Development of an Energy-Efficient, Ultra-Thin LED Luminaire
Prototype of the ultra-thin LED luminaire.
Beam distribution of the ultra-thin LED luminaire.
Electricity generation shortages have affected the United States since the late 1990s. One of the most promising avenues to limiting future electricity shortages is through lighting. Energy-efficient lighting offers a technically and economically feasible means to reduce electric load demand, electric energy use, and toxic emissions into the environment as a result of electricity generation.
Downlights, accent lights, and wall-wash luminaires using halogen or incandescent lamps are found in 60 percent of all commercial office buildings and a much higher percentage of retail and residential applications. Recent surveys show that new houses now have an average of 23 recessed downlights. These luminaires, and the lamps they house, are inefficient and waste a tremendous amount of energy. Downlights and recessed accent lights housing incandescent and halogen lamps typically have efficacies between 6 and 15 lumens per watt (lm/W). However, these luminaires continue to enjoy a significant portion of market share because no alternative has been developed that exhibits superior qualities.
LEDs offer the most potential to replace incandescent and halogen lamps in these applications, thus saving energy while maintaining or improving the quality of lighting for end users. The Lighting Research Center explored a new "ultrathin" luminaire concept for these applications that:
- can be installed in ceilings with virtually no plenum depth
- has optics that can be adjusted easily to a wide range of beam distributions
- uses 70 percent less energy than current incandescent and halogen luminaires
- lasts up to 50 times longer than incandescent or halogen lamp technology
The overarching goal of this project was to determine the feasibility of an energy-efficient, ultra-thin, LED-based luminaire that would effectively replace downlights, accent lights, and wall-wash luminaires using incandescent and halogen technologies in commercial and residential applications. Specifically, this project aimed to:
Develop a benchtop prototype that exhibits similar lighting characteristics (i.e., light output, beam distribution, color appearance, and color rendering properties) as luminaires using halogen lamps while meeting the following performance specifications:
- light output of approximately 650 lumens
- correlated color temperature in the range 2800 K to 3200 K with a general color rendering index of at least 80
- system luminous efficacy of at least 45 lm/W
- total depth of less than one inch
- six beam distributions with interchangeable optical micro-lenses with an efficiency of at least 92 percent (e.g., beam angles of 10°, 30°, 60°, 45° by 75°)
- useful lamp life of over 50,000 hours
- operation from line voltage (120 Vac)
Demonstrate an LED luminaire that allows energy-efficient lighting to be used in a wider array of applications than is possible with current technologies; for example, in areas with reduced or no plenum at all.
Determine the conditions under which such an LED luminaire can be manufactured, assembled, and distributed cost-effectively in order to provide a three-year payback to the consumer through energy and maintenance savings.
The research conducted under this project resulted in the following outcomes:
The LRC produced a prototype of an ultra-thin LED luminaire that allows energy-efficient lighting to be used in residential and commercial applications with minimal or no plenum.
The performance of the ultra-thin LED luminaire prototype is as follows:
- Luminaire light output: 645 lumens
- Luminaire power: 11.4 watts
- Luminaire luminous efficacy: 57 lm/W at 6500 K (67 general color rendering index)
- 35 lm/W (calculated) at 3100 K (82 general color rendering index)
- Beam distributions: 10°, 30°, 80°, 45° by 75°, 20° tilt with secondary lenses and micro-lenses (efficiencies ranging from 78 percent to 85 percent), and 8° and 25° with secondary lenses alone (efficiencies ranging from 80 to 88 percent)
- Total depth: 0.875 inches (not including driver)
- Useful lamp life: estimated at 50,000 hours to 70 percent of initial light output, based on the LEDs’ measured operating temperature
- Input voltage: 120 Vac or 24 Vdc
The ten-year life cycle cost of the ultra-thin LED luminaire in commercial applications was calculated at $642, compared to $1475 for an incandescent-based luminaire. The long-term benefits of the ultra-thin LED luminaire are predicated on the energy and maintenance cost savings afforded by the long useful life and long hours of operation (12 hours per day). In the near term, at an estimated retail cost of $425, the ultra-thin LED luminaire would provide a simple payback period of five years due to the higher initial purchasing cost (compared to $250 for an incandescent luminaire).
In residential applications, the ten-year life cycle cost of the ultra-thin LED luminaire was calculated at $464, compared to $369 for an incandescent-based luminaire. This result can be expected because in residential applications the capital cost of incandescent luminaires is lower and the energy and maintenance savings are very small. The life-cycle cost of the ultra-thin LED luminaire becomes lower than that of the incandescent fixture only if a 30-year period is considered, or if the selling price is reduced to less than $250 to the consumer. A reasonable payback of less than five years is only possible if the ultra-thin LED luminaire can be sold for less than $100 to the consumer. This target price may be within reach in the next few years. Further price reductions for LEDs and other associated components are likely to happen over the next few years, enabling the cost-effectiveness of LED technology in more applications.
Profile of the ultra-thin LED luminaire.
Project Summary Sheet
California Energy Commission’s (CEC)Public Interest Energy Research (PIER) program’s Energy Innovation Small Grant (EISG)