What defines an environmental friendly LED linear lamp?

What defines an environmental friendly LED linear lamp?

Linear lamps are light sources preferred in the office and commercial sectors, with billions of linear lamps installed in buldings across the world, operating 11 hours, on average, daily. Summed up, the office and commercial sectors account for near half of the lighting electricity consumed on the planet.

Upgrading this lighting time with LED fixtures should have beneficial results if LED linear fixtures are environmental friendly with focus on energy efficiency, durability, and exclusion of dangerous substances.

The lamps they replace, with fluorescent tubes, are not environmental friendly because of short lifespan, high mercury content and UV light emissions.  

What defines an environmental friendly LED linear lamp?

1: Improved energy efficiency

According to DOE tests and literature, the energy efficiency of the most popular form of fluorescent tube, the T8, is:

Is recommended to take into consideration the useful lumens inside the fixture and not the data sheet luminous flux of the bare lamp. This value is seldom reached in an actual installation. Two important factors have a negative impact:

  • ballast factor 
  • light loss from converting a 360 degree lamp in a 180 degree (or less) lighting fixture.

From an average of data sheet values, a 0.87 ballast factor correction and a 17% further lumen loss is minimum correction.

The LED linear fixture should have at least 55 lm/w actual energy efficiency and at least 20% more luminous flux, because of the faster depreciation of the luminous output of LED compared to fluorescent, over the course of its useful lifetime.

2.  Longer lifetime 

LEDs are considered to reach end of life when they have lost 30% of the initial brightness. In contrast, fluorescent lamps loose on average 6% of their light output until their end of life, roughly at 25.000 hours, at which point they fail completely.

This results in the requirement that after 25.000 hours the LED linear fixture should have at least 70% of the initial luminous flux.

A sample lifetime of an 50.000 hours LED compared with other lighting technologies:

 

To be an environmental friendly LED linear lamp, we recommend the following performance targets:

Minimum Lumens: at least 20% more,  due to the faster depreciation of the luminous output of LED compared to fluorescent

Minimum Energy Efficiency: 104 lm/w, a 50% increase in energy efficiency, that results in a 50% cut in energy use & costs. Relevant from an economic and environmental point of view and a convincing argument for factors of decision in the business sector.

Lifetime: at least 50.000 hours, as LED lamps are complex products with a higher manufacturing cost and environmental foot print of their production.  Compared with a fluorescent linear lamp that has an average life of 25.000 hours, LED linear lamps should have minimum twice that.

Design considerations:

The LED linear lamp can be made from a majority of parts built in house or outsourced.

Using outsourced parts is the better course of action. Furthermore, for this particular product these parts should be almost entirely off  the shelf versions, not custom build.  

Example: parts you need to build a LED tube

 

As the above shows, the parts of a LED tube are:

  • LED module or strip -  one or more rows of LEDs on a circuit board/PCB (E,F)
  • Cover  - A polycarbonate or arcyilic sheet for protection and light distribution purposes (G)
  • Aluminum heat sink (under the LED module and/or on the back of the tube, C, H) - required to protect the LEDs from their overheating, a phenomenon that will result in a whole array of unwanted effects.
  • Power supply - needed to power the low voltage LEDs from the mains 110/230V. (A)
  • G13 end caps - to make the LED tube compatible with the fixtures in which it is to replace the fluorescent tubes (1,2,3)
  • Other small parts: wires, glue, thermal paste, screws - to put the assembly together.

 Choose the LED module for superior performance

For superior lifetime compared to linear fluorescent, the LED module used in the tube or linear fixture should have at least 30.000 hours L70 lifetime, with an optimum of 50.000 hours. The LED manufacturer must have lifetime data testing of 10.000 hours with various currents and temperatures. A sample is below

Lifetime depends on temperature and current. This means that a certain LED lifetime does not guarantee a similar product lifetime.

For superior performance the luminous flux of the LED module has to be 30% higher than fluorescent of the same length while having an energy efficiency of at least 95 lumens per watt, with 110 being an optimum, equivalent with 50% energy savings.

The increased flux is required to attenuate the light loss due to the cover and the gradual lumen depreciation over time.

Ensure proper heat management for reliable performance

Even the best LEDs will fail if heat is not managed well. Furthermore, until mechanical failure, an entire host of negative effects occur. For superior, reliable performance, very good thermal management is a key condition.

The heat management system for a LED linear tube or fixture is made of three key elements which have to remove the Heat from the LEDs to the ambient:

  • Circuit Board (PCB)
  • Thermal paste or tape 
  • Heat sink

A combination of aluminum PCB, high quality thermal tape and a finned aluminum heat sink constitute the optimum thermal solution. Ample testing was done to confirm this fact.

Choose a reliable power supply and decide where to put it

The power supply must have at least the lifetime of the LED module, otherwise a LED tube with even the best components and design will be a downgrade from a linear fluorescent installation.  This aspect is many times overlooked by manufacturers and customers a like. Too often, the focus is on LED lifetime and not the lifetime of the "weakest link".

The location of the power supply is also a key element. Currently, there are three main approaches:

A. Small, internal. Jam its components on a small pcb and place it inside the LED tube or fixture, usually at its end. The components could also be placed on the LED PCB itself.

B. Long, internal. Spread its components on a long narrow pcb and place it inside the tube, on the bottom.

C. External, enclosed. The power supply is a standalone, external unit with its own case and thermal management, connected to the tube or fixture with wires.

They key advantages and disadvantages of each approach are for a LED tube or constant current linear LED fixture:

Do not ignore the quality of the other parts

The poly-carbonate cover is important also. It  must have adequate shock protection and deliver a very good optic result.

A poly-carbonate diffuser with perfect uniformity, no hot spots and at least 75% light transmission should be used. The diffuser will also increase the view angle of the LED module from 120 degrees to at least 160, a requirement for replacing fluorescent tubes in many applications.

While a transparent cover is used by some manufacturers,  the higher light transmission of  90% does not offset the significantly increased glare factor, multiple shadows effect or decreased view angle. A LED tube with a transparent cover actually has a very narrow application scope.

The glue, wiring, connectors, screws and end sockets must be selected carefully as each and any of them can be the "weakest link".

Our LinearZ linear LED modules are great for high performance, environmentally friendly linear fixtures. They use long life LED, are plug and play and respect the Zhaga standard, for easy service and/or future upgrades. With the new technologies such as SunLike from Toshiba Seoul Semiconductor or Optisolis from Nichia they also have a much improved light spectrum compared with fluorescent lamps, with CRI as high as 98.

https://www.lumistrips.com/lumistrips/lumistrips-plug-play-led/linearz-sunlike-tri-r-led-modules-cri97-zhaga-2700-lm-m.htmlhttps://www.lumistrips.com/lumistrips/lumistrips-plug-play-led/linearz-nichia-led-modules-zhaga-2800-4000-lm-m.html

 

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