No overhead wires or underground conduits lead to the flashing-light and speed-display signs erected last month along several treacherous curves on I-75 near downtown Toledo. Nor are gasoline engines powering the programmable message signs at the approaches to nearby construction zones.
All are powered by the sun.
Solar technology is “just beginning to grow,” said Mack Corbin, the vice president for solar-sign distributor M.H. Corbin, Inc., of Plain City, Ohio. “You're going to see more and more of it.”
Ohio Department of Transportation officials agree that it's a wave of the future. Not only are solar-cell signs environmentally friendly, they're cheaper.
Four pairs of “slippery when wet” signs went up in both directions on I-75 at the Detroit Avenue and Bancroft Street curves on Aug. 30.
The solar-powered lights cost about $3,125 each, said Joe Rutherford, a spokesman at ODOT's district office in Bowling Green. Running a cable from the nearest power line costs $5,000 to $10,000, he said.
Mr. Rutherford said he did not know the cost difference between solar and gasoline-powered portable message signs, because those are leased by construction contractors, not by ODOT. But the solar versions do not spew emissions, as their noisy, gasoline-powered peers do.
Solar signs are beginning to multiply because the technology has become standardized, Mr. Rutherford said.
Until recently, detailed specifications had to be provided for custom-made devices, but now there are “off-the-shelf” solar cell systems that are much less expensive, said Brian Cunningham, a spokesman at ODOT's Columbus headquarters.
Mr. Corbin said there's another important element: light-emitting diodes.
Incandescent light bulbs consume more electricity than a small solar array can generate, but the LED's used on the newest signs and lights are very thrifty, he said.
“Even in a northern climate, we can generate and store enough power to keep one of these signs running,” Mr. Corbin said.
Should Toledo endure an overwhelmingly long string of cloudy days - as the city sometimes does in late fall and early winter - the marine batteries that the signs use can be recharged from any electric power source, he added.
“We try to put enough solar panels up there, and enough battery power, so [a complete drain] doesn't happen,” Mr. Corbin said.
Several of the new signs in Toledo stopped working shortly after installation, which Mr. Rutherford said was caused by battery problems.
The batteries will be replaced, he said.
Mr. Cunningham said it's unlikely the state will retrofit its older flashing-light signs - such as one warning southbound U.S. 23 motorists of a curve on the Sylvania Township ramp to eastbound I-475 - to use solar power.
The power source will depend on how close the signs are to electric lines, he said.
“If there's a power source nearby, obviously we would go that route. We are not just going to pop [solar signs] up everywhere,” Mr. Cunningham said.
But sometime this fall, when the state puts up stop signs at the State Rts. 64 and 65 intersection near the east end of the Waterville Bridge, they will have solar-powered flashing red lights.
“There's no good place out there to get an electrical hookup, and [with solar] you don't have to dig a trench to bury a line,” Mr. Rutherford said. “The solar technology is pretty well proven.”