Bright ideas could have long lasting effects

Changing the way we change a bulb

Cambridge University Professor of Metallurgy Colin Humphreys sees the light. But unlike normal flashes of brilliance, this unique advance will probably last a while. Humphreys' new technology could signal the end to the way we all change light bulbs. Humphreys is betting on a radical technology for longer-lasting, low energy-light bulbs, the gallium-nitride computer chip. Gallium-nitride, already widely used in the computer industry as a processing chip, can also be used to make light emitting diodes (LEDs), which burn a fraction of the energy used by conventional, incandescent light bulbs. "With normal intermittent use, they would last a lifetime," said Professor Humphreys. "So once fitted, you may never have to change another light bulb. Without a doubt this is the most important new invention in electrical materials since silicon." Typical household light bulbs emit light only after the heating of a metal filament. The gallium chip allows a small amount of electricity to excite electrons on its surface. As these electrons change from one quantum energy-state to another, they emit a brilliant "blue" light. This blue light can be captured by a thin coat of phosphor on the inside of the bulb and converted into visible white light in a process known as photon reduction. By eliminating the heating element, this lighting technology can operate 90 percent more efficiently. Conventional light bulb technology will continue to be counted on for consumer use for at least five to 10 years, but in the meantime, gallium LEDs are being put to the test in applications that typically have had high replacement rates and costs such as traffic lights and billboards. Conventional traffic lights burn out every six months and the average replacement cost is $600 per light. Some problems must be overcome before this latest technology becomes mainstream. The current infrastructure in the U.S. has offices and houses wired for 120-volt appliances. Gallium LEDs run on 12-volt. In addition, there is some fear concerning the long-term impact of the light on human health. The gallium LEDs share common physics and chemistry with fluorescent lights - which emit low levels of ultra-violet (UV) rays. Some scientists are concerned that this technology will also emit UV rays. If it turns out these new LEDs emit more UV than they should, then I wouldn't care how long they last," said Joan Roberts, a chemist at Fordham University. For more information about Professor Colin Humphreys and his research, visit the University of Cambridge Department of Materials Science and Metallurgy.


Solar energy from space may power future

In order to provide sustainable energy for the expected 10 billion global population by the year 2050, new breakthrough energy concepts must be implemented. Beaming electricity from space-based power systems could provide the solution as well as brighten our environmental outlook.

The Electric Power Research Institute (EPRI) says that solar energy from space could supply a 2050 world population of 10 billion people with enough energy to meet all basic human needs at low cost, and with few, if any, of the environmental downsides of other energy alternatives. "Solving the 'trilemma' of population growth, resource consumption and environmental cost, and providing a sustainable global supply of electricity will require some 'outside the box' thinking," said EPRI president and CEO Kurt Yeager. "To look beyond the planet for a solutions is indeed thinking outside the box."

EPRI's latest journal issue, Roadmap, says that photovoltaic (PV) arrays in stationary Earth orbit at an altitude of 22,300 miles would receive eight times as much sunlight as they would at the Earth's surface. Space arrays would also be unaffected by Earth's day-night cycle, cloud cover or atmospheric dust.

The idea of beaming solar power from space was first proposed more than 30 years ago and PV technology has steadily been growing with current applications used to power billboard lighting, construction warning lights, utility switches and telecommunications gear. Developments in recent years in electronics, power generation and robotics, in conjunction with a perceived need for an alternative energy source, have led to the latest push in solar power.

Scientists have envisioned that building solar collectors on the moon will ultimately provide an elegant solution to launching the heavy mass of satellite components into orbit. The lunar soil could provide silicon to build solar arrays and metals such as iron and aluminum for support structures and electrical wiring. David Criswell, director of the Institute for Space Systems Operations at the University of Houston, says, "The moon's environment is extremely dry and there is absolutely no weather. All the things that make solar energy difficult on the Earth are absent on the moon."

"Whether solar power satellites or lunar solar power bases will eventually come to pass remains to be seen," says EPRI's Kurt Yeager. The costs of PV technology must come down while efficiency must simultaneously improve. Under the best of conditions, grid-delivered PV power is still expected to be more costly than electricity generated by traditional fossil fuels.

EPRI researchers believe that by 2050, photovoltaics will be a significant contributor to worldwide power, but that the surest route to cost-effective solar power is not increasing the use of current technology but increasing support for improved research and development.

For more information visit the EPRI Web site at www.epri.com.

This article originally appeared in the 05/01/2000 issue of Environmental Protection.

About the Author

Hu Fleming, PhD, is vice president of the Water Purification Solutions Group, Severn Trent Services Inc., Ft. Washington, Penn.

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