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How Silver Spring Networks saw the light on LED-lit cities

How many technologies does it take to change a city's light bulbs?

That's a question being addressed, more or less, around the world as major metropolitan areas retrofit their street lights, traffic signals and signage with higher-efficiency bulbs and technologies, notably LEDs. Such efforts are often part of a larger project to modernize and digitize much of the information around energy use — the so-called smart grid — making it easier to control and optimize it.

For a city, lighting can be a "gateway drug" to a larger smart-grid implementation.

A smart grid is a complex puzzle of utilities, buildings, cities, vehicles and devices using electricity — not to mention the transmission and distribution lines that distribute it. Throw in the so-called Internet of things — billions of computer-addressable objects and devices — and you've created a complex system.
led lamp
Like all such systems, they can be powerful tools or an unwieldy mess. Creating the former, and doing so profitably, will be one of the great business opportunities of the 21st century.

Much of that action is happening inside cities, which are spawning grounds for a wide range of technologies designed to optimize city services while reducing their citizens' energy use and carbon footprints. Many of these technologies are nascent, continually improving in both price and performance. For cities, figuring out which technologies to deploy — and when, and from which vendors — is a complicated and sometimes confounding question.

Earlier this year, Silver Spring was selected to participate in a streetlight and traffic signal management project for Paris, part of the city's efforts to reduce its public lighting energy consumption by 30 percent over 10 years. The project in which Silver Spring is participating is the first part of a multistep process to manage a complex array of thousands of streetlights, streetlight control boxes, traffic signal control boxes, and other elements of Paris' public lighting and traffic control infrastructure. It's also part of an effort to upgrade Paris' electricity grid and turn Paris into a "smart city."

Doing the latter requires first doing the former. That is: A city can cost-justify a citywide rollout of the wireless network it needs for a smart grid because light poles are pretty much everywhere.

"Smart cities is a very broad term, but for us it starts with a network throughout the city for all of the city services. It then enables people to build software applications on top of that," Hughes told me. Those additional applications can be used to improve a range of city services, from electricity delivery to traffic control.

Retrofitting street lighting with efficient LED bulbs makes sense beyond the reduced electricity costs

, though those can be considerable: New York City expects a 35 percent reduction in lighting energy costs when its citywide retrofit is completed in 2019. That's lower than other cities report, however. According to Hughes, energy savings from LED street lighting is more typically around 65 percent.

There are also maintenance cost savings — primarily, the labor it takes to replace bulbs when they are no longer effective. (Unlike other light sources, LEDs usually don't "burn out"; instead, they get progressively dimmer over time, referred to as "lumen depreciation.") Good-quality white LEDs in well-designed fixtures are expected to have a useful life of 30,000 to 50,000 hours or longer. In comparison, a typical incandescent lamp lasts about 1,000 hours; a comparable CFL lasts 8,000 to 10,000 hours. The cost of replacing a single streetlight bulb — sending a crew out with a bucket truck, sometimes having to close lanes or roadways — can be hundreds of dollars, many times the cost of the bulb itself. Click on their website hmhid for more information.

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