Demonstration Assessment of LED Roadway Lighting: Philadelphia, PA
- Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
For this demonstration assessment, 10 different groups of LED luminaires were installed at three sites in Philadelphia, PA. Each of the three sites represented a different set of conditions, most importantly with regard to the incumbent HPS luminaires, which were nominally 100 W, 150 W, and 250 W. The performance of each product was evaluated based on manufacturer data, illuminance calculations, field measurements of illuminance, and the subjective impressions of both regular and expert observers. Most, but not all, of the LED luminaires had a higher rated luminous efficacy compared to the HPS product they were replacing. Some provided more lumens than their HPS counterpart, whereas others emitted fewer, and they drew between 10% and 40% less power. All of the LED luminaires had improved color rendering and a higher CCT. Field illuminance measurements were taken at each site, but the large difference in pole spacing for each area limited the usefulness of that dataset for comparing performance. However, it did reveal that the difference in measured and calculated illuminance was up to approximately 40%, and that the HPS luminaires were more likely to provide lower illuminance than predicted by calculations. In order to compare luminaire performance, supplemental calculations were performed using a single representative model of each of the three sites. These calculations showed that the delivered illuminance from the LED luminaires was generally similar to the baseline HPS luminaires. On average, the LED luminaires were predicted to provide 24% higher initial illuminance on the roadway surface, but 13 % less on the bicycle lanes and 11% less on the adjacent sidewalks. Based on the lumen depreciation factor applied to each luminaire type, the difference in predicted maintained illuminance would change. Two of the three HPS luminaires and seven of the ten LED luminaires were predicted not to meet at least one of the maintained illuminance design criteria. These results are dependent on both the lumen output and luminous intensity distribution characteristics of the luminaires. Importantly, the LED systems were designed with the intent of providing performance similar to the HPS luminaires, rather than to meet illuminance criteria. Despite lower input power for the LED luminaires, energy cost savings are not currently possible for Philadelphia because they have yet to reach an agreement for a new tariff for LED street lighting with the local utility, a situation that is common throughout the country. Even with a new tariff, energy savings alone are unlikely to result in a reasonable payback period given current LED efficacy levels. However, additional cost savings from reduced maintenance could make widespread luminaire replacement cost effective. In particular, the LED luminaires installed at one of the three sites—where the luminaires were mounted on an elevated rail track—were less susceptible the premature failure from strong vibrations. Two sets of subjective evaluations were collected: one included local residents and passersby, whereas the other was completed by lighting professionals. In general, there were only small deviations in the perception of the luminaires, and it would be difficult to select any products that were clearly superior to the others in the same category. Nonetheless, both groups generally viewed the demonstration LED lighting favorably, especially compared to the typical HPS luminaires used in Philadelphia.
- Research Organization:
- Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1072912
- Report Number(s):
- PNNL--21860; BT0301000
- Country of Publication:
- United States
- Language:
- English
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