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IAEEL newsletter 1/95

Dedicated CFL Fixtures Bring Savings Home



Even though screw-based compact fluorescent lamps represent a large residential savings potential, much of these savings have not been realized. Dedicated pin-based CFL fixtures for the home are one answer to the challenge.

Recent federal initiatives in the US, including the Energy Policy Act of 1992 and the Climate Change Action Plan, call for a renewed commitment to energy savings. These actions reflect the consensus that the potential for saving energy during the two decades since the term "energy crisis" became a household word has not been fully realized. While most end-use areas have seen 30% to 50% improvements in efficiency, there remain numerous opportunities that have not been exploited. However, measures for improving energy efficiency have, at times, been implemented in a somewhat clumsy manner that has not been well received by consumers.

Residential lighting is a microcosm of these larger trends. Each year the energy used to light US homes amounts to about 150 billion kilowatt-hours, at a cost of nearly US$11 billion, and is responsible for emissions of approximately 100 million tons of carbon dioxide, the primary " greenhouse gas".

The compact fluorescent lamp (CFL) is the most dramatic example of an untapped potential for energy savings. Unfortunately, in practice, CFLs have often failed to deliver on the promise of equivalent light quality, quantity, and light distribution at lower cost. Simply replacing incandescent sources with "screw-in" CFLs, without considering the entire luminaire, often results in unanticipated losses in light output, severe degradation of the optical performance and visual discomfort caused by glare.

Permanent energy savings can be reliably achieved when the luminaire is treated as a unified system. "Dedicated" CFL luminaires-with lamp, ballast, and fixture holistically optimized-are one viable substitute for incandescent systems. The development of dedicated pin-based CFL fixtures represents one of the largest new business opportunities for both the lamp and fixture industries. It is with this in mind that we are working to unite the diverse stakeholders within the lighting industry, utilities, and government agencies, and to develop consumer information to further the acceptance and penetration of the CFL fixture into this new market.

STORM CLOUDS
The central obstacle is that most existing fixtures in the home have been designed for operating general service incandescent lamps, which have a luminous distribution very different from that of the more linear and asymmetrical CFL. Replacing an incandescent A-lamp with a compact fluorescent will change the optical distribution of the existing fixture, potentially reducing perceived brightness and adding to consumer dissatisfaction.

We conducted a series of photometric studies to measure the candlepower distribution of typical residential table lamp fixtures with a cylindrical shade operating with a variety of screw-based CFLs. With the CFL source, less light exits the fixture directly below and above it. The elongated CFL distributes relatively more light flux horizontally, towards the shade, than does the more uniform A-lamp.

Compounding problems of fixture optics, significant losses in lamp light output and efficacy can occur as a function of operating conditions encountered within the fixture or when CFLs are operated in a base-down position (see IAEEL Newsletter 2/93 "Not Cool to Be Hot"). True light output can be as little as 75% of the rated lumens if temperatures around the lamp exceed about 35°C. Since incandescent lamp performance isn't sensitive to temperature, this issue has never been addressed by incandescent fixture designers.

In our measurements of a range of lamp and fixture combinations, the optimal range of 60-70 lumens per watt was achieved only with a bare, electronically ballasted lamp operating in a base-up position. As indicated in the diagram, significant losses in lumen output can occur in fixtures, reducing efficacy to 30-50 lumens per watt, which is well short of the expected performance for these sources. This occurs mainly from lumen losses experienced as a function of ambient temperature, burning position, ballast losses, and optical factors.

Problems with screw-in CFLs are of more than academic interest. Many utilities have already "derated" their assumptions about the performance of CFLs to reflect the gap between idealized and actual operation. Southern California Edison, for example, assumes that lamps are in service for 6 300 hours rather than 10 000 hours life which is the typical rated life of a CFL.

This low estimate reflects expectations that there will be premature reversion to incandescents, that some lamps obtained by consumers will never be installed, and that the operating life will be reduced owing to adverse conditions in certain fixtures. From the utility's perspective, this translates into poorer cost-effectiveness and means that rebates and other promotion efforts are less often justified.

THE PIN-BASED OPTION
Shifting to dedicated fixtures with pin-based (versus screw-in) lamps makes it possible to address each of the concerns listed above. The advantages include:

  • thermal and optical performance can be optimized

  • replacement lamps are less expensive

  • mercury recovery costs 50% less when lamp and ballast are separate

  • less solid waste is generated since the ballast is not discarded when each lamp fails

  • the likelihood of reversion to incandescent lamps ("snapback") is vastly reduced

  • it is easier to address power quality and dimming in the hard-wired ballast.


Although introducing a new technology (pin- versus screw base) into residential fixtures might seem to be a great hurdle, it is worth recalling that this same transformation took place in the 1940s, with the advent of pin-based linear fluorescent lighting systems for the commercial sector, and again several decades later with the success of pin-based halogen fixtures in homes and businesses. Key to the success of halogens in the home is the way consumers have come to view them as "furniture" (worthy of considerable extra investment) rather than as strictly utilitarian light sources.

MARKET TRANSFORMATION
Developing and accelerating the use of dedicated CFL fixtures for the home is a worthy but elusive goal. Part of the difficulty stems from fragmentation among the various "stakeholder" groups that could potentially work together-lamp manufacturers, fixture manufacturers, ballast manufacturers, wholesalers, retailers, home builders, third-party buyers, lighting designers and specifiers, and consumers. An integrated program should have the following elements:

  • industry cooperation

  • market information

  • financial incentives and market pull (utility or manufacturer rebates, innovative procurement) design competitions

  • professional education and demonstration

  • institutional and governmental leadership through high-visibility demonstrations and coordinated purchasing power

  • government initiatives to foster cooperation among various stakeholder groups, R&D, provision of objective information, and building codes calling for dedicated fixtures in appropriate applications.


About 175 million residential light fixtures are sold in the US each year (half of which are imported), and roughly a billion of the existing fixtures are suitable for CFLs. This represents a truly immense opportunity-and challenge-for market transformation and energy efficiency gains in residential lighting.

See also: Letters (2/95), and about UK dedicated CFL luminaire program: "Cooperative procurement on improved GLS lamp" (IAEEL 1/96) .

Evan Mills
Michael Siminovitch

Evan Mills is Acting Director of Lawrence Berkeley Laboratory's Center for Building Science, and Michael Siminovitch heads the Compact Fluorescent Laboratory at LBL.

Scatter plot of variations in efficacy for a range of CFL screw-based systems measured inside a photometric integrating sphere ( a range of incandescent sources are included for comparison).

About 75% of the US residential lighting energy consumption can be accounted for by just 30% of a typical home's fixtures, i.e. the "high-use" sockets. These sockets, which include some surface mounts for kitchens and bathrooms, table and floor fixtures in living rooms, and exterior/outdoor fixtures, make good first targets for replacement or conversion to CFLs. Successfully converting that 30% fraction of sockets to CFLs would save 85 billion kilowatt-hours annually, corresponding to a reduction in CO_2 emissions of approximately 56 million metric tons, 6 billion dollars in utility bills, and 68 new 250-megawatt power plants.

Candlepower distribution diagrams comparing incandescents and CFLs. (Candelas)

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