LED tube lamps

LED tube lights are designed to physically fit in fixtures intended for fluorescent tubes. Some LED tube lamps are intended to be a drop-in replacement into existing fixtures if appropriate ballast is used. Others require rewiring of the fixtures to remove the ballast. An LED tube lamp generally uses many individual Surface-Mounted LEDs which are directional and require proper orientation during installation as opposed to Fluorescent tube lamps emit light in all directions around the tube. Most LED tube lights available can be used in place of T8, T10, or T12 tube designations, T8 is D26mm, T10 is D30mm, in lengths of 590 mm (23 in), 1,200 mm (47 in) and 1,500 mm (59 in).

Lighting designed for LEDs

Newer light fittings designed for LED lamps, or indeed with long-lived LEDs built-in, have been coming into use as the need for compatibility with existing fittings diminishes. Such lighting does not require each bulb to contain circuitry to operate from mains voltage.

Specialty uses

White LED lamps have achieved market dominance in applications where high efficiency is important at low power levels. Some of these applications include flashlights, solar-powered garden or walkway lights, and bicycle lights. Monochromatic (colored) LED lamps are now commercially used for traffic signal lamps, where the ability to emit bright monochromatic light is a desired feature, and in strings of holiday lights. LED automotive lamps are widely used for their long life and small size (allowing for multiple bulbs), improving road safety. LED lamps are also becoming popular in homes, especially for bathroom and medicine cabinet lighting.

Comparison to other lighting technologies

See luminous efficacy for an efficiency chart comparing various technologies.

• Incandescent lamps (light bulbs) generate light by passing electric current through a resistive filament, thereby heating the filament to a very high temperature so that it glows and emits visible light over a broad range of wavelengths. Incandescent sources yield a "warm" yellow or white color quality depending on the filament operating temperature. Incandescent lamps emit 98% of the energy input as heat. A 100 W light bulb for 120 V operation emits about 1,700 lumens, about 17 lumens/W; for 230 V bulbs the figures are 1340 lm and 13.4 lm/W. Incandescent lamps are relatively inexpensive to make. The typical lifespan of an AC incandescent lamp is 750 to 1,000 hours. They work well with dimmers. Most older light fixtures are designed for the size and shape of these traditional bulbs. In the U.S. the regular sockets are E26 and E11, and E27 and E14 in some European countries.
• Fluorescent lamps work by passing electricity through mercury vapor, which in turn emits ultraviolet light. The ultraviolet light is then absorbed by a phosphor coating inside the lamp, causing it to glow, or fluoresce. Conventional linear fluorescent lamps have life spans around 20,000 and 30,000 hours based on 3 hours per cycle according to lamps NLPIP reviewed in 2006. Induction fluorescent relies on electromagnetism rather than the cathodes used to start conventional linear fluorescent. The newer rare earth triphosphor blend linear fluorescent lamps made by Osram, Philips, Crompton and others have a life expectancy greater than 40,000 hours, if coupled with a warm-start electronic ballast. The life expectancy depends on the number of on/off cycles, and is lower if the light is cycled often. The ballast-lamp combined system efficacy for then current linear fluorescent systems in 1998 as tested by NLPIP ranged from 80 to 90 lm/W.
• Compact fluorescent lamps' specified lifespan typically ranges from 6,000 hours to 15,000 hours.
• Electricity prices vary in different areas of the world, and are customer dependent. In the US generally, commercial (0.103 USD/kWh) and industrial (0.068 USD/kWh) electricity prices are lower than residential (0.123 USD/kWh) due to fewer transmission losses.

