamp emits it covers a broader section under the sensitivity curve than the LED lamp shown in the red line. The LED by virtue of it's narrow bandwidth, would claim it is more energy efficient as they don't waste light unnecessarily in the least important 520-610 regions. With that statement the manufacturer is being disingenuous since these are not regions that can be completely ignored in the interest of promoting energy efficiencies over plant response or competing technologies.
The other problem that LED manufacturers face when relying solely on the chlorophyll absorption charts to promote their spectral values is that these ranges are set for isolated chlorophyll molecules suspended in a solvent and do not reflect total photosynthetic activity. Even within the Chlorophyll Absorption Charts, shown below, different solvents will give slightly different numbers.
Since plants absorb light within the
400-700 nm bandwidths for an LED to direct narrow spectrums of light
instead of the broader spectrums like they would see in nature. The lack
of spectrums may create stress conditions in the plants that inhibit
normal photomorphogenisis that would not be seen under broad spectrum
light source distribution. Narrow spectrum, highly directional LED's are
inherently incapable of emitting the homogenous blend of spectrums as
they would see in nature.
If you were take a 100 watt LED lamp putting out lighting levels of roughly 140 uMol/sec how far does that 140 uMol/sec of light take you? To put that energy into perspective, full sunlight is 2000 uMol/meter^2/sec. As plants have evolved under these sunlight intensities the photo saturation point for many food crops is around 1000 uMol/meter^2/sec and most food crops thrive at 500 uMol/meter^2/sec especially in flowering. So for that 100 watt LED to reach an intensity of 500 umol/meter^2/sec would cover an area of three square feet (21" x 21"). So while the 100 watt LED lamp can definitely grow plants in a smaller area, in a larger area, the rate of photosynthesis will proportionally go down.
Most LED grow light manufacturers will claim their lamps will last for a 50,000 hour lifespan. We’ve even seen others that have advertised 100,000 hour lifespans. To that I can only say that Chinese made LED lamps have had a very poor track record in meeting the advertised lifespans. When they do fail early the warranty claims tend to be denied and blamed on a customer responsible heat management issue. Compounding these issues is that Chinese specifications or 'white sheets' are not always reliable.
For the grower to make an informed decision regarding the lifespans of that particular manufacturers LED lamp, they’ll want to identify two things from the white sheets and having been confirmed by independent testing labs;
As a rule; the harder that you drive a LED the shorter its L70/B50 life will be as the higher temperatures lead to shorter lifespans. This is a hidden cost that one must consider when making a long term capital investment in an LED lighting system that costs anywhere from between $3-5 per watt. When an LED does fail it affects your plants health with lighting downtime. To keep the downtime to a minimum and to get the LED grow lights back on the plants you have options; make the repairs yourself or return it to the manufacturer for the repair. If you have a replacement LED lamp and are able and willing to replace the failed lamp, which has been soldered onto the fixtures circuit board. Assuming you can get the proper replacement part you’ll have some down time while you install the replacement LED lamp. Otherwise you’ll be sending the entire fixture back to the manufacturer and if it’s still within the warranty period, would hopefully make the timely repair or replacement without having to ‘regretfully inform you that the fixture is no longer within warranty period’ or determine ‘customer responsible failure not covered under warranty’.
Of note: on March 18, 2010 the US AIR FORCE issued a memorandum in which they removed LED lamps as an option for energy retrofit area lighting projects as a result of many of the LED installations having proven themselves to not have delivered sufficient lumen levels and not having met the published L70 and B50 standards within previous installations.