OPTIMIZATION OF SOLAR HAY DRYING IN A STEP-FLOW DRYER

Artificially drying lucerne immediately after cutting eliminates quality losses during field drying and minimizes the number of field operations. The average potential saving, calculated over a 20-year period for southeast Queensland, is about $40 (Australian)/t of hay, minus drying costs. The optimum technique of hay drying (immediately after cutting) in a solar-supplemented, step-flow dryer was investigated. A computer model was developed to minimize the cost of drying and to define the optimum drying parameters. Sensitivity analyses were carried out for drying air temperatures in tiie range of 30 to 70° C. The results show that there is an optimum number of hours of operation per day (8 h/d) for any combination of the other variables. The most critical factors affecting annual savings are the temperature of drying air, the length of the drying season, the cost of fuel, and the specific cost of the collector. An economic analysis showed that an average annual increase in profit of about $16/t of dried hay (at 12% w.b.) could be attained under optimum sets of operating conditions.