Americans burn millions of barrels of oil to light up the sky each night. This represents a huge burden, not only in terms of energy outlay, but for the constant river of equipment, time, and effort needed to keep the process going. Street lighting also adds significantly to our national health care bill. Normal sleep behavior in humans is easily disturbed by artificial light, and there’s substantial cause to think it complicates our health by interfering with normal sleep patterns.
LED (Light Emitting Diode) is an emerging lighting technology which offers new ways to cope with these problems. In its early years LEDs were only capable of emitting specific colors, notably Red and Green. But blue LEDs have recently become available in large numbers, and with them comes the prospect of using LEDs to create light of any color. Since the 1960’s the efficiency and light output of LED technology has been doubling every thirty-six months. As a result LEDs have become an order of magnitude more efficient than incandescent bulbs, and are starting to eclipse fluorescents as well. Other key advantages of LEDs include a much longer life span, low heat emissions, and superior susceptibility to complex computer control. LEDs are virtually instant-on devices which can be cycled on/off many times more often than other forms of lighting. They are also much more directional than normal lights, a fact which can be used to both increase efficiency and lower light pollution. Last, but not least, LEDs fail gradually by slowly growing dim, in stark contrast to the abrupt failure of incandescent bulbs.
All these advantages add up to a tremendous opportunity for America to save energy and fight global warming. A 2008 white paper funded by the Ford Foundation found that if the our ten largest metropolitan areas convert to more efficient lighting, CO2 emissions will be cut by 1.2 million tons a year, the amount produced by 212,000 cars! The long life of LEDs would also save money by slowing the rate at which municipalities need to buy and install replacement lights.
But LEDs may make a radical new kind of economy possible, one based on not bothering to light empty streets where no one is stirring! It has been our habit to light millions of empty streets each night all across America, streets which for long stretches of time are completely devoid of traffic, where no one is even awake enough to know if lights are on! This is a colossal waste of energy which LEDs are ideally suited to put an end to. Equipping LED street lights with motion sensor detectors will let us turn lights on only when there are actually people there to see and use them. LEDs can accomplish this because unlike incandescent lights they can power up/down a huge number of times without breaking, and unlike florescent lights they turn on instantaneously.
Under this scenario a street would light up before you as you drove or walked down it, only to fade back into darkness when no traffic is present. Some might object this would lead to a “strobe light” effect all over town. But LEDs are ideally suited for sophisticated network control which could provide many options. One might be to simply dim lights slowly on streets with little or no traffic, instead of shutting them off completely. Programming for a new generation of street lights could be split between the local intelligence of individual lights designed to react to real-time traffic, and a central control center which could override their behavior with its own programming. Such systems might consist of street lights with flash memory software which could be updated from a central office. This would allow the programmed behavior of an entire municipal lighting system to be updated on the fly without needing to send workmen into the streets.
What’s needed at this point is a grand experiment, one designed to test these possibilities in the interest of arriving at an optimal solution, one which balances our desire to conserve energy while providing nighttime illumination people find useful and comfortable. Only by conducting such an experiment can we learn what will work best. I also suggest that this needs to be a national experiment sponsored by the federal government. If we are to move on this into the 21st century as a people, it won’t do for each town to have their own way of programming street lights. However inefficient our current way of lighting up the night may be, it has the advantage of being predictable. Regardless of the state or city we’re in, we know what to expect from street lights. But as with all systems which contain significant software, this new technology will be capable of surprising us with unexpected behavior. Such surprises can be good or bad. To make sure it’s the former, we need to coordinate our efforts to create a standard way to use this new potential, one tested by real experience.
(Originally posted by R. Guenette 01.10.09)