The aim of this study was to establish the optimal conditions of distinct factors affecting the performance of a closed solar dryer in drying Gracilaria chilensis, a commercially important red algae. The evaluated factors were algae arrangement (vertical versus horizontal), baffle existence (present versus absent), and air fan use (on versus off). Process productivity was maximized when the algae were arranged horizontally, a baffle was present, and the air fan was turned on. Of these, air fan use was the most important determinant of process performance. This optimized solar dryer system was then compared against the productivity of an open-air system. The solar dryer achieved a greater degree of moisture evaporation than open-air drying (86.1% versus 67.6%, respectively). This result is directly associated with the recorded peaks in air temperature (41.3 degrees C in the solar dryer versus 21.7 degrees C outside of the solar dryer). The specific energy consumption required for the optimized solar dryer process was 1.64 kWh/kg, as due to the energy requirements of the air fan and recirculation pump. Solar drying is very effective in drying G. chilensis when parameters are optimized. (C) 2018 Elsevier Ltd. All rights reserved.