LED Standards and Challenges - Role of Standardization Dr.Sandeep Garg
The Large Market Acceleration strategy
by the Government of India has made way for LED acceleration strategy coupled
with the co-existence of the “Make in India” campaign. Because of the high
energy efficiency of LED products, which are typically characterized using
efficacy, which in basic terms is the ratio of power input to light output—or
more technically, emitted flux (lumens) divided by power drawn (watts), the key
question now figures around the compliance to the standard, which the Bureau of
Indian Standard is making effort to ensure that India is the forerunner in
quality of the products being offered.
The Bureau of Indian Standard along with the Department of Electronics are coming out with complementary policies to ensure that most of the products made in India, comply to Indian standards and over a period develop an ecosystem for conformance to quality. However, large product requirement currently envisaged by government also throws many challenges in terms of meeting the standards. There are several important nuances that must not be overlooked as enumerated below.
1. LED packages have their own efficacy, which is different from the efficacy of an integrated LED lamp or an LED luminaire; the difference stems from driver, thermal, and optical losses. The efficacy of both LED packages and complete products depends on many factors, which range from electrical efficiency to internal quantum efficiency to spectral efficiency. It is also necessary to understand the different procedures and conditions used for measuring conventional and LED products, as well as the difference between commercially available products and laboratory samples.
BIS has specified that LED packages meet LM-80 or IS 16105: 2012 standard as specified. This Indian Standard for LED specifically takes care of the higher junction temperatures. While globally, all the chip manufactures meet the temperature of 25, 55 and 85, the Indian standard defines the temperature as 55, 85 and 105. The Report being published by the manufactures therefore needs to be carefully evaluated for packages. Enough resources should be invested to cross-check claims as this will ensure market deterrent for spurious products. This singular test will determine the performance of chip packages in the long run with respect to their efficacy in light output, colour shift and other parameters respectively.
2. Lamp and Luminaire Efficacy: Thermal effects, driver losses, and optical inefficiencies all combine to reduce the efficacy of LED luminaires compared to the included LED packages. Considered collectively, these loss mechanisms can result in a decrease in efficacy of greater than 30%. Therefore, considering the Chip efficacy, the standard also complies the manufactures to design their products, to ensure that the best luminaire gives the best efficacy. In some of the best designed luminaries the efficacy can go as high as 95%, indicating that a chip package of 100 l/watt can deliver 95 l/w light when designed effectively. Notably, the efficacy of complete LED lamps and luminaires is most relevant to building energy use and will directly impact the light output.
3. Thermal Effects: A major factor in determining the lumen output of an LED is junction temperature. As temperature increases, the light-generation process becomes less efficient and fewer lumens are emitted. For this reason, LED lamps and luminaires generally require a thermal management system. However, even in a well-designed product, the junction temperature may rise significantly above laboratory conditions, ultimately resulting in up to a 15% decrease in efficacy. Unlike driver and optical losses, thermal effects are generally unique to LEDs; this is one of the key reasons why LEDs are tested using absolute photometry rather than relative photometry. IS 16105 or LM-79 prescribes absolute photometry and stipulates the ambient air temperature (25 °C), mounting, airflow, power supply characteristics, seasoning and stabilization, testing orientation, electrical settings, and instrumentation for both integrating sphere and goniophotometer measurements. The Type of Goniophotometer described in test, has to be dealt carefully with, to ensure that the readings submitted are common to manufactures across labs. Therefore, ILC (Inter Lab Comparison) and PT (Proficiency testing) makes an intelligent choice for buyers to comply with this standard.
4. Driver Losses: LEDs require a driver, which is comprised of both a power source and electronic control circuitry. Most drivers convert line voltage to low voltage and current from AC to DC, and may also include supplementary electronics for dimming and/or color correction. Currently available LED drivers are typically about 85% efficient, with some improvement projected. The Indian Standard for drivers takes care of such efficacy levels and testing of the driver in the pre-stages of procurement by manufactures is therefore important for extending life of the finished product. Specifying, Compulsory registration for drivers by BIS should be adhered and must be respected as a lawful compliance.
