DOE releases report on LED lighting for New York freeway
A two-year study of LED-lighting on Franklin D. Roosevelt Drive in New York City reveals that SSL offers marginally lower lifecycle costs than the incumbent HPS lighting.
A new US Department of Energy (DOE) report details the results of a two-year trial of LED lighting on Franklin D. Roosevelt Drive (FDR Drive) in New York City. Conducted under the DOE's Gateway demonstration program, the project included solid-state lighting (SSL) fixtures from four manufacturers and concluded that the LED lights offer lower lifecycle costs than the existing high-pressure sodium (HPS) lamps, but the payback period is quite lengthy.
The FDR Drive Gateway demonstration was a joint project of the DOE, the New York City Department of Transportation (NYCDOT), and The Climate Group. The study revealed energy savings of 26-57% for the tested LED lights relative to the legacy HPS lights. Still, high upfront costs yielded payback periods of 8 to 16 years for the tested luminaires.
Products and site
In 2009, the NYCDOT selected luminaires from LSI Industries, LED Roadway Lighting, Elumen Lighting Networks, and BetaLED (a Ruud Lighting brand, now a division of Cree Lighting). The agency bought and installed six luminaires from each vendor on a section of FDR Drive - an elevated roadway that runs along the east side of the New York City borough of Manhattan.
The participants chose the FDR Drive location in part because of the difficulty of performing maintenance on such a roadway. Traffic levels relegate maintenance to night, and servicing the elevated portions of the road is complicated. Lighting with lower maintenance requirements would presumably help reduce the high maintenance costs associated with the roadway.
Light poles are located in the median of FDR Drive with paired fixtures installed back to back to illuminate the north and south-bound lanes. In the case of each of the selected SSL fixtures, NYCDOT installed pairs of fixtures on three consecutive poles.
Energy and photometric data
The project participants collected substantial data on the tested luminaires including energy used and photometric performance. The incumbent HPS lights offer the highest lumen output at 13,002 lm compared to a range of 6,296-8,181 lm for the LED fixtures. The HPS lights also offer an efficacy advantage but consume more power than any of the LED lights. But three of the four LED fixtures deliver more illuminance on the roadway than do the HPS lights. The LEDs clearly offer better beam control.
At installation, all but the Elumen fixtures would meet the Illuminating Engineering Society (IES) RP-8, roadway-lighting requirements for the Freeway Class A category of the FDR Drive location. When dirt and lumen depreciation are considered, however, none of the tested lights, including the legacy HPS lights, would meet RP-8 requirements after 8 years.
The LED lights all offer superior CRI to the incumbent HPS lights. The report noted that the enhanced color rendering capabilities of the LED lights could enable better visual acuity for drivers and safety officers. The LED fixtures are also noted as superior in terms of minimal to no up light, or light pollution.
Lifecycle cost and payback
Lifecycle cost comparisons and payback period calculations summarized in the report are quite complex and there are numerous variables in play. For example, New York City electrical rates vary, and even along the FDR Drive roadway the NYCDOT couldn't precisely determine electrical costs. The report uses a range of rates from $0.120-$0.169/kWh.
Lifecycle costs were based on a 24.4 year lifetime. That number was derived from the 100,000-hour specification on the LSI Industries luminaire – the product with longest claimed lifetime. HPS lamp maintenance costs were estimated based on a lamp life of 5.7 years. Moreover the study made other assumptions on maintenance. The report also presents lifecycle costs based on different discount rates that are used to calculate the present value of future expenditures.
Indeed the financial tables presented in the report are seemingly in disagreement at times with the summary of results in the text of the report. In reality, the report simply considers an incredibly broad set of variables while the text – specifically the stated 8-16-year payback period – apparently represents the most likely economic scenario.
For our purposes here, we will look at one specific scenario based on a 0% discount rate and $0.169/kWh electrical rate. Lifecycle cost of the HPS lamps is $5,392. The lifecycle costs of the LED fixtures ranges from $3,896 for the LED Roadway Lighting products to $5,211 for the BetaLED products. With higher discount rates factored in, only the LED Roadway Lighting lifecycle cost remain lower than the cost of the HPS lights.
Luminaire pricing and performance
At first glance, the new Gateway report sheds significant doubt on the economic viability of LED lights despite the reduction in energy usage. But as the report itself notes, the economic analysis is based on the price of LED fixtures in 2009 that were purchased in very small quantities.
The fixtures evaluated in the Gateway demonstration ranged in price from $695 for the LED Roadway Lighting luminaire to $1022.63 for the BetaLED luminaire. Clearly prices have since declined considerably.
In February 2011, we covered a Caledon, Canada outdoor-lighting project in which The Climate Group was involved. Similarly, the tested luminaires had prices well above what you could expect for present-day purchases. At that time, Climate Group’s Cities and Technology Director Philip Jessup said, "Higher volume purchases in larger cities will bring the price down. For example, consider Los Angeles where they’ve gotten the price for street-light LED luminaries down to around $400 each."
As prices drop, LED luminaires are also improving in terms of light output and efficacy. Indeed you could expect to get the same light output today from luminaires with fewer LEDs relative to the products evaluated in the Gateway demonstration. Indeed the economic analysis would likely be far more favorable to the LED alternative were it performed based on the latest SSL products.