Cool and efficient LED lights: Their time is now

Editor’s Note: This article by IEEE Member Frank Shinneman is the first in a series of six special features the IEEE is preparing for Greenbang.

Perhaps the most fundamental technology developed by man was his control of fire, and with it, the availability of light. Hundreds of thousands of years later, we’re looking forward to solid state LED lighting that promises to help to “save the planet,” reduce heat and last for decades while providing pleasing illumination.

As with most new technology, the LED lighting roll-out is taking longer than hoped, with price points still uncompetitive, choices limited and many quality issues unresolved. The pricing transition from a consumable to an investment is difficult and only a few common light shapes and intensities are available on the market. Most troubling is the number of offerings, many of which don’t meet any of their own specifications and few of which meet all specifications.

However, from 1 September of this year, the EU is phasing out the use of high-energy light bulbs in households as part of a package of measures to significantly reduce the energy consumed by electrical devices. The time is right for LED lighting to come to the fore.

An important distinction in LED lighting is that between socket-compatible retrofit bulbs (a bulb is the glass ball holding hot wires and gas that we refer to as a light. Industrially, it is called a lamp, which covers all types of light sources) and built-in fixtures. Here is a status report on the development and benefits of each for home and commercial use:

RETROFIT LAMPS

Retrofit lamps are lights which fit into existing sockets so conventional bulbs can be replaced. Energy usage of retrofit LED lamps is a third or less than that of conventional incandescent bulbs or about the same as the currently popular Compact Fluorescent Lamps (CFLs). Features of today’s retrofit LEDs include:

• Lower energy costs: Retrofit lamps are designed to last for 34 years and will generally pay for themselves in five to six years, based upon an average use of four hours per day. The remaining 28 years of their claimed lifetime would save an average consumer around $15 per year per lamp (assuming a 50- to 60-watt incandescent equivalent). For commercial use (12 hours/day), the payback on electricity alone is around two years, with the lamps themselves lasting another 10 years.
• Lower maintenance: Pay the price and they should last longer than you’ll keep your house, eliminating the need to change burnt-out bulbs. LEDs should last 20-50 times longer than incandescents and three to six times longer than CFLs. For commercial users, lower maintenance represents the single largest source of cost savings, with the payback in as little as 60 days. Be aware, however, that no retrofit LED light has been in existence — let alone run — for 10 years yet, so the lifetime and quality (colour, intensity, etc.) are only calculated, not tested.
• Quality of light: LEDs are far superior to CFLs in colour, consistency, instant-on, lifetime and lack of flicker. Being solid state, they are also exceptionally durable, so no more broken bulbs. The one present limitation of LED replacement lamps is their intensity. Because bulbs were designed to retain heat, it is difficult to remove heat from them. Above the equivalent of a 50-watt incandescent lamp, LED lamps in this shape cannot dissipate enough heat to operate correctly. Improvements will come slowly. Retrofitted fixtures (built-in LEDs), however, can be designed to solve this limitation and can give more light than is generally wanted (or legal) in most applications.
• Dimming: Unlike CFLs, LEDs are fundamentally dimmable. Unlike incandescents, the choice of dimmer will determine how smooth and how dim a lamp can go. In a few cases, a dimmer can cause flickering. Unlike incandescent bulbs, LEDs won’t provide the rosy candlelight glow when dimmed but will maintain whatever shade is obtained at full intensity.
• Low-temperature operation: LED lamp temperatures are low enough to touch without being burned, although their lifetime, intensity, efficiency and colour are very sensitive to high temperature so most models need to have good air circulation. This means most can’t be used in sealed cans or insulated ceilings. On the other hand, unlike fluorescents, they are not sensitive to winter freezing temperatures.
• Mercury-free: Absolutely true. No toxics are released when the lamps burn out and are landfilled. By comparison, each CFL disposed in a landfill adds a person’s one-year-maximum-dose of mercury to the world.
• Replacement formats: “Screw-in” (A-Lamp) LED retrofit lamps are available in intensities of up 900 lumens, or the equivalent of about a 50-watt incandescent. MR-16 replacements are available only up to the equivalent of 30-watt halogens. While fluorescent tube replacements are being demonstrated, their appearance is still jarring unless well hidden behind a diffuser or cove. The difference between the electrical feed and shape for fluorescent tubes and that of LEDs makes tube replacements much less attractive than other formats.

LED replacement lamps are hitting the consumer and commercial markets. Home centre offerings are very price sensitive and therefore tend to have the lowest quality. As in any other product, recognised brand names are likely to have invested more in product testing and quality. However, many recognisable brands are selling products actually made by other makers, so there are discounts to be found for commercial volume users who can identify and work directly with the source.

REPLACEMENT FIXTURES

Replacement fixtures have built-in LED light sources and all the benefits of LED retrofit lamps. However, because there is no socket, they can’t be changed back to another type of light if problems occur. Unit prices are higher, but the payback is faster and the intensity of light can be as high as desired (see “Quality of Light” above).

Compared to replacement lamps, LED fixtures are designed for LEDs and are therefore more reliable and can produce very high levels of illumination. The average consumer, however, won’t be installing an entire fixture so these are typically commercial products. All major lighting fixture-makers now have LED offerings, whether designed in-house or outsourced. Ceiling “troffers” of 2 X 2 or 2 X 4 size are very limited but recessed cans and sconces are widely available and competitively priced.

Light bulbs are one of the last vestiges of consistency in product design and performance, surpassed only by water faucets. Many potential customers are delaying purchase of LEDs fearing buyer’s remorse when the next improved model arrives with a lower price and better performance. If one considers how many working computers, phones and mp3 players are obsolete in drawers and closets, this should not be a fear. If the LED lamp provides the desired light and the existing lamp has died, a good quality LED will easily pay for itself and give great quality light.