New research at Rutgers University has shown how to slash the cost of highly efficient light emitting diodes (LEDs) and significantly reduce lighting's energy requirements. The energy savings, however, will likely be eroded as people find new uses for the inexpensive lights.
It's a classic example of how a solution to a problem may cause more problems, or at least nullify the solution.
"I am doubtful that we will save any energy by going to LED lights," said Thomas Theis, director of the Institute for Environmental Science and Policy at the University of Illinois at Chicago.
LED lights use just 10 percent of the energy of incandescent lights and less than half the energy of today's compact fluorescent (CFL) bulbs. An LED that uses 6 watts of electricity, for example, produces the same amount of light as a 14-watt CFL bulb or a 60-watt incandescent bulb. According to the U.S. Department of Energy, electricity used for artificial lighting in the U.S. could be cut nearly in half by 2030 through the adoption of high efficiency LEDs.
The lights are commercially available today but haven't been widely adopted because they are more expensive than either CFLs or incandescents. The high cost of LEDs is due in part to their reliance on rare earth elements for their phosphors, materials that shift the blue light emitted by most LEDs into a broad spectrum of white light.
A new class of phosphors made from earth-abundant materials could slash the cost of LEDs by as much as 90 percent according to their developers.
The work has been driven by a dramatic increase in the cost of rare earth elements -- by as much as 1600 percent over the past decade -- due to increased demand and decreased exportation of the materials from China, which has historically produced more than 90 percent of the world's rare earth elements.
"The prices of these rare earth elements have gone through the roof," said Zhichao Hu of Rutgers University who presented his group's work at the American Chemical Society's annual conference in Boston earlier this week. "That makes us think, 'is there a way we can bypass these rare earth elements, is there a way that we can use earth abundant elements to make phosphors that have the same properties, emit the same light, but are cheaper?'"
Starting at a molecular level, Hu and colleagues developed novel combinations of materials to create new classes of phosphors that are free of rare earth elements as well as toxic materials like cadmium and selenium that others are employing in competing phosphor materials.
"We have made many phosphors covering the entire visible spectrum," Hu says. "All of these materials are new and they are free of rare earth elements and toxic materials."
Ram Seshadri, a materials science professor at the University of California Santa Barbara questions whether a 90 percent cost savings in phosphors would translate to similar savings on an entire LED device but says the new technique looks promising.
"It could lead to lower costs, better tunability and higher efficiency," Seshadri says. "The proof of the pudding is going to be whether industry picks up [their] strategies."
Moving from laboratory research to commercial production is always challenging but even if the new technique does significantly reduce the cost of highly efficient LED lights, their use won't necessarily result in energy savings. A number of recent studies have in fact found the opposite. Known as the "rebound effect" they show that reductions in the cost of lighting result in increased consumption as people use more and more lights
A 2010 study looked at lighting use around the world for the past 300 years as lighting technology improved from whale oil lamps to gas and kerosene lamps to electric incandescent bulbs. The study, conducted by researchers at Sandia National Laboratories in Albuquerque, New Mexico found a direct relationship between decreased cost and increased consumption.
Looking at the current transition from incandescent lights to CFLs and ultimately LEDs, the authors concluded "there is a massive potential for growth in the consumption of light if new lighting technologies are developed with higher luminous efficacies and lower cost of light."
A study published earlier this year in the Journal of Industrial Ecology concluded we will likely see a drop in energy use for residential lighting in the short term, but energy savings will likely be reduced or perhaps eliminated entirely as the amount of lit space increases.
"It's not just a question of turning on a light to read a book or to see something on your kitchen counter, you can do lots of stuff with LEDs that you really couldn't do very well with other kinds of artificial light sources," said Theis, a co-author of the study. "They are being incorporated into wearable lighting now, there is just no end to it."
In order to realize long-term energy savings, Theis and colleagues concluded that efficiency improvements may need to be combined with policy interventions.
But finding a solution to curb our appetite for more and more light won't be easy.
"We're addicted to light," Theis said. "If we can consume more, we do."