Comparison table

Cost Comparison for 60 watt incandescent equivalent lightbulb (U.S. residential electricity prices)
	Incandescent	Halogen	CFL	LED (Cree)	LED (Philips)	LED (LEDNovation)	LED (Nanoleaf NL02-1200)
Purchase price	$0.41	$1.50	$0.99	$9.97	$4.35	$31.50	$24.99
PF	1	1	0.5	0.75[citation needed]	0.5	0.5	0.5
Real power used (watts)	60	35	14	9.5	8.5	9.4	10
lumens (mean)	860	860	775	800	800	810	1200
lumens/watt	14.3	24.6	55.4	84	94.1	86.2	120
Color Temperature kelvin	2700	2900	2700	2700	2700	2700	3000
CRI	100	100	82	80	80	94	80
Lifespan (hours)	1,000	4,000	10,000	25,000	10,000	50,000	30,000
Bulb lifetime in years @ 6 hours/day	0.46	1.83	4.6	11.4	4.6	22.8	13.7
Energy cost over 20 years @ 13 cents/kWh	$342	$199	$159	$72	$97	$107	$114
Total cost over 20 years	$360	$216	$164	$90	$116	$135	$150
Total cost per 860 lumens	$360	$216	$182	$96	$125	$143	$108
Comparison based on 6 hours use per day (43,800 hours over 20 yrs)

In keeping with the long life claimed for LED lamps, long warranties are offered. One manufacturer warrants lamps for professional use, depending upon type, for periods of (defined) "normal use" ranging from 1 year or 2,000 hours (whichever comes first) to 5 years or 20,000 hours. A typical domestic LED lamp is stated to have an "average life" of 15,000 hours (15 years at 3 hours/day), and to support 50,000 switch cycles.

Incandescent and Halogen have a natural Power factor of 1, but Compact fluorescent and LED lamps are using input rectifier and this causes high harmonics content in input current and also reactive power consumption. This causes extra loss (harmonics) and power transfer cost (copper usage) toward the power plant and energy cost will be distributed to all customers by rising energy bills. Future developments may implement PFC-circuits to bring the PF up to 1, but higher material cost and volume of electronics will result. Dimmable LED-Lamps typical have higher PF by using so called Valley-fill circuits, non-dimmable uses cheaper bridge rectifiers. The EU-Standard requires a PF better than 0.5 for power up to 25 Watt.

Energy Star qualification

Energy Star is an international standard for energy efficient consumer products. Devices carrying the Energy Star service mark generally use 20–30% less energy than required by US standards.

Energy Star LED qualifications:

• Reduces energy costs — uses at least 75% less energy than incandescent lighting, saving on operating expenses.
• Reduces maintenance costs — lasts 35 to 50 times longer than incandescent lighting and about 2 to 5 times longer than fluorescent lighting. No bulb-replacements, no ladders, no ongoing disposal program.
• Reduces cooling costs — LEDs produce very little heat.
• Is guaranteed — comes with a minimum three-year warranty — far beyond the industry standard.
• Offers convenient features — available with dimming on some indoor models and automatic daylight shut-off and motion sensors on some outdoor models.
• Is durable — won’t break like a bulb.

To qualify for Energy Star certification, LED lighting products must pass a variety of tests to prove that the products will display the following characteristics:

• Brightness is equal to or greater than existing lighting technologies (incandescent or fluorescent) and light is well distributed over the area lit by the fixture.
• Light output remains constant over time, only decreasing towards the end of the rated lifetime (at least 35,000 hours or 12 years based on use of 8 hours per day).
• Excellent color quality. The shade of white light appears clear and consistent over time.
• Efficiency is as good as or better than fluorescent lighting.
• Light comes on instantly when turned on.
• No flicker when dimmed.
• No off-state power draw. The fixture does not use power when it is turned off, with the exception of external controls, whose power should not exceed 0.5 watts in the off state.

Limitations

Color rendering is not identical to incandescent lamps which emit close to perfect Black-body radiation as that from the sun and what eyes have evolved for. A measurement unit called CRI is used to express how the light source's ability to render the eight color sample chips compare to a reference on a scale from 0 to 100. LEDs with CRI below 75 are not recommended for use in indoor lighting.

