Categories Lighting

LED Grow Lights Reshape Agriculture

For photosynthesis, plants use more red  and blue wavelength light than green light within RGB full spectrum.  LED technology enables the delivery of only the wavelengths that are needed most, resulting in reduced electricity operating cost to “feed” the plants and increased ROI of plant harvests.

The next decade offers many opportunities for LED manufacturers, distributors, installers, and the whole host of energy professionals and solution providers. Saving energy and money is the key driver in the adoption of LED lights with high ROI and low Total Cost of Ownership (TCO). Low operating costs and low equipment costs move the needle.  For LED grow lights, the market is about making more of something vs less of something. More plant growth often trumps energy savings!

While LEDs can reduce the operating expense over metal halide and fluorescent grow lights, the real win is when the LED grow lights can shave 10 percent or more off of the grow time to harvest. As an example with lettuce or basil, the average grow time is about 30 days, and LED lights can accelerate the growth to deliver the same harvest weight in 27 days. Over a year, the farmer can deliver 13 harvest cycles vs just 12. One more harvest is meaningful. A 20,000 sq. ft. grow operation (about half an acre and half the size of a football field) can yield over $1.5 million in basil every year. Now, LED lights are about production vs reduction.

Here are some insights about the 21st century that provide perspective on why the LED Grow Light market is poised for dramatic market growth:

The Challenges:

  • Global population has doubled to over 7 billion since the first Earth Day in 1970.
  • Humankind may deplete fresh water resources before running out of fossil fuels.
  • In America, food travels hundreds and thousands of miles to its destination in many areas.
  • America faces increasing health challenges from childhood obesity and an overweight population.
  • Low-income households are at the highest risk, given limited access to affordable fresh produce.
  • The developing world faces increasing food challenges, given droughts and extreme weather.

The Solutions:

  • Leverage the advantages of Light Emitting Diode (LED) technology to provide cost-effective, fresh and organic produce at local levels.


  • Fresh and Cost-Effective Food for the World.

LED Grow Lights = $ Money. The available LED technology and “Smart Controls” enable next generation farmers to grow indoors during the day and at night. They also reduce shipping costs to increase net profit. LEDs will reshape agriculture, because a new generation of urban farmers will use abandoned and un-leased industrial buildings to grow organic food close to the communities that will eat it. This reduces the farm to table distance and cuts the pesticides out of the process.

Not all LED Grow Light are created equal.
If you are in the market to use LED grow lights or seek to expand your sales offerings through a strategic relationship, look for grow lights that meet certain standards. Specifically, look for LED Grow Lights with highest Photosynthetic Active Radiation (PAR) per dollar for vegetation and flowering.

In addition to LED vegetation and flowering fixtures, look for manufacturers that offer custom solutions to meet growers’ needs. Modular design can deliver Photosynthetic Photon Flux Density (PPFD) at varying wavelengths to give growers a competitive advantage.

Look for external driver technology with the ability to program, through smart controls, the cycles to optimize plant growth over multiple growth sessions within a 24 hour period, based on the different types of plants.

Look for fixtures with dimming capabilities to simulate sunrise and sunset and/or to optimize plant growth over multiple growth sessions.

Look for adjustable suspension systems so that the elevation of the light source above the plants is optimized for plant growth.

Look for opportunities to integrate hydroponic and also aquaponics systems into the LED grow operations.  A pound of feed may only yield an ounce of protein from livestock, while a pound of feed for fish will yield closer to a one-to-one pound of protein from a fish, such as tilapia.  Plus, vegetables such as kale are nutrient rich “superfoods” with numerous health benefits:

Top Tip on LED Grow Lights:
Choose a commercial LED lighting manufacturer or solutions provider that has the highest Photosynthetic Active Radiation (PAR) per dollar of fixture cost. While higher watts are a negative in building illumination, they are typically a positive with grow lights (all things equal in the wavelengths), because more watts translate into more light for plant growth. The $/watt analysis is also relevant in comparing LED fixtures if the light of the different fixtures is distributed across the grow surface rather than creating hot spots. You can look at the cost per watt as a way to short list LED Grow Lights. Just divide the fixture cost by the wattage and this is a great first line of comparison.

