The LED industry had been advancing in a steady linear pattern.  The development of LED technology has caused their efficiency and light output to rise exponentially, with a doubling occurring approximately every 36 months since the 1960s. This trend is generally attributed to the parallel development of other semiconductor technologies and advances in optics and material science.  In 2001 and 2002, processes for growing gallium nitride (GaN) LEDs on silicon were successfully demonstrated. In January 2012, high-power LEDs such “GaN on Si” LEDs were demonstrated commercially.  It has been speculated that the use of six-inch silicon wafers instead of two-inch sapphire wafers and epitaxy manufacturing processes could reduce production costs by up to 90%

Here are some advantages of LEDs:

  • Efficiency: LEDs emit more light per watt than incandescent light bulbs. Their efficiency is not affected by shape and size, unlike fluorescent light bulbs or tubes.
  • Color: LEDs can emit light of an intended color without using any color filters as traditional lighting methods need. This is more efficient and can lower initial costs.
  • Size: LEDs can be very small (smaller than 2 mm2) and are easily attached to printed circuit boards.
  • On/Off time: LEDs light up very quickly. A typical red indicator LED will achieve full brightness in under a microsecond. LEDs used in communications devices can have even faster response times.
  • Cycling: LEDs are ideal for uses subject to frequent on-off cycling, unlike HPS that fail faster when cycled often, or HID lamps that require a long time before restarting.
  • Dimming: LEDs can very easily be dimmed either by pulse-width modulation or lowering the forward current.
  • Cool light: In contrast to most light sources, LEDs radiate very little heat in the form of IR that can cause damage to sensitive objects or fabrics. Wasted energy is dispersed as heat through the base of the LED.
  • Slow failure: LEDs mostly fail by dimming over time, rather than the abrupt failure of incandescent bulbs.
  • Lifetime: LEDs can have a relatively long useful life. One report estimates 35,000 to 50,000 hours of useful life, though time to complete failure may be longer. Fluorescent tubes typically are rated at about 10,000 to 15,000 hours, depending partly on the conditions of use, and incandescent light bulbs at 1,000 to 2,000 hours. Several DOE demonstrations have shown that reduced maintenance costs from this extended lifetime, rather than energy savings, is the primary factor in determining the payback period for an LED product.
  • Cool light: In contrast to most light sources, LEDs radiate very little heat in the form of IR that can cause damage to sensitive objects or fabrics. Wasted energy is dispersed as heat through the base of the LED.
  • Slow failure: LEDs mostly fail by dimming over time, rather than the abrupt failure of incandescent bulbs.
  • Lifetime: LEDs can have a relatively long useful life. If the LED is cooled correctly, it should perform [LM-70] for 100,000 hours. Fluorescent tubes typically are rated at about 10,000 to 15,000 hours, depending partly on the conditions of use, and incandescent light bulbs at 1,000 to 2,000 hours. Several DOE demonstrations have shown that reduced maintenance costs from this extended lifetime, rather than energy savings, is the primary factor in determining the payback period for an LED product.
  • Shock resistance: LEDs, being solid-state components, are difficult to damage with external shock, unlike fluorescent and incandescent bulbs, which are fragile.
  • Focus: The solid package of the LED can be designed to focus its light. Incandescent and fluorescent sources often require an external reflector to collect light and direct it in a usable manner. For larger LED packages total internal reflection (TIR) lenses are often used to the same effect. However, when large quantities of light is needed many light sources are usually deployed, which are difficult to focus or collimate towards the same target.
  • Sustainable lighting: Efficient lighting is needed for sustainable architecture. In 2009, a typical 13-watt LED lamp emitted 450 to 650 lumens, which is equivalent to a standard 40-watt incandescent bulb. In 2011, LEDs have become more efficient, so that a 6-watt LED can easily achieve the same results. A standard 40-watt incandescent bulb has an expected lifespan of 1,000 hours, whereas an LED can continue to operate with reduced efficiency for more than 50,000 hours, 50 times longer than the incandescent bulb.

LED Life Span

Many LED luminaires are designed to last over 100,000 hours.

The environmental temperature must be taken under consideration. Many of LED manufacturers claim to last 100,000 hours but at 25° C. Room temperature is not always the case and as we know, heat rises. This means that the temperature at the ceiling of any structure will not be the same as ground level. Lights designed in high temperature environments must take this into account.

What does a 100,000 hours means?

 

Efficacy

Efficacy is effected by a myriad of factors. Typical units of light efficacy are lumens per watt (lm/W). Light output (lumens, lm) are affected by drive current, heat dissipation from LED, and optical losses from lenses and such. Input wattage is primarily affected by the power drawn by the LED, losses within the LED driver to heat—which affects light output as well—and peripheral systems in the LED lighting system. Current LED technology can reach upwards to 200 lm/W in controlled test environments. Realistically however, typical LED lighting systems can reach from 80 lm/W towards an upward limit of 120 lm/W. The limit is constantly being pushed up as LED technology and thermal management technology improve.

Many lights will perform in different temperature environments. The efficacy of the LED chip itself is directly related to temperature of the  (junction temperature) of the LED.

What is a HPS [high pressure sodium], HID [high intensity discharged] light? Since HPS is used the most for high bay applications, we will be focusing on it. So, what is an HPS Light?

There are two kinds of sodium lights: Low Pressure (LPS) and High Pressure (HPS). These lamps are mostly used for street lighting as well as industrial uses. The lamp works by creating an electric arc through vaporized sodium metal.

Here is a representation on how the light behaves once it leaves the bulb.

Some points to considered regarding HPS high bays:

  • The light must warm up before working at full capacity, anywhere from 2 to 15 minutes.
  • They use a noise ballast, typically consuming anywhere from 20% to 50% on top of the consumption of the light bulb [depending on the ballast].
  • Dimming capabilities can be up to 50% of the total light output.
  • These lights produce a surface heat of around 215° Celsius.
  • A 100 Watt HPS lamp contains around 6mg of mercury which is harmful to people.
  • HPS operational temperature is -30° to 65°

“There’s a fundamental flaw with fan-and-heatsink cooling systems: no matter how hard the fan blows, a boundary layer of motionless, highly-insulating air remains on the heatsink. You can increase the size of the heatsink and you can blow more air, but ultimately the boundary layer prevents the system from being efficient; it’s simply a physical limitation of fan-and-heatsink cooling systems in specific, and every kind of air-cooled heat exchanger in general, including air conditioning and refrigeration units.” –from ExtremeTech.com

The cooling system of lights does not rely solely on a “fan blowing” over the fins of the heat sink. We designed our system to use the fan as an extra component to achieve a desired efficiency.

The design of the heat sink was carefully mapped base on the specific foot print of the LED. Each LED releases a heat signature. This heat signature was mapped and the location of the fins placed accordingly. The fans just help so the system does not saturate and only a 10% of the total volume of the system is used.

A function of the heat sink is to transfer heat from one place to another. The problem is that the heat sink must saturate first before it starts dissipating heat.

Our design does not wait for this phenomenon to happens, it gets rid of the heat right where the heat signature of the LED happens. This is our proprietary technology and it is our “DIFFERENCE”.

By utilizing this technique, we can maintain a constant temperature of 30° C to 35°C at the junction temperature, . This is an important factor since temperature of the LED will determine several factors:

  • Light efficiency
  • Longevity
  • LM-70 of the fixture

The heat sink was designed to perform even if the fans were not there. The LEDs we utilize for our new lights, can safely perform at 105° C at the .

Extrusion VS. Die Casting

Casting was not an option. Casting cannot be used where wall thickness varied and required wall thickness of 1mm of less.

Sand and permanent mold casting results in parts that may need extensive finishing before use. Aluminum extruding produces a wrought structure with relatively close dimensional control. This was a major, key factor for us, since the location of the fins cannot vary due to heat signatures of the LED.

We opted to use new aluminum and not recycled aluminum for our heat sinks. Thermal properties can vary drastically between the two.

There was no way for us to control the molecular structure and flow of aluminum in casting. Our design requires high precision and constant material properties in order for the heat to flow at certain speed.

The design of the heat sink was done with aluminum extrusion in mind.