Design, construction and performance testing of a solar dryer for agroindustrial by-products

Spain generates a big amount of agroindustrial by-products of high moisture that produce a high environmental impact. This fact motivates the aim of this paper, in which a solar dryer prototype is designed, constructed, and performance tested for the analysis of the drying kinetics of these by-products and their possible power valuation. The characteristics of the prototype are presented, together with the variations of the properties of temperature, relative humidity, air mass flow, and efficiency for indirect, mixed, passive, active, and hybrid operation modes. The most efficient operation mode will be the forced-hybrid one, followed by the passive and active modes. The analysis of the drying kinetics of the olive pomace shows the better performance of the hybrid and mixed modes, obtaining reductions of the drying time of a 50% in both cases.