Thermal evaluation of a hybrid dryer with solar and geothermal energy for agroindustry application

Abstract

The process of drying at the agroindustry level is considered the most important stage for the storage and conservation of food, but an inadequate sizing of the systems can generate an excessive consumption of fuel and energy. In the case of the agricultural sector, especially in small and medium producers in Ecuador, they tend to dry cereals outdoors, spreading the product over black plastics, asphalt floors, or cements called "tendal". This process depends on the weather conditions of the area and can take between one or four days of drying, tending to damage the product by fungi. On the other hand, certain producers build dryers empirically, using as the main fuel gas for domestic use, diesel, or firewood. Among the problems presented for these types of dryers are heat losses in the drying chamber as it is not thermally insolated, a lack of temperature control (above 60 °C) and drying speed, excessive fuel use, and 10% burned product, which are essential to control to obtain a quality product and savings in the energy consumption of the dryer. With regard to the problem raised above, the design and construction of a hybrid dryer that worked with 80% of thermal solar and low enthalpy aerogeothermal energy and 20% with electric power was conducted to optimize the drying process and ensure a quality dry product. The work proposes the dimensioning of each component of the dryer. As a result, it was found that the efficiency of the equipment was around 60%, reaching a maximum operating temperature of 52 °C, with a stabilization time of the system in the first hour within 40 min. It should be noted that the design of the prototype is easy to adapt and replicate.