Categories LED

Narrowing the Field of LED Luminaires

You know it’s a hot topic when the Wall Street Journal is writing about it. A few weeks ago, the WSJ wrote about a LED manufacturer’s product qualifying for utility rebates through the DesignLights Consortium (DLC). So what makes this so newsworthy? With the prices of LED luminaires already decreasing over the years, the opportunity for end-users to receive utility rebates for upgrading to energy efficient LEDs really helps shorten the ROI and drive more adoption of this technology. Essentially, utility rebates are lowering the upfront cost of new energy efficient lighting.

What is the DLC?
For those of you not aware, the DLC is collaborative effort between utility companies and regional energy efficiency organizations, to help buyers implement improved design practices in all areas of the commercial lighting market. According to their website, “the DLC promotes quality, performance and energy efficient commercial sector lighting solutions through collaboration among its federal, regional, state, utility and energy efficiency program members; luminaire manufacturers; lighting designers and other industry stakeholders throughout the US and Canada.”

Throughout its 17-year history, the DLC program has driven the lighting market towards innovation by providing information, education, tools and technical expertise for cutting-edge technologies. Since 2010, the DLC has administered the Qualified Products List (QPL), a leading resource that distinguishes quality, high efficiency LED products for the commercial sector. Today, the QPL sets the bar for efficiency program incentives across the US and into Canada while informing manufacturer product development.

Utility Rebate Programs
Utilities offer two types of rebate programs: prescriptive and custom. Prescriptive rebates provide a set amount for each fixture replaced. The dollar value of custom rebates is based on the total energy savings of a specific project.

In a report by Groom Energy and GTM Research, Enterprise LED 2012: Commercial and Industrial Market Trends, Opportunities and Leading Companies, utilities across the country show limited prescriptive rebate support for LED lighting. However, as the LED market matures, utilities will aggressively start moving. Additionally, this report states, “When satisfied that savings can be successfully achieved, utility program managers will typically authorize custom rebate amounts of up to 50 percent of the entire cost of the project, as opposed to a prescriptive rebate for each fixture.” And some of this is already occurring at a rapid pace. For example, New York is second only to California in dollars spent by utilities in energy efficiency rebate incentive programs. According to an article in Green Tech Efficiency, in 2008, there was approximately $3.1 billion available in total US rebate dollars, with the money concentrated in 10 states. The figures are expected to more than double in the coming years, with $7.4 billion to $12.4 billion available by 2020.

California, New York, Florida and Massachusetts have some of the most robust energy efficiency programs, but others, according to the Consortium for Energy Efficiency, like Pennsylvania, Illinois, Arizona and Ohio, have started building new programs entirely, North Carolina and Michigan are also increasing spending, according to the Lawrence Berkeley National Laboratory.

The most accurate resource for energy rebates and incentives is the Database of State Incentives for Renewables and Efficiency, which is available online here. It details a comprehensive list of rebates and programs by federal, state and utility companies to help buyers determine whether projects qualify for rebates and incentives. It’s also a dependable resource for energy professionals and lighting distributors to use as a cross check against the DLC lighting lists.

Do Your Homework
Typically, when retrofitting with LEDs or choosing to install LED luminaires in new construction, the facility manager or building owner will hang a number of lights from different manufacturers for comparison. While this is an important part of the lighting selection process, reviewing the DLC’s Qualified Products List and the Database of State Incentives for Renewables and Efficiency streamlines fixture choices and aids in making the best decision.

Categories LED

LED Match Making – The Value of Photometric Analysis

Many commercial building owners and operators may have more light than they need in certain areas and less light than they need in other areas. When considering an LED retrofit, do not just buy new lights for the energy savings, but take the time to get the right type of lights to meet your business operating needs. Photometrics Analysis is a great way to “see” a plan and elevations of the current foot candle light levels and the potential to increase or decrease levels where needed.

