LEDs (Light emitting diodes)

Last updated Wednesday 30 April 2008

Play it cool with a bright alternative to halogen spotlights

Heralded as the lighting of the future, LEDs are the most efficient form of lighting to date - and they're stylish and versatile to boot. So are they set to eclipse traditional lights?

LEDs are about 90% more energy-efficient than the standard incandescent bulb, and about twice as efficient as Compact Fluorescent Lightbulbs. Thanks to efficiency, LEDs cost more upfront than their tungsten rivals but win back huge savings in the long run.

They don't flicker and last five times longer than conventional bulbs - and because they produce a powerful, focused light they are an ideal substitute for halogen spotlights, indoors or out.

They also come as dimmers, recessed 'cove' lights and translucent tiles, and can even change colour to match your mood. (Hot tip: the colour blue is almost as effective as coffee at waking you up in the morning.)

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Photo: LEDs (Light emitting diodes)

Saves 300kg of CO2 a year (30kg per bulb)

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How do they work?

Pub Fact

  • There are 3.2 billion conventional lights in use
  • Homes currently account for 27% of the UK's greenhouse gasemissions at around 40 million tonnes of CO2 a year
  • Europeans buy about 2.1bn traditional light bulbs every year
  • When incandescent bulbs first hit the market, people didn't like them because they had difficulty adapting to the glare of the light

Basically, LEDs are just tiny light bulbs that can be screwed directly into the fittings used by conventional bulbs. But unlike ordinary incandescents, they don't have a filament that will burn out, and they don't heat up much. Light is produced solely by the rush of electrons in a semiconductive material.

LEDs are available with Edison (screw-in type) bases to retrofit existing fixtures, strips that can be used in the floor - and even in outdoor landscaping fixtures.

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How will it make a difference?

Traditional incandescent light bulbs are ovens in disguise, releasing about 95% of their energy as heat. LEDs are far more efficient than normal bulbs and have a far longer lifespan - so although they cost a little more up front, they are money savers too.

LEDs use very little energy - retrofit bulbs use about one to seven watts, which is less than CFLs.

As a result, all things considered, LEDs cost significantly less to run than conventional bulbs and produce half as much CO2. (See below for an explanation of why LEDs tend not to cut your emissions as much as they could.)

In fact, if every household in Britain switched from traditional festive lights over Christmas to coloured LEDs, we'd save over 44m on electricity bills and about 200,000 tonnes of CO2. That's the equivalent of taking 70,000 cars off the road, according to the Local Government Association.

Plus, LEDs last much longer than other bulbs - on average about 50,000 hours according to the Alliance for Solid-State Illumination Systems and Technologies (ASSIST).

In addition, LEDs are also fully dimmable unlike the majority of CFLs - and they don't change their colour tint when dimmed like incandescent lamps (which turn yellow). Significantly, LEDs are also free of the toxin mercury, unlike CFLs.

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What's the debate?

LEDs are made of complex alloys of exotic metals like indium and gallium, so require a lot of energy to manufacture. However, their superb energy-efficiency easily outweighs these embodied emissions over the light's lifetime.

Individual LEDs are considerably more efficient than rival light bulbs, but when they are incorporated into a lamp or fixture that efficiency is markedly reduced. That said, LEDs in any form still use less energy than conventional bulbs.

You may not save as much CO2 as expected from switching to LEDs or CFLs if you end up turning the heating up to compensate for their lack of waste heat. Energy-saving lamps make your home cooler because they don't waste as much heat as incandescents - but it's worth noting that heating your home with light bulbs is much less efficient than leaving the central heating to do its job. The EST estimates that due to the 'heat replacement effect', a 100W incandescent replaced by a 20W CFL would save around 26kg CO2 per year per bulb while replacing it with a 10W LED would save around 29kg CO2 per year per bulb.

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What's stopping me?

"I can't afford fancy LED lighting"

Although LED light bulbs are more expensive than incandescent bulbs, they save money in the long run because they use much less electricity and last much longer. Plus, manufacturers claim LED production is increasing rapidly, lowering prices: by 2011 the LED market is expected to have jumped by 20% according to Strategy Analytics.

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How do I do it?

  • Buy some LED bulbs. Online supplies are available. Look on the Ban the Bulb website for suppliers
  • Get the right fixture. LEDs generate heat internally, which, if not drawn away from the light fixture, can cut their useful life and cause colour shifts
  • Expect a bit of variation in colour. Devices from the same batch can vary slightly in colour due to the manufacturing process
  • If you have the money, go for an LED installation - intelligent lighting can change the way a room looks with the flick of a switch

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Comments

Steve, Croydon 2009-06-19

Why hasn't the government taken action against halogens? They put out adverts encouraging us to replace incandescents, ignoring the fact that people are busily installing halogens often tripling the wattage in a room. If the halogens are dimmable and ceiling recessed, then there are no low energy alternatives.
LED lights are great and I have successfully replaced most of my halogens but at the moment the market is complex with a large range of bulbs and still developing and it is easy to make a mistake when buying and some sellers over-claim on the wattage equivalence.
LED light technology also has other green applications. For instance back lighting for TVs potentially halving the wattage used by a large TV. When such TV's come down in cost that will surely deserve a bigger bean than at present.

