Gwi Hyun Lee

Utilization of Solar Energy in Agricultural Machinery Engineering: A Review

Background: Various solar energy collecting systems have been developed and analyzed for agricultural applications. They include solar thermal and electric devices such as solar crop dryers, solar water pumps, solar greenhouse heating, ventilation for livestock, solar aeration pumps, solar electricity, and many more. Purpose: This review provides the current status of research and development in the field as well as the solar energy systems that are currently in use in the agriculture sector across the globe. Review: Solar energy is the largest and cheapest energy resource on earth; one hour of solar radiation exceeds the complete global energy consumption in one year. The potential annual total solar radiation in South Korea is 3.58–5.4 kWh/m 2 /day. The available solar energy is sufficient for agricultural applications across the entire country. Conclusion: The scope of solar energy utilization in agricultural machinery engineering in South Korea and in other countries is promising.

A Study for the Use of Solar Energy for Agricultural Industry - Solar Drying System Using Evacuated Tubular Solar Collector and Auxiliary Heater -

Purpose: The objectives of this study were to construct the solar drying system with evacuated tubular solar collector and to investigate its performance in comparison with indoor and outdoor dryings. Methods: Solar drying system was constructed with using CPC (compound parabolic concentrator) evacuated tubular solar collector. Solar drying system is mainly composed of evacuated tubular solar collector with CPC reflecto r, storage tank, water-to-air heat exchanger, auxiliary heater, and drying chamber. Performance test of solar drying system was conducted with drying of agricultural products such as sliced radish, potato, carrot, and oyster mushroom. Drying characteristics of agricultural products in solar drying system were compared with those of indoor and outdoor ones. Results: Solar drying system showed considerable effect on reducing the half drying time for all drying samples. However, outdoor drying was more effective than indoor drying on shortening the half drying time for all of drying samples. Solar drying system and outdoor drying for oyster mushroom showed the same half drying time. Conclusions: Oyster mushroom could be dried easily under outdoor drying until MR (Moisture Ratio) was reached to about 0.2. However, solar drying system showed great effect on drying for most samples compared with indoor and outdoor dryings, when MR was less than 0.5.

Drying Characteristics of Carrot and Green Pumpkin Slices in Waste Heat Dryer

th , 2012; Revised: February 21 th , 2012; Accepted: February 29 th , 2012 Purpose: Drying characteristics of the sliced carrot and green pumpkin were investigated by using the waste heat dryer. Methods: The effects of drying temperature ( ) and slice thickness affecting drying time were analyzed. Mathematical models for the drying curves were determined with statistical analysis of drying data. Effective diffusivity was determined for the slices of carrot and green pumpkin under various drying conditions. Results: Drying time was reduced at the drying conditions of thinner slice and higher drying temperature. Mois ture ratio () according to drying time () was well presented as an exponential function at all of drying conditions for the slices of carrot and green pumpkin with the determination coefficient (  ) of >0.99. The values of effective diffusivity (  ) of the slices for carrot and green pumpkin were increased with increasing the drying temperature. The relationship between Ln(  ) and 1/ was linear with the determination coefficient (  ) of >0.97. Conclusions: Drying model was well established as an exponential function at all of