As an example, for a national auto service chain, Monro Muffler and Breaks, one of the managers at a Connecticut location spoke about the need for more light in the service bays to show customers what needed to be fixed on their cars. The managers also spoke about a brighter more appealing overall look to their service centers to attract more customers. For a top BMW dealership in Virginia, the requests included improved light quality to showcase the vehicles. They wanted customers to be able to see the vehicles with brighter light and with color temperatures to more closely match how the vehicles appear outside in daylight. Since color temperature is measured in Kelvin and Kelvin impacts output in lumens, the lumens impact the foot candles. A photometric analysis helps shape the optimal lighting solution. In another example, an Anheuser Bush beer distributor, in Pennsylvania, with over 300,000 sq. ft. wanted to ensure 30 foot candles at the floor as well as on the storage racks. They wanted to be able to load the trucks more quickly with fork lift truck operators clearly seeing the palette labels under brighter light. In this case, the photometric analysis included both floor plans and elevations. The results of the study drove the inclusion of reflector systems where appropriate on the LED high Bay light fixtures. In each of these examples the right amount of light played a role in improving the operations of the business not just a reduced energy bill.

To better understand photometric analysis, here are some highlights from Wiki.

Photometry is the science of the measurement of light, in terms of its perceived brightness to the human eye.It is distinct from radiometry, which is the science of measurement of radiant energy (including light) in terms of absolute power. In modern photometry, the radiant power at each wavelength is weighted by a luminosity function that models human brightness sensitivity. Typically, this weighting function is the photopic sensitivity function, although the scotopic function or other functions may also be applied in the same way.

The human eye is not equally sensitive to all wavelengths of visible light. Photometry attempts to account for this by weighing the measured power at each wavelength with a factor that represents how sensitive the eye is at that wavelength. The standardized model of the eye’s response to light as a function of wavelength is given by the luminosity function. The eye has different responses as a function of wavelength when it is adapted to light conditions (photopic vision) and dark conditions (scotopic vision). Photometry is typically based on the eye’s photopic response, and so photometric measurements may not accurately indicate the perceived brightness of sources in dim lighting conditions where colors are not discernible, such as under just moonlight or starlight. Photopic vision is characteristic of the eye’s response at luminance levels over three candela per square metre. Scotopic vision occurs below 2 × 10−5 cd/m2. Mesopic vision occurs between these limits and is not well characterized for spectral response.

Based on this description above, the net of the photometry science is that it is more complicated than most business owners or operators care to learn. So, the tip below is as simple as working with the right people to navigate the complexity.

Top Tip on LED Light Matching with Photometrics:
Choose a commercial LED lighting manufacturer or solutions provider that has the software to run photometric analysis on your facility before making a major LED purchase. This gives you the power to review your options with objective data laid out in easy to review, multi-color floor plans and elevations.

Categories Lighting

Optimizing Lighting Efficiency with Glass

In last month’s blog post, I kicked off a series of about glass in lighting by providing a brief history and mentioned possible ways in which glass could effectively be used to increase lighting performance.  In particular, how it can be modified through glass chemistries (low iron), applied coatings (anti-reflective, conductive, etc.) and surface treatments (acid-etching, patterning, etc.) to optimize optical performance.  In this blog post, I want to continue the series by reviewing and discussing each of these areas in more detail to provide a more comprehensive understanding on how glass can be wisely used to optimize lighting efficiency in lighting applications.

The first major challenge of using glass as a material in lighting is with its inherent material properties.  Glass, as a material, loses 9 to 10 percent of lighting efficiency through reflection and absorption losses as shown in the graphic below.



Diagram courtesy of Guardian Industries


As you can see, 4 percent of light is lost through reflecting off of the first surface, another 2 percent lost through absorption from the FeOx content (0.11 to 0.08 percent) in standard soda lime glass chemistry, and still another 4 percent lost through reflecting off of the second surface.  In today’s world of high-efficiency and high-efficacy luminaire requirements, this is an unacceptable sacrifice and has unfortunately caused glass to be designed out of many lighting fixtures.  However, there are innovative and readily available ways to address this problem with glass and reduce reflection and absorption losses and increase overall light transmission and efficiency. These include using:

  • Low Iron Soda Lime Glass;
  • Anti-Reflective (AR) Coatings; and
  • Surface Treatments and Textures.

