Application of solar energy to industrial drying of soybeans: Phase III, performance evaluation. Final report

A 15-month performance evaluation was conducted on a solar system designed and constructed to augment the industrial drying of soybeans at the Gold Kist, Inc., extraction plant in Decatur, Alabama. The plant employs three oil-fired, continuous-flow dryers of 3,000 bu/hr each. The solar system consists of 672 Solaron air collectors that temper the airflow into the existing dryers. Since the requirement for energy exceeds the peak solar system capacity, no storage is provided. The interface with the existing facility is simply accomplished by three ducts that release the solar heated air directly adjacent to the dryer air intakes, and no mechanical coupling is needed. The solar system was operated for 1,752 hr on 290 days during the 15-month period without a single failure sufficient to cause shutdown. No interference with normal plant operations was experienced. Maintenance of the solar system, consisting of service to the air handling unit, cleaning of collector glazing, and minor duct repair, totaled $1,564. System utilization was only 46.3%. This was primarily due to daytime routine maintenance performed on the conventional drying and processing equipment. The solar fraction was not large enough to justify maintenance shift changes. An average collector efficiency of 26.2% was experienced. Contamination caused by the local plant environment reduced the average collector efficiency by 9.3 percentage points. A prototype of an automatic cleaning system was constructed and tested