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Land of the midnight melons?

Land of the midnight melons?

Though fresh produce can be flown in to grace Arctic dinner tables this time of year, the costs are high. Indeed, imported $5 cucumbers are not uncommon in Canada's remote north, observes Dennis R. St. George at the University of Alberta in Edmonton. And the high cost of supplying high-latitude greenhouses and artificially lit growth chambers with heat and/or electricity renders their yields comparably expensive. So St. George is now investigating what he hopes will prove a money-saving alternative: fiber-optic transmission of rays from the sun or from growth lamps to Arctic crops nurtured in heavily insulated indoor gardens.

At a meeting of the American Society of Agricultural Engineers in New Orleans last week, he and colleague John J.R. Feddes reported initial data on their prototype lighting system. To maximize the collection of natural light, its two solar panels track the sun across the sky. Each of the 96 Fresnel lenses on these panels concentrates the sun's light and delivers it to the 15-meter-long, silica-core optical fiber with which the lens is paired. In field tests conducted Nov. 29, the system "operated as designed," the researchers say, though the transmission efficiency of photosynthetically active wavelengths was only 16.4 percent -- far below the 70 percent suggested possible with optical-fiber systems tested by other researchers for different applications.

The Canadian team suspects problems in the prototype's solar tracking led to its initial weak showing. But if overall efficiency can be substantially upgraded, they maintain, the approach holds promise for year-round lighting control in indoor gardens. In the depths of winter, high-latitude gardeners might pipe in artificial lighting to counter the 24-hour-per-day darkness, they say. And in the perpetual daylight of summer's peak, the system could allow growers to parcel out natural rays in doses that permit normal growth.
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Title Annotation:fiber-optic transmission of heat to grow produce in the Arctic
Publication:Science News
Date:Dec 23, 1989
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