LED lamps may flicker. The effect can be seen on a slow motion video of such a lamp. The extent of flicker is based on the quality of the DC power supply built into the lamp structure, usually located in the lamp base. Longer exposures to flickering light contribute to headaches and eye strain.^{[citation needed]}

LED lamps are high intensity point sources of light. As such looking directly at them is damaging for the eye. The reason for this is the same as for looking at the sun on a solar eclipse. At daytime the bright light causes the pupil to contract and activates a reflex to blink or look away. With a point light source this reflex does not activate but the damage to the retina is the same just to a smaller area of it.^{[citation needed]}

LED efficiency and life span drop at higher temperatures, which limits the power that can be used in lamps that physically replace existing filament and compact fluorescent types. Thermal management of high-power LEDs is a significant factor in design of solid state lighting equipment.

LED lamps are sensitive to excessive heat, like most solid state electronic components. LED lamps should be checked for compatibility for use in totally or partially enclosed fixtures before installation since heat build-up could cause lamp failure and/or fire.

Depending on the design of the lamp, the LED lamp may be sensitive to electrical surges.^{[citation needed]} This is generally not an issue with incandescents, but can be an issue with LED and compact fluorescent bulbs. Power circuits that supply LED lamps can be protected from electrical surges through the use of surge protection devices.^{[citation needed]}

The long life of LEDs, expected to be about 50 times that of the most common incandescent bulbs and significantly longer than fluorescent types, is advantageous for users but will affect manufacturers as it reduces the market for replacements in the distant future.

Efficiency droop

The term "efficiency droop" refers to the decrease in luminous efficacy of LEDs as the electric current increases above tens of milliamps (mA). Instead of increasing current levels, luminance is usually increased by combining multiple LEDs in one bulb. Solving the problem of efficiency droop would mean that household LED light bulbs would need fewer LEDs, which would significantly reduce costs.

In addition to being less efficient, operating LEDs at higher electric currents creates higher heat levels which compromise the lifetime of the LED. Because of this increased heating at higher currents, high-brightness LEDs have an industry standard of operating at only 350 mA. 350 mA is a good compromise between light output, efficiency, and longevity.

Early suspicions were that the LED droop was caused by elevated temperatures. Scientists proved the opposite to be true that, although the life of the LED would be shortened, elevated temperatures actually improved the efficiency of the LED. The mechanism causing efficiency droop was identified in 2007 as Auger recombination, which was taken with mixed reaction. In 2013, a study conclusively identified Auger recombination as the cause of efficiency droop.

Development and adoption history

The first LEDs were developed in the early 1960s, however, they were low-powered and only produced light in the low, red frequencies of the spectrum. The first high-brightness blue LED was demonstrated by Shuji Nakamura of Nichia Corporation in 1994. The existence of blue LEDs and high-efficiency LEDs led to the development of the first 'white LED', which employed a phosphor coating to partially convert the emitted blue light to red and green frequencies creating a light that appears white.^{[not in citation given]} Isamu Akasaki, Hiroshi Amano and Nakamura were later awarded the 2014 Nobel prize in physics for the invention of the blue LED.

The Energy Independence and Security Act (EISA) of 2007 authorized the Department of Energy (DOE) to establish the Bright Tomorrow Lighting Prize competition, known as the "L Prize", the first government-sponsored technology competition designed to challenge industry to develop replacements for 60 W incandescent lamps and PAR 38 halogen lamps. The EISA legislation established basic requirements and prize amounts for each of the two competition categories, and authorized up to $20 million in cash prizes. The competition also included the possibility for winners to obtain federal purchasing agreements, utility programs, and other incentives. In May 2008, they announced details of the competition and technical requirements for each category. Lighting products meeting the competition requirements could use just 17% of the energy used by most incandescent lamps in use today. That same year the DOE also launched the Energy Star program for solid-state lighting products. The EISA legislation also authorized an additional L Prize program for developing a new "21st Century Lamp".