5. Optical Losses: Regardless of source type, the use of lenses, reflectors, or other optical systems to shape a product’s distribution, ultimately reduces the total amount of emitted light. For LEDs, this is another contributing factor in the difference between package efficacy and lamp or luminaire efficacy. However, the magnitude of the effect is difficult to state given the large diversity of fixtures in the marketplace. Therefore, enforcing absolute photometry in labs for LED fixtures makes them differ from conventional products measured using relative photometry. Compliance to the Standards for LED lamps therefore makes a perfect choice for buyers of LED lamps.
6. Application Efficacy: Lamp and luminaire efficacy are important indicators of energy efficiency, but they may not tell the whole story. Application efficacy, defined as the power drawn necessary to achieve specified illuminance criteria, may provide valuable data when comparing products for a specific application. If a luminaire directs a greater percentage of light to the target area — a roadway, for example — it may have a higher application efficacy despite having a lower luminaire efficacy. Importantly, it is not possible to quantify application efficacy for all uses of a given product, nor should application efficacy be compared for different situations. There is no generic value that can be reported as a product characteristic, so application efficacy must be calculated on a case-by-case basis. Compliance mechanism and defining these criteria into the detailed specification is therefore very important.
7. Initial and Maintained Efficacy: The lumen output of almost all lighting products depreciates over time, while—at least in theory—input power remains constant. Thus, the luminous efficacy at the beginning of life is greater than the luminous efficacy when the end of rated life is approaching. Even though TM-21 test in the LM-80 or IS 16106 defines the time period of lumen depreciation, yet, the rate of lumen depreciation and the overall amount of decline are different for different source types, or even for different products using the same source type. Also, the efficacy is dependent on other factors and will also critically impact just as CCT etc. . . . Thus, the source that is more efficacious may change over the life of the products. Also, the change of the source is also likely see a dramatic rise over future years as the lumens efficacy of the lamp source is likely to see a rise in future. Therefore, the procurers must ensure and be cautious about the tall claims raised by the manufacturers as LEDs may allow for a smaller connected load initially, but the efficacy will decrease over time and energy use will increase. This approach may or may not lead to less energy use over the lifetime of the system, and it can make product comparisons more challenging.
8. Efficacy versus Energy Use: Efficacy is related to energy efficiency, but it cannot be used to establish energy use. Energy use is the power drawn over time, and is typically reported in units of kilowatt-hours (kWh). A less efficacious product may in fact use less energy if it is operated for fewer hours. Control systems can be an important tool for realizing energy savings. When comparing the usage hours over time, the use of IT driven system, which can be integrated in future with the latest technology should also figure as an important criteria for buyers.
The efficacy of LED products has steadily improved since their introduction as a source for general illumination. This trend is expected to continue, thanks to new materials, better manufacturing processes, and new configurations. Currently, the efficacy of LED packages compares very favorably to conventional light sources, and many integrated LED lamps and LED luminaires have efficacies that are comparable to their traditional counterparts. However, the variability in LED products is greater than for the more mature technologies and the products are changing rapidly. Importantly, efficacy should not be the only factor when comparing products. Other performance characteristics, such as color quality, luminous intensity distribution, and dimmability must be included in a holistic decision. Although high efficacy is an important attribute for energy savings, it is unperceivable to the users of a space. To have a singularity of market acceptance, it is important that the Standards defined plays a very critical role in ensuring that the product offered and accepted are compared equally and rigorously for longer life and better market acceptance by consumers.
About the Author
Dr Sandeep Garg is a
Fellow (Life) Member of the Indian Society of Lighting Engineers. He is the
Chair of the LED Panel Committee in BIS and actively engaged in the Standardization
activities of LED modules and products. Presently Dr.Garg
is Chief Technical Specialist in SIDBI ( Small Industries
Development Bank of India) looking after Energy Efficiency Verticals.