The use of low iron soda lime glass attacks the 1 to 2 percent absorption losses mentioned above by reducing the FeOx content of the glass chemistry down to 0.2 to 0.3 percent and all but eliminates absorption losses.  The spectral graph below compares the transmission curves at NADIR (0 degree incident angle) of standard soda lime glass and low iron glass with special attention given to the visible range where luminaires perform in:



Diagram courtesy of Guardian Industries


You can clearly see a boost of 1 to 2 percent of light transmission gained just from the replacement of the substrate material itself with low iron glass.  However, that still leaves 8 percent of lost light transmission due to reflectance losses to recover to gain optimum luminaire efficiency.  How can that be undone?

Anti-Reflective (AR) coatings can be effectively used to reduce reflection losses and increase light transmission in lighting as well as many other commercial applications.  In fact, they are already commonly used in eyeglasses, picture frames, and photovoltaics.  The principle of AR coatings is to minimize the interference of light traveling through a given material’s surface versus that of its immediate surrounding environment (in this case, air).  Therefore, the goal of an AR coating with a glass lens in lighting is to create this interference layer with a refractive index (n) as close as possible to air (n = 1) and the glass surface (n = 1.52) to filter the reflection losses and bridge that optical gap.

Adding a 3-layer AR coating (medium, high, and low index gradient) to a low iron substrate, mentioned above, allows most of the 8 percent reflection losses to be recovered in light transmission and efficiency.  The spectral graph below compares the transmission curves at NADIR (0 degree incident angle) of standard soda lime glass and low iron glass as well as application of an AR coating on one (singled sided or SS AR) and both (double sided or DS AR) sides of the low iron glass (again with special attention given to the visible range where luminaires perform in):


Diagram courtesy of Guardian Industries


A reduction of reflection losses from 4 percent down to 0.5 percent per surface can clearly be seen and allows a Low Iron substrate with Double-Sided Anti-Reflective coatings to reach 99 percent light transmission (efficiency) in the visible range.  The absorption and refection losses seen earlier with using standard soda lime glass have been all but removed at the 0 degree incident angle.

But what about angular losses in light transmission? Since most LED-based luminaires are dispersing light in very aggressive light distribution patterns there is limited value in maximizing light transmission at a 0 degree incident angle only.

The combination of Low Iron glass and AR coatings also help with the reduction of angular losses as shown in the material output files from LTI Optics of standard soda lime glass, low iron glass, and Single-Sided and Double-Sided AR coatings on low iron glass:


Diagram courtesy of Guardian Industries

Where:  τ = Transmission, α = Absorption, and ρ = Reflection

As these plots show, the average light transmission achieved with standard soda lime glass from 0 to 75 degree incident angles is only 86 percent whereas low iron reaches 88 percent, SS AR on low iron 90 percent, and DS AR 94 percent and holds > 90 percent light transmission up to 55 degrees (when standard glass only reaches that at 0 degrees).  Clearly, the combination of low iron glass and AR coatings help reduce angular light losses as well.

Finally, another method of reducing reflection losses with glass is by modifying its surface texture.  There are two commercially ready methods of doing this:

  • Acid-etching the surface to make the glass “frosted” or “diffuse”; and
  • Texturing (or patterning) the surface while the glass is still in its molten form.

Comparing standard clear glass (as a reference) to various acid-etched and textured products combinations (with and without an AR coating), you can clearly see benefits of modifying the glass surface to increase your light capture over angle with all cases providing superior performance versus standard soda lime glass:


Chart courtesy of Guardian Industries

In summary, glass indeed has some inherent challenges for effective use in the high-performance and energy-efficient LED luminaires of today.  However, with the use of innovative glass chemistries (low iron), coatings (AR), and surface modifications (acid-etch, texturing) these challenges can not only be removed but also allow for even higher levels of efficiency and efficacy to be achieved.

In my next post, I will provide some case study examples of effectively using these innovative uses of glass lenses, which provide both performance and economic (ROI, TCO, etc.) benefits in selected applications.