Philips Lighting ceased research on compact fluorescents in 2008 and began devoting the bulk of its research and development budget to solid-state lighting. On 24 September 2009, Philips Lighting North America became the first to submit lamps in the category to replace the standard 60 W A-19 "Edison screw fixture" light bulb, with a design based on their earlier "AmbientLED" consumer product. On 3 August 2011, DOE awarded the prize in the 60 W replacement category to a Philips' LED lamp after 18 months of extensive testing.

Early LED lamps varied greatly in chromaticity from the incandescent lamps they were replacing. A standard was developed, ANSI C78.377-2008, that specified the recommended color ranges for solid-state lighting products using cool to warm white LEDs with various correlated color temperatures. In June 2008, NIST announced the first two standards for solid-state lighting in the United States. These standards detail performance specifications for LED light sources and prescribe test methods for solid-state lighting products.

Also in 2008 in the United States and Canada, the Energy Star program began to label lamps that meet a set of standards for starting time, life expectancy, color, and consistency of performance. The intent of the program is to reduce consumer concerns due to variable quality of products, by providing transparency and standards for the labeling and usability of products available in the market. Energy Star Light Bulbs for Consumers is a resource for finding and comparing Energy Star qualified lamps. A similar program in the United Kingdom (run by the Energy Saving Trust) was launched to identify lighting products that meet energy conservation and performance guidelines.

The Illuminating Engineering Society of North America (IESNA) in 2008 published a documentary standard LM-79, which describes the methods for testing solid-state lighting products for their light output (lumens), efficacy (lumens per watt) and chromaticity.

In January 2009, it was reported that researchers at Cambridge University had developed an LED bulb that costs £2 (about $3 U.S.), is 12 times as energy efficient as a tungsten bulb, and lasts for 100,000 hours. Honeywell Electrical Devices and Systems (ED&S) recommend worldwide usage of LED lighting as it is energy efficient and can help save the climate.

As of 2016, in the opinion of Noah Horowitz of the Natural Resources Defense Council, new standards proposed by the United States Department of Energy would likely mean most light bulbs used in the future would be LED.

Examples of early adoption

In 2008 Sentry Equipment Corporation in Oconomowoc, Wisconsin, US, was able to light its new factory interior and exterior almost solely with LEDs. Initial cost was three times that of a traditional mix of incandescent and fluorescent lamps, but the extra cost was recovered within two years via electricity savings, and the lamps should not need replacing for 20 years. In 2009 the Manapakkam, Chennai office of the Indian IT company, iGate, spent ?3,700,000 (US$80,000) to light 57,000 sq ft (5,300 m²) of office space with LEDs. The firm expected the new lighting to pay for itself fully within 5 years.

In 2009 the exceptionally large Christmas tree standing in front of the Turku Cathedral in Finland was hung with 710 LED bulbs, each using 2 watts. It has been calculated that these LED lamps paid for themselves in three and a half years, even though the lights run for only 48 days per year.

In 2009 a new highway (A29) was inaugurated in Aveiro, Portugal, it included the first European public LED-based lighting highway.

By 2010 mass installations of LED lighting for commercial and public uses were becoming common. LED lamps were used for a number of demonstration projects for outdoor lighting and LED street lights. The United States Department of Energy made several reports available on the results of many pilot projects for municipal outdoor lighting, and many additional streetlight and municipal outdoor lighting projects soon followed.

See also

• LED display
• LED headlamp
• LED filament
• List of emerging technologies
• List of light sources
• Lux
• Photometry (optics)
• Radiation angle
• Solar lamp
• Spectrometer

References

Further reading

• E. F. Schubert (2006) Light Emitting Diodes, Second edition. Cambridge University Press. ISBN 0-521-86538-7

External links

• e-lumen.eu – a website from the European Commission about the second generation of energy-saving lightbulbs
• myIQshop – a website that display different types of LED lights

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