|Advancing the effective use of light for society and the environment. |
| Thursday, October 20, 2005 |
DELTA Evaluates Solar-powered Lighting for Bus SheltersBy Jennifer Taylor
Field test of the PV-powered
retrofit kit for bus shelters
The DELTA program at the Lighting Research Center has released a new publication that documents a field test of a photovoltaic (PV) lighting retrofit kit for bus shelters. The kit is designed to power the backlighting system for advertising signs through the use of solar cells mounted on top of the shelter. DELTA tested the commercially available PV bus shelter kit to verify its performance over an extended period of time and to gauge public reaction to the bus shelter at night.
The PV retrofit kit is installed on existing bus shelters and contains PV panels, mounting hardware, batteries, a controller, a timer relay, a photosensor, and a fluorescent wrap luminaire. The flexible solar panels integrate well with the barrel-vaulted roof and can collect solar energy over a range of orientations. The panels charge the batteries, and the controller determines the charging duration. The photosensor informs the controller when to turn on the backlighting, and the timer relay turns the system off after a prescribed period.
Components of the PV-powered
DELTA evaluated 12 retrofitted shelters throughout Long Island, N.Y. by:
- Testing the electrical conditions provided by the ballast
- Measuring photometric conditions on a prototype unit
- Checking for consistent operation
- Calculating energy savings and environmental implications
- Verifying visibility and collecting subjective opinions from bus shelter users
Sample findings and recommendations
- The PV lighting systems operated reliably and effectively with no utility-powered electricity, providing significant energy savings over similar, non-retrofitted bus shelters (0 kWh vs. 4993 kWh per year).
- People equally accepted the PV shelters and shelters with much higher-wattage mercury vapor lamps.
- The luminance of the advertising sign was comfortable to look at, but may need to be increased to visually “compete” in typical commercial boulevard environments.
- Diffusers mounted both behind the posters and on the luminaire are not necessary. Removing one would increase the sign luminance with little or no impact on uniformity.
DELTA (Demonstration and Evaluation of Lighting Technologies and Applications) is an LRC program established in 1994 to design, evaluate, and publicize energy-efficient lighting solutions. The field test sites selected contain lighting and controls systems that are evaluated for energy use, human response, cost, how well the technologies work, and how easy they are to maintain. Plans, details, and color photos illustrate each DELTA case study.
DELTA case studies and publications are available free on the DELTA program Web site.
The Lighting Research Center (LRC) is part of Rensselaer Polytechnic Institute and is the leading university-based research center devoted to lighting. Founded in 1988, the Lighting Research Center has built an international reputation as a trusted and reliable source for objective information about lighting technologies, applications, and products. Its mission is to advance the effective use of light and create a positive legacy of change for society and the environment.