DESIGN, EXPERIMENTAL AND ECONOMIC-EVALUATION OF A COMMERCIAL-TYPE SOLAR DRYER FOR PRODUCTION OF HIGH-QUALITY HAY

Design features, development, experimental functional performance and economic evaluation of an energy efficient solar energy dryer for comm ercial production of high-quality hay and processed forage products ar e presented. The solar hay dryer consists of an improved solar collect or with selective coated aluminum absorber plate and spaced fins, and a drying shed connected to the collector by an insulated duct and havi ng a perforated metal grate floor, swing-away plywood frames and polye thylene curtains for effectively sealing the hay stack, and a crawl sp ace 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, 19 96, 160 small rectangular bales of alfalfa hay with about 25% bromegra ss were successfully dried from 33% initial moisture content to 13%, a nd from 25% to 11% moisture in 4 and 3 days, respectively, under avera ge weather conditions in Saskatoon, Saskatchewan, Canada. With about 1 8 m(3)/min per tome airflow, 10-15 degrees C temperature rise above am bient was obtained during peak bright sunshine hours. Relatively high daily average collector Efficiency of 76%, high drying effectiveness, drying uniformity, uniform air distribution and tight seating of the s tack were achieved which resulted in an attractive green color of hay, no mold growth on hay, and an overall system drying efficiency of abo ut 79%. Compared to a conventional natural gas drying system or field- drying method, the payback period on extra investment costs recovered through drying cost savings of $3/t to $6/t or through over two times higher prices for high-quality hay produced by the solar drying system may be just one or two years, respectively.