Baz, Shrewsbury 2009-01-21

The efficiency , or should I say efficacy of these devices is very good, the goal of the manufacturers appears to be around 180 lumens of light foe each Watt of electricity. this compares very well with a typical CFL at 60 lumes / Watt or an incandecent lamp at 13 to 21 Lm/W. Once again we must factor into our calculations any losses in the control gear for these devices, if they can be run from a 12 volt DC supply, perhaps a wind generator or solar voltaic array, losses will be small compared with a 230 volt unit. On the down side, some of the materials used in the LED may be toxic, but they are encased in sealed package, so exposure is unkikely. The light output is very directional and some commentators believe it does not travel well, so it would appear that the applicaton for this technology should be carefully considered before purchase. LED's are well established in automotive applications, the rear lights anr AUDI front sidelights use LED's. Dimming is usually achieved using pulse width modulation, some of us are aware of the flash rate in PWM. Overall, it,s a technology I have embraced

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Glossary terms used on this page
Alloy
A mixture of two or more elements, at least one of which is a metal.
CFL bulbs
CFLs are compact fluorescent lamps. They operate on the same principle as fluorescent lights but the tube is folded into a more compact design so they are more versatile and can be used in devices designed to take traditional incandescent bulbs. They use about 80% less electricity than traditional bulbs to produce the same light and last considerably longer. Their mercury content means disposal, especially of broken bulbs, requires extra care. Also referred to as low-energy lightbulbs.
CO2
CO2, or carbon dioxide, is made up of the elements carbon and oxygen. It exists quite naturally in our atmosphere, as part of the carbon cycle. Everyday processes in the plant and animal world both add CO2 to the atmosphere and take it out. However, because it is a greenhouse gas - meaning it affects the temperature of the earth - the exact level of CO2 is important. Burning fossil fuels releases CO2 into the atmosphere, hence the anxiety that extensive use of these fuels is causing climate change.
Embodied energy
Embodied energy - sometimes referred to as 'embedded energy' - is the energy used (and therefore the CO2 emissions) in manufacturing, packaging and transporting a product, material or service. So when calculating the CO2 savings from a new energy-efficient product such as a boiler or washing machine, its embodied energy needs to be taken into account. Usually the energy saved in use will quickly compensate for the embodied energy, but in some cases - such as small urban wind turbines - it may be that a product will use more energy in its manufacture than it will save across its lifetime.
Emissions
Emissions are the CO2 (and other greenhouse gases) produced by energy use, usually calculated and stated as an annual tally: also referred to as your carbon footprint. Your personal emissions can be direct - such as the gas you personally use to heat your home or the petrol you burn to power your car - or indirect - meaning the energy use that has gone into the products or services you buy. The latter, such as the emissions caused by the manufacture of your new TV, or the packaging your food comes in, are also referred to as embodied emissions.
Greenhouse gases
Greenhouse gases raise the earth's temperature through the greenhouse effect. There are six main examples. As well as carbon dioxide, they include: water vapour, methane, nitrous oxide, ozone and CFCs (which include sulphur hexafluoride, HFCs, and PFCs). Of these, carbon dioxide, methane, nitrous oxide, sulphur hexafluoride, HFCs, and PFCs are controlled under the Kyoto Protocol to limit their concentration in the atmosphere. The heat warming capacity of each gas is measured by its 'global warming potential': how much heat it traps depends on its chemical make-up and how long it stays in the atmosphere.
Incandescent bulbs
Incandescents are traditional lightbulbs that use a filament (a thin thread of metal, usually tungsten wire) inside a glass bulb that glows white hot as electricity passes through it. The filament is prevented from burning either by creating a vacuum inside the bulb or filling it with inert gas. They are far less energy efficient than fluorescents/CFLs or LEDs because most of their radiation is given off as heat rather than visible light.
LEDs
An LED is a light-emitting diode. Its light is produced by an electrical current passing through a semiconductive material, so it does not require a filament like an incandescent bulb. They have a long life span, are durable, more energy efficient than CFLs, or incandescent bulbs cool to the touch and, while they have traditionally been used as small indicator lights, multiple LEDs are increasingly being used for household lighting.
Mercury
Mercury (chemical symbol Hg) is a metal that is liquid at standard temperature and pressure. It is used in the manufacture of low-energy lightbulbs (CFLs and other fluorescent lights), and extra care must be taken in their disposal, especially when they are broken, because of mercury's toxicity.
Toxins
A toxin is a chemical compound from one organism that is harmful to another organism.
Watt
A watt is a unit of power. Power is the rate at which energy is used, and a watt is equal to a rate of one joule of energy per second. Watts are commonly used when referring to the energy consumption of relatively small things like lightbulbs, while kilowatts (a thousand watts) are used for larger machines. Megawatts (a million watts) are used to measure the electricity generation of power stations. See also kilowatt-hours.

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