GE solar collector captures more light in less space

A new type of solar collector now being tested by the General Electric Company may be just what the struggling renewables industry and skeptical homeowner need.

The collector, developed at GE's Research and Development Center here, is termed ''revolutionary'' by the scientists who designed it. Why? Because the unit can collect sunlight and turn it into 100 percent space heat on a cold, cloudy Northern day, that notorious battleground where the mettle of many a conventional flat-plate collector has been tested and defeated.

Better yet, the unit is made of low-cost plastic, which would, when marketed, cost about a third of those collectors now on the market shelf. It is also lightweight - a little more than three pounds per square foot.

At the present cost of $30 a square foot, a consumer has a lot of thinking to do before retrofitting his roof with a standard array of four heavy, 4-by-12 -foot collectors; and more if he lives in a Northern state where low seasonal performance in winter (sometimes as low as 15 percent) can extend the system's payback time.

Admittedly, such considerations have stalled widespread acceptance of solar space heating. But GE officials are optimistic that consumer pessimism can be replaced by enthusiasm, provided they are given the proper incentives.

In this case, the incentives lay in redesigning the collector's cover. Unlike standard ''flat-top'' units, which have flat glass or plastic covering the absorbers that transfer heat into circulating air or, in the case of domestic hot-water systems, water or another liquid, the GE cover is an array of clean, cylindrical vacuum tubes.

Intentional or not, the collector resembles a fluorescent lighting panel rather than a solar, air-type unit. It is this type of design that allows more light to be absorbed in less area by the collector, even under heavy cloud cover , says John Flock, manager of GE's chemical engineering technical unit at the research facility.

''During cloudy days, the sunlight hits the cloud and becomes diffuse,'' Mr. Flock says. ''Unlike direct sunlight, more light is bounced off the clouds. The collector tubes, then, help to collect more energy at more angles.''

This, Flock notes, makes the collector up to three times as efficient as the standard flat-top unit.

To prove its efficiency, GE did a projected, 25-year computerized study of seasonal performance in several areas of the United States, including Albuquerque, N.M.; Seattle; Madison, Wis.; and Boston.

While Albuquerque won kudos as the ideal locale for a space-heat solar system , Flock says the collector can be modified in design to accommodate 100 percent space heating in the other areas as well.

''Albuquerque, to be sure, is the best place to live with solar and Seattle is the worst,'' he adds. ''But if you modify the system you'll get the same performance. In other words, increase the square footage of the collector so you can come up with a better total number of Btu for storage.''

Is this the perfect solution to the solar-energy-collector efficiency problem? Maybe, says Flock, but he warns consumers not to come ''beating down the door'' at GE. The unit is still in its prototype stage and GE is hesitant to say if plans to market the unit will materialize ''next year, three years from now, or even in five years.''

''To go with the collector we would need a large market size,'' Flock asserts. ''Right now the major (domestic solar) market is not in residential heating, but in hot water.''

What if the GE product itself could boost demand?

''Well,'' he concludes, ''we're really in a chicken-before-the-egg situation. We'll have to wait and see.'

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