How can a tiny pinpoint of LED light illuminate a porch, or a pathway?
That's the question being studied by Lawrence Berkeley National Laboratory (LBNL).
In fact, using LEDs for exterior illumination purposes could dramatically reduce energy consumption in the state of California alone, according to research sponsored by the California Energy Commission's Public Interest Energy Research (PIER) Program.
Potential energy savings center on a 2000 study of 1,000 California residences, which found that:
- About 80% of all porch lights use incandescent bulbs
- 6% use compact fluorescents
- Only 15% of all porch lights are equipped with some form of control device such as a motion detector, photocell or timer.
Now, a major study is underway to determine how to best integrate LEDs into porch lights and landscape lighting for residential, commercial and industrial lighting applications. The study is funded by PIER, and being conducted by LBNL.
This year at LightFair, Steve Johnson, group leader of the Lighting Research Group at LBNL described some of the research.
Porch light design considerations will follow Illuminating Engineering Society (IES) recommended illuminance levels for:
- Facial identification (security lighting): 8 lx (0.8 footcandles)
- Floor, walkway: 5.4 lx (0.5 footcandles)
He said common white LED lighting problems do not apply to LED porch lights. Fixtures with diffusers and indirect fixtures eliminate the discomfort of glare from high-brightness point sources.
Johnson showed two designs under consideration.
Beyond that, LBNL is focusing on a fixture design that will be used in conjunction with any standard fixture in new construction to match a specific decor.
A hybrid LED/incandescent security fixture is one of the designs. It includes a feature that provides LED-lit wall and ground area after dark, with a sensor that turns on an incandescent bulb when motion is detected. Horizontal and vertical examples of this design have been drawn.
The overall objective of this project is to work with one or more manufacturing partners to design, prototype and evaluate a series of three to eight exterior porch lighting systems that integrate high efficiency optics/distribution, LED light sources and lighting controls into one system.
Part of the design consideration is the fact that the electronic driver used to control light output of the LEDs can also be configured to perform daylight and motion sensing.
Prototype evaluation will include laboratory testing and field research and application evaluation. Field monitoring protocols will be developed and made available for use by other California groups.
The individual objectives of this project are to:
- Develop a series of advanced fixture prototypes for residential, commercial and institutional applications.
- Develop fixture and optical geometries that mitigate sky pollution.
- Develop source configurations and optical geometries that match or exceed the vertical and horizontal illuminance of conventional A lamps.
- Reduce the energy consumption of incandescent porch and perimeter light fixtures by 75 percent.
- Develop integrated control systems that extend the savings opportunities for these applications.
A significant niche market exists for porch lights that utilize yellow "bug lights." This is of interest for this project as the color of these lamps is not substantially different than that of amber LEDs. Amber LEDs are some of the cheapest, brightest and most efficient of the LEDs that are currently on the market.
You can learn more about this project from the Lighting Research Group's Web site.
The following reports are available online:
