Design and experimental evaluation of a solar dryer for commercial high-quality hay production

Design, experimental functional performance and economic evaluation of an energy efficient commercial-type solar energy dryer for production of high-quality hay, especially for the export market are presented. The newly developed solar hay dryer consists of a solar collector with aluminum absorber plate and spaced fins, a drying shed with perforated metal grate floor above the ground level, swing-away plywood frames and polyethylene curtains for effectively sealing the hay stack dining drying operations, an insulated duct, and a crawl space below the floor where a 3-hp in-line centrifugal fan is housed for air circulation by suction. In late August and in early September, 1996, 160 small rectangular bales of alfalfa hay with about 25% bromegrass were successfully dried from 33% initial moisture content to 13% moisture and from 25% to 11% moisture in 4 and 3 days, respectively, under average weather conditions in Saskatoon, Canada The air temperature rise above ambient was 13-15 degrees C during peak bright sunshine hours in August and 10-13 degrees C in September. Ambient relative humidities ranged from 30-90%. Unlike field-cured hay, the hay produced by the dryer was of high-quality and remained green in colour and attractive after drying. Compared to field drying or conventional natural gas drying system, the payback period on investment in full-scale solar hay drying system may be just one to two years. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.