Bi-Level Demand-Sensitive LED Street Lighting Systems
Dr. Saifur Rahman | Virginia Tech - Advanced Research Institute
Objectives of the Demonstration
The objective of this demonstration project was to deploy an energy efficient light emitting diode (LED) street lighting system with an intelligent controller as a retrofit to an existing system at Naval Surface Warfare Center, Carderock Division (NSWCCD) Headquarters in West Bethesda, Maryland.
The specific objectives were to:
- Validate the performance and expected operational costs and benefits of the bi‐level demand‐sensitive LED street lighting systems for energy efficiency.
- Work with Carderock Division Headquarters to evaluate technology acceptance, seek feedback, and provide appropriate guidance to assist in full‐scale deployment.
- Provide field experience data and an energy efficiency streetlight model that can be applied at other Department of Defense (DoD) installations around the United States.
During the course of the project, Virginia Tech and Old Dominion University, working in collaboration with Echelon Corp., developed, deployed, and evaluated the operational performance of a smart bi-level demand-sensitive LED lighting system for outdoor street lighting applications that allows dimming as well as traffic sensing capability through a centralized controller. The existing eight units of High Pressure Sodium (HPS) lamps were monitored for 1 year to capture their electrical energy consumption and operational performance, including illumination level and color rendition index. The set of LED lamps, together with their sensing and control unit, were then installed, and post-installation monitoring was performed during the subsequent year.
Results indicate a significant reduction in energy usage at about 74% electricity savings with the conversion of HPS to the demonstrated LED street lighting system. This is shown in Figure 1, where monthly electricity consumption (kilowatt hour [kWh]) of the HPS and LED street lighting systems during the monitoring period is compared. The data were recorded during a series of monitoring periods between January and December 2011 for the HPS system and between January and December 2012 for the LED system.
Figure 1. Monthly electricity consumption (kWh) of the HPS and LED systems.
The annual electricity savings of the LED as compared to its HPS counterparts were recorded at 11,060 kWh, which can be translated to avoided carbon dioxide (CO2) emissions of 16,081 pounds (lbs) during the same period. The new LED-based system is expected to pay back its investment within 6 years with the savings-to-investment (SIR) ratio of 2.15 and the adjusted internal rate of return (AIRR) of 9.77%.
Feedback from individuals at NSWCCD indicates a high level of user satisfaction with the light quality and operation of the newly installed LED street lighting system. Users also experienced a significantly better light quality (see Figure 2) and a 100% reduction in mercury waste disposal requirements. The system is also 100% available and reliable without any failure since its installation.
Figure 2. Light quality comparison.
This project demonstrated how existing street lighting units can be made more efficient using current state-of-the-art technologies and prudent engineering in the design and operation of the lighting control systems. The outcome of this project also includes best practices and field experience that can help with full-scale implementation at other DoD facilities around the United States. The project is expected to lead to significant cost and energy savings, as well as contribute to reducing carbon dioxide emissions for DoD.
Points of Contact
Dr. Saifur Rahman
Virginia Tech - Advanced Research Institute
Energy and Water
SERDP and ESTCP