Lamps that are touted as longer lasting than incandescent lamps can burn out faster in some cases

Lamps that are touted as longer lasting than incandescent lamps can burn out faster in some cases

When the LED bulb replaces the old Edison bulb, it is expected to achieve higher energy efficiency and longer service life.

According to the US Department of Energy, LEDs consume at least 75% less power than incandescent bulbs and have a life span of 25 times.

But it is not clear how long modern lamps can last outside of ideal laboratory conditions, and in some cases, their lifespan may not be longer than that of traditional bulbs that have fallen off the shelf.

Nadarajah Narendran, research director of the Lighting Research Center at Rensselaer Polytechnic Institute, said: "People have a lot of expectations. If you buy an LED bulb, you don't have to replace it. Now is the time for us to reset these." Expectations. "

When the incandescent bulb burns out, it will go out as the glowing filament breaks.

Light-emitting diodes (the components that provide illumination in LED bulbs) are different. They do not die suddenly, but become darker and darker over time. According to industry standards, when their brightness is reduced by 30%, their useful life is over.

There is no convenient way to measure it at home. If the bulb does not look bright enough, it may be time to replace it.

To help consumers understand what will happen, the Federal Trade Commission requires manufacturers to print the expected lifespan of LED bulbs on product packaging. Usually, the period is expressed in hours or years, and it is assumed that the light bulb provides three hours of illumination per day.

The lifetime is determined by testing a single LED package in the laboratory. Each package contains an LED chip, similar to Christmas lights. According to Dr. Narendran, according to the standards set by the Lighting Engineering Society, the ambient temperature of the laboratory is 75 degrees Fahrenheit, and the LED package runs continuously for 6,000 hours without switching.

The resulting life rating is a statistical estimate of the median operating life. If the rated life of the bulb is 10,000 hours, it means that laboratory analysis has found that under the operating conditions and failure standards specified by the manufacturer, 50% of the tested products can last this long.

A program developed by the Environmental Protection Agency and the Department of Energy to improve energy efficiency, an Energy Star certified bulb may have a rated life of 20,000 hours, or approximately 18 years based on 3 hours of use per day.

But in daily use, there may be as many as a dozen LEDs in series in a bulb; one or more bulbs may be enclosed in a luminaire that obstructs air circulation; and the lights may be turned on and off many times a day-all of these All circumstances will cause the LED to dim faster than promised.

"The way and where the bulb is used affects its lifespan, and it is always detrimental," said Dr. Narendran. "It will reduce rather than increase lifespan."

Dr. Narendran said that lumen degradation can usually be traced to the effects of heat and humidity or power cycling. When the lamp is turned off and on, other components in the bulb may also malfunction, resulting in a shortened lifespan.

If the test procedure is modified to take into account all these conditions, it will change the life expectancy.

"You will find that the life span of an LED is not 20 years," said Dr. Narendran. "It will be much shorter. In some cases, it may be worse than an incandescent lamp. If you trap three bulbs in one bulb, you can only get 500 hours. Surface-mounted fixtures", where the airflow is affected by limit.

In contrast, incandescent bulbs are expected to last 1,000 hours.

In June, after reviewing reports published in global journals, conference proceedings, white papers, and government websites since 2011, Dr. Narendran and his colleagues, who have been studying the life of LEDs since 1999, confirmed that LEDs have the longest service life. Potential for all lighting technologies.

However, they stated that instead of evaluating LED bulbs based on the length of time required for a single component (light-emitting diode) to degrade, the industry needs to define "LED system life" and develop corresponding tests to accurately estimate its length.

Dr. Narendran said: “Testing a single LED is very different from testing everything together as a bulb. Consumers should understand that if you buy LED bulbs and place them in a desk lamp with open ventilation, they will be different from the bulb. The fixtures that are confined in the air are different. If you don’t turn on and off the desk lamp multiple times, the desk lamp will get the requirements on the package."

The literature review was commissioned by the International Energy Agency, which was established in 1974 and consists of 30 member states to promote sustainable energy policies. The goal is to help regulators develop meaningful LED life requirements.

To this end, researchers recommend evaluating lumen decay and catastrophic failures caused by power outages or other component failures.

They said that the system lifetime should be defined by a shorter span.

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