Energy worth millions of dollars never makes it from the power plant to the consumer. Instead, it's eaten up by the electrical transformers commonly located near households, on utility poles, or on transmission lines.
Now a University of Rochester professor has discovered a way to overcome the manufacturing difficulties associated with a class of materials, called amorphous metals, which can cut the energy loss in those transformers by two-thirds.
James C.M. Li, Albert Arendt Hopeman Professor of Engineering, and former graduate student Der-Ray Huang recently patented a process to make the metals much more ductile (that is, much less brittle). The process should make the materials less expensive to manufacture and could result in their widespread use by utilities.
In a transformer, engineers use the magnetic properties of the core material to vary the voltage and current. The easier the core material is to magnetize, the less power is required to vary the voltage and the less expensive the transformer is to operate.
Some amorphous metals (such as those consisting of a mixture of iron, boron, and silicon) are more easily magnetized than any known material and are ideal candidates for use in transformers. Indeed, distribution transformers with an amorphous core typically require 65-70 percent less energy than conventional core materials such as silicon steel, according to Ben Damsky, senior project manager at the Electric Power Research Institute (EPRI) in Palo Alto, Ca.
Despite the energy savings, only a small number (3-4 percent) of the 1 million distribution transformers shipped to utilities in the U.S. by EPRI during the past year had amorphous cores. The reason: amorphous cores typically cost about 30 percent more than conventional ones.
The higher price is due mainly to manufacturing difficulties related to the brittleness of amorphous materials. Engineers heat the materials in a furnace to improve their magnetic properties, but this makes the metals nearly as brittle as glass. The materials are difficult to cut, shape, or even ship, since an amorphous core typically consists of a few thousand closely packed layers of these metals, each about one-thousandth of an inch thick.
Instead of heating the metals in a furnace, Li heats them with a pulsed high current (approximately 1,000 amperes per cm2) for anywhere from one second to two minutes, with a pulse duration ranging from one-billionth to one-tenth of a second. The method is faster and the resulting materials are much less brittle.
Transformers made of amorphous cores typically require about $20 less in energy each year to perform the same function. According to Damsky, utilities put into service about one million new transformers each year; each transformer has a lifetime of approximately 30 years. If Li's work makes the price of an amorphous core competitive with traditional materials, substantial energy savings will result.
"The savings per transformer might be only $20 per year," says Damsky. "But if you install one million of these transformers in a year, and do that each year for 30 years, you're saving a huge amount." Indeed, if every transformer in the nation had an amorphous core, savings could reach $600 million per year.
Li's work could also be utilized in security systems for department stores, where amorphous metals are now sometimes used, and in libraries, where thin magnetic metal strips prevent readers from secretly removing books. Li believes the use of amorphous metals in library books, for example, would result in shorter, less expensive strips of metal.
This work was sponsored by China Steel Corp., which also holds the patent (#4,950,337).
James Li will receive the 1990 Acta Metallurgica Gold Medal, the top honor a materials scientist can earn, at a meeting of ASM International (formerly the American Society for Metals) during Materials Week `90 in Detroit next week. The prize is awarded by Acta Metallurgica Inc. to only one scientist among 27 professional societies in 17 countries.
Li has made fundamental contributions to many areas of materials science and is credited with making amorphous metals (metals in which the atoms are arranged randomly) widely available for commercial use.
Li had extensive experience with Allied Chemical Corp., United States Steel Corp. and Westinghouse before joining the University in 1971 as professor of mechanical engineering. Under Li's leadership materials science research in the Department of Mechanical Engineering now involves five professors working with more than $1 million annually.
Just two years ago Li added to his collection of honors the Lu Tse-Hon Medal, the highest award of the Chinese Society for Materials Science in Taiwan. A fellow of ASM International, the American Physical Society, and The Mineral, Metals & Materials Society (TMS), Li has also received the Champion Mathewson Gold Medal and was named the Institute of Metals Lecturer and Mehl Medalist in 1978 by TMS.