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Ammonia power for efficiency.

At a time when a 1 or 2 percent increase in the efficiency of an electricity-generating power plant can mean millions of dollars in fuel savings, the claim of a 10 percent or greater improvement is both hard to believe and tantalizing. Such savings are possible, says Houston inventor Alexander I. Kalina, if the water normally used in boilers is replaced by an ammonia-water mixture.

when water is heated, its temperture rises until it reaches the boiling point. The temperature then stays constant until all the water turns to steam; further heating raises the steam's temperature. An ammonia-water mixture behaves differently. Its boiling point doesn't stay constant but changes. As a result, when heated to make ammonia vapor and steam, the mixture absorbs energy more efficiently than does water alone.

The idea of using an ammonia-water mixture is an old one. However, Kalina solved a problem that previous engineers had failed to master. He invented a way of condensing the ammonia-water mixture at standard temperatures and pressures so that it can be recycled.

"Instead of a simple condenser," says Myron Tribus, director of the Center for Advanced Engineering Study at the Massachusetts Institute of Technology, "you have this combination distillation, condensing and mixing unit. However, the overall gain in efficiency is quite impressive."

Last week, Tribus, who has been studying the theoretical thermal properties of ammonia-water mixtures, organized a seminar to explain how the Kalina cycle works. "The conclusion was that this was a promising cycle that ought to be developed further," says Tribus.

Later this summer, the Fayette Manufacturing Corp. in Tracy, Calif., will begin building a 6.5-megawatt power plant, which it hopes will demonstrate that the Kalina cycle works in practice. The company holds a worldwide, exclusive license covering Kalina's patented technology.

So far, the utility industry has shown some interest but has been reluctant to jump into a still unproven technology. The electric Power Research Institute, based in Palo alto, calif., is just starting to study ways in which current power plants can be modified to take advantage of the Kalina cycle. The cycle works with any kind of heat source, from nuclear to geothermal, says Fayette's H.M. Leibowitz.

Typical power plants now run at perhaps 35 or 37 percent efficiency, says Tribus. Schemes have been proposed that raise the efficiency to 45 percent. The Kalina cycle could take that as high as 55 percent, he says.

"There's an itense competition in this field," says Tribus, "but at the moment, [the Kalina cycle] looks as though it has a very distinct advantage over other systems."
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Title Annotation:10 per cent savings possible by using ammonia-water mixture in electric power-plant boilers
Author:Peterson, ivars
Publication:Science News
Date:Feb 1, 1986
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