Peanut Drying with Solar Energy

A solar drying facility was constructed for comparing three full-size peanut drying systems: (a) solar-heated water, (b) solar-heated air with rock storage, and (c) conventional liquified petroleum gas (LPG). Thirty six wagons of peanuts averaging 4180 kg initial weight and 17.5 percent initial moisture content (m.c.) were dried. Dryers had conventional drying fans and LPG burners. Heat energy from solar storage was used to preheat the air entering the fan. The water system with 82 m2 collector area and 5300 kg of storage, provided 41 percent of the heat energy used. The air/rock system with 140 m2 collector area and 103 Mg of rock storage averaged 74 percent solar con-tribution over the season. Total heat energy used per wagon was comparable for the conventional and air/rock systems. The water system used more heat energy than either of the other systems because of higher airflow and unlimited temperature rise, up to a maximum thermostat setting. Drying time was not significantly different among the three systems. Milling quality, as estimated by the Federal-State grading system, was not significantly dif-ferent among the systems but it did vary betwen tests. The results showed that the use of solar energy to reduce fossil fuel consumption for peanut drying is feasi-ble.