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As a light source, light-emitting diodes have a lot going for them: long lives and high efficiencies, to name two advantages. But they tend to be more expensive than standard incandescent bulbs, so researchers have been working to ramp up the amount of light put out by each diode. Now a group at Rensselaer Polytechnic Institute in Troy, N.Y., has found a way to get up to 60 percent more light per watt from a white LED.
Commercially available white LEDs produce many more photons than they emit. More than half the photons produced by the phosphor that sits on top of the light-emitting semiconductor are sent backwards or sideways. Most of this light is absorbed and lost. Boosting efficiency of white LEDs should help them compete in applications such as indoor lighting.
The researchers have found a way to avoid that problem by changing the orientation of the phosphor and the semiconductor. They moved the phosphor away from the semiconductor and shaped the lens of the LED to capture more photons. As a result, more light is directed outward.
The new LED can produce as many as 80 lumens per watt, more than five times as many as a typical incandescent bulb. It is hoped that by decreasing the number of LEDs needed to replicate the work of a light bulb, the costs will come down enough to make the energy-saving technology more competitive.
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When people promote a hydrogen economy, more often than not they talk about the potential for wind turbines to power the hydrogen-making process. Wind power is emission-free, while many other sources of electricity that could be used for the job, such as coal plants, typically produce just the kind of pollution the switch to hydrogen is supposed to banish.
But are wind turbines really up to the job? To find out, in April the University of Minnesota dedicated a 230-foot wind turbine intended to provide data on the feasibility of wind-to-hydrogen projects.
Some of the estimated 5.6 million kilowatt-hours produced annually will power a hydrolysis operation, while the balance will supply electricity to the University of Minnesota's Morris campus.
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New York may be the city that doesn't sleep, but its residents are still subject to other bodily functions. That makes it an inviting target for an Arkansas company with patents on a process that can convert sewage into fuel.
ThermoEnergy, a Little Rock-based technology company, signed an agreement in April to use its ammonia-removal process at a New York City wastewater treatment plant. The $7 million contract with the city's Environmental Protection Agency calls for the company to remove 99.9 percent of the ammonia in the liquid extracted from solid waste at the 150 million gallon-a-day Bowery Bay Water Pollution Control Plant in Queens.
But the company may have its sights set on bigger game. In addition to its ammonia-treatment process, ThermoEnergy has also developed a means of turning sludge into a biosolid with a high-energy content. The process has been tested in a U.S. EPA program, and the company received a patent on the technology in April.
Even if ThermoEnergy can get its fuel technology into New York City wastewater plants, don't expect an energy bonanza: Unless a facility is as large as the Newtown Creek station in Queens (shown above), it won't produce enough sludge to cover more than its own energy demand. But recycling the sewage as fuel could cut down on transportation and landfill costs.