This article was originally published in the January/February 1994 issue of Home Energy Magazine. Some formatting inconsistencies may be evident in older archive content.



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Home Energy Magazine Online January/February 1994




Trends in Energy is a bulletin of residential energy conservation issues. It covers items ranging from the latest policy issues to the newest energy technologies. If you have items that would be of interest, please send them to: Trends Department, Home Energy, 2124 Kittredge St., No. 95, Berkeley, CA 94704.


Downsizing the CFL

A new generation of compact fluorescent lamps has emerged, offering advantages that may translate into tens of millions of new retrofit opportunities. Several major lamp companies have unveiled electronically ballasted CFLs that are more than an inch shorter than their predecessors. Some of these CFLs even have higher-rated lumen output than earlier CFLs of similar wattage.

The bulbs, called triple tube or triple CFLs, have three U-bends in the tube, rather than one in the twin-tube or two in the quad-tube CFLs. Designed to replace 4.4-in. long incandescents, the 60-watt versions, for example, range from 4.9 to 6.0 inches in length.

Osram first introduced its triple-tube Delta lamp in Europe, and the technology has now been adapted to operate at U.S. voltages. The 120-volt model was released in early 1993 by Osram, which has now combined with Sylvania as Osram Sylvania. The Delta's three U-bends face inward in a triangular shape. The 23 W, electronically ballasted, 1,550 lumen version replaces a 90 W incandescent and is almost 7-in. long. Osram Sylvania is targeting the residential market and hotels.

General Electric's Triple Biax lamp has a hexagonal shape similar to the Delta, but its ballast electronics are different. The 20 W version was the first introduced, and it is aimed at both the residential and commercial markets. In response to utility concerns about power quality, all of GE's triple-biax lamps have power factor greater than 90% and total harmonic distortion of 20% or less (see Understanding Power Quality, HE Nov/Dec '93, p.36, and So Many Sockets, So Little Time, HE Mar/Apr '93, p.7). The company is working on a triple-tube design with a separable lamp/ballast, already available in a quad-tube version.

Philips was the first manufacturer to market a triple-tube lamp in the United States. Its Earth Light SLS appeared in hardware stores and utility rebate programs in May 1993. The lamp's design called for three parallel U-bends. Philips calls this design bend and bridge, because it combines the tube-bending technology of the SL lamp with the bridge-forming technology of the PL lamp. The company claims this lamp gives more light output at its end because it has more tube area per phosphor compared to other designs. The 15 W version fits inside 8-in. lamp harps, and the 20 W and 23 W versions fit in 81/2- to 9-in. harps. These CFLs are available in standard versions or with high power quality. Philips, like Osram Sylvania, is aiming primarily at the residential market.

Another feature touted by Philips is the use of amalgams (alloys or composite materials) inside the lamp to maintain lumen output in a wide range of temperature conditions. Research by the Lighting Systems Research Group at Lawrence Berkeley Laboratory (LBL) has shown that a CFL used in a base-down position (for example in table lamps) loses up to 20% of its rated lumen output, a unit measured in the base-up position. Consumers often complain that CFLs are not bright enough to read by (see Consumers and Compact Fluorescents, HE Nov/Dec '93, p.11). Amalgams allow the lamp to operate closer to its optimal light output in the base-down position. They also help maintain stable light output at lower outdoor temperatures.

An additional solution to the position problem is under study at LBL. This method uses a metal thermal bridge to dissipate heat from the base of the lamp. The thermal bridge method costs much less than using amalgams, but amalgams may still be useful in special situations where fixtures can't be vented, such as enclosed outdoor fixtures or security lights.

Two lamp companies are reportedly very interested in using thermal bridge technology for their next generation of CFLs. LBL is also researching ventilation of CFL fixtures for a more optimal thermal environment, a technology that is being commercialized.

How are the new CFLs faring in the marketplace? Philips says demand for its Earthlight SLS series has been higher than expected. White Electric, a lighting specialty store in Berkeley, California, reports that most customers purchase the new shorter lamps. They want lamps that fit in fixtures, says owner Doralee White. At least one utility rebate program in the Northwest has featured the Philips Earthlight SLS series, the only triple-tube lamp that was available at the time of the program in mid-1993. Anne Ducey of Seattle City Light says that these lamps were their best-sellers, chosen for their small size and high lumen-per-watt output.

CFL length is not as critical an issue as some utilities make it, according to Fred Davis, a Massachusetts-based wholesale distributor of efficient lighting products. Davis maintains that careful CFL program design allows plenty of retrofit opportunities using the older lamps. He points out that the new CFLs typically cost more than their longer predecessors. For a comparison between the various new CFL options and the incandescent lamps they replace, see Table 1.

Coming Attractions

Panasonic's contribution to the new generation of CFLs will appear as the pocket-size light capsule in early 1994. These bulbs feature a radically smaller microprocessor-controlled electronic ballast. The fluorescent tubes themselves are in a double U-bend configuration, rather than a triple-tube. The tubes are not any shorter than their predecessors, but the ballast is.

The microchip operation will eventually allow three-way switching and dimming in future versions of the light capsule. The first version will come in both a globe and tapered shape. The intention is to look like a standard light bulb in appearance, size, and performance, says John Cunningham, Panasonic's national account manager. The new CFL will be offered in both warm (~3,000 K) and cool (~4,000 K) color temperatures. The product received the Retailer Choice Award at the Hardware Show in Chicago in August 1993.

-- Barbara Atkinson

Barbara Atkinson is a principal research associate specializing in energy-efficient lighting policy analysis at Lawrence Berkeley Laboratory in Berkeley, California.

Table 1. Comparison of New CFL and Incandescent Lamp Options


Rated Efficacy Rated Length Width* lumen (lumens per lifetime Lamp Wattage inches cm inches cm output watt) (hours) Incandescent A-19 (60 W) 60 4.4 11 2.4 6.0 870-890 14-15 1,000 Philips Earth Light SLS 15 4.9 13 2.0 5.1 900 60 10,000 Panasonic EFT 16 LE or EFT 16 EX (Tubular) 16 5.4 14 2.6 6.9 800** 50 10,000 GE FLE15TBX 15 6.0 15 2.3 5.8 900 60 10,000

Incandescent A-19 (75 W) 75 4.4 11 2.4 6.0 1,190-1,220 16 750 Philips Earth Light SLS 20 5.6 14 2.0 5.1 1,200 60 10,000 GE FLE20TBX 20 6.6 17 2.3 5.8 1,200 60 10,000

Incandescent A-19 (90W) 90 4.4 11 2.4 6.0 1,540-1,620 17-18 750 Philips Earth Light SLS 23 6.2 16 2.0 5.1 1,550 67 10,000 GE FLE23TBX 23 6.9 18 2.3 5.8 1,500 65 10,000 Osram Sylvania DULUX EL 23 W 23 6.9 18 2.3 5.8 1,550 67 10,000

* Maximum width occurs in different places along the bulb for different CFLs, affecting fit.

** Approximately 10% less light than 60 W incandescent



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