Lumistrips LED Lighting Blog

Nichia Optisolis LEDs with the full spectrum of sunlight

The latest innovation in LED development is the Optisolis technology form world market leader Nichia. Optisolis™ LED emitters provide a natural light source with a spectrum which achieves the industry’s closest match to that of the standard illuminants, sunlight and incandescent artificial light, having a CRI higher than 98.

Industrial scale indoor agriculture under artificial lighting in closed and fully controlled environments could become the main factor that keeps at bay famine and related conflicts. With increasing population, diminishing area of agricultural land, pollution, global warming and migration to grow plants in a reliable, predictable and efficient way will become even more important in the future. For this reason it is important to understand and corectly apply the concepts of lighting for plant growth and development.

Concepts related to Horticulture lighting

A key factor in the success of indoor plant growth is the efficiency of the lighting system compared with sunlight, in the process of plant growth.

Plants grow via a process called Photosynthesis that converts electromagnetic radiation (light) into the chemical energy needed for growth and development. The other ingredients required are carbon dioxide (CO2), nutrients and water. 

Photosynthesis and PAR radiation

The electromagnetic radiation required for Photosynthesis is defined as photosynthetically active radiation (PAR) and 400 to 700 nanometers has spectral range. Only radiation in this interval can be used by photosynthetic organisms in the process of photosynthesis, to fix the carbon in CO2 into carbohydrates.

Electromagnetic radiation called visible light or simply light for a typical human eye has a spectral range from about 380 to 740 nanometers.

A common unit of measurement for Photosynthetically active radiation PAR is the photosynthetic photon flux (PPF in short), measured in units of moles per second. For many practical applications this unit is extended to PPFD, units of moles per second per square meter.

The theory behind PPF is that every absorbed photon, regardless of its wavelength and energy, has an equal contribution to the photosynthetic process. As in accordance with the Stark-Einstein law, every photon (or quantum) that is absorbed will excite one electron, regardless of the photon’s energy, between 400 nm and 700 nm. 

However, only some of photons are absorbed by a plant leaf, as determined by its optical properties and the concentration of plant pigments. The pigments are Chlorophyll A, Chlorophyll B, and Carotenoids (a/-Carotene, Lycopene, Xanthophyll).

The Chlorophylls A and B give plant leaves the characteristic green color because they reflect most of the radiation between 500 and 600 nanometres.  Plants Where more Carotenoids than Chlorophylls are present plant leaves reflect wavelengths beyond 540nm and have yellow, orange, and red colors. This includes autumn leaves when Chlorophylls have dried away. 

The graph below shows the typical absorptance spectra for Chlorophyll A, Chlorophyll B and Chlorophyll (beta-carotene). Each are explained briefly afterwards:

 

 

 

Product lifetime, Light Bulb vs LED

The typical product lifetime of an incandescent light bulb is 1000 hours. When the bulb reaches the end of its product lifetime, it cannot emit light anymore. Typically, just before, there is spark or pop, as the filament inside breaks down.

LEDs use a different meaning for product life. They are the only light sources that over time lose brightness, even up to 90% of initial flux. Eventually, LEDs will also fail completely. However, some emit visible light even after decades.

For example, a Nichia LED with 60,000 hours typical product lifetime will continue to light well beyond the 60,000 hours rated life. Under normal operating conditions, it will even after 200,000 hours.

LED lifetime is the time interval the product can still serve its intended purpose.  The time passed until a LED has 70% of the initial brightness is equal with the product life, L70 lifetime.

For all reputable lighting manufacturers and sellers, LED lifetime is equal with L70 lifetime. At this point, the LED is considered end-of-life and has to be replaced.

The innovative SunLike LEDs from Seoul Semiconductor are the first natural spectrum LEDs on the global market. For the first time an LED can emit light that closely matches the spectrum of natural sunlight.

The special ability to have a spectrum close to sunlight comes from using a new LED design, with a purple emitter in combination with a red, green, and blue (RGB) phosphor mix, unlike conventional white LED that use a blue emitter and yellow phosphor.  By removing the blue LED chip and replacing it with a purple light one, lighting technology is fundamentally transformed. For the first time it is possible to render colors accurately with very low energy use and positive effects on health. Compared with other LED lights, the new SunLike Series do not have a blue energy peak associated with eye discomfort and poor sleep patterns.

For LED technology, from the LED chip to related products such as LED lamps, modules and fixtures, high operating temperature can result in mechanical failure and significant drop of performance.

How a LED behaves when subjected to higher operating temperatures is directly related to its quality. High quality LEDs (such as Nichia or Cree) will function within parameters at high temperatures too, while low quality LEDs will break down, change their color, loose brightness or a combination of these. 

1. complete failure of the LED
2. light output is decreased permanently (Lumen Degradation) even if the issue with high temperature is solved
3. light output is decreased temporally while the LED functions at high temperature
4. the color temperature of the white LED changes

 When designing, building or installing a UV light, two key questions must be answered first:

"How irradiance does it need to have?"

 

"What is the required exposure time?"

While there are many studies that show the effectiveness of UV light in disinfection or sterilization, a high variance of the results exists, which presents a challenge to find an answer to these questions. 

We will present our recommendations by analyzing the results of 413 reasearch papers, as found in the compilation "Fluence (UV Dose) Required for up to 99% disinfection from Viruses, Bacteria, Protozoa and Algae"  that can be downloaded at the links below:

PDF: Fluence (UV Dose) Required to Achieve Incremental Log Inactivation of Bacteria, Protozoa, Viruses and Algae

The research studies present the fluence required to achieve a log reduction from 1 to 5, for different types of UV sources.

 

LED backlighting is a popular and versatile lighting solution that can be used in various applications, from linear lighting fixtures to luminous ceilings and illuminated signs. Achieving the perfect balance of total luminous flux and individual LED visibility is crucial for successful implementation. This article delves into the essential aspects of selecting and positioning LEDs for backlighting applications, ensuring optimal performance while meeting project requirements.

Understanding the Basics of LED Backlighting

LED backlighting involves placing light-emitting diodes (LEDs) behind a diffuse cover to create uniform and visually appealing illumination. Common applications include:

1. Linear lighting fixtures: LED strips or tubes used for accent, task, or general lighting in residential or commercial spaces.
2. Luminous ceilings: Large, uniformly lit surfaces that create a sense of spaciousness and enhance the aesthetics of interiors.
3. Illuminated signs: LED backlighting is used to create vibrant and eye-catching signs for branding, advertising, or wayfinding.

 

LED strips and modules used for lighting fixture use, in general, multiple LEDs.

As operating a single LED generates heat, more is generated when multiple LEDs are mounted on a PCB, due to the mutual effect. As such, in the case of LED strips or modules, the junction temperature (TJ) of each LED gets higher, compared to a single light source. This leads to the decrease in the LEDs lifetime and luminous flux.

For LED strips and modules, a better thermal management is required to minimize TJ and allow a longer lifetime of the installed products. For this purpose, the LED pitch, the PCB base material and the use of aluminum profile must be taken in consideration.