Early streetlights relied on a flickering flame, while later versions got a bulb and electric-power lines.
Now a new streetlight is poised to rule the road, one that taps the sun's energy by day and turns it into a bright glow by night. Several are already on the job in Central Florida.
Managers at Lockheed Martin Corp.'s east Orange County campus have opted to toss out 25-year-old streetlights riddled with rust and lightning damage. They were wired to underground utility lines for electricity.
Their replacements plug into solar panels and use a fraction of the power of ordinary streetlights. Lockheed Martin thought the swap would be good for the environment and better for the balance sheet.
Robert Carey, chief facilities engineer, said the 35 solar streetlights will cost about $342,000 over 20 years, including purchase price and maintenance — with zero expense for the sunlight.
The comparable figure for conventional streetlights, including new wiring and ongoing utility bills, would have been about $563,000.
Not a hard choice, Carey said.
Solar streetlights like the ones at Lockheed show the steady advance of efficiency and clean energy into ordinary living. Residential landscape lights that run on the sun now cost less than a specialty cup of coffee — about $3 each at do-it-yourself stores.
Solar streetlights, according to their maker, reached the realm of doable only last year because of improvements in what makes them shine.
They're equipped with a light-emitting diode, or LED, which sort of marries the idea of a light bulb to the technology of computer chips to produce an extremely efficient, long-lasting and adjustable source of light.
Carey said he evaluated six companies, including two in Florida, and settled on the Canadian firm Carmanah Technologies of Victoria, British Columbia.
As solar streetlights become more common, drivers won't have a hard time noticing them. Conventional streetlights produce a yellowish tint. The LEDs of solar streetlights have a bluish cast.
Greg Miller, Carmanah's manager of market development, said his company's solar-streetlight LEDs burn about as much energy as conventional streetlights to produce comparable amounts of light overall.
The big difference is the bulbs of conventional streetlights shine in too many directions, including not just the pavement below but into adjoining yards and homes and even into the night sky.
But the LEDs in solar streetlights aim the light only where it is needed. In the case of the new streetlights at Lockheed Martin, mounted 25 feet high, they brighten 125 feet of road and little more.
Since the solar streetlights don't waste light, they need just 100 watts to do the job of a 250-watt conventional streetlight, Carey said.
Carmanah doesn't suggest its lights are always the cheapest option. At development sites where the ground is still bare, for example, it can be more affordable to put in conventional lights along with other utilities, Miller said.
But when replacement of streetlights is a challenge or when tapping existing power lines is costly, Miller said, solar lighting can be the more affordable choice.
Solar lights also reduce planet-warming carbon emissions from power plants. Lockheed thinks the solar lights over 20 years will avoid putting more than 17,000 tons of carbon into the atmosphere — about as much as 3,000 typical cars produce in a year.
The solar streetlights will work during prolonged periods of cloudiness. Each one has four car-size batteries capable of powering the lights through at least five nights. The 41-by-42-inch solar panels also continue to produce electricity on overcast days, but at a reduced rate.
Kevin Spear can be reached at firstname.lastname@example.org or 407-420-5062.