UTILIZATION OF SOLAR ENERGY IN AGRICULTURAL PURPOSES APPLICATIONS OF SOLAR ENERGY COLLECTED BY A PLASTIC GREENHOUSE FOR DRYING AND AERATING OF WHEAT CROP

Abstract

Wheat is considered the back - bone of the Egyptian diet for the majority of the people. It is a highly versatile food product; non-perishable and it can be stored safely for long periods of time and transported in bulk over long distances. Wheat is harvested at a relatively high moisture level to clear the land early enough for the next crop cultivation and to avoid the heavy scattering losses. This investigation deals with the two-post harvest processes, i.e., drying and aerating, which are believed to play a vital part in the better management of the grain production. Drying is one of the processes necessary to cut down losses and prevent grain deterioration after early harvesting. Resistance to airflow is an important factor in the design and the performance of the drying system. The need for drying has made it necessary to obtain infonnation on the resistance to airflow. In Egypt, the main reason for delaying harvesting of wheat is the lack in the efficient drying systems having high capacities to accomplish the drying to coincide with the high rate of mechanical harvesting. The feasibility of using the natural air dryer was investigated. The feasibility of using a plastic greenhouse as a simple solar collector to increase the drying efficiency of the natural dryer was also shtdied. A span form greenhouse having a net volumetric capacity of 82.4m 3 of air, which serves as a simple solar collector for heating the drying air, was used. Two centrifugal fans, air distribution pipes, and two cylindrical steel grain columns were also manufactured with local materials. The current study was tackled to investigate the behavior of the natural and solar - heated air drying systems using the principle of forced air as pressure systems. The two drying systems were built and installed at Meet El- Deeba, Kafr El - Sheikh Governorate, to investigate the performance of both of them. The experiments were conducted during the 1997 - 1998 harvest season. The effects of airflow rates, initial moisture contents of the grain, grain bulk density, and varying weather conditions on the airflow resistance characteristics within wheat bulks were studied using two 0.31m diameter cylindrical steel bins. Airflow resistance was measured at airflow rates ranging

from 298.8 to 997.2m3

per m2 of cross sectional area of the test colmnn. Bulk

densities and grain initial moisture contents ranged from 620 and 798kg/m3 and from 12.39 to 21.93% (w.b.) respectively. From among the main objectives of the present study is to test a solar­ heated air dryer constructed for drying the Egyptian wheat (Sakha 61). The performance of the drying model as compared with the natural air dryer was carried out regarding the grain layer thickness and the initial moisture content of wheat cultivar. The layer thickness of wheat grain was classified in the range between 10 and 40cm measured from the drying floor of the test column.