2001 - Volume #25, Issue #3, Page #42[ Sample Stories From This Issue | List of All Stories In This Issue | Print this story | Read this issue]
Solar Dryer Beats High Energy Costs
Leroy Bader, an extension agrologist with Saskatchewan Agriculture and Food and one of a team of people who collaborated on the project, says that tests of the unit proved that it could successfully dry about 3,000 bushels of wheat from 17 per cent moisture to 13 per cent moisture in about four days (under suitable environmental conditions).
"The solar collector design is a 12 by 28-ft triangular shape with the transparent fiberglass face inclined at a 70 degree angle. The bottom and sides are insulated and there are openings on each end for air circulation," he explains. "A 7- hp. centrifugal fan was mounted in the insulated outlet duct to draw warm air from inside the unit and out into the grain bin. We've tested it through three consecutive harvest seasons and it has worked well."
Thin copper sheets painted flat black were mounted on 1/2-in. plywood and located behind the fiberglass. Bader says aluminum or steel sheets painted black could also be substituted.
Since the prototype was also designed to heat an insulated water storage unit for storing heat to be used on days when the sun is not out, the unit also incorporated a network of half-inch copper tubing attached to copper plates. An anti-freeze solution could be circulated in the tubes to absorb the heat and carry it to the water tank.
The fan costs between $300 and $500 and the rest of the dryer cost $3,000 to build, but that amount could be reduced depending on the materials used. For example, the fiberglass could be replaced with greenhouse plastic sheeting.
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