In Thailand, natural sun drying is one of the most common ways to preserve agricultural products. Many agricultural products are spread on the ground to be dried by sun and wind. During the drying, these products are neither protected against dust and rain, nor against rodents, birds and insects. This results in poor quality products due to contamination and high loss caused by uneven or incomplete dehydration. In order to meet the food requirements of the growing population and moreover to provide high quality products, Thailand is developing dryers that respond to such demand. In addition, to overcome the dependence on solar energy which is the most common energy source for drying, different sources of energy are envisaged. Geothermal is one with relatively high potential at industrial scale. In fact, Thailand has more than forty medium-enthalpy geothermal resources scattered throughout the country, particularly in the north. In Fang district, Chiang-Mai province, the Electricity Generating Authority of Thailand (EGAT) has installed a geothermal power plant. It is a binary cycle system with a total generating capacity of 300kWe. The rejected temperature of hot water is about 80C. Hence, the idea of using this waste heat for drying of chili and garlic