Q: What’s the difference between LED lighting and other energy-efficient lighting technologies?
A: LEDs offer the potential for cutting general lighting energy use nearly in half by 2030, saving energy dollars and carbon emissions in the process. Their unique characteristics—including compact size, long life, resistance to breakage and vibration, good performance in cold temperatures, lack of infrared or ultraviolet emissions, and instant-on performance—are beneficial in many lighting applications. The ability to be dimmed and to provide color control are other benefits of the LED lighting technology platform.
One of the defining features of LEDs is that they emit light in a specific direction, which reduces the need for reflectors and diffusers that can lower efficiency. In contrast, fluorescent and “bulb”-shaped incandescent lamps emit light in all directions, with the result that much of the light they produce is lost within the fixture, escapes in a direction not useful for the intended application, or requires pricey and bulky optics to get the light in the right place. With many fixture types, including recessed downlights, troffers, and undercabinet fixtures, it is not uncommon for only 50 to 60% of the total light produced to be emitted.
In addition, LED sources are inherently dimmable and instantaneously controllable, and they can be readily integrated with sensor and control systems, thus enabling further energy savings through the use of occupancy sensing, daylight harvesting, and local control of light levels. LED technology also offers the prospect of full color control over the light spectrum. What this all adds up to is the potential to improve the performance and value of lighting in totally new ways.
Q: How do LEDs Work?
A：LEDs are comprised of 3 main components: the LED’s (the chip set that produces light), the driver (converts AC to DC) and the heat sink (to keep everything cool). LEDs take DC power from the driver and create light. The heat sink captures heat from the LEDs and the drivers. Although LEDs produce significantly less heat than the light bulbs we have been used to over the past century, the heat they produce must be managed. The better this is done, the longer the life of the product.
LED’s also performs the job of converting electricity to light more efficiently than other light sources, that is why we can replace a 400W metal halide bulb with a LED 100W retrofit.
Q: How is white light created ?
A：Unlike incandescent lamps, LEDs are not inherently white light sources. Instead, LEDs emit nearly monochromatic light, making them highly efficient for colored light applications such as traffic lights and exit signs. However, to be used as a general light source, white light is needed. White light can be achieved with LEDs in three ways:
Phosphor conversion, in which a phosphor is used on or near the LED to convert the colored light to white light
RGB systems, in which light from multiple monochromatic LEDs (e.g., red, green, and blue) is mixed, resulting in white light
A hybrid method, which uses both phosphor-converted (PC) and monochromatic LEDs.
The potential of LED technology to produce high-quality white light with unprecedented energy efficiency is the primary motivation for the intense level of research and development.
Q: What are the benefits of replacing the conventional lighting with LEDs?
A：There are many benefits. Here is a list of a few:
a. An immediate reduction in your electricity bill.
b. Less heat. LED fixtures are extremely efficient converting electricity into light.
c. LED Bulbs last a very long time, typically 50,000 to 100,000 hours.
d. They are virtually indestructible.
e. They do not contain mercury or other hazardous materials
f. Highly recyclable – with no hazardous parts, you can easily reclaim most of the parts in an environmentally safe way.
Q: How are LEDs dimmed?
A：LEDs are dimmed either by Pulse Width Modulation PWM, or by Constant Current Reduction CCR. PWM dimming involves switching current at a high frequency from zero to the rated output current. CCR dimming: The lighting level required is proportional to the current flowing through the LED . Current flows through the LED continuously and is reduced or increased based on whether the LED is to be dimmed further or made brighter.
Q: How long do LEDs last?
A：LED luminaire useful life is often described by the number of operating hours until the LED luminaire is emitting 70 percent of its initial light output. Good-quality white LED lighting products are expected to have a useful life of 30,000 to 50,000 hours or even longer. A typical incandescent lamp lasts about 1,000 hours; a comparable CFL, 8,000 to 10,000 hours; and the best linear fluorescent lamps, more than 30,000 hours. Learn more about LED lifetime and reliability.
Other aspects of reliability should also be considered. Catastrophic failure describes the situation where a luminaire no longer emits light, typically due to an electronics failure. The long life of the LED means that there is ample opportunity for the electronics to fail before the LEDs go bad. Another type of failure is due to color shift. All light sources change color over time. The long expected life of an LED lighting product means that before the LED fails, the color of the light may shift to an unacceptable degree, depending on the application. In general, LED lighting lives up to its promise for long life, but all aspects of reliability should be considered when selecting a product.
Q: Are LEDs cost-effective?
A：Costs of LED lighting products vary widely. Some LED bulbs can cost as little as $1 – $2, but other LED lighting products may carry a significant cost premium compared to standard lighting technologies. In general, LED lighting products are still more expensive than their conventional counterparts, but when the costs of energy and maintenance are included in the total cost of ownership, LED-based products can have a distinct advantage. And differences among LED lighting products typically correspond with differences in various lighting performance features, such as color quality, lifetime, optical performance, and dimmability.
Q: Do LEDs provide high-quality light?
A：Key aspects of high-quality light are the color appearance of the light itself, which is described by its color coordinates but is often condensed (with significant loss of information) to correlated color temperature (CCT), and how the light affects the color appearance of objects, which is referred to as color fidelity. Color fidelity can be quantified using the color rendering index (CRI), or with one of several other recently developed metrics. LED light sources have demonstrated that they can achieve a wide range of color qualities, depending on the demands of the lighting application. However, to achieve high levels of color quality, there are typically cost and efficiency tradeoffs. In general, a minimum CRI of 80 is recommended for interior lighting, and LED products can readily achieve this performance. CRI of 90 or higher indicates excellent color fidelity; LEDs can also meet this threshold. CRI is far from a perfect metric and is especially poor at predicting the fidelity of saturated reds, for which the supplemental value R9 is often used. New metrics, such as the fidelity index (Rf) and the gamut index (Rg), which are described in IES TM-30-15, can provide a more comprehensive evaluation of color rendering.
Q: What are the typical types of LED modules available in the market?
A：LED modules may be available in the following forms:
a. Prefabricated chip on board which can be used for specific applications by luminaire manufacturers who design the heat sink and mounting conditions.
b. Chip on board with an optical lens or diffuser as a prefabricated piece with or without integrated heatsink. That can be used by luminaire manufacturers to integrate into luminaire.
c. Retrofit lamps to replace older (halogen) technology. This comes with an integrated heat sink and standard lamp base that can fitted directly into existing luminaires with a standard lamp holder.
d. Prefabricated luminaire with an integrated LED light source and heat sink complete with luminaire housing that is available as a sealed piece. The driver may be integral in the housing or may be remote.
Q: What are LED IP Ratings?
A：IP is an acronym “Ingress Protection”. It is a measurement of the protection an item will have against solid objects (dust, sand, dirt, etc.) and liquids.
An IP rating is comprised of 2 numbers. The first number refers to the protection against solid objects (dust, etc) and the second number refers to protection against liquids.
Low IP ratings are appropriate for:
– Indoor use
– Protected use inside sealed products
– Inside sealed signage
– When using aluminum extrusions
High IP ratings are appropriate for:
– Unsealed outdoor locations
– Places that have a lot of debris
– Areas with heavy foot traffic
– High splash areas
– High contact areas (people touching them)
– Wet locations