How'd you like to treat your street-lighting system as a control network rather than a collection of electrical circuits? The recent coming of age of specialized networking hardware and control software has made such an approach not only feasible, but also economical and relatively easy to install. It's also proving to be a good way to cut operating and maintenance costs.

With 90 million streetlights in Europe and 63 million in North America, it's easy to see why their efficient use of energy is important. Recent studies have shown electricity used for street lighting accounts for as much as 40% of some municipal electrical bills. Fortunately, components and systems are now available to manage, monitor, and reduce that electrical demand.

Such a system relies on several key elements: electronic ballasts, power line communication hardware, and local network controllers that are interconnected with specialized control and reporting software. Deployed together, they create a flexible and powerful control system that simplifies day-to-day operation and facilitates the implementation of cost-cutting strategies. Establishing two-way communication with each fixture in a street-lighting network introduces the potential to control the lighting level of each device, turn it on and off, and monitor its condition.

As recently as five years ago, such control wasn't feasible. But the recent development of electronic ballasts for streetlights, combined with advances in networking technology, have made it a reality.

Electronic ballasts. Ballasts are required for various types of lighting devices, including high-intensity discharge (HID) lamps used for street lighting. Traditional magnetic ballasts use a core-and-coil design that requires a significant amount of energy — 15% to 18% — compared to the light itself. Electronic ballasts, which were developed more than 30 years ago, use 3% to 4%.

Early electronic ballasts were used in interior applications, including fluorescent fixtures for office buildings and HID lighting in industrial settings. In recent years manufacturers have added electronic ballasts for streetlights, opening the door to additional energy savings in an area where more efficient lamps already have been developed and installed.

Because electronic ballasts use solid-state circuitry, they can be designed with digital electronic dimming that reduces energy use and extends lamp life. Lamp manufacturers recommend dimming by no more than 50%.

Communication. Digitally controlled electronic ballasts can communicate with other devices based on the protocol and interface capabilities with which they are provided. The data can include storing a ballast address, receiving control signals, and sending status information.

That would be only moderately useful if it weren't for power line communication technology, which enables the data to be exchanged over the existing wiring that supplies power to each streetlight. In most cases this requires a transceiver similar to the modem that allows a PC to communicate over an analog telephone line, but which in this case attaches to the incoming power line.

This year, though, Albion, N.Y.-based ROMlight International introduced a line of HID ballasts that incorporate LonWorks power line communication technology, eliminating the need for the additional